These release notes cover new developer and user-facing incompatibilities, important issues, features, and major improvements.
FsShell mkdir now accepts a -p flag. Like unix, mkdir -p will not fail if the directory already exists. Unlike unix, intermediate directories are always created, regardless of the flag, to avoid incompatibilities.
DistCp v1 currently copies files to a temporary location and then renames that to the specified destination. This can cause performance issues on file systems such as S3. A -skiptmp flag is added to bypass this step and copy directly to the destination.
Has dependency on MAPREDUCE-1285/MAPREDUCE-5698
WARNING: No release note provided for this incompatible change.
Allow logging level of map/reduce tasks to be configurable. Configuration changes: add mapred.map.child.log.level add mapred.reduce.child.log.level
Allow ReduceTask loading a third party plugin for shuffle (and merge) instead of the default shuffle.