[HDFS-5042] Completed files lost after power failure

• Type: Bug
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Fix Version/s: 2.9.0, 2.7.4, 3.0.0-alpha4, 2.8.2

Environment

ext3 on CentOS 5.7 (kernel 2.6.18-274.el5)

• Hadoop Flags: Reviewed
• Assignee: Vinayakumar B
• Reporter: Dave Latham
• Created: 29/Jul/13 20:54
• Updated: 24/Apr/18 20:51
• Resolved: 31/May/17 16:24

Description

We suffered a cluster wide power failure after which HDFS lost data that it had acknowledged as closed and complete.

The client was HBase which compacted a set of HFiles into a new HFile, then after closing the file successfully, deleted the previous versions of the file. The cluster then lost power, and when brought back up the newly created file was marked CORRUPT.

Based on reading the logs it looks like the replicas were created by the DataNodes in the 'blocksBeingWritten' directory. Then when the file was closed they were moved to the 'current' directory. After the power cycle those replicas were again in the blocksBeingWritten directory of the underlying file system (ext3). When those DataNodes reported in to the NameNode it deleted those replicas and lost the file.

Some possible fixes could be having the DataNode fsync the directory(s) after moving the block from blocksBeingWritten to current to ensure the rename is durable or having the NameNode accept replicas from blocksBeingWritten under certain circumstances.

Log snippets from RS (RegionServer), NN (NameNode), DN (DataNode):

RS 2013-06-29 11:16:06,812 DEBUG org.apache.hadoop.hbase.util.FSUtils: Creating file=hdfs://hm3:9000/hbase/users-6/b5b0820cde759ae68e333b2f4015bb7e/.tmp/6e0cc30af6e64e56ba5a539fdf159c4c with permission=rwxrwxrwx
NN 2013-06-29 11:16:06,830 INFO org.apache.hadoop.hdfs.StateChange: BLOCK* NameSystem.allocateBlock: /hbase/users-6/b5b0820cde759ae68e333b2f4015bb7e/.tmp/6e0cc30af6e64e56ba5a539fdf159c4c. blk_1395839728632046111_357084589
DN 2013-06-29 11:16:06,832 INFO org.apache.hadoop.hdfs.server.datanode.DataNode: Receiving block blk_1395839728632046111_357084589 src: /10.0.5.237:14327 dest: /10.0.5.237:50010
NN 2013-06-29 11:16:11,370 INFO org.apache.hadoop.hdfs.StateChange: BLOCK* NameSystem.addStoredBlock: blockMap updated: 10.0.6.1:50010 is added to blk_1395839728632046111_357084589 size 25418340
NN 2013-06-29 11:16:11,370 INFO org.apache.hadoop.hdfs.StateChange: BLOCK* NameSystem.addStoredBlock: blockMap updated: 10.0.6.24:50010 is added to blk_1395839728632046111_357084589 size 25418340
NN 2013-06-29 11:16:11,385 INFO org.apache.hadoop.hdfs.StateChange: BLOCK* NameSystem.addStoredBlock: blockMap updated: 10.0.5.237:50010 is added to blk_1395839728632046111_357084589 size 25418340
DN 2013-06-29 11:16:11,385 INFO org.apache.hadoop.hdfs.server.datanode.DataNode: Received block blk_1395839728632046111_357084589 of size 25418340 from /10.0.5.237:14327
DN 2013-06-29 11:16:11,385 INFO org.apache.hadoop.hdfs.server.datanode.DataNode: PacketResponder 2 for block blk_1395839728632046111_357084589 terminating
NN 2013-06-29 11:16:11,385 INFO org.apache.hadoop.hdfs.StateChange: Removing lease on  file /hbase/users-6/b5b0820cde759ae68e333b2f4015bb7e/.tmp/6e0cc30af6e64e56ba5a539fdf159c4c from client DFSClient_hb_rs_hs745,60020,1372470111932
NN 2013-06-29 11:16:11,385 INFO org.apache.hadoop.hdfs.StateChange: DIR* NameSystem.completeFile: file /hbase/users-6/b5b0820cde759ae68e333b2f4015bb7e/.tmp/6e0cc30af6e64e56ba5a539fdf159c4c is closed by DFSClient_hb_rs_hs745,60020,1372470111932
RS 2013-06-29 11:16:11,393 INFO org.apache.hadoop.hbase.regionserver.Store: Renaming compacted file at hdfs://hm3:9000/hbase/users-6/b5b0820cde759ae68e333b2f4015bb7e/.tmp/6e0cc30af6e64e56ba5a539fdf159c4c to hdfs://hm3:9000/hbase/users-6/b5b0820cde759ae68e333b2f4015bb7e/n/6e0cc30af6e64e56ba5a539fdf159c4c
RS 2013-06-29 11:16:11,505 INFO org.apache.hadoop.hbase.regionserver.Store: Completed major compaction of 7 file(s) in n of users-6,\x12\xBDp\xA3,1359426311784.b5b0820cde759ae68e333b2f4015bb7e. into 6e0cc30af6e64e56ba5a539fdf159c4c, size=24.2m; total size for store is 24.2m

