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Date: Tue, 8 Aug 2017 20:48:00 +0000 (UTC)
From: "Rushabh S Shah (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.13093299.1502225099000.121319.1502225280084@Atlassian.JIRA>
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Subject: [jira] [Updated] (HDFS-12278) LeaseManager#removeLease operation is
 inefficient in 2.8.
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archived-at: Tue, 08 Aug 2017 20:48:05 -0000


     [ https://issues.apache.org/jira/browse/HDFS-12278?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Rushabh S Shah updated HDFS-12278:
----------------------------------
    Description: 
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.

  was:
After HDFS-6757, 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.


> LeaseManager#removeLease operation is 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
>
> 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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