[HDFS-142] In 0.20, move blocks being written into a blocksBeingWritten directory

• Type: Bug
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 0.20-append
• Fix Version/s: 0.20-append, 0.20.205.0
• Tags: hbase
• Assignee: Dhruba Borthakur
• Reporter: Raghu Angadi
• Created: 15/Nov/08 00:55
• Updated: 02/May/13 02:29
• Resolved: 16/Jun/10 22:30

Description

Before 0.18, when Datanode restarts, it deletes files under data-dir/tmp directory since these files are not valid anymore. But in 0.18 it moves these files to normal directory incorrectly making them valid blocks. One of the following would work :

• remove the tmp files during upgrade, or
• if the files under /tmp are in pre-18 format (i.e. no generation), delete them.

Currently effect of this bug is that, these files end up failing block verification and eventually get deleted. But cause incorrect over-replication at the namenode before that.

Also it looks like our policy regd treating files under tmp needs to be defined better. Right now there are probably one or two more bugs with it. Dhruba, please file them if you rememeber.

Issue Links

• depends upon: HDFS-101 DFS write pipeline : DFSClient sometimes does not detect second datanode failure
• depends upon: HDFS-793 DataNode should first receive the whole packet ack message before it constructs and sends its own ack message for the packet
• depends upon: HDFS-988 saveNamespace race can corrupt the edits log
• depends upon: HDFS-606 ConcurrentModificationException in invalidateCorruptReplicas()
• depends upon: HDFS-826 Allow a mechanism for an application to detect that datanode(s) have died in the write pipeline
• incorporates: HADOOP-4997 workaround for tmp file handling on DataNodes in 0.18 (HADOOP-4663)
• relates to: HDFS-57 A Datanode's datadir could have lots of blocks in the top-level directory
• relates to: HADOOP-4702 Failed block replication leaves an incomplete block in receiver's tmp data directory
• relates to: HADOOP-4810 Data lost at cluster startup time
• relates to: HDFS-29 In Datanode, update block may fail due to length inconsistency