wolfstudy opened a new issue #687:
URL: https://github.com/apache/pulsar-client-go/issues/687
Currently, when sending and consuming messages, we use eventsCh to receive
command requests for message sending and receiving:
```
func (p *partitionProducer) runEventsLoop() {
for {
select {
case i := <-p.eventsChan:
switch v := i.(type) {
case *sendRequest:
p.internalSend(v)
case *flushRequest:
p.internalFlush(v)
case *closeProducer:
p.internalClose(v)
return
}
case <-p.connectClosedCh:
p.reconnectToBroker()
case <-p.batchFlushTicker.C:
if p.batchBuilder.IsMultiBatches() {
p.internalFlushCurrentBatches()
} else {
p.internalFlushCurrentBatch()
}
}
}
}
```
This looks OK under normal circumstances, but in extreme cases they may
affect each other. For example, for send command, we have a parameter of
maxPendingMessages locally, which is used as the size of the eventsCh
cache(default: 1000):
```
eventsChan: make(chan interface{}, maxPendingMessages),
```
Assuming that the local maxPendingMessages reaches the default threshold at
this time, then the channel will enter a blocking state (in fact, this is
completely possible), at this time related flush or close requests will also be
blocked by this eventsCh, because they use the same channel(`eventsCh`).
Once runEventsLoop is blocked, it will cause the following series of
problems:
1. send message TimoutError
2. the `receiveCommand()` stuck and the gorutine is `gopark`
[pprof.gateway.goroutine.008.pb.gz](https://github.com/apache/pulsar-client-go/files/7767543/pprof.gateway.goroutine.008.pb.gz)
In this case, when we try to `bin/pulsar-admin topics unload` this topic, it
doesn't work, because in fact it is the block inside the Go SDK that caused the
**sending timeout**. At this point, assuming that the Go SDK is restarted, this
service can be restored immediately.
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