UBA caspida-realtimeruleexec Service Crash with OutOfMemoryError on 7-node Deployment

[aldo]

Hi Splunk Community,

I'm currently running a 7-node UBA deployment and encountering persistent errors with the `caspida-realtimeruleexec` service.

The service fails to respond in the UBA Health Monitor UI, and upon checking the logs at:

/var/vcap/sys/log/caspida/ruleengine/realtimeruleexecutor.log :


I see the following error:

java.lang.OutOfMemoryError: Java heap space

When inspecting the JVM options in the `/opt/caspida/bin/CaspidaCommonEnv.sh` file, I found that the heap size was set as:
-Xmx4M

This seems too low for a rule executor component. My node has around 64 GB of RAM and ~34 GB free memory available (`free -m` confirms this). I am planning to increase the heap size to `-Xmx8192m`.

### My Questions:

1. Is this the correct cause of the crash?
2. Is it safe and recommended to increase the heap size to 8 GB or more for `caspida-realtimeruleexec` in a 7-node cluster?
3. Are there any best practices or official docs on tuning JVM heap for this component?
4. Should I also consider increasing other services' heap sizes?

Thanks in advance for your help!

[livehybrid]

Hi @aldo 

This is a slightly tricky one because the documentation is so light on the subject! However my take on this is that, yes, you should be okay to increase the heap size across the deployment for this service *however* what we dont know is how the other services will behave once this service is back up and running. e.g. just because there is 30gb RAM available now, when everything starts working properly and other services start working together the RAM Usage could increase (if that makes sense).

I'd be tempted to increase is gradually until you see the issue resolve and then closely monitor the usage moving forwards. I dont know if you've seen https://help.splunk.com/en/security-offerings/splunk-user-behavior-analytics/administer/5.4.1/monito... but there is some good info here on monitoring your UBA deployment so that might help once things have stabilised.

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