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https://issues.apache.org/jira/browse/HDFS-13243?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16392812#comment-16392812
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Wei-Chiu Chuang commented on HDFS-13243:
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[~gzh1992n] thanks for the comments. That makes a lot more sense now.
{quote}Client call sync() with a *corrent* length, but sync request could be
sent after close().
The root cause is that DFSOutputStream#flushOrSync() is not thread-safe. See
following simplified code:
{quote}
If the problem is client side race condition, I would recommend fixing it at
client side. Suppose client calls fsync() but server ignores it because of the
client race condition, doesn't that mean the block is not sync'ed? Client
expects that if it calls fsync() and that if it does not throw an IOException,
the call succeeds.
{quote}I'm not sure that data reliability would be affected if minimal
replication set to 1. Do you have some experience about this
{quote}
This is a typical misunderstanding. Minimal replication is not replication
factor. And setting minimal replication to 2 is not a well tested
configuration, at least in CDH. I work for Cloudera and we have thousands of
customers. Almost no use sets minimal replication factor to 2. There's just one
that I am aware, and that customer reports quite a few tricky issues because of
it.
File can not be closed because DataNode block reports are not processed in time
in a large cluster and you need two DNs reporting an updated block for it to
become COMPLETE and get closed. Decommissioning does not complete at all due to
a corner case ... etc.
Long story short, I suspect this race condition happens because of this unusual
setting. (or makes it more prone to this bug)
{quote}I don't understand this. There is no API that set impl of FSNamesystem
in MiniCluster. Could you give me a sample in another test case? I will rewrite
this patch.
{quote}
There's none. But you can make one :)
{quote}In server-side, we could log warn for wrong length and throw exception
for invalid state. Is this better than current version?
{quote}
That sounds like a plan.
Thank you
> Get CorruptBlock because of calling close and sync in same time
> ---------------------------------------------------------------
>
> Key: HDFS-13243
> URL: https://issues.apache.org/jira/browse/HDFS-13243
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Affects Versions: 2.7.2, 3.2.0
> Reporter: Zephyr Guo
> Assignee: Zephyr Guo
> Priority: Critical
> Fix For: 3.2.0
>
> Attachments: HDFS-13243-v1.patch, HDFS-13243-v2.patch
>
>
> HDFS File might get broken because of corrupt block(s) that could be produced
> by calling close and sync in the same time.
> When calling close was not successful, UCBlock status would change to
> COMMITTED, and if a sync request gets popped from queue and processed, sync
> operation would change the last block length.
> After that, DataNode would report all received block to NameNode, and will
> check Block length of all COMMITTED Blocks. But the block length was already
> different between recorded in NameNode memory and reported by DataNode, and
> consequently, the last block is marked as corruptted because of inconsistent
> length.
>
> {panel:title=Log in my hdfs}
> 2018-03-05 04:05:39,261 INFO org.apache.hadoop.hdfs.StateChange: BLOCK*
> allocate blk_1085498930_11758129\{UCState=UNDER_CONSTRUCTION,
