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https://issues.apache.org/jira/browse/HDFS-7820?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14342696#comment-14342696
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J.Andreina commented on HDFS-7820:
----------------------------------
Hi Arpit Agarwal thanks for looking at this issue.
bq.One thing I did not understand - the finalized block does not belong to any
file after rollback. Hence it should never be added to the BlockInfo list and
should be marked for deletion on the DN immediately.
Block would be marked for deletion only on the second block report ( which
would take 6 hrs, as default value for dfs.blockreport.intervalMsec=6hrs). So
within this time after rollback any client write operation will fail since
block with the same id already exist at DN .
To avoid the duplicate block id being assigned after rollback , i gave an
initial patch considering there could be 10 million blocks written in worst
case after upgrade and before rollback, hence incremented the block id by 10
million after rollback.
Please correct me if I'am wrong.
> Client Write fails after rolling upgrade rollback with "<block_id> already
> exist in finalized state"
> ----------------------------------------------------------------------------------------------------
>
> Key: HDFS-7820
> URL: https://issues.apache.org/jira/browse/HDFS-7820
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: J.Andreina
> Assignee: J.Andreina
> Attachments: HDFS-7820.1.patch
>
>
> Steps to Reproduce:
> ===================
> Step 1: Prepare rolling upgrade using "hdfs dfsadmin -rollingUpgrade prepare"
> Step 2: Shutdown SNN and NN
> Step 3: Start NN with the "hdfs namenode -rollingUpgrade started" option.
> Step 4: Executed "hdfs dfsadmin -shutdownDatanode <DATANODE_HOST:IPC_PORT>
> upgrade" and restarted Datanode
> Step 5: Write 3 files to hdfs ( block id assigned are : blk_1073741831_1007,
> blk_1073741832_1008,blk_1073741833_1009 )
> Step 6: Shutdown both NN and DN
> Step 7: Start NNs with the "hdfs namenode -rollingUpgrade rollback" option.
> Start DNs with the "-rollback" option.
> Step 8: Write 2 files to hdfs.
> Issue:
> =======
> Client write failed with below exception
> {noformat}
> 2015-02-23 16:00:12,896 INFO org.apache.hadoop.hdfs.server.datanode.DataNode:
> Receiving BP-1837556285-XXXXXXXXXXX-1423130389269:blk_1073741832_1008 src:
> /XXXXXXXXXXX:48545 dest: /XXXXXXXXXXX:50010
> 2015-02-23 16:00:12,897 INFO org.apache.hadoop.hdfs.server.datanode.DataNode:
> opWriteBlock BP-1837556285-XXXXXXXXXXX-1423130389269:blk_1073741832_1008
> received exception
> org.apache.hadoop.hdfs.server.datanode.ReplicaAlreadyExistsException: Block
> BP-1837556285-XXXXXXXXXXX-1423130389269:blk_1073741832_1008 already exists in
> state FINALIZED and thus cannot be created.
> {noformat}
> Observations:
> =============
> 1. At Namenode side block invalidate is been sent only to 2 blocks.
> {noformat}
> 15/02/23 14:59:56 INFO BlockStateChange: BLOCK* InvalidateBlocks: add
> blk_1073741833_1009 to XXXXXXXXXXX:50010
> 15/02/23 14:59:56 INFO BlockStateChange: BLOCK* InvalidateBlocks: add
> blk_1073741831_1007 to XXXXXXXXXXX:50010
> {noformat}
> 2. fsck report does not show information on blk_1073741832_1008
> {noformat}
> FSCK started by Rex (auth:SIMPLE) from /XXXXXXXXXXX for path / at Mon Feb 23
> 16:17:57 CST 2015
> /File1: Under replicated
> BP-1837556285-XXXXXXXXXXX-1423130389269:blk_1073741825_1001. Target Replicas
> is 3 but found 1 replica(s).
> /File11: Under replicated
> BP-1837556285-XXXXXXXXXXX-1423130389269:blk_1073741827_1003. Target Replicas
> is 3 but found 1 replica(s).
> /File2: Under replicated
> BP-1837556285-XXXXXXXXXXX-1423130389269:blk_1073741826_1002. Target Replicas
> is 3 but found 1 replica(s).
> /AfterRollback_2: Under replicated
> BP-1837556285-XXXXXXXXXXX-1423130389269:blk_1073741831_1007. Target Replicas
> is 3 but found 1 replica(s).
> /Test1: Under replicated
> BP-1837556285-XXXXXXXXXXX-1423130389269:blk_1073741828_1004. Target Replicas
> is 3 but found 1 replica(s).
> Status: HEALTHY
> Total size: 31620 B
> Total dirs: 7
> Total files: 6
> Total symlinks: 0
> Total blocks (validated): 5 (avg. block size 6324 B)
> Minimally replicated blocks: 5 (100.0 %)
> Over-replicated blocks: 0 (0.0 %)
> Under-replicated blocks: 5 (100.0 %)
> Mis-replicated blocks: 0 (0.0 %)
> Default replication factor: 3
> Average block replication: 1.0
> Corrupt blocks: 0
> Missing replicas: 10 (66.666664 %)
> Number of data-nodes: 1
> Number of racks: 1
> FSCK ended at Mon Feb 23 16:17:57 CST 2015 in 3 milliseconds
> {noformat}
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