arun-gupta
commented
6 years ago @PaulSandoz FYI, could not find Mikael's github handle.
Open jetztgradnet opened 6 years ago
arun-gupta
commented
6 years ago @PaulSandoz FYI, could not find Mikael's github handle.
sgandon
commented
6 years ago I suppose this is the link https://github.com/fabric8io-images/java/blob/84dddb5c8a72650e12c02d2056b86146edddac66/images/centos/openjdk8/jdk/container-limits But it has been replaced with a single run-java.sh script https://github.com/fabric8io-images/java/blob/7f696790875d1ff005bf98d05dae33d879d844e5/images/centos/openjdk8/jdk/run-java.sh#L162
pgordon9
commented
5 years ago Would love to see points on how to estimate how much off-heap memory is typically needed.
Which lab is it that you're having issues with? Lab: Docker for Java Developers
Description
When deploying Java applications in production one usually specifies the amount of memory available to the JVM (-Xmx) and other assorted configuration settings. Unfortunately, this is (usually) static configuration and therefore fixed in the container image. When specifying memory constraints (using cgroups) this is unfortunately not picked up by the JVM automatically, so there should be a section on memory management for dockerized Java apps.
Java9 and Java8 > u131 provide limited support for this, see https://bugs.openjdk.java.net/browse/JDK-8170888 for details.
For older Java releases there is a good script from @fabric8io-images: https://github.com/fabric8io-images/java/blob/master/images/centos/openjdk8/jdk/container-limits
Also, it is not easy to calculate the amount of JVM heap and the resulting cgroup limits, as the JVM also needs memory for other things, e.g. metaspace, JIT, ...
A few words on the whole topic of JVM memory management for containers would be a very good addition. Articles like https://developers.redhat.com/blog/2017/03/14/java-inside-docker/ provide a good starting point.