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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-8797) WebHdfsFileSystem creates too many connections for pread
Date Wed, 22 Jul 2015 21:20:05 GMT

    [ https://issues.apache.org/jira/browse/HDFS-8797?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14637650#comment-14637650
] 

Hadoop QA commented on HDFS-8797:
---------------------------------

\\
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| (x) *{color:red}-1 overall{color}* |
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|| Vote || Subsystem || Runtime || Comment ||
| {color:blue}0{color} | pre-patch |  18m 37s | Pre-patch trunk compilation is healthy. |
| {color:green}+1{color} | @author |   0m  0s | The patch does not contain any @author tags.
|
| {color:green}+1{color} | tests included |   0m  0s | The patch appears to include 2 new
or modified test files. |
| {color:green}+1{color} | javac |   7m 36s | There were no new javac warning messages. |
| {color:green}+1{color} | javadoc |   9m 36s | There were no new javadoc warning messages.
|
| {color:green}+1{color} | release audit |   0m 23s | The applied patch does not increase
the total number of release audit warnings. |
| {color:red}-1{color} | checkstyle |   2m 33s | The applied patch generated  5 new checkstyle
issues (total was 25, now 30). |
| {color:green}+1{color} | whitespace |   0m  1s | The patch has no lines that end in whitespace.
|
| {color:green}+1{color} | install |   1m 23s | mvn install still works. |
| {color:green}+1{color} | eclipse:eclipse |   0m 33s | The patch built with eclipse:eclipse.
|
| {color:green}+1{color} | findbugs |   4m 22s | The patch does not introduce any new Findbugs
(version 3.0.0) warnings. |
| {color:green}+1{color} | native |   3m  0s | Pre-build of native portion |
| {color:red}-1{color} | hdfs tests | 160m 24s | Tests failed in hadoop-hdfs. |
| {color:green}+1{color} | hdfs tests |   0m 26s | Tests passed in hadoop-hdfs-client. |
| | | 208m 57s | |
\\
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|| Reason || Tests ||
| Failed unit tests | hadoop.hdfs.server.namenode.ha.TestStandbyIsHot |
|   | hadoop.hdfs.TestDistributedFileSystem |
\\
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|| Subsystem || Report/Notes ||
| Patch URL | http://issues.apache.org/jira/secure/attachment/12746589/HDFS-8797.003.patch
|
| Optional Tests | javadoc javac unit findbugs checkstyle |
| git revision | trunk / 4025326 |
| checkstyle |  https://builds.apache.org/job/PreCommit-HDFS-Build/11790/artifact/patchprocess/diffcheckstylehadoop-hdfs-client.txt
|
| hadoop-hdfs test log | https://builds.apache.org/job/PreCommit-HDFS-Build/11790/artifact/patchprocess/testrun_hadoop-hdfs.txt
|
| hadoop-hdfs-client test log | https://builds.apache.org/job/PreCommit-HDFS-Build/11790/artifact/patchprocess/testrun_hadoop-hdfs-client.txt
|
| Test Results | https://builds.apache.org/job/PreCommit-HDFS-Build/11790/testReport/ |
| Java | 1.7.0_55 |
| uname | Linux asf902.gq1.ygridcore.net 3.13.0-36-lowlatency #63-Ubuntu SMP PREEMPT Wed Sep
3 21:56:12 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux |
| Console output | https://builds.apache.org/job/PreCommit-HDFS-Build/11790/console |


This message was automatically generated.

> WebHdfsFileSystem creates too many connections for pread
> --------------------------------------------------------
>
>                 Key: HDFS-8797
>                 URL: https://issues.apache.org/jira/browse/HDFS-8797
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: webhdfs
>            Reporter: Jing Zhao
>            Assignee: Jing Zhao
>         Attachments: HDFS-8797.000.patch, HDFS-8797.001.patch, HDFS-8797.002.patch, HDFS-8797.003.patch
>
>
> While running a test we found that WebHdfsFileSystem can create several thousand connections
when doing a position read of a 200MB file. For each connection the client will connect to
the DataNode again and the DataNode will create a new DFSClient instance to handle the read
request. This also leads to several thousand {{getBlockLocations}} call to the NameNode.
> The cause of the issue is that in {{FSInputStream#read(long, byte[], int, int)}}, each
time the inputstream reads some time, it seeks back to the old position and resets its state
to SEEK. Thus the next read will regenerate the connection.
> {code}
>   public int read(long position, byte[] buffer, int offset, int length)
>     throws IOException {
>     synchronized (this) {
>       long oldPos = getPos();
>       int nread = -1;
>       try {
>         seek(position);
>         nread = read(buffer, offset, length);
>       } finally {
>         seek(oldPos);
>       }
>       return nread;
>     }
>   }
> {code}



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