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From "Jakob Homan (JIRA)" <j...@apache.org>
Subject [jira] Created: (HDFS-1353) Optimize number of block access tokens returned by getBlockLocations
Date Wed, 25 Aug 2010 00:37:18 GMT
Optimize number of block access tokens returned by getBlockLocations
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                 Key: HDFS-1353
                 URL: https://issues.apache.org/jira/browse/HDFS-1353
             Project: Hadoop HDFS
          Issue Type: Improvement
          Components: name-node
    Affects Versions: 0.22.0
            Reporter: Jakob Homan
            Assignee: Jakob Homan
             Fix For: 0.22.0


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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