Just over two weeks ago, Heroku announced (the long-awaited) experimental support for WebSockets. Just like you would expect from Heroku, getting set up is painless and there's good documentation and good sample code to help you.
I was curious to see what kind of performance one could expect, so I did a quick performance test to find out. (I used Heavy Artillery to generate the load)
For comparison, an entry-level box from Digital Ocean (512MB RAM, Ubuntu 13.10) can handle 350+ new connections/sec, and seems to max out at around 7,200 open connections.
Here is the code for the server:
As you can see, it does nothing apart from accepting connections.
The client sessions were very simple: connect and do nothing until disconnected by the server.
Draw your own conclusions whether the numbers above are good or not.
I ran 7 tests in total.
The first one created 1000 connections/second for 30 seconds - that obviously didn't go well. The other 5 were me doing a binary search to find the number of connections/second one could make without seeing H11 errors pop up. I got bored between 160 (okay) and 175 (H11's start popping up).
I will be updating this post with more numbers as I run more benchmarks. Scaling WebSocket-based apps is a subject dear to my heart.