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Date: Wed, 11 Mar 2015 22:36:40 +0000 (UTC)
From: "Jing Zhao (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.12757448.1416848953000.69112.1426113400122@Atlassian.JIRA>
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 <JIRA.12757448.1416848953730@arcas>
Subject: [jira] [Commented] (HDFS-7435) PB encoding of block reports is very
 inefficient
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    [ https://issues.apache.org/jira/browse/HDFS-7435?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14357734#comment-14357734 ] 

Jing Zhao commented on HDFS-7435:
---------------------------------

nit-pick:
# s/blocksBuffer/blocksBuf/ in the javadoc
{code}
  /**
   * Prepare an instance to in-place decode the given ByteString buffer
   * @param numBlocks - blocks in the buffer
   * @param blocksBuffer - ByteString encoded varints
   * @return BlockListAsLongs
   */
  public static BlockListAsLongs decodeBuffer(final int numBlocks,
      final ByteString blocksBuf) {
    return new BufferDecoder(numBlocks, blocksBuf);
  }
{code}

+1 after fixing it.

> PB encoding of block reports is very inefficient
> ------------------------------------------------
>
>                 Key: HDFS-7435
>                 URL: https://issues.apache.org/jira/browse/HDFS-7435
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: datanode, namenode
>    Affects Versions: 2.0.0-alpha, 3.0.0
>            Reporter: Daryn Sharp
>            Assignee: Daryn Sharp
>            Priority: Critical
>         Attachments: HDFS-7435.000.patch, HDFS-7435.001.patch, HDFS-7435.002.patch, HDFS-7435.patch, HDFS-7435.patch, HDFS-7435.patch, HDFS-7435.patch, HDFS-7435.patch, HDFS-7435.patch, HDFS-7435.patch, HDFS-7435.patch
>
>
> Block reports are encoded as a PB repeating long.  Repeating fields use an {{ArrayList}} with default capacity of 10.  A block report containing tens or hundreds of thousand of longs (3 for each replica) is extremely expensive since the {{ArrayList}} must realloc many times.  Also, decoding repeating fields will box the primitive longs which must then be unboxed.


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