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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-11280) Allow WebHDFS to reuse HTTP connections to NN
Date Tue, 03 Jan 2017 21:59:58 GMT

    [ https://issues.apache.org/jira/browse/HDFS-11280?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15796310#comment-15796310
] 

Hadoop QA commented on HDFS-11280:
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| (x) *{color:red}-1 overall{color}* |
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|| Vote || Subsystem || Runtime || Comment ||
| {color:blue}0{color} | {color:blue} reexec {color} | {color:blue}  0m  0s{color} | {color:blue}
Docker mode activated. {color} |
| {color:red}-1{color} | {color:red} patch {color} | {color:red}  0m  5s{color} | {color:red}
HDFS-11280 does not apply to trunk. Rebase required? Wrong Branch? See https://wiki.apache.org/hadoop/HowToContribute
for help. {color} |
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|| Subsystem || Report/Notes ||
| JIRA Issue | HDFS-11280 |
| JIRA Patch URL | https://issues.apache.org/jira/secure/attachment/12845434/HDFS-11280.for.2.7.and.below.patch
|
| Console output | https://builds.apache.org/job/PreCommit-HDFS-Build/18009/console |
| Powered by | Apache Yetus 0.5.0-SNAPSHOT   http://yetus.apache.org |


This message was automatically generated.



> Allow WebHDFS to reuse HTTP connections to NN
> ---------------------------------------------
>
>                 Key: HDFS-11280
>                 URL: https://issues.apache.org/jira/browse/HDFS-11280
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: hdfs
>    Affects Versions: 2.7.3, 2.6.5, 3.0.0-alpha1
>            Reporter: Zheng Shao
>            Assignee: Zheng Shao
>         Attachments: HDFS-11280.for.2.7.and.below.patch, HDFS-11280.for.2.7.and.below.patch,
HDFS-11280.for.2.8.and.beyond.2.patch, HDFS-11280.for.2.8.and.beyond.3.patch, HDFS-11280.for.2.8.and.beyond.4.patch,
HDFS-11280.for.2.8.and.beyond.patch
>
>
> WebHDFSClient calls "conn.disconnect()", which disconnects from the NameNode.  When we
use webhdfs as the source in distcp, this used up all ephemeral ports on the client side since
all closed connections continue to occupy the port with TIME_WAIT status for some time.
> According to http://tinyurl.com/java7-http-keepalive, we should call conn.getInputStream().close()
instead to make sure the connection is kept alive.  This will get rid of the ephemeral port
problem.
> Manual steps used to verify the bug fix:
> 1. Build original hadoop jar.
> 2. Try out distcp from webhdfs as source, and "netstat -n | grep TIME_WAIT | grep -c
50070" on the local machine shows a big number (100s).
> 3. Build hadoop jar with this diff.
> 4. Try out distcp from webhdfs as source, and "netstat -n | grep TIME_WAIT | grep -c
50070" on the local machine shows 0.
> 5. The explanation:  distcp's client side does a lot of directory scanning, which would
create and close a lot of connections to the namenode HTTP port.
> Reference:
> 2.7 and below: https://github.com/apache/hadoop/blob/branch-2.6/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/web/WebHdfsFileSystem.java#L743
> 2.8 and above: https://github.com/apache/hadoop/blob/branch-2.8/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/web/WebHdfsFileSystem.java#L898



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