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https://issues.apache.org/jira/browse/HDFS-1072?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12854185#action_12854185
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Erik Steffl commented on HDFS-1072:
-----------------------------------
Further investigation revealed that the following sequence leads to
AlreadyBeingCreatedException:
- LEASE_LIMIT=500; cluster.setLeasePeriod(LEASE_LIMIT, LEASE_LIMIT);
- thread A gets a lease on a file
- thread B sleeps 2*soft limit
- thread B tries to get lease on a file, triggers lease recovery and gets
RecoveryInProgressException
- before lease recovery ends, namenode LeaseManager.java:checkLeases finds
out that hard limit was also expired, start a new recovery, resets timeouts
- thread B tries to get lease again, timeout is not expired (it was reset in
previous step) so it gets AlreadyBeingCreatedException
There are two problems in the code that lead to this:
- hard limit should not be set to such a low value, it makes it very likely
for recovery to not finish before it's taken over by another recovery (because
of expired hard limit)
- namenode should recognize that even though limit is not expired the
recovery is ongoing and return RecoveryInProgressException instead of
AlreadyBeingCreatedException (in FSNamesystem.java:startFileInternal, when it's
deciding what to do if the file is under construction)
> AlreadyBeingCreatedException with HDFS_NameNode as the lease holder
> -------------------------------------------------------------------
>
> Key: HDFS-1072
> URL: https://issues.apache.org/jira/browse/HDFS-1072
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: hdfs client, name-node
> Affects Versions: 0.21.0
> Reporter: Tsz Wo (Nicholas), SZE
> Assignee: Erik Steffl
> Fix For: 0.21.0
>
>
> TestReadWhileWriting may fail by AlreadyBeingCreatedException with
> HDFS_NameNode as the lease holder, which indicates that lease recovery is in
> an inconsistent state.
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