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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6698) try to optimize DFSInputStream.getFileLength()
Date Wed, 23 Jul 2014 07:54:39 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6698?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14071472#comment-14071472
] 

Hadoop QA commented on HDFS-6698:
---------------------------------

{color:red}-1 overall{color}.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12657281/HDFS-6698.txt
  against trunk revision .

    {color:green}+1 @author{color}.  The patch does not contain any @author tags.

    {color:red}-1 tests included{color}.  The patch doesn't appear to include any new or modified
tests.
                        Please justify why no new tests are needed for this patch.
                        Also please list what manual steps were performed to verify this patch.

    {color:green}+1 javac{color}.  The applied patch does not increase the total number of
javac compiler warnings.

    {color:green}+1 javadoc{color}.  There were no new javadoc warning messages.

    {color:green}+1 eclipse:eclipse{color}.  The patch built with eclipse:eclipse.

    {color:green}+1 findbugs{color}.  The patch does not introduce any new Findbugs (version
2.0.3) warnings.

    {color:green}+1 release audit{color}.  The applied patch does not increase the total number
of release audit warnings.

    {color:red}-1 core tests{color}.  The patch failed these unit tests in hadoop-hdfs-project/hadoop-hdfs:

                  org.apache.hadoop.hdfs.server.namenode.TestNamenodeCapacityReport
                  org.apache.hadoop.hdfs.server.namenode.ha.TestPipelinesFailover

    {color:green}+1 contrib tests{color}.  The patch passed contrib unit tests.

Test results: https://builds.apache.org/job/PreCommit-HDFS-Build/7433//testReport/
Console output: https://builds.apache.org/job/PreCommit-HDFS-Build/7433//console

This message is automatically generated.

> try to optimize DFSInputStream.getFileLength()
> ----------------------------------------------
>
>                 Key: HDFS-6698
>                 URL: https://issues.apache.org/jira/browse/HDFS-6698
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: hdfs-client
>    Affects Versions: 3.0.0
>            Reporter: Liang Xie
>            Assignee: Liang Xie
>         Attachments: HDFS-6698.txt, HDFS-6698.txt
>
>
> HBase prefers to invoke read() serving scan request, and invoke pread() serving get reqeust.
Because pread() almost holds no lock.
> Let's image there's a read() running, because the definition is:
> {code}
> public synchronized int read
> {code}
> so no other read() request could run concurrently, this is known, but pread() also could
not run...  because:
> {code}
>   public int read(long position, byte[] buffer, int offset, int length)
>     throws IOException {
>     // sanity checks
>     dfsClient.checkOpen();
>     if (closed) {
>       throw new IOException("Stream closed");
>     }
>     failures = 0;
>     long filelen = getFileLength();
> {code}
> the getFileLength() also needs lock.  so we need to figure out a no lock impl for getFileLength()
before HBase multi stream feature done. [~saint.ack@gmail.com]



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