[Bug] Zookeeper OutOfMemoryError After Upgrading to Pulsar 3.3.0 with Zookeeper 3.9.2

[jamesvsshark]

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• I searched in the issues and found nothing similar.

Read release policy

• I understand that unsupported versions don't get bug fixes. I will attempt to reproduce the issue on a supported version of Pulsar client and Pulsar broker.

Version

Pulsar version: 3.3.0
Zookeeper version: 3.9.2
Kubernetes environment: Helm chart deployment
Zookeeper resource configuration:
Request/limit: 6GB memory, 2 CPU
Heap settings: -Xms5632m -Xmx5632m
GC settings:

-XX:+UseG1GC
-XX:MaxGCPauseMillis=10
-XX:+ParallelRefProcEnabled
-XX:+UnlockExperimentalVMOptions
-XX:+DoEscapeAnalysis
-XX:+DisableExplicitGC
-XX:+ExitOnOutOfMemoryError
-XX:+PerfDisableSharedMem

Minimal reproduce step

1. Upgrade Pulsar to version 3.3.0 and Zookeeper to 3.9.2.
2. Deploy the Zookeeper quorum using default GC and memory settings from the Helm chart.
3. Observe memory consumption and monitor for crashes after a few days of running.

What did you expect to see?

Zookeeper should run without constantly increasing memory usage or exhausting resources.

What did you see instead?

Error observed:

java.lang.OutOfMemoryError: unable to create a native thread: possibly out of memory or process/resource limits reached.

Anything else?

Additional Context:

After downgrading Zookeeper to version 3.2.2, the OOM issue stopped, and no pod restarts occurred.
Autorecovery pods running 3.3.0 are also encountering Java heap memory issues.
Reviewing the Pulsar 3.3.0 release notes and PIP-324 (#22054), I suspect changes to the Alpine base image could be affecting thread creation and memory management.

Possible Solution:

It may be necessary to modify the Dockerfile to increase the stack size by setting the PTHREAD_STACK_MIN environment variable:

ENV PTHREAD_STACK_MIN 2097152

Are you willing to submit a PR?

• I'm willing to submit a PR!

[lhotari]

@jamesvsshark do you have a chance to test with 3.3.2 version of Pulsar to see if this reproduces?

[lhotari]

Deploy the Zookeeper quorum using default GC and memory settings from the Helm chart.

@jamesvsshark Is this a Helm chart issue instead? The support for 3.3.x requires the release that is pending. https://lists.apache.org/thread/p2fzmj31r5or65hr0yy4qgkfvnqlwzwk . Can you reproduce with that Helm chart?
The defaults in the Helm chart aren't great. Contributions are welcome to improve this.

[jamesvsshark]

@jamesvsshark do you have a chance to test with 3.3.2 version of Pulsar to see if this reproduces?

Yes, I can do this. I will test and report back asap.