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From "Benoy Antony (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-6363) Improve concurrency while checking inclusion and exclusion of datanodes
Date Sat, 10 May 2014 22:15:24 GMT

     [ https://issues.apache.org/jira/browse/HDFS-6363?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Benoy Antony updated HDFS-6363:
-------------------------------

    Attachment: HDFS-6363.patch

A new container class _HostSetPair_ is defined. This holds includes and excludes as its fields.
 The instance of _HostSetPair_ in HostFileManager is defined _volatile_ 
Since _HostSetPair_ is immutable and is safely published via volatile, its state can be accessed
from different threads without lock.

To understand more on the validity of this safe publication approach, please seehttps://issues.apache.org/jira/browse/HADOOP-10448?focusedCommentId=13980112

Since there is no change in functionality , no tests are modified or added.

> Improve concurrency while checking inclusion and exclusion of datanodes
> -----------------------------------------------------------------------
>
>                 Key: HDFS-6363
>                 URL: https://issues.apache.org/jira/browse/HDFS-6363
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>            Reporter: Benoy Antony
>            Assignee: Benoy Antony
>         Attachments: HDFS-6363.patch
>
>
> HostFileManager holds two effectively immutable objects - includes and excludes. These
two objects can be safely published together using a volatile container instead of synchronizing
for all mutators and accessors.
> This improves the concurrency while using HostFileManager.



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