[HDFS-988] saveNamespace race can corrupt the edits log

• Type: Bug
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 0.20-append, 0.21.0, 0.22.0
• Fix Version/s: 0.20-append, 0.20.205.0, 0.22.0
• Component/s: namenode
• Hadoop Flags: Reviewed
• Tags: hbase
• Assignee: Eli Collins
• Reporter: Dhruba Borthakur
• Created: 18/Feb/10 21:11
• Updated: 12/Jul/13 18:34
• Resolved: 12/Jun/11 18:19

Description

The adminstrator puts the namenode is safemode and then issues the savenamespace command. This can corrupt the edits log. The problem is that when the NN enters safemode, there could still be pending logSycs occuring from other threads. Now, the saveNamespace command, when executed, would save a edits log with partial writes. I have seen this happen on 0.20.

https://issues.apache.org/jira/browse/HDFS-909?focusedCommentId=12828853&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12828853

Issue Links

• breaks: HDFS-2229 Deadlock in NameNode
• duplicates: HDFS-1775 getContentSummary should hold the FSNamesystem readlock
• is depended upon by: HDFS-142 In 0.20, move blocks being written into a blocksBeingWritten directory
• is related to: HDFS-955 FSImage.saveFSImage can lose edits
• is related to: HDFS-909 Race condition between rollEditLog or rollFSImage ant FSEditsLog.write operations corrupts edits log
• is related to: HDFS-2052 FSNamesystem should not sync the log with the write lock held
• requires: HDFS-956 Improper synchronization in some FSNamesystem methods