transport: Servers may emit extra channelz stream metrics on cancellation

[arjan-bal]

The deleteStream method can be called multiple times due to stream cancellation, timeout expiry and the handler function returning. This can result in the overcounting the number of stream failures/successes.

grpc-go/internal/transport/http2_server.go

Lines 1306 to 1323 in 5ed7cf6

	func (t *http2Server) deleteStream(s *ServerStream, eosReceived bool) {
	t.mu.Lock()
	if _, ok := t.activeStreams[s.id]; ok {
	delete(t.activeStreams, s.id)
	if len(t.activeStreams) == 0 {
	t.idle = time.Now()
	}
	}
	t.mu.Unlock()
	if channelz.IsOn() {
	if eosReceived {
	t.channelz.SocketMetrics.StreamsSucceeded.Add(1)
	} else {
	t.channelz.SocketMetrics.StreamsFailed.Add(1)
	}
	}
	}

To fix this we should only increment the metrics when the stream is found in the activeStreams map. We should also add a test to verify this behaviour.

[arjan-bal]

This issue was originally reported in #8504 (comment)