How to control heap memory of the jenkins-k8s-operator charm

The jenkins-k8s-operator charm uses Juju constraints to limit the amount of memory a charm can use. To deploy the charm with constraints, use the --constraints "<key>=<value>" option when running juju deploy:

juju deploy jenkins-k8s --channel=latest/edge --constraints "mem=2048M"

To change this value after deployment, use the set-constraints command.

juju set-constraints jenkins-k8s "mem=4096M"

Other types of constraints (like cores, disk, etc.) can also be applied. Note that this value affects the shared maximum memory between the charm container and jenkins container.

Considerations when applying memory constraints

Constraints set this way directly influence the amount of heap memory available to the JVM, with a ratio JVM heap / Container Memory limit of 0.5. For example, a jenkins-k8s-operator charm deployed with --constraints "mem=1024M" would set a maximum heap memory size of 512Mb. Too little heap memory can result in the controller getting restarted due to Out-of-memory (OOM) error. Make sure to adapt the memory constraints based on your workload.