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From "Xiaoyu Yao (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-7066) LazyWriter#evictBlocks misses a null check for replicaState
Date Mon, 15 Sep 2014 22:02:34 GMT
Xiaoyu Yao created HDFS-7066:
--------------------------------

             Summary: LazyWriter#evictBlocks misses a null check for replicaState
                 Key: HDFS-7066
                 URL: https://issues.apache.org/jira/browse/HDFS-7066
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: datanode
    Affects Versions: 2.5.1
            Reporter: Xiaoyu Yao
            Assignee: Xiaoyu Yao
            Priority: Minor


LazyWriter#evictBlocks (added for HDFS-6581) misses a null check for replicaState. As a result,
there are many NPEs in the debug log. 

2014-09-15 14:27:10,820 DEBUG impl.FsDatasetImpl (FsDatasetImpl.java:evictBlocks(2335)) -
Evicting block null
2014-09-15 14:27:10,821 WARN  impl.FsDatasetImpl (FsDatasetImpl.java:run(2409)) - Ignoring
exception in LazyWriter:
java.lang.NullPointerException
	at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl$LazyWriter.evictBlocks(FsDatasetImpl.java:2343)
	at org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl$LazyWriter.run(FsDatasetImpl.java:2396)
	at java.lang.Thread.run(Thread.java:745)

The proposed fix is to break if there is no candidate available to evict.

{code}

	while (iterations++ < MAX_BLOCK_EVICTIONS_PER_ITERATION &&
            transientFreeSpaceBelowThreshold()) {
       LazyWriteReplicaTracker.ReplicaState replicaState =
           lazyWriteReplicaTracker.getNextCandidateForEviction();

       ++++++++++++++++++++
	if (replicaState == null) {
          break;
       }
       ++++++++++++++++++++

       if (LOG.isDebugEnabled()) {
         LOG.debug("Evicting block " + replicaState);
       }

{code}



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