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I am trying to set up socketio on multiple nodes for load balancing between them. I came up with something like this in socketio docs: Using multiple nodes.

It does the work perfectly for event passing through redis between multiple nodes, but the question is, for example, I have this scenario:

I have Server A and Server B up and running with a load balancer (nginx)

Client A is connected to Server A.

Client B is connected to Server B.

Is there any way to make sure if Server A gets down (node gets disconnected, or shuts down for any reason) all the clients connected to Server A should be redirected to Server B automatically as a fallback? Does socketio support it? what manual configuration I have to do to make sure this happens?

I am using Express with nginx.

Hassan Mehdi
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If one of your socket.io servers goes offline while in use, its clients should (eventually) get disconnect messages. You should organize your code so your disconnect event handler can establish a new connection via your load-balancer.

I wrote "eventually." It's possible a few seconds will pass between server crash and client event delivery. You may want to set up some sort of keepalive scheme where your client sends a 'ping' event once in a while, and expects a prompt 'pong' response from your server. Then, if a ping is not answered in the allotted time, your client can reconnect, just as if it got a disconnect event.

If you have a mobile client, you'll want to test all this by starting a session on wifi, then moving the device out of wifi range so it switches to wireless.

O. Jones
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