Job openapi: Failed to start thread "Unknown thread"

[Patrick Pugh]

Hello,

I'm running into memory problems with the openapi jobs. I have several openapi jobs, one for each of the different api our webapp uses. I'm using the automation framework with Docker.

Example:

Job openapi started
Job openapi added 6 URLs
Job openapi finished, time taken: 00:00:03
Job openapi started
[2118.331s][warning][os,thread] Failed to start thread "Unknown thread" - pthread_create failed (EAGAIN) for attributes: stacksize: 1024k, guardsize: 0k, detached.
[2118.332s][warning][os,thread] Failed to start the native thread for java.lang.Thread "JdkHttpClient-8468-2"
[2118.464s][warning][os,thread] Failed to start thread "Unknown thread" - pthread_create failed (EAGAIN) for attributes: stacksize: 1024k, guardsize: 0k, detached.
[2118.466s][warning][os,thread] Failed to start the native thread for java.lang.Thread "ForkJoinPool.commonPool-worker-3"
[2118.737s][warning][os,thread] Failed to start thread "Unknown thread" - pthread_create failed (EAGAIN) for attributes: stacksize: 1024k, guardsize: 0k, detached.
[2118.738s][warning][os,thread] Failed to start the native thread for java.lang.Thread "JdkHttpClient-8469-2"
[2118.739s][warning][os,thread] Failed to start thread "Unknown thread" - pthread_create failed (EAGAIN) for attributes: stacksize: 1024k, guardsize: 0k, detached.
[2118.740s][warning][os,thread] Failed to start the native thread for java.lang.Thread "ForkJoinPool.commonPool-worker-4"
[2118.740s][warning][os,thread] Failed to start thread "Unknown thread" - pthread_create failed (EAGAIN) for attributes: stacksize: 1024k, guardsize: 0k, detached.
[2118.741s][warning][os,thread] Failed to start the native thread for java.lang.Thread "JdkHttpClient-8469-3"
[2118.824s][warning][os,thread] Failed to start thread "Unknown thread" - pthread_create failed (EAGAIN) for attributes: stacksize: 1024k, guardsize: 0k, detached.
[2118.825s][warning][os,thread] Failed to start the native thread for java.lang.Thread "JdkHttpClient-8470-1"
[2118.826s][warning][os,thread] Failed to start thread "Unknown thread" - pthread_create failed (EAGAIN) for attributes: stacksize: 1024k, guardsize: 0k, detached.
[2118.827s][warning][os,thread] Failed to start the native thread for java.lang.Thread "ForkJoinPool.commonPool-worker-5"

After this, zap exits with a return code of 1.

Are there options or command line arguments that could help me resolve this issue?

Thanks!

[Simon Bennetts]

Hiya,

That doesnt look good :/

You could have a look in the zap.log which will might give more details: https://www.zaproxy.org/faq/somethings-not-working-what-should-i-do/#check-the-log-file

For details of how to access that in docker see https://www.zaproxy.org/docs/docker/diagnosing-problems/#zap-fails-for-another-reason 

But in general, ZAP will struggle if it does not have enough memory.

Can you increase the amount of memory available to ZAP?

Or can you split the current plan into multiple plans, each of which targets a different API?

Cheers,

Simon

[Patrick Pugh]

Hello, thank you for your reply.  The log ends with this:

2025-11-28 19:10:13,534 [main ] INFO  CommandLineBootstrap - ZAP 2.16.1 terminated.
2025-11-28 19:10:13,534 [main ] ERROR UncaughtExceptionLogger - Exception in thread "main"
java.lang.OutOfMemoryError: unable to create native thread: possibly out of memory or process/resource limits reached

This is running on an agent with 8g of memory.  I have successfully completed the same job in the same docker image on my development computer, which has 32g and it looks like the image used up to 15g. I think assigning more resources to the agent might be our only option then.

