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From "Colin Patrick McCabe (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-9576) HTrace: collect position/length information on read operations
Date Tue, 19 Jan 2016 21:48:39 GMT

    [ https://issues.apache.org/jira/browse/HDFS-9576?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15107522#comment-15107522
] 

Colin Patrick McCabe commented on HDFS-9576:
--------------------------------------------

Thanks, [~zhz].

{code}
993	      int retLen = readWithStrategy(byteBufferReader, 0, buf.remaining());
994	      if (retLen < buf.remaining()) {
995	        dfsClient.addRetLenToReaderScope(scope, retLen);
996	      }
{code}
Hmm.  Isn't buf#remaining going to change between lines 993 and 994?  It seems like this should
be loaded into a variable.

> HTrace: collect position/length information on read operations
> --------------------------------------------------------------
>
>                 Key: HDFS-9576
>                 URL: https://issues.apache.org/jira/browse/HDFS-9576
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: hdfs-client, tracing
>    Affects Versions: 2.7.1
>            Reporter: Zhe Zhang
>            Assignee: Zhe Zhang
>         Attachments: HDFS-9576.00.patch, HDFS-9576.01.patch, HDFS-9576.02.patch, HDFS-9576.03.patch,
HDFS-9576.04.patch, HDFS-9576.05.patch, HDFS-9576.06.patch
>
>
> HTrace currently collects the path of each read operation (both stateful and position
reads). To better understand applications' I/O behavior, it is also useful to track the position
and length of read operations.



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