All posts in Erlang

A journey to Syn v2, a better Erlang & Elixir Process Registry and Group manager

For those who don’t know it, Syn (short for synonym) is a global Process Registry and Process Group manager for Erlang and Elixir that I’ve written a few years back. It has been around for some time now, and it has served me well on many occasions. Through the years, I’ve built up a series of considerations and ideas for improvement, and now the time has come to put all of these back into Syn.

Syn v2 has been rewritten from the grounds up, and I’d like to share the reasoning and the architectural choices behind this work. Since Syn is written in Erlang, the few portions of the code here below will show Erlang syntax. Don’t let that discourage you if you are an Elixir developer though, as the same principles apply.

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An evaluation of Erlang global process registries: meet Syn

Due to my personal interests and history, I often find myself building applications in field of the Internet Of Things. Most of the times I end up using Erlang: it is based on the Actor’s Model and is an ideological (and practical) perfect match to manage IoT interactions.

I recently built an application where devices can connect to, and interact with each other. Every device is identified via a unique ID (its serial number) and based on this ID the devices can send and receive messages. Nothing new here: it’s a standard messaging platform, which supports a custom protocol.

Due to the large amount of devices that I needed to support, this application runs on a cluster of Erlang nodes. Once a device connects to one of those nodes, the related TCP socket events are handled by a process running on that node. To send a message to a specific device, you send a message to the process that handles the devices’s TCP socket.

While building this application, I was early in the process faced with a very common problem: I needed a global process registry that would allow me to globally register a process based on its serial number, so that messages can be sent from anywhere in the cluster. This registry would need to have the following main characteristics:

  • Distributed.
  • Fast write speeds (>10,000 / sec).
  • Handle naming conflict resolution.
  • Allow for adding/removal of nodes.

Therefore I started to search for possible solutions (which included posting to the Erlang Questions mailing list), and these came out as my options:

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A comparison between Misultin, Mochiweb, Cowboy, NodeJS and Tornadoweb

As some of you already know, I’m the author of Misultin, an Erlang HTTP lightweight server library. I’m interested in HTTP servers, I spend quite some time trying them out and am always interested in comparing them from different perspectives.

Today I wanted to try the same benchmark against various HTTP server libraries:

I’ve chosen these libraries because they are the ones which currently interest me the most. Misultin, obviously since I wrote it; Mochiweb, since it’s a very solid library widely used in production (afaik it has been used or is still used to empower the Facebook Chat, amongst other things); Cowboy, a newly born lib whose programmer is very active in the Erlang community; NodeJS, since bringing javascript to the backend has opened up a new whole world of possibilities (code reusable in frontend, ease of access to various programmers,…); and finally, Tornadoweb, since Python still remains one of my favourites languages out there, and Tornadoweb has been excelling in loads of benchmarks and in production, empowering FriendFeed.

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Misultin: erlang and websockets

Inspired by Joe Armstrong’s post, I’ve recently added websocket support to misultin v0.4, my Erlang library for building fast lightweight HTTP servers.

Basically, websockets allow a two-way asynchronous communication between browser and servers, filling the gap that some technologies such as ajax and comet have tried to fulfill in these recent years. If you want to try this out yourself, you will first need to grab a browser which implements websockets, such as Google Chrome.

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Misultin library

Today I’ve released Misultin (pronounced mee-sul-teen), an Erlang library for building fast lightweight HTTP servers. The first benchmarks are quite satisfying, even though there still is work to do.

Here is the simple code for Misultin’s Hello World.

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Boost message passing between Erlang nodes

Message passing between Erlang nodes is considerably slower than within the same node. This is normal, and is due to the fact that messages sent between nodes are actually copied from the area of the sender to that of the receiver, then sent over from one node to the other via TCP/IP.

I was getting interested when a server could achieve amazing performance over a single node, performance which got much lower once the server got distributed over two Erlang nodes. I therefore tried a small benchmark test to somehow measure the difference in message passing speed within/across Erlang nodes.

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