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Date: Tue, 7 Jul 2015 21:22:04 +0000 (UTC)
From: "Hadoop QA (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.12843246.1436291037000.122686.1436304124943@Atlassian.JIRA>
In-Reply-To: <JIRA.12843246.1436291037000@Atlassian.JIRA>
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 <JIRA.12843246.1436291037361@arcas>
Subject: [jira] [Commented] (HDFS-8722) Optimize datanode writes for small
 writes and flushes
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    [ https://issues.apache.org/jira/browse/HDFS-8722?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14617447#comment-14617447 ] 

Hadoop QA commented on HDFS-8722:
---------------------------------

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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 21s | 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: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 47s | There were no new javac warning messages. |
| {color:green}+1{color} | javadoc |   9m 44s | There were no new javadoc warning messages. |
| {color:green}+1{color} | release audit |   0m 25s | The applied patch does not increase the total number of release audit warnings. |
| {color:red}-1{color} | checkstyle |   2m 17s | The applied patch generated  1 new checkstyle issues (total was 60, now 60). |
| {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:green}+1{color} | findbugs |   3m 21s | The patch does not introduce any new Findbugs (version 3.0.0) warnings. |
| {color:green}+1{color} | native |   3m 21s | Pre-build of native portion |
| {color:red}-1{color} | hdfs tests | 162m 34s | Tests failed in hadoop-hdfs. |
| | | 210m  3s | |
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|| Reason || Tests ||
| Failed unit tests | hadoop.hdfs.TestFileAppend4 |
|   | hadoop.hdfs.server.namenode.snapshot.TestSnapshotFileLength |
|   | hadoop.hdfs.TestAppendSnapshotTruncate |
|   | hadoop.hdfs.TestEncryptedTransfer |
|   | hadoop.hdfs.TestFileAppend2 |
|   | hadoop.hdfs.TestGetFileChecksum |
|   | hadoop.hdfs.server.namenode.ha.TestDNFencing |
|   | hadoop.hdfs.TestDataTransferProtocol |
|   | hadoop.hdfs.web.TestWebHdfsFileSystemContract |
|   | hadoop.hdfs.TestFileAppend |
|   | hadoop.hdfs.server.namenode.TestLargeDirectoryDelete |
|   | hadoop.hdfs.server.namenode.TestFileTruncate |
|   | hadoop.hdfs.server.blockmanagement.TestBlockTokenWithDFS |
|   | hadoop.hdfs.web.TestWebHdfsWithMultipleNameNodes |
|   | hadoop.hdfs.TestAppendDifferentChecksum |
|   | hadoop.hdfs.TestHDFSFileSystemContract |
|   | hadoop.hdfs.TestFileAppend3 |
|   | hadoop.hdfs.server.namenode.ha.TestHAAppend |
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|| Subsystem || Report/Notes ||
| Patch URL | http://issues.apache.org/jira/secure/attachment/12744005/HDFS-8722.patch |
| Optional Tests | javadoc javac unit findbugs checkstyle |
| git revision | trunk / 7e2fe8c |
| Pre-patch Findbugs warnings | https://builds.apache.org/job/PreCommit-HDFS-Build/11605/artifact/patchprocess/trunkFindbugsWarningshadoop-hdfs.html |
| checkstyle |  https://builds.apache.org/job/PreCommit-HDFS-Build/11605/artifact/patchprocess/diffcheckstylehadoop-hdfs.txt |
| hadoop-hdfs test log | https://builds.apache.org/job/PreCommit-HDFS-Build/11605/artifact/patchprocess/testrun_hadoop-hdfs.txt |
| Test Results | https://builds.apache.org/job/PreCommit-HDFS-Build/11605/testReport/ |
| Java | 1.7.0_55 |
| uname | Linux asf903.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/11605/console |


This message was automatically generated.

> Optimize datanode writes for small writes and flushes
> -----------------------------------------------------
>
>                 Key: HDFS-8722
>                 URL: https://issues.apache.org/jira/browse/HDFS-8722
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>            Reporter: Kihwal Lee
>            Assignee: Kihwal Lee
>            Priority: Critical
>         Attachments: HDFS-8722.patch
>
>
> After the data corruption fix by HDFS-4660, the CRC recalculation for partial chunk is executed more frequently, if the client repeats writing few bytes and calling hflush/hsync.  This is because the generic logic forces CRC recalculation if on-disk data is not CRC chunk aligned. Prior to HDFS-4660, datanode blindly accepted whatever CRC client provided, if the incoming data is chunk-aligned. This was the source of the corruption.
> We can still optimize for the most common case where a client is repeatedly writing small number of bytes followed by hflush/hsync with no pipeline recovery or append, by allowing the previous behavior for this specific case.  If the incoming data has a duplicate portion and that is at the last chunk-boundary before the partial chunk on disk, datanode can use the checksum supplied by the client without redoing the checksum on its own.  This reduces disk reads as well as CPU load for the checksum calculation.
> If the incoming packet data goes back further than the last on-disk chunk boundary, datanode will still do a recalculation, but this occurs rarely during pipeline recoveries. Thus the optimization for this specific case should be sufficient to speed up the vast majority of cases.


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