Apache Hadoop 3.0.4 Release Notes

These release notes cover new developer and user-facing incompatibilities, important issues, features, and major improvements.

Updated checkstyle to 8.8 and updated maven-checkstyle-plugin to 3.0.0.

WASB: Fix Spark process hang at shutdown due to use of non-daemon threads by updating Azure Storage Java SDK to 7.0

Mover could have fail after 20+ minutes if a block move was enqueued for this long, between two DataNodes due to an internal constant that was introduced for Balancer, but affected Mover as well. The internal constant can be configured with the dfs.balancer.max-iteration-time parameter after the patch, and affects only the Balancer. Default is 20 minutes.

Restore the KMS accept queue size to 500 in Hadoop 3.x, making it the same as in Hadoop 2.x.