My Choice of Programming Languages

When I was a kid, I used to spend days tinkering with woodworking tools. I was lucky enough to have a wide set of tools at my disposal. However, there was no one around to give me a hint about what tool to use when. So, I quickly came up with a heuristic: if my fingers and a tool survived an exercise, I've used the right tool; if either the fingers or the tool got damaged, I'd try other tools for the same task until I find the right one. And it worked quite well for me! Since then, I'm an apologist of the idea that every tool is good only for a certain set of tasks.

A programming language is yet another kind of tool. When I became a software developer, I adapted my heuristic to the new reality: if, while solving a task using a certain language, I suffer too much (fingers damage) or I need to hack things more often than not (tool damage), it's a wrong choice of a language.

Since the language is just a tool, my programming toolbox is defined by the tasks I work on the most often. Since 2010, I've worked in many domains, starting from web UI development and ending with writing code for infrastructure components. I find pleasure in being a generalist (jack of all trades), but there is always a pitfall of spreading yourself too thin (master of none). So, for the past few years, I've been trying to limit my sphere of expertise with the server-side, distributed systems, and infrastructure. Hence, the following choice of languages.

Language logos

Read more

Writing Web Server in Python: sockets

What is a web server?

Let's start by answering the question: What is a web server?

First off, it's a server (no pun intended). A server is a process [sic] serving clients. Surprisingly or not, a server has nothing to do with hardware. It's just a regular piece of software run by an operating system. Like most other programs around, a server gets some data on its input, transforms data in accordance with some business logic, and then produces some output data. In the case of a web server, the input and output happen over the network via Hypertext Transfer Protocol (HTTP). For a web server, the input consists of HTTP requests from its clients - web browsers, mobile applications, IoT devices, or even other web services. And the output consists of HTTP responses, oftentimes in form of HTML pages, but other formats are also supported.

Client talking to server over network

Read more

How to use Flask with gevent (uWSGI and Gunicorn editions)

Python is booming and Flask is a pretty popular web-framework nowadays. Probably, quite some new projects are being started in Flask. But people should be aware, it's synchronous by design and ASGI is not a thing yet. So, if someday you realize that your project really needs asynchronous I/O but you already have a considerable codebase on top of Flask, this tutorial is for you. The charming gevent library will enable you to keep using Flask while start benefiting from all the I/O being asynchronous. In the tutorial we will see:

  • How to monkey patch a Flask app to make it asynchronous w/o changing its code.
  • How to run the patched application using gevent.pywsgi application server.
  • How to run the patched application using Gunicorn application server.
  • How to run the patched application using uWSGI application server.
  • How to configure Nginx proxy in front of the application server.
  • [Bonus] How to use psycopg2 with psycogreen to make PostgreSQL access non-blocking.

Read more

Explaining async/await in 200 lines of code

In the previous article, we learned how to implement a simple but workable event loop. However, programs which are supposed to be run by the event loop are full of callbacks. This is the usual problem of event-loop-driven environments. When business logic becomes reasonably complicated, callbacks make program's code hardly readable and painfully maintainable. And the callback hell begins! There is plenty of ways to deal with the artificial complexity arose due to callbacks, but the most impressive one is to make the code great flat again. And by flat, I mean callback-less and synchronous-like. Usually, it's done by introducing async/await syntactic feature. But every high-level abstraction is built on top of some basic and fundamental ideas. Let's check the async/await sugar out and see what exactly happens under the hood.

Callbacks vs. async/await (code excerpt).

Read more

Explaining event loop in 100 lines of code

There is plenty of articles out there about the event loop. However, as a software engineer, I prefer to read code, not text. And there is no better way of learning a new concept than implementing it yourself. So, let's try to grasp the idea of the event loop by coding a new and shiny one.

In the article, I'll try to describe the idea of the event loop in general, not a specific implementation of the event loop in Node.js or Python, or some other language/library.

Roller coaster

Read more