Note on thread safety when using SockJSConnection.send()

[ssche]

The examples are misleading in the sense that they are directly using SockJSConnection.send() method which adds messages into Tornado's IOStream send buffer (_write_buffer). If this happens on a separate thread, messages sent to the web socket can get corrupted, especially under heavy load (this method isn't thread-safe).

To avoid this, the messages should be handled by Tornado's ioloop (by adding a callback, etc). An example for the thread-safe implementation is how sockjs-tornado emits heartbeats.

A note in the documentation or a modified example would be nice as it could help people (like me) to save a lot of time.

[mrjoes]

sockjs-tornado is single-threaded and assumes that everything is happening in a single thread. If you plan to use threads, then you will have to handle synchronization as well.

As far as I know, Tornado does not use threads on its own, but I was not following latest developments.

[ssche]

I know now ;-). Just a gentle note somewhere in the docs would be great (or perhaps there's already one that I didn't find).

[mrjoes]

Good idea, I will add a word about it. In general, none of the Tornado libraries are thread safe and there was nice blog post why and how to work around it (by calling add_callback on the ioloop instance). But I can't find the link right now.

[ssche]

Thanks. That link would also be great in the docs. I started using Tornado because of sockjs and your library (which is great, btw) and learnt about the tread safety the hard way...