-------  CRASH, RESTART ---------

NN 2013-06-29 12:01:19,743 INFO org.apache.hadoop.hdfs.StateChange: BLOCK* NameSystem.addStoredBlock: addStoredBlock request received for blk_1395839728632046111_357084589 on 10.0.6.1:50010 size 21978112 but was rejected: Reported as block being written but is a block of closed file.
NN 2013-06-29 12:01:19,743 INFO org.apache.hadoop.hdfs.StateChange: BLOCK* NameSystem.addToInvalidates: blk_1395839728632046111 is added to invalidSet of 10.0.6.1:50010
NN 2013-06-29 12:01:20,155 INFO org.apache.hadoop.hdfs.StateChange: BLOCK* NameSystem.addStoredBlock: addStoredBlock request received for blk_1395839728632046111_357084589 on 10.0.5.237:50010 size 16971264 but was rejected: Reported as block being written but is a block of closed file.
NN 2013-06-29 12:01:20,155 INFO org.apache.hadoop.hdfs.StateChange: BLOCK* NameSystem.addToInvalidates: blk_1395839728632046111 is added to invalidSet of 10.0.5.237:50010
NN 2013-06-29 12:01:20,175 INFO org.apache.hadoop.hdfs.StateChange: BLOCK* NameSystem.addStoredBlock: addStoredBlock request received for blk_1395839728632046111_357084589 on 10.0.6.24:50010 size 21913088 but was rejected: Reported as block being written but is a block of closed file.
NN 2013-06-29 12:01:20,175 INFO org.apache.hadoop.hdfs.StateChange: BLOCK* NameSystem.addToInvalidates: blk_1395839728632046111 is added to invalidSet of 10.0.6.24:50010
(note the clock on the server running DN is wrong after restart.  I believe timestamps are off by 6 hours:)
DN 2013-06-29 06:07:22,877 INFO org.apache.hadoop.hdfs.server.datanode.DataNode: Scheduling block blk_1395839728632046111_357084589 file /data/hadoop/dfs/data/blocksBeingWritten/blk_1395839728632046111 for deletion
DN 2013-06-29 06:07:24,952 INFO org.apache.hadoop.hdfs.server.datanode.DataNode: Deleted block blk_1395839728632046111_357084589 at file /data/hadoop/dfs/data/blocksBeingWritten/blk_1395839728632046111

There was some additional discussion on this thread on the mailing list:

http://mail-archives.apache.org/mod_mbox/hadoop-hdfs-user/201307.mbox/%3CCA+qbEUPuf19PL_EVeWi1104+scLVrcS0LTFUvBPw=[e-mail]%3E

Issue Links

• breaks: HDFS-12157 Do fsyncDirectory(..) outside of FSDataset lock
• is related to: CASSANDRA-3250 fsync the directory after new sstable or commit log segment are created
• is related to: HDFS-1539 prevent data loss when a cluster suffers a power loss
• relates to: HDFS-11915 Sync rbw dir on the first hsync() to avoid file lost on power failure