These release notes cover new developer and user-facing incompatibilities, important issues, features, and major improvements.
In the Dockerfile, nodejs is upgraded to 8.17.0 and yarn 1.12.1 is installed.
The build image has been upgraded to Bionic.
The default value of the configuration hadoop.http.idle_timeout.ms (how long does Jetty disconnect an idle connection) is changed from 10000 to 60000. This property is inlined during compile time, so an application that references this property must be recompiled in order for it to take effect.
Removed findbugs from the hadoop build images and added spotbugs instead. Upgraded SpotBugs to 4.2.2 and spotbugs-maven-plugin to 4.2.0.
The default quota initialization thread count during the NameNode startup process (dfs.namenode.quota.init-threads) is increased from 4 to 12.