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From "Rushabh S Shah (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-12278) LeaseManager#removeLease operation is inefficient in 2.8.
Date Tue, 08 Aug 2017 20:46:00 GMT
Rushabh S Shah created HDFS-12278:

             Summary: 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, 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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