[Bug] Skywalking-java-agent SWDescriptionStrategy causes memory leaks

[hyhyf]

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• I had searched in the issues and found no similar issues.

Apache SkyWalking Component

Java Agent (apache/skywalking-java)

What happened

I used the nashorn script engine for stress testing in my project. After running continuously for 2 hours, SWTypeDescriptionWrapper occupied more than 90% of the memory, and the old GC was frequently.

What you expected to happen

When dynamic class creation methods are used, they are put into the type cache. If this operation is repeated indefinitely, it will form a large collection that cannot be garbage collected, thereby consuming memory resources.

How to reproduce

Jdk: 1.8
Java agent: 9.2.0
Excute scripts using nashorn script engine

Anything else

No response

Are you willing to submit a pull request to fix on your own?

• Yes I am willing to submit a pull request on my own!

Code of Conduct

• I agree to follow this project's Code of Conduct

[wu-sheng]

We don't support unlimited dynamic classes. I think this is the current case. And I don't see any reason to do this in product env.

[hyhyf]

We don't support unlimited dynamic classes. I think this is the current case. And I don't see any reason to do this in product env.

This is a business interface we use in the production env to help execute scripts and analyze results. With a high volume of requests, an unexpected incident occurred just two days after the agent was upgraded.

[hyhyf]

The cache is necessary to speed up the analysis process and booting, also to better support for retransfer.

Yes, I understand, but is it possible to provide some mechanism to prevent such accidents, such as discarding expired cache after exceeding size limits? If a microservice has the capability to dynamically create classes, even with reasonable use, the type cache may eventually occupy more than 50% of the memory over time, which seems unreasonable.

[wu-sheng]

I don't think so. Because this would cause expected changes to the codes and execution processes.
Such as half of plugin interceptors are instrumented due of this mechanism, then still memory leak happens.

[hyhyf]

You're right, but I think someone will face the same problem as me in the future.

[wu-sheng]

Yes, maybe, but there is no proper solution for that.