Add an option to periodicaly ping idle websockets to keep proxies happy

[asvetlov]

See tornadoweb/tornado#1640 for explanation

[fafhrd91]

can we use keep-alive timers for that?

[asvetlov]

So you mean utilizing SO_KEEPALIVE from low-level server.py code?
It's only hop-to-hop setting, proxies don't cope with it.

[fafhrd91]

I thought we have timer for keep alive, but it just ceil on time. Ok, np

[rutsky]

What is intended interface and behavior?

Currently WebSocketResponse has only autoping=True parameter which tells to auto-send PONG replies for each received PING message.

Behavior that can implemented for this feature:

1. WebSocketResponse sends PING messages every ping_interval seconds,
2. if no PONG messages are received for pong_timeout seconds, WebSocketResponse closes connection.

Should received from client data reset pong_timeout?

What if client doesn't implement PONG sending? His connection will be closed according to described above behavior (which is OK if this behavior is not enabled by default).

Do we need separate option for current autoping=True behavior, or we can put both behaviors under same option?

[asvetlov]

Let me re-read RFC prior to keeping conversation

[fafhrd91]

added heartbeat option to client and server web sockets

[lock]

This thread has been automatically locked since there has not been
any recent activity after it was closed. Please open a new issue for
related bugs.

If you feel like there's important points made in this discussion,
please include those exceprts into that new issue.