[Simon Bennetts]

Yes, you will either need to assign more memory or do less :)

[Patrick Pugh]

Hello,

After assigning more memory to the agent, we are now able to complete the scan, however there are still errors in the log despite the job completing successfully and generating reports normally.  Should I be worried about those?

I have tried using different values for the threadPerHost parameter, but even down to 1 I still get those errors.

Job activeScan started
Job activeScan set default strength to MEDIUM
Job activeScan set default threshold to MEDIUM
[4005.601s][warning][os,thread] Failed to start thread "Unknown thread" - pthread_create failed (EAGAIN) for attributes: stacksize: 1024k, guardsize: 0k, detached.
[4005.601s][warning][os,thread] Failed to start the native thread for java.lang.Thread "JdkHttpClient-17471-2"
[4005.603s][warning][os,thread] Failed to start thread "Unknown thread" - pthread_create failed (EAGAIN) for attributes: stacksize: 1024k, guardsize: 0k, detached.
[4005.604s][warning][os,thread] Failed to start the native thread for java.lang.Thread "ForkJoinPool.commonPool-worker-4"
[4005.605s][warning][os,thread] Failed to start thread "Unknown thread" - pthread_create failed (EAGAIN) for attributes: stacksize: 1024k, guardsize: 0k, detached.
[4005.605s][warning][os,thread] Failed to start the native thread for java.lang.Thread "JdkHttpClient-17471-3"
[4005.607s][warning][os,thread] Failed to start thread "Unknown thread" - pthread_create failed (EAGAIN) for attributes: stacksize: 1024k, guardsize: 0k, detached.
[4005.607s][warning][os,thread] Failed to start the native thread for java.lang.Thread "JdkHttpClient-17471-4"
[4005.635s][warning][os,thread] Failed to start thread "Unknown thread" - pthread_create failed (EAGAIN) for attributes: stacksize: 1024k, guardsize: 0k, detached.
[4005.635s][warning][os,thread] Failed to start the native thread for java.lang.Thread "JdkHttpClient-17472-0"
[4005.676s][warning][os,thread] Failed to start thread "Unknown thread" - pthread_create failed (EAGAIN) for attributes: stacksize: 1024k, guardsize: 0k, detached.
[4005.676s][warning][os,thread] Failed to start the native thread for java.lang.Thread "Driver Service Executor"
[4005.708s][warning][os,thread] Failed to start thread "Unknown thread" - pthread_create failed (EAGAIN) for attributes: stacksize: 1024k, guardsize: 0k, detached.
[4005.709s][warning][os,thread] Failed to start the native thread for java.lang.Thread "HttpClient-17475-SelectorManager"
[4005.723s][warning][os,thread] Failed to start thread "Unknown thread" - pthread_create failed (EAGAIN) for attributes: stacksize: 1024k, guardsize: 0k, detached.
[4005.723s][warning][os,thread] Failed to start the native thread for java.lang.Thread "HttpClient-17476-SelectorManager"
[4005.771s][warning][os,thread] Failed to start thread "Unknown thread" - pthread_create failed (EAGAIN) for attributes: stacksize: 1024k, guardsize: 0k, detached.
[4005.772s][warning][os,thread] Failed to start the native thread for java.lang.Thread "HttpClient-17478-SelectorManager"
[4005.933s][warning][os,thread] Failed to start thread "Unknown thread" - pthread_create failed (EAGAIN) for attributes: stacksize: 136k, guardsize: 0k, detached.
[4005.934s][warning][os,thread] Failed to start the native thread for java.lang.Thread "process reaper"
[4005.943s][warning][os,thread] Failed to start thread "Unknown thread" - pthread_create failed (EAGAIN) for attributes: stacksize: 1024k, guardsize: 0k, detached.

Thanks!

[Simon Bennetts]

That is not a ZAP error message.

It looks like you are running out of OS threads.

Try either increasing them or get ZAP to do less (again).

Cheers,

Simon