Configure Generational ZGC in HBase

To configure Generational ZGC in HBase on Amazon EMR, you need to ensure that both JAVA_HOME and the appropriate garbage collection options are properly set.

For Generational ZGC, which was introduced in JDK 21, you must explicitly set the JAVA_HOME environment variable. This is a requirement specifically for using the generational mode of ZGC. If you're using non-generational mode of ZGC (without the -XX:+ZGenerational flag), setting JAVA_HOME isn't necessary. However, be aware that in JDK 24, the non-generational mode of ZGC has been removed.

To modify these settings, you should use EMR's configuration classifications. For HBase environment variables, you'll need to use the "hbase-env" classification. You can set these configurations when creating your EMR cluster.

Here's how you can configure it:

1. Use the "hbase-env" classification to modify HBase's environment variables
2. Within this classification, use the "export" sub-classification to set your environment variables
3. Set both JAVA_HOME and HBASE_REGIONSERVER_GC_OPTS appropriately

For example, you can set the garbage collection options for RegionServers using HBASE_REGIONSERVER_OPTS or HBASE_REGIONSERVER_GC_OPTS.

If you're still experiencing issues where your configurations aren't being applied, verify that you're using the correct configuration classification structure and that your cluster has the appropriate permissions to modify these files.
Sources
Configure HBase - Amazon EMR
AWS Open Data Analytics
Amazon EMR release 5.5.2 - Amazon EMR