22.03.2018

Java 10 released: java with some enhancements for running inside docker

After the release of Java 9 in october 2017 with its new features
Oracle released Java 10:
 A short summary of the new feature can be found
at https://blogs.oracle.com/java-platform-group/introducing-java-se-10
or you can take a look a the release notes:
http://www.oracle.com/technetwork/java/javase/10-relnote-issues-4108729.html#NewFeature

My favourites are:
  • JEP 307 Parallel Full GC for G1  Improves G1 worst-case latencies by making the full GC parallel. The G1 garbage collector is designed to avoid full collections, but when the concurrent collections can't reclaim memory fast enough a fall back full GC will occur. The old implementation of the full GC for G1 used a single threaded mark-sweep-compact algorithm. With JEP 307 the full GC has been parallelized and now use the same amount of parallel worker threads as the young and mixed collections.
and the docker enhancements:
  • JDK-8146115 Improve docker container detection and resource configuration usage
The JVM has been modified to be aware that it is running in a Docker container and will extract container specific configuration information instead of querying the operating system. The information being extracted is the number of CPUs and total memory that have been allocated to the container. The total number of CPUs available to the Java process is calculated from any specified cpu sets, cpu shares or cpu quotas. This support is only available on Linux-based platforms. This new support is enabled by default and can be disabled in the command line with the JVM option:
-XX:-UseContainerSupport
In addition, this change adds a JVM option that provides the ability to specify the number of CPUs that the JVM will use:
-XX:ActiveProcessorCount=count
This count overrides any other automatic CPU detection logic in the JVM.
  • JDK-8186248 Allow more flexibility in selecting Heap % of available RAM
Three new JVM options have been added to allow Docker container users to gain more fine grained control over the amount of system memory that will be used for the Java Heap:
-XX:InitialRAMPercentage
-XX:MaxRAMPercentage
-XX:MinRAMPercentage
These options replace the deprecated Fraction forms (-XX:InitialRAMFraction, -XX:MaxRAMFraction, and -XX:MinRAMFraction).
  • JDK-8179498 attach in Linux should be relative to /proc/pid/root and namespace aware
This bug fix corrects the attach mechanism when trying to attach from a host process to a Java process that is running in a Docker container.
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