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https://issues.apache.org/jira/browse/HDFS-9092?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14934434#comment-14934434
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Hadoop QA commented on HDFS-9092:
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| (x) *{color:red}-1 overall{color}* |
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|| Vote || Subsystem || Runtime || Comment ||
| {color:red}-1{color} | pre-patch |  18m 38s | Pre-patch trunk has 1 extant 
Findbugs (version 3.0.0) warnings. |
| {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 1 new or modified test files. |
| {color:green}+1{color} | javac |   7m 57s | There were no new javac warning 
messages. |
| {color:green}+1{color} | javadoc |  10m 23s | There were no new javadoc 
warning messages. |
| {color:red}-1{color} | release audit |   0m 20s | The applied patch generated 
1 release audit warnings. |
| {color:green}+1{color} | checkstyle |   1m 47s | There were no new checkstyle 
issues. |
| {color:red}-1{color} | whitespace |   0m  1s | The patch has 3  line(s) that 
end in whitespace. Use git apply --whitespace=fix. |
| {color:green}+1{color} | install |   1m 30s | mvn install still works. |
| {color:green}+1{color} | eclipse:eclipse |   0m 34s | The patch built with 
eclipse:eclipse. |
| {color:red}-1{color} | findbugs |   3m 23s | The patch appears to introduce 2 
new Findbugs (version 3.0.0) warnings. |
| {color:green}+1{color} | native |   3m 13s | Pre-build of native portion |
| {color:red}-1{color} | hdfs tests | 162m 40s | Tests failed in hadoop-hdfs. |
| {color:green}+1{color} | hdfs tests |   1m 47s | Tests passed in 
hadoop-hdfs-nfs. |
| | | 212m 19s | |
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|| Reason || Tests ||
| FindBugs | module:hadoop-hdfs-nfs |
| Failed unit tests | hadoop.hdfs.server.namenode.TestStartupProgressServlet |
|   | hadoop.hdfs.server.namenode.TestFileTruncate |
|   | hadoop.hdfs.tools.TestDFSAdminWithHA |
|   | hadoop.hdfs.web.TestWebHDFSOAuth2 |
|   | hadoop.hdfs.server.namenode.TestCacheDirectives |
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|| Subsystem || Report/Notes ||
| Patch URL | 
http://issues.apache.org/jira/secure/attachment/12764084/HDFS-9092.002.patch |
| Optional Tests | javadoc javac unit findbugs checkstyle |
| git revision | trunk / e5992ef |
| Pre-patch Findbugs warnings | 
https://builds.apache.org/job/PreCommit-HDFS-Build/12719/artifact/patchprocess/trunkFindbugsWarningshadoop-hdfs.html
 |
| Release Audit | 
https://builds.apache.org/job/PreCommit-HDFS-Build/12719/artifact/patchprocess/patchReleaseAuditProblems.txt
 |
| whitespace | 
https://builds.apache.org/job/PreCommit-HDFS-Build/12719/artifact/patchprocess/whitespace.txt
 |
| Findbugs warnings | 
https://builds.apache.org/job/PreCommit-HDFS-Build/12719/artifact/patchprocess/newPatchFindbugsWarningshadoop-hdfs-nfs.html
 |
| hadoop-hdfs test log | 
https://builds.apache.org/job/PreCommit-HDFS-Build/12719/artifact/patchprocess/testrun_hadoop-hdfs.txt
 |
| hadoop-hdfs-nfs test log | 
https://builds.apache.org/job/PreCommit-HDFS-Build/12719/artifact/patchprocess/testrun_hadoop-hdfs-nfs.txt
 |
| Test Results | 
https://builds.apache.org/job/PreCommit-HDFS-Build/12719/testReport/ |
| Java | 1.7.0_55 |
| uname | Linux asf900.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/12719/console |


This message was automatically generated.

> Nfs silently drops overlapping write requests and causes data copying to fail
> -----------------------------------------------------------------------------
>
>                 Key: HDFS-9092
>                 URL: https://issues.apache.org/jira/browse/HDFS-9092
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: nfs
>    Affects Versions: 2.7.1
>            Reporter: Yongjun Zhang
>            Assignee: Yongjun Zhang
>         Attachments: HDFS-9092.001.patch, HDFS-9092.002.patch
>
>
> When NOT using 'sync' option, the NFS writes may issue the following warning:
> org.apache.hadoop.hdfs.nfs.nfs3.OpenFileCtx: Got an overlapping write 
> (1248751616, 1249677312), nextOffset=1248752400. Silently drop it now
> and the size of data copied via NFS will stay at 1248752400.
> Found what happened is:
> 1. The write requests from client are sent asynchronously. 
> 2. The NFS gateway has handler to handle the incoming requests by creating an 
> internal write request structuire and put it into cache;
> 3. In parallel, a separate thread in NFS gateway takes requests out from the 
> cache and writes the data to HDFS.
> The current offset is how much data has been written by the write thread in 
> 3. The detection of overlapping write request happens in 2, but it only 
> checks the write request against the curent offset, and trim the request if 
> necessary. Because the write requests are sent asynchronously, if two 
> requests are beyond the current offset, and they overlap, it's not detected 
> and both are put into the cache. This cause the symptom reported in this case 
> at step 3.



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