[Bug] Memory leak in Pulsar Proxy with TopicName

[frankjkelly]

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• I searched in the issues and found nothing similar.

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• 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.

User environment

Broker Version: 3.3.2
Broker Operating System: Linux platform-pulsar-broker-0 5.10.237-230.949.amzn2.x86_64 #1 SMP Thu Jun 5 23:30:10 UTC 2025 x86_64 Linux
Java Version: openjdk version "21.0.4" 2024-07-16 LTS
OpenJDK Runtime Environment Corretto-21.0.4.7.1 (build 21.0.4+7-LTS)
OpenJDK 64-Bit Server VM Corretto-21.0.4.7.1 (build 21.0.4+7-LTS, mixed mode)

Issue Description

Starting in Pulsar 3.3.2 (after upgrading from Pulsar 2.11.3) we noticed an increase in proxy heap memory usage that eventually leads to Proxy getting OOMKilled

I analyzed a recent case with Eclipse MAT

In communication with @lhotari he said

That definitely seems to be a memory leak in the Proxy. Well it's a memory leak in a form of a cache that will never expire.
It looks like this leak was introduced by https://github.com/apache/pulsar/pull/23052, added in Pulsar 3.0.6 / 3.3.1
One possible workaround would be to pass JVM option -XX:+UseStringDeduplication so that duplicate java.lang.String instances referred by the cache would be de-duplicated. That doesn't fix the issue, but would reduce the amount of heap memory spent by duplicate domain, tenant and namespace String instances in memory.
The TopicName cache memory issue should be addressed by using a soft reference cache and by deduplicating the parsed parts which are commonly shared across multiple instances(domain, tenant, namespace). A long time ago when I was in the Gradle build tool team, I solved a similar problem using Guava's Interner class, ( https://github.com/gradle/gradle/blob/master/platforms/core-runtime/base-services/src/main/java/org/gradle/api/internal/cache/StringInterner.java  in Gradle).

Error messages

Reproducing the issue

In our use case we create a lot of topics which probably leads to this issue.

Additional information

No response

Are you willing to submit a PR?

• I'm willing to submit a PR!