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https://issues.apache.org/jira/browse/HADOOP-4951?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12659875#action_12659875
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Konstantin Shvachko commented on HADOOP-4951:
---------------------------------------------
This is the exception and the stack trace.
{code}
Exception in thread "org.apache.hadoop.dfs.leasemanager$moni...@3dbe8711"
java.util.ConcurrentModificationException
at java.util.TreeMap$PrivateEntryIterator.nextEntry(TreeMap.java:1100)
at java.util.TreeMap$KeyIterator.next(TreeMap.java:1154)
at
org.apache.hadoop.dfs.LeaseManager$Monitor.checkLeases(LeaseManager.java:370)
at org.apache.hadoop.dfs.LeaseManager$Monitor.run(LeaseManager.java:346)
at java.lang.Thread.run(Thread.java:619)
{code}
Another problem with this issue is that the name-node was running without lease
monitor as if nothing happened. As a result, a lot of abandoned files have not
been garbage collected.
This patch fixes the {{ConcurrentModificationException}} but does not fix the
problem of NN running without the lease monitor. I'll file another jira for
that.
> Lease monitor does not own the LeaseManager lock in changing leases.
> --------------------------------------------------------------------
>
> Key: HADOOP-4951
> URL: https://issues.apache.org/jira/browse/HADOOP-4951
> Project: Hadoop Core
> Issue Type: Bug
> Components: dfs
> Affects Versions: 0.18.2
> Reporter: Tsz Wo (Nicholas), SZE
> Assignee: Tsz Wo (Nicholas), SZE
> Priority: Blocker
> Fix For: 0.18.3
>
> Attachments: 4951_20081229.patch, 4951_20081229b.patch,
> 4951_20081229c.patch, 4951_20081229c_0.18.patch, 4951_20081229c_0.19.patch
>
>
> In Monitor.checkLeases(), the monitor thread does not own the LeaseManager
> lock but it may modify the leases.
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