Cassandra on Azul Platform Prime

When using Azul Platform Prime for Cassandra you don't need to spend time in tuning the JVM Garbage Collection parameters. 

Here a quick overview for switching from other JREs/JDKs to Azul Zing on a Cassandra node:

First, after stopping the Cassandra service on the node, install Azul Zing (rpm/deb package zing-jdk1.8.0). Then change the JAVA_HOME setting for Cassandra in its configuration file to the newly installed location:

 JAVA_HOME=/opt/zing/zing-jdk8

That's all. You don't need to change any other JVM parameter in the cassandra-env.sh configuration. Azul Zing is ignoring non-Azul -XX parameters which you might have added before to tune other GC implementations.

After restarting the Cassandra node you can check with the following command if the switch to Azul Zing was successful and the java command used is actually the correct one and not a different JVM. The Azul Zing java process returns "Zing 64-Bit" as version information:

jcmd JAVAPID VM.version

With JAVAPID the process ID of the java command as listed by just running "jcmd" without parameters.

For production systems, the following change is recommended in addition:

• Disable the Cassandra GCInspector log messages as it might report long running GC phases which are of no concern when using Azul Zing as those logged times are phases of the GC which are run in parallel to the application and don't pause the application when using Azul Zing. The log messages written to the Cassandra system.log are of the following pattern:
  INFO  [Service Thread] DATE  GCInspector.java:284 - GPGC New GC in 300ms. GenPauseless
  To disable them, add the following line to cassandra_install_location/conf/logback.xml:

  <logger name="org.apache.cassandra.service.GCInspector" level="ERROR"/>

Most Cassandra installations require Java 8 and won't run on newer Java 11. Only since Cassandra 4.0.2, Java 11 is supported, and for DSE since 6.8.22 only for certain workloads:

https://cassandra.apache.org/doc/stable/cassandra/getting_started/java11.html
https://github.com/datastax/release-notes/blob/master/DSE_6.8_Release_Notes.md

If you have further questions about Azul Zing configuration, please ask Azul Support.