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From: kihwal@apache.org
To: common-commits@hadoop.apache.org
Message-Id: <db4cd189da454d25b592ab1735c55d4e@git.apache.org>
Subject: hadoop git commit: HDFS-10987. Make Decommission less expensive when
 lot of blocks present. Contributed by Brahma Reddy Battula.
Date: Thu, 13 Oct 2016 19:58:10 +0000 (UTC)
archived-at: Thu, 13 Oct 2016 19:58:12 -0000

Repository: hadoop
Updated Branches:
  refs/heads/branch-2.8 7a5aaa789 -> ded91992a


HDFS-10987. Make Decommission less expensive when lot of blocks present. Contributed by Brahma Reddy Battula.

(cherry picked from commit c5a13037048eb1e3b5a500aeec0e2e953e7d509a)


Project: http://git-wip-us.apache.org/repos/asf/hadoop/repo
Commit: http://git-wip-us.apache.org/repos/asf/hadoop/commit/ded91992
Tree: http://git-wip-us.apache.org/repos/asf/hadoop/tree/ded91992
Diff: http://git-wip-us.apache.org/repos/asf/hadoop/diff/ded91992

Branch: refs/heads/branch-2.8
Commit: ded91992adc08c5ac5cff00abcb9f05c148d8daa
Parents: 7a5aaa7
Author: Kihwal Lee <kihwal@apache.org>
Authored: Thu Oct 13 14:57:44 2016 -0500
Committer: Kihwal Lee <kihwal@apache.org>
Committed: Thu Oct 13 14:57:44 2016 -0500

----------------------------------------------------------------------
 .../blockmanagement/DecommissionManager.java    | 29 +++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/hadoop/blob/ded91992/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DecommissionManager.java
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DecommissionManager.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DecommissionManager.java
index 073332b..be4771d 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DecommissionManager.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DecommissionManager.java
@@ -355,6 +355,10 @@ public class DecommissionManager {
      */
     private int numBlocksChecked = 0;
     /**
+     * The number of blocks checked after (re)holding lock.
+     */
+    private int numBlocksCheckedPerLock = 0;
+    /**
      * The number of nodes that have been checked on this tick. Used for 
      * testing.
      */
@@ -392,6 +396,7 @@ public class DecommissionManager {
       }
       // Reset the checked count at beginning of each iteration
       numBlocksChecked = 0;
+      numBlocksCheckedPerLock = 0;
       numNodesChecked = 0;
       // Check decom progress
       namesystem.writeLock();
@@ -426,7 +431,8 @@ public class DecommissionManager {
 
       while (it.hasNext()
           && !exceededNumBlocksPerCheck()
-          && !exceededNumNodesPerCheck()) {
+          && !exceededNumNodesPerCheck()
+          && namesystem.isRunning()) {
         numNodesChecked++;
         final Map.Entry<DatanodeDescriptor, AbstractList<BlockInfo>>
             entry = it.next();
@@ -544,7 +550,28 @@ public class DecommissionManager {
       int decommissionOnlyReplicas = 0;
       int underReplicatedInOpenFiles = 0;
       while (it.hasNext()) {
+        if (insufficientlyReplicated == null
+            && numBlocksCheckedPerLock >= numBlocksPerCheck) {
+          // During fullscan insufficientlyReplicated will NOT be null, iterator
+          // will be DN's iterator. So should not yield lock, otherwise
+          // ConcurrentModificationException could occur.
+          // Once the fullscan done, iterator will be a copy. So can yield the
+          // lock.
+          // Yielding is required in case of block number is greater than the
+          // configured per-iteration-limit.
+          namesystem.writeUnlock();
+          try {
+            LOG.debug("Yielded lock during decommission check");
+            Thread.sleep(0, 500);
+          } catch (InterruptedException ignored) {
+            return;
+          }
+          // reset
+          numBlocksCheckedPerLock = 0;
+          namesystem.writeLock();
+        }
         numBlocksChecked++;
+        numBlocksCheckedPerLock++;
         final BlockInfo block = it.next();
         // Remove the block from the list if it's no longer in the block map,
         // e.g. the containing file has been deleted


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