在Go中使用活动的WebSocket连接正常重启服务器

Question

I had a look at this library from Facebook:

https://github.com/facebookgo/grace

And some others like this one:

https://github.com/fvbock/endless

That let's me do graceful restarts of Go servers so that I have zero downtime and so that I can finish up the ongoing requests preventing data to be corrupted and so on.

But I am wondering how this would work if I had active WebSocket connections while doing this? Would the old server never stop running since there are active WebSocket connections? I don't care too much about the WebSocket connections I only care about the normal requests being served before shutting down the old server and firing up the new updated compiled file that will serve the new logic.

How will this behave with WebSockets?

Answer 1

Write the application to handle reconnects. Server restarts are just one reason that a connection might be dropped.

To restart a server with websockets (or any type of long-lived connection), start the new server, stop listening for connections on the old server and drain the connections on the old server by closing the connections. If the application is written to handle reconnects, then the server restart should not be visible to the user.

It's helpful to drain the connections instead of closing them all in one fell swoop. This avoids a denial of service attack by your own clients as they reconnect, authenticate, query database for message backlogs, etc. etc.