Use container memory limits to manage memory in reference environments

Right now, backend modules launched as containers by Okapi have no memory limits imposed by default. In addition, for Java-based modules, in a container, the JVM by default sees all system memory as available to it, regardless of any container memory limit.

We are currently managing this by setting an environment variable JAVA_OPTIONS=-Xmx256m (or whatever is required according to the developer) for all Java-based modules. This solution works OK, but it requires that the DevOps team configure each module individually, and the memory requirements of the module are not documented except in the deployment variables file in folio-ansible.

A better solution might be:

• Update the launch descriptors in each module's module descriptor template to set the HostConfig/Memory key in dockerArgs to the appropriate default as determined by the module development team. This will limit each container's memory usage. It could still be overridden in a deployment descriptor

• Update the base Java image for FOLIO Docker containers to use the -XX:+UnlockExperimentalVMOptions -XX:+UseCGroupMemoryLimitForHeap switches as part of the Java command line to allow the JVM to see the container memory limit