Wei-Chiu Chuang created HDFS-11019:
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Summary: Inconsistent number of corrupt replicas if a corrupt
replica is reported multiple times
Key: HDFS-11019
URL: https://issues.apache.org/jira/browse/HDFS-11019
Project: Hadoop HDFS
Issue Type: Bug
Components: namenode
Environment: CDH5.7.2
Reporter: Wei-Chiu Chuang
While investigating a block corruption issue, I found the following warning
message in the namenode log:
{noformat}
(a client reports a block replica is corrupt)
2016-10-12 10:07:37,166 INFO BlockStateChange: BLOCK
NameSystem.addToCorruptReplicasMap: blk_1073803461 added as corrupt on
10.0.0.63:50010 by /10.0.0.62 because client machine reported it
2016-10-12 10:07:37,166 INFO BlockStateChange: BLOCK* invalidateBlock:
blk_1073803461_74513(stored=blk_1073803461_74553) on 10.0.0.63:50010
2016-10-12 10:07:37,166 INFO BlockStateChange: BLOCK* InvalidateBlocks: add
blk_1073803461_74513 to 10.0.0.63:50010
(another client reports a block replica is corrupt)
2016-10-12 10:07:37,728 INFO BlockStateChange: BLOCK
NameSystem.addToCorruptReplicasMap: blk_1073803461 added as corrupt on
10.0.0.63:50010 by /10.0.0.64 because client machine reported it
2016-10-12 10:07:37,728 INFO BlockStateChange: BLOCK* invalidateBlock:
blk_1073803461_74513(stored=blk_1073803461_74553) on 10.0.0.63:50010
(ReplicationMonitor thread kicks in to invalidate the replica and add a new one)
2016-10-12 10:07:37,888 INFO BlockStateChange: BLOCK* ask 10.0.0.56:50010 to
replicate blk_1073803461_74553 to datanode(s) 10.0.0.63:50010
2016-10-12 10:07:37,888 INFO BlockStateChange: BLOCK* BlockManager: ask
10.0.0.63:50010 to delete [blk_1073803461_74513]
(the two maps are inconsistent)
2016-10-12 10:08:00,335 WARN
org.apache.hadoop.hdfs.server.blockmanagement.BlockManager: Inconsistent number
of corrupt replicas for blk_1073803461_74553 blockMap has 0 but corrupt
replicas map has 1
{noformat}
It seems that when a corrupt block replica is reported twice, blockMap corrupt
and corrupt replica map becomes inconsistent.
Looking at the log, I suspect the bug is in {{BlockManager#removeStoredBlock}}.
When a corrupt replica is reported, BlockManager removes the block from
blocksMap. If the block is already removed (that is, the corrupt replica is
reported twice), return; Otherwise (that is, the corrupt replica is reported
the first time), remove the block from corruptReplicasMap (The block is added
into corruptReplicasMap in BlockerManager#markBlockAsCorrupt) Therefore, after
the second corruption report, the corrupt replica is removed from blocksMap,
but the one in corruptReplicasMap is not removed.
I can’t tell what’s the impact that they are inconsistent. But I feel it's a
good idea to fix it.
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