Memory Limit

Java Heap Memory Limit in Docker

Java Heap Memory Limit in Docker

Note: This is the issue with JDK 8 for 1.6.x and 1.5.x releases. If you are using JDK11 with the 2.0.x release, you don’t need to worry about it.

The issue is that if the Xmx option is not defined explicitly, then JVM uses 1/4th of all memory available for the host OS due to a default internal garbage collection (GC) ergonomic algorithm. This can lead to killing the Java process by the kernel if JVM memory usage grows over the cgroups limit defined for a Docker container.

To solve this problem, one improvement was recently implemented in OpenJDK 9 and backported to OpenJDK 8 in version 8u131.

https://github.com/docker-library/openjdk/pull/71 https://bugs.openjdk.java.net/browse/JDK-8175898 https://bugs.openjdk.java.net/browse/JDK-8170888 https://blog.csanchez.org/2017/05/31/running-a-jvm-in-a-container-without-getting-killed/

The command line to set it up is:

java -XX:+UnlockExperimentalVMOptions -XX:+UseCGroupMemoryLimitForHeap -XX:MaxRAMFraction=1 -XshowSettings:vm -version

As we are using a later version of Java 8 on both Alpine and Redhat containers, we are going to update the light-codegen to add these options in the Java command line. Once this is done, we can control the container memory limitation with the Kubernetes deployment configuration file.