Scalability issues related to socket.io

Question

On the socket.io homepage, it says nothing about scalability issues. Does anyone know how many simultaneous connections it can handle at the same time? I want to deploy socket.io in my project for large-scale comet processing. For example, it states that nodejs can easily handle up to 100K concurrent connections. Will socket.io be able to handle as many requests as it does at a time?

Answer 1

There are many variables that affect performance and define restrictions on socket.io.

Perhaps the most important thing is your hardware, especially RAM. There is also a difference between regular concurrency and message processing. Message processing seems to consume more processor than just concurrency.

I would recommend this article written by Mikito Takada. Excerpt from it:

Node (0.4.12) using tcp ~ 8000 compounds on one core

socket.io 0.6.17 using web interfaces ~ 2300 connections on one core

socket.io 0.7.11 using web interfaces ~ 1800 connections on one core

socket.io 0.8.6 using web interfaces ~ 1900 connections on one core

So, to answer your question, I would say that you cannot expect socket.io to handle the same level of concurrency as that node.js can give the same setup.

For more information on socket.io performance, read this from Drew Harry.