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https://issues.apache.org/jira/browse/HDFS-12177?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16095832#comment-16095832
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Jiandan Yang commented on HDFS-12177:
--------------------------------------
OK, I have uploaded patch with branch-2.8 and branch-2.7
> NameNode exits due to setting BlockPlacementPolicy loglevel to Debug
> ---------------------------------------------------------------------
>
> Key: HDFS-12177
> URL: https://issues.apache.org/jira/browse/HDFS-12177
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: block placement
> Affects Versions: 2.8.1
> Reporter: Jiandan Yang
> Assignee: Jiandan Yang
> Attachments: HDFS-12177-001-branch-2.7.patch,
> HDFS-12177-001-branch-2.8.patch, HDFS_9668_1.patch
>
>
> NameNode exits because the ReplicationMonitor thread internally throws NPE.
> The reason for throwing NPE is that the builder field is not initialized whe
> do log.
> Solution: before appending it should determine whether the builder is null
> {code:java}
> if (LOG.isDebugEnabled()) {
> builder = debugLoggingBuilder.get();
> builder.setLength(0);
> builder.append("[");
> }
> some other codes ...
> if (LOG.isDebugEnabled()) {
> builder.append("\nNode ").append(NodeBase.getPath(chosenNode))
> .append(" [");
> }
> some other codes ...
> if (LOG.isDebugEnabled()) {
> builder.append("\n]");
> }
> {code}
> NN exception log is :
> {code:java}
> java.lang.NullPointerException
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault.chooseRandom(BlockPlacementPolicyDefault.java:722)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault.chooseRandom(BlockPlacementPolicyDefault.java:689)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault.chooseFromNextRack(BlockPlacementPolicyDefault.java:640)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault.chooseLocalRack(BlockPlacementPolicyDefault.java:608)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault.chooseTargetInOrder(BlockPlacementPolicyDefault.java:483)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault.chooseTarget(BlockPlacementPolicyDefault.java:390)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault.chooseTarget(BlockPlacementPolicyDefault.java:419)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault.chooseTarget(BlockPlacementPolicyDefault.java:266)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault.chooseTarget(BlockPlacementPolicyDefault.java:119)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.ReplicationWork.chooseTargets(ReplicationWork.java:55)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.computeReplicationWorkForBlocks(BlockManager.java:1532)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.computeReplicationWork(BlockManager.java:1491)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.computeDatanodeWork(BlockManager.java:3768)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockManager$ReplicationMonitor.run(BlockManager.java:3720)
> at java.lang.Thread.run(Thread.java:834)
> {code}
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