> truncateBlock=null, primaryNodeIndex=-1,
> replicas=[ReplicaUC[[DISK]DS-32c7e479-3845-4a44-adf1-831edec7506b:NORMAL:10.0.0.219:50010|RBW],
>
> ReplicaUC[[DISK]DS-a9a5d653-c049-463d-8e4a-d1f0dc14409c:NORMAL:10.0.0.220:50010|RBW],
>
> ReplicaUC[[DISK]DS-f2b7c04a-b724-4c69-abbf-d2e416f70706:NORMAL:10.0.0.218:50010|RBW]]}
> for
> /hbase/WALs/hb-j5e517al6xib80rkb-006.hbase.rds.aliyuncs.com,16020,1519845790686/hb-j5e517al6xib80rkb-006.hbase.rds.aliyuncs.com%2C16020%2C1519845790686.default.1520193926515
> 2018-03-05 04:05:39,760 INFO org.apache.hadoop.hdfs.StateChange: BLOCK*
> fsync:
> /hbase/WALs/hb-j5e517al6xib80rkb-006.hbase.rds.aliyuncs.com,16020,1519845790686/hb-j5e517al6xib80rkb-006.hbase.rds.aliyuncs.com%2C16020%2C1519845790686.default.1520193926515
> for DFSClient_NONMAPREDUCE_1077513762_1
> 2018-03-05 04:05:39,761 INFO
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem: BLOCK*
> blk_1085498930_11758129\{UCState=COMMITTED, truncateBlock=null,
> primaryNodeIndex=-1,
> replicas=[ReplicaUC[[DISK]DS-32c7e479-3845-4a44-adf1-831edec7506b:NORMAL:10.0.0.219:50010|RBW],
>
> ReplicaUC[[DISK]DS-a9a5d653-c049-463d-8e4a-d1f0dc14409c:NORMAL:10.0.0.220:50010|RBW],
>
> ReplicaUC[[DISK]DS-f2b7c04a-b724-4c69-abbf-d2e416f70706:NORMAL:10.0.0.218:50010|RBW]]}
> is not COMPLETE (ucState = COMMITTED, replication# = 0 < minimum = 2) in
> file
> /hbase/WALs/hb-j5e517al6xib80rkb-006.hbase.rds.aliyuncs.com,16020,1519845790686/hb-j5e517al6xib80rkb-006.hbase.rds.aliyuncs.com%2C16020%2C1519845790686.default.1520193926515
> 2018-03-05 04:05:39,761 INFO BlockStateChange: BLOCK* addStoredBlock:
> blockMap updated: 10.0.0.220:50010 is added to
> blk_1085498930_11758129\{UCState=COMMITTED, truncateBlock=null,
> primaryNodeIndex=-1,
> replicas=[ReplicaUC[[DISK]DS-32c7e479-3845-4a44-adf1-831edec7506b:NORMAL:10.0.0.219:50010|RBW],
>
> ReplicaUC[[DISK]DS-a9a5d653-c049-463d-8e4a-d1f0dc14409c:NORMAL:10.0.0.220:50010|RBW],
>
> ReplicaUC[[DISK]DS-f2b7c04a-b724-4c69-abbf-d2e416f70706:NORMAL:10.0.0.218:50010|RBW]]}
> size 2054413
> 2018-03-05 04:05:39,761 INFO BlockStateChange: BLOCK
> NameSystem.addToCorruptReplicasMap: blk_1085498930 added as corrupt on
> 10.0.0.219:50010 by
> hb-j5e517al6xib80rkb-006.hbase.rds.aliyuncs.com/10.0.0.219 because block is
> COMMITTED and reported length 2054413 does not match length in block map
> 141232
> 2018-03-05 04:05:39,762 INFO BlockStateChange: BLOCK
> NameSystem.addToCorruptReplicasMap: blk_1085498930 added as corrupt on
> 10.0.0.218:50010 by
> hb-j5e517al6xib80rkb-004.hbase.rds.aliyuncs.com/10.0.0.218 because block is
> COMMITTED and reported length 2054413 does not match length in block map
> 141232
> 2018-03-05 04:05:40,162 INFO
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem: BLOCK*
> blk_1085498930_11758129\{UCState=COMMITTED, truncateBlock=null,
> primaryNodeIndex=-1,
> replicas=[ReplicaUC[[DISK]DS-32c7e479-3845-4a44-adf1-831edec7506b:NORMAL:10.0.0.219:50010|RBW],
>
> ReplicaUC[[DISK]DS-a9a5d653-c049-463d-8e4a-d1f0dc14409c:NORMAL:10.0.0.220:50010|RBW],
>
> ReplicaUC[[DISK]DS-f2b7c04a-b724-4c69-abbf-d2e416f70706:NORMAL:10.0.0.218:50010|RBW]]}
> is not COMPLETE (ucState = COMMITTED, replication# = 3 >= minimum = 2) in
> file
> /hbase/WALs/hb-j5e517al6xib80rkb-006.hbase.rds.aliyuncs.com,16020,1519845790686/hb-j5e517al6xib80rkb-006.hbase.rds.aliyuncs.com%2C16020%2C1519845790686.default.1520193926515
> {panel}
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