hadoop-hdfs-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-4677) Editlog should support synchronous writes
Date Tue, 21 May 2013 21:20:22 GMT

    [ https://issues.apache.org/jira/browse/HDFS-4677?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13663414#comment-13663414
] 

Hadoop QA commented on HDFS-4677:
---------------------------------

{color:green}+1 overall{color}.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12584057/HDFS-4677.3.patch
  against trunk revision .

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

    {color:green}+1 tests included{color}.  The patch appears to include 6 new or modified
test files.

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

    {color:green}+1 javadoc{color}.  The javadoc tool did not generate any 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
1.3.9) warnings.

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

    {color:green}+1 core tests{color}.  The patch passed unit tests in hadoop-hdfs-project/hadoop-hdfs.

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

Test results: https://builds.apache.org/job/PreCommit-HDFS-Build/4421//testReport/
Console output: https://builds.apache.org/job/PreCommit-HDFS-Build/4421//console

This message is automatically generated.
                
> Editlog should support synchronous writes
> -----------------------------------------
>
>                 Key: HDFS-4677
>                 URL: https://issues.apache.org/jira/browse/HDFS-4677
>             Project: Hadoop HDFS
>          Issue Type: Bug
>    Affects Versions: 3.0.0, 1-win
>            Reporter: Ivan Mitic
>            Assignee: Ivan Mitic
>         Attachments: HDFS-4677.2.patch, HDFS-4677.3.patch, HDFS-4677.patch
>
>
> In the current implementation, NameNode editlog performs syncs to the persistent storage
using the {{FileChannel#force}} Java APIs. This API is documented to be slower compared to
an alternative where {{RandomAccessFile}} is opened with "rws" flags (synchronous writes).

> We instrumented {{FileChannel#force}} on Windows and it some software/hardware configurations
it can perform significantly slower than the “rws” alternative.
> In terms of the Windows APIs, FileChannel#force internally calls [FlushFileBuffers|http://msdn.microsoft.com/en-us/library/windows/desktop/aa364439(v=vs.85).aspx]
while RandomAccessFile (“rws”) opens the file with the [FILE_FLAG_WRITE_THROUGH flag|http://support.microsoft.com/kb/99794].

> With this Jira I'd like to introduce a flag that provide means to configure NameNode
to use synchronous writes. There is a catch though, the behavior of the "rws" flags is platform
and hardware specific and might not provide the same level of guarantees as {{FileChannel#force}}
w.r.t. flushing the on-disk cache. This is an expert level setting, and it should be documented
as such.

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira

Mime
View raw message