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From "Jakob Homan (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1353) Remove most of getBlockLocation optimization
Date Sat, 04 Sep 2010 00:34:33 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1353?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12906188#action_12906188
] 

Jakob Homan commented on HDFS-1353:
-----------------------------------

Ran tests manually.  All past except known bad TestHDFSTrash and TestFileConcurrentReader.
 Test-patch: 
{noformat}
     [exec] -1 overall.  
     [exec] 
     [exec]     +1 @author.  The patch does not contain any @author tags.
     [exec] 
     [exec]     +1 tests included.  The patch appears to include 3 new or modified tests.
     [exec] 
     [exec]     -1 javadoc.  The javadoc tool appears to have generated 1 warning messages.
     [exec] 
     [exec]     +1 javac.  The applied patch does not increase the total number of javac compiler
warnings.
     [exec] 
     [exec]     +1 findbugs.  The patch does not introduce any new Findbugs warnings.
     [exec] 
     [exec]     +1 release audit.  The applied patch does not increase the total number of
release audit warnings.
     [exec] 
     [exec]     +1 system tests framework.  The patch passed system tests framework compile.
{noformat}
Javadoc warning has been around and is bogus.  I plan to commit this.

> Remove most of getBlockLocation optimization
> --------------------------------------------
>
>                 Key: HDFS-1353
>                 URL: https://issues.apache.org/jira/browse/HDFS-1353
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node
>    Affects Versions: 0.21.0
>            Reporter: Jakob Homan
>            Assignee: Jakob Homan
>             Fix For: 0.21.1, 0.22.0
>
>         Attachments: Benchmarking results.xlsx, HDFS-1353-y20.patch, HDFS-1353.patch
>
>
> <This description is not valid. See comment.>
> HDFS-1081 optimized the number of block access tokens (BATs) created in a single call
to getBlockLocations, as this is an expensive operation.  However, that JIRA put off another
optimization which was then made possible, which is to just send a single block access token
across the wire (and maintain a single BAT on the client side).  This JIRA is for implementing
that optimization.  Since a single BAT is generated for all the blocks, we just write that
single BAT to the wire, rather than writing n BATs for n blocks, as is currently done.  This
turns out to be a useful optimization for files with very large numbers of blocks, as the
new lone BAT is much larger than was a BAT previously.

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