HADOOP-9618.  thread which detects GC pauses (Todd Lipcon via Colin Patrick McCabe)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1503810 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-9683. [RPC v9] Wrap IpcConnectionContext in RPC headers (daryn)


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1503830 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4657.  Limit the number of blocks logged by the NN after a block report to a configurable value.  (Aaron Twinning Meyers via Colin Patrick McCabe)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1503864 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4999. Fix TestShortCircuitLocalRead on branch-2. Contributed by Colin Patrick McCabe.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1503898 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/branch-2' into branch-2-gd
Merge remote branch 'origin/branch-2-gd' into fb-HADOOP-9315-branch-2-gd