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From "Rushabh S Shah (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-12278) LeaseManager operations are inefficient in 2.8.
Date Wed, 09 Aug 2017 20:39:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-12278?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16120620#comment-16120620
] 

Rushabh S Shah commented on HDFS-12278:
---------------------------------------

{{TestDFSStripedOutputStreamWithFailure150}} and {{TestDFSStripedOutputStreamWithFailure080}}
are well known flaky tests.
Both have failed number of times. I ran 4 times each test. Fails with a probability of 50%
{{TestUnderReplicatedBlocks#testSetRepIncWithUnderReplicatedBlocks}} is timing out. Tracked
via HDFS-9243.

There are no new tests since all the existing test covers the correctness.
Will attach a branch-2.8 patch soon.

> LeaseManager operations are inefficient in 2.8.
> -----------------------------------------------
>
>                 Key: HDFS-12278
>                 URL: https://issues.apache.org/jira/browse/HDFS-12278
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>    Affects Versions: 2.8.0
>            Reporter: Rushabh S Shah
>            Assignee: Rushabh S Shah
>            Priority: Blocker
>         Attachments: HDFS-12278.patch
>
>
> After HDFS-6757, LeaseManager #removeLease became expensive. 
> HDFS-6757 changed the {{sortedLeases}} object from TreeSet to PriorityQueue. 
> Previously the {{remove(Object)}} operation from {{sortedLeases}} was {{O(log n)}} but
after the change it became {{O( n)}} since it has to find the object first. 
> Recently we had an incident in one of our production cluster just hours after we upgraded
from 2.7 to 2.8 
> The {{sortledLeases}} object had approximately 100,000 items within it. 
> While removing the lease, it will acquire the LeaseManager lock and that will slow down
the lookup of lease also.  
> HDFS-6757 is a good improvement which replaced the path by inode id.



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