Ylan Segal

The REPL: Issue 33 - April 2017

A Visual Introduction to Machine Learning

This stunning presentation will give you a quick introduction to machine learning and how it applies statistical learning techniques to identify patterns in data. In turn, those patterns are then used to make highly accurate predictions. The visualization are beautiful and explain intuitively the concepts described. I commend the R2D3 team behind this work and look forward to the second installment.

On-call at Any Size

This article is part of the first issue of Increment, a new digital magazine about how teams build and operate software at scale. The post is a report on what they found after interviewing teams of many sizes. There are some commonalities and best-practices that emerged from their interviews, some of which only apply at certain scales.

One of the things I love about being in software is the current environment of openness that a lot of companies operate in. They publish how they work, what they have tried. Everyone benefits.

Moneyball Teams

Brian Graham takes on hiring at software teams and makes an analogy to Moneyball (book and movie). His concept is that hiring only “the best” is hardly an effective strategy. The focus should be on building a team that can deliver on needs. Each developer brings different capabilities and are rarely interchangeable with each other. By looking at the needs of your team, your are in a better position to make good hiring choices.

Book Review: Programming Phoenix

Programming Phoenix: Productive -> Reliable -> Fast by Chris McCord, Bruce Tate, José Valim is an introduction to Phoenix, a web application framework written in Elixir. The authors bring a lot to the table: Chris is the main author and manitainer of Phoenix. José is the author of Elixir, prolific contributor to Phoenix and once a Rails core member. Bruce is author on several books about Java and Rails.

The book walks through building a complete web-application with Phoenix from scratch, covering it’s particular take on MVC, testing, database access and web-sockets. The book itself is written in clear language and can be easily followed by beginners and advanced programmers alike. Along the way, it explains not only how to use the framework, but why it was designed to work that way in the first place – usually to address a shortcoming that the author’s perceived in other web frameworks. The explanations in the book are thorough, without being repetitive. Meticulous, without being pedantic or condescending. It’s a great example of what technical writing should be.

In a lot of ways Phoenix feels very similar to Rails. The places where it differs matter. In general, it prefers being more explicit and less magic-like. The different parts of the framework, like the router, controllers, models and views are less coupled to each other than Rails, but still fit together nicely. In practice, this means that following the “Elixir Way” is as easy as following the “Rails Way”, but it makes it much easier to test functionality and hook into the framework when needed.

One of the places where Phoenix really shines is Channels. Channels allow a near real-time connection between the server and it’s client, outside of the regular request/response cycle. Channels typically will use web-sockets, but can fall back to long-polling. The abstractions exposed make it easy to reason about how data flows from and to clients. They are also very efficient and use few server resources, due to Elixir underpinnings in the Erlang VM.

Elixir in general, and Phoenix in particular, have great tooling. mix is usually the entry-point from the command line to dependency management, running tests, starting processes, etc. For Rubyists, it’s like gem, bundle, rake and rails rolled into one well-rounded tool.

Although Elixir and Phoenix are relatively new, they have reached a high level of maturity by building on tried and tested technology. This book will get you up to speed on writting Phoenix applications fast.

The REPL: Issue 32 - March 2017

Use the Unofficial Bash Strict Mode (Unless You Looove Debugging)

Bash is ubiquitous. Even Windows runs it now. Often, it’s the minimum common denominator you can expect a computer to have, without needing to install extra dependencies, which is why I often find myself writing bash scripts. In this article, Aaron Maxwell explains how to set a few options that will make it easier to avoid bash’s many pitfalls.

Validation, Database Constraint, or Both?

Derek Prior brings a well-articulated argument of when to use Rails validations and when to rely on database constraints. His advice is solid, for Rails, which doesn’t handle constraint violation in the database well. After reading this article, I found out that Ecto – an Elixir database wrapper – does handle database constraints and makes them errors to the rest of the application. I wish Rails had that!

So you want to be a wizard

Julia Evans made available a transcription of a keynote talk she gave recently. I really liked how show approached learning and breaking down big problems into manageable pieces. At some level, what she proposes is basic curiosity, without getting hung-up on your current level of understanding. Do you need to debug tcp networking in Linux, but don’t know about it? Read some books on it. Is that not enough? Open up the source code and read that. Inspiring, yet refreshing. We can all learn anything, as long as we do it methodically and with dedication.

I Also Built a CLI Application in Crystal

Recently, I’ve read about porting a Ruby application or writing a command-line application to Crystal. As it happens, I had started doing the same thing myself a while ago and recently finished it. My motivation was intellectual curiosity. Learning a new language is useful in itself, but I have also found that it learning paradigms in a new language influences how we use other languages as well.

Crystal is inspired by Ruby. Much of it’s syntax is the same. Much of the standard library is very similar. It also has it’s differences. Mainly it’s type system and the fact that it’s compiled, as opposed to interpreted.

I decided to write a port of franklin, a toy project of mine. I wrote about it before. It’s on Github. All the code for the port to crystal is also on Github.

The REPL: Issue 31 - Februrary 2017

Online migrations at scale

Performing database migrations – changes in the underlying schema – is a necessity for many web systems, usually because they don’t want to disrupt customer traffic. This post described how they solve this at Stripe. In my team, we follow a similar approach, but instead of dual-writing, we solve the problem by dual-reading. In any case, I commend Strip and other companies like it for detailing their successes in articles like these. The whole software engineering community gains.

The Security Impact of HTTPS Interception

In this fascinating article, researches from academics and industry detail how they went about measuring the use HTTPS interception products and it’s impact on security. HTTPS interception is usually deployed by IT systems so that they can decrypt HTTPS traffic and scan it. Essentially, it’s like a man-in-the-middle attack that the user consents to. Not surprisingly, in most cases, the use of HTTPS interception results in downgraded security.

Software Engineering at Google

Fergus Henderson describes Google’s key software engineering practices. There are great insights into their process and approach, as would be expected from one of the most successful software companies today. It includes things like how they store their source code, which languages they use, their build system, code review process, debugging and profiling, 20% investment time and project and people management. Not every company can or should adopt all their practices, but most would benefit from some of them.