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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-12107) long running apps may have a huge number of StatisticsData instances under FileSystem
Date Sat, 20 Jun 2015 12:30:00 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-12107?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14594570#comment-14594570
] 

Hadoop QA commented on HADOOP-12107:
------------------------------------

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| (x) *{color:red}-1 overall{color}* |
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|| Vote || Subsystem || Runtime || Comment ||
| {color:blue}0{color} | pre-patch |  16m 26s | Pre-patch trunk compilation is healthy. |
| {color:green}+1{color} | @author |   0m  0s | The patch does not contain any @author tags.
|
| {color:red}-1{color} | tests included |   0m  0s | 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{color} | javac |   7m 29s | There were no new javac warning messages. |
| {color:green}+1{color} | javadoc |   9m 39s | There were no new javadoc warning messages.
|
| {color:green}+1{color} | release audit |   0m 22s | The applied patch does not increase
the total number of release audit warnings. |
| {color:red}-1{color} | checkstyle |   1m  4s | The applied patch generated  1 new checkstyle
issues (total was 142, now 140). |
| {color:green}+1{color} | whitespace |   0m  0s | The patch has no lines that end in whitespace.
|
| {color:green}+1{color} | install |   1m 34s | mvn install still works. |
| {color:green}+1{color} | eclipse:eclipse |   0m 34s | The patch built with eclipse:eclipse.
|
| {color:red}-1{color} | findbugs |   1m 56s | The patch appears to introduce 1 new Findbugs
(version 3.0.0) warnings. |
| {color:green}+1{color} | common tests |  21m 55s | Tests passed in hadoop-common. |
| | |  61m  3s | |
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|| Reason || Tests ||
| FindBugs | module:hadoop-common |
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|| Subsystem || Report/Notes ||
| Patch URL | http://issues.apache.org/jira/secure/attachment/12740755/HADOOP-12107.001.patch
|
| Optional Tests | javadoc javac unit findbugs checkstyle |
| git revision | trunk / 20c03c9 |
| checkstyle |  https://builds.apache.org/job/PreCommit-HADOOP-Build/6997/artifact/patchprocess/diffcheckstylehadoop-common.txt
|
| Findbugs warnings | https://builds.apache.org/job/PreCommit-HADOOP-Build/6997/artifact/patchprocess/newPatchFindbugsWarningshadoop-common.html
|
| hadoop-common test log | https://builds.apache.org/job/PreCommit-HADOOP-Build/6997/artifact/patchprocess/testrun_hadoop-common.txt
|
| Test Results | https://builds.apache.org/job/PreCommit-HADOOP-Build/6997/testReport/ |
| Java | 1.7.0_55 |
| uname | Linux asf909.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-HADOOP-Build/6997/console |


This message was automatically generated.

> long running apps may have a huge number of StatisticsData instances under FileSystem
> -------------------------------------------------------------------------------------
>
>                 Key: HADOOP-12107
>                 URL: https://issues.apache.org/jira/browse/HADOOP-12107
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: fs
>    Affects Versions: 2.7.0
>            Reporter: Sangjin Lee
>            Assignee: Sangjin Lee
>            Priority: Minor
>         Attachments: HADOOP-12107.001.patch
>
>
> We observed with some of our apps (non-mapreduce apps that use filesystems) that they
end up accumulating a huge memory footprint coming from {{FileSystem$Statistics$StatisticsData}}
(in the {{allData}} list of {{Statistics}}).
> Although the thread reference from {{StatisticsData}} is a weak reference, and thus can
get cleared once a thread goes away, the actual {{StatisticsData}} instances in the list won't
get cleared until any of these following methods is called on {{Statistics}}:
> - {{getBytesRead()}}
> - {{getBytesWritten()}}
> - {{getReadOps()}}
> - {{getLargeReadOps()}}
> - {{getWriteOps()}}
> - {{toString()}}
> It is quite possible to have an application that interacts with a filesystem but does
not call any of these methods on the {{Statistics}}. If such an application runs for a long
time and has a large amount of thread churn, the memory footprint will grow significantly.
> The current workaround is either to limit the thread churn or to invoke these operations
occasionally to pare down the memory. However, this is still a deficiency with {{FileSystem$Statistics}}
itself in that the memory is controlled only as a side effect of those operations.



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