Why do lost targets remain visible in the Cryostat target list?

[Prasunamadasu]

I have noticed that when a target becomes unavailable or its readiness probe fails, it still appears in the Cryostat target list. Can someone explain why this happens? Is there a specific reason Cryostat maintains visibility of these lost targets, and how does this affect its ability to monitor and interact with them?

Thank you!

[andrewazores]

It isn't supposed to do that, this is a bug. Which discovery mechanism are these targets found by? I guess since you mention readiness probes, it's Kubernetes discovery?

[andrewazores]

It also just occurred to me that this readiness probe idea is very related to #717 .

[andrewazores]

^ #740

[Prasunamadasu]

Thank you for your detailed response.

• I've confirmed that the JMX port is correctly configured.
• I can access Cryostat via port forwarding and have successfully added the credentials.
• Cryostat is able to determine the JVM ID.
• When attempting to create a recording, I'm still encountering the 504 Gateway Timeout error.

Upon checking the Cryostat pod logs, I've noticed a recurring warning that seems to be related to this issue:

WARN [io.cry.tar.TargetConnectionManager] (executor-thread-118) java.lang.IllegalAccessError: class jdk.jfr.internal.SecuritySupport$$Lambda$2313/0x000000010183f840 (in module jdk.jfr) cannot access class com.singularity.ee.agent.appagent.entrypoint.bciengine.FastMethodInterceptorDelegatorBoot (in unnamed module @0x6615435c) because module jdk.jfr does not read unnamed module @0x6615435c

[andrewazores]

Interesting. I haven't seen anything like that before, but it sounds like it makes sense as the root cause for your issue. Are you doing anything in particular with JPMS or JLink in your application?

https://stackoverflow.com/questions/57457317/unnamed-modules-cannot-be-read

https://community.appdynamics.com/t5/Java-Java-Agent-Installation-JVM-and-Controller-Installation/APM-Agent-won-t-load-in-WebLogic-14-1/td-p/53583

Can you try adding --add-reads jdk.jfr=ALL-UNNAMED to your application's JVM arguments?

[andrewazores]

Somewhat similar: #682