Should sending GOAWAY also block SUBSCRIBE, etc.?

[martinduke]

Sec 7.3 (GOAWAY) says:

Upon receiving a GOAWAY, an endpoint SHOULD NOT initiate new requests to the peer including SUBSCRIBE, FETCH, ANNOUNCE and SUBSCRIBE_ANNOUNCE.

Would the same be true after sending GOAWAY?

[ianswett]

I think that would be fine in every case I can think of.

[afrind]

If #905 is merged, we can add the last processed request ID to the GOAWAY message, and have implementations discard requests with higher IDs.

If we add PUBLISH, we might need to allow more than one GOAWAY, similar to HTTP. If PUBLISH can also send data before PUBLISH_OK, then the publisher might discard that data immediately, only to later receive a GOAWAY indicating the receiver also discarded it.

[afrind]

I wonder if our failover logic and multi-publisher rules effectively require this though. eg:

C1 -> R:  PUBLISH_NAMESPACE (foo)
R -> C1: GOAWAY

C1 starts connecting to a new relay

C2 -> R: SUBSCRIBE foo/bar

Doesn't R have to send SUBSCRIBE foo/bar to C1?

Eventually, C1 gets a new connection to R', then sends

C1 -> R: PUBLISH_NAMESPACE_DONE

I'm inclined to say nothing. The sender of the GOAWAY can continue to send requests until the peer sends GOAWAY, or closes.

[ianswett]

In Toronto:

Allowing new requests after sending a GOAWAY seems unwise, so the group felt it was a SHOULD NOT on the sender of the GOAWAY as well as the receiver.

Related issue: Now that we have Request ID, should that be placed into the GOAWAY?

[ianswett]

As a follow-up, both of the editors lean towards the idea that the GOAWAY only tells the receiver of the GOAWAY to stop initiating requests, not the sender, though admittedly one would typically expect to receive a GOAWAY in response soon after sending one.

[afrind]

I'm concerned that we have multi-publisher language that says we MUST send a SUBSCRIBE as long as the Publisher is connected and has advertised the namespace. Having language that says you also SHOULD NOT do that if you have sent a GOAWAY seems like conflicting advice that could result in worse behavior for a subscriber.