BewareMyPower commented on issue #116:
URL:
https://github.com/apache/pulsar-client-python/issues/116#issuecomment-1537049348
From the threads info, the root cause is still related to the
`NegativeAcksTracker`. Here are the simplified threads info:
```
Thread 2 stuck at:
acquiring lock in NegativeAcksTracker::add
Thread 14 stuck at:
acquiring GIL in LoggerWrapper::log
ConsumerImpl::redeliverMessages
NegativeAcksTracker::handleTimer
----
Thread 6 stuck at:
acquiring GIL in LoggerWrapper::log
ClientConnection::handleIncomingCommand
Thread 8 stuck at:
acquiring GIL in LoggerWrapper::log
ClientConnection::getConnectionAsync
PartitionedConsumerImpl::getPartitionMetadata
Thread 15 stuck at:
acquiring GIL in LoggerWrapper::LoggerWrapper
ConsumerStatsImpl::flushAndReset
Thread 13 stuck at
acquiring GIL in LoggerWrapper::log
ClientConnection::handleIncomingCommand
```
Nearly all threads except thread 2 are stuck at acquiring GIL in
`LoggerWrapper`'s methods. It means the GIL was hold by another thread, which
is likely thread 2 because it calls `negative_acknowledge`. However, thread 2
is also stuck because the lock in `NegativeAcksTracker` is hold by thread 14.
In conclusion:
- Thread 2 holds the GIL, then tries to acquire `NegativeAcksTracker#mutex_`
- Thread 14 holds the `NegativeAcksTracker#mutex_`, then tries to acquire
the GIL
Since the GIL won't be released, all threads that try to acquire the GIL
will be stuck. It will block nearly all threads when the Python logger is
customized because all methods of `LoggerWrapper` requires the GIL.
I'm going to check the code in further progress and see how could we fix
this deadlock.
(BTW, this threads info is strange that I see `CaptivePythonObjectMixin` in
it. But this class was first introduced in 3.0.0)
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