These release notes cover new developer and user-facing incompatibilities, important issues, features, and major improvements.
Fix couple of JavaDoc warnings.
Revert tmp files handling on DataNodes back to 0.17. sync() introduced in 0.18 has less gaurantees.
A long (unexpected) delay at datanodes could make subsequent block reports from many datanode at the same time.
Improve how RPC server reads and writes large buffers. Avoids soft-leak of direct buffers and excess copies in NIO layer.
WARNING: No release note provided for this incompatible change.
fix memory leak of user/group information in fuse-dfs
This patch HADOOP-4620.patch (1) solves the hanging problem on map side with empty input and nonempty output — this map task generates output properly to intermediate files similar to other map tasks. (2) solves the problem of hanging reducer with empty input to reduce task and nonempty output — this reduce task doesn’t generate output if input to reduce task is empty.
TestDistributedUpgrade used succeed for wrong reasons.
Included librecordio in release for use by xerces-c (ant -Dlibrecordio=true -Dxercescroot=<path to the xerces-c root>)
Added a new conf property dfs.namenode.decommission.nodes.per.interval so that NameNode checks decommission status of x nodes for every y seconds, where x is the value of dfs.namenode.decommission.nodes.per.interval and y is the value of dfs.namenode.decommission.interval.