HDFS-7413. Some unit tests should use NameNodeProtocols instead of FSNameSystem. Contributed by Haohui Mai.
HADOOP-11323. WritableComparator#compare keeps reference to byte array. Contributed by Wilfred Spiegelenburg.
MAPREDUCE-6169. MergeQueue should release reference to the current item from key and value at the end of the iteration to save memory. (Zhihai Xu via kasha)
HDFS-7415. Move FSNameSystem.resolvePath() to FSDirectory. Contributed by Haohui Mai.
YARN-2375. Allow enabling/disabling timeline server per framework. (Mit Desai via jeagles)
YARN-2604. Scheduler should consider max-allocation-* in conjunction with the largest node. (Robert Kanter via kasha)
HDFS-7420. Delegate permission checks to FSDirectory. Contributed by Haohui Mai.
YARN-2679. Add metric for container launch duration. (Zhihai Xu via kasha)
Update release date for 2.5.2
YARN-2669. FairScheduler: queue names shouldn't allow periods (Wei Yan via Sandy Ryza)
HDFS-7425. NameNode block deletion logging uses incorrect appender. Contributed by Chris Nauroth.
HDFS-7331. Add Datanode network counts to datanode jmx page. Contributed by Charles Lamb.
MAPREDUCE-5785. Derive heap size or mapreduce.*.memory.mb automatically. (Gera Shegalov and Karthik Kambatla via kasha)
HDFS-7403. Inaccurate javadoc of  BlockUCState#COMPLETE state. (Yongjun Zhang via yliu)
HDFS-4882. Prevent the Namenode's LeaseManager from looping forever in checkLeases (Ravi Prakash via Colin P. McCabe)
HDFS-7419. Improve error messages for DataNode hot swap drive feature (Lei Xu via Colin P. Mccabe)
HDFS-7412. Move RetryCache to NameNodeRpcServer. Contributed by Haohui Mai.
CHANGES.txt: add HDFS-4882
CHANGES.txt: add HDFS-7419
HADOOP-10926. Improve smart-apply-patch.sh to apply binary diffs (cmccabe)