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https://issues.apache.org/jira/browse/HDFS-12191?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16146411#comment-16146411
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Hudson commented on HDFS-12191:
-------------------------------

SUCCESS: Integrated in Jenkins build Hadoop-trunk-Commit #12267 (See 
[https://builds.apache.org/job/Hadoop-trunk-Commit/12267/])
HDFS-12191. Provide option to not capture the accessTime change of a (yzhang: 
rev cf93d60d3f032000e5b78a08d320793d78799f3d)
* (edit) 
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirAttrOp.java
* (edit) 
hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestFSDirAttrOp.java
* (edit) 
hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestSnapshotDiffReport.java
* (edit) 
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogLoader.java
* (edit) 
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/SnapshotManager.java
* (edit) 
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/INode.java
* (edit) 
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java
* (edit) hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml


> Provide option to not capture the accessTime change of a file to snapshot if 
> no other modification has been done to this file
> -----------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-12191
>                 URL: https://issues.apache.org/jira/browse/HDFS-12191
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: hdfs, namenode
>    Affects Versions: 3.0.0-beta1
>            Reporter: Yongjun Zhang
>            Assignee: Yongjun Zhang
>         Attachments: HDFS-12191.001.patch, HDFS-12191.002.patch, 
> HDFS-12191.003.patch, HDFS-12191.004.patch, HDFS-12191.005.patch
>
>
> Currently, if the accessTime of a file changed before a snapshot is taken, 
> this accessTime will be captured in the snapshot, even if there is no other 
> modifications made to this file.
> Because of this, when we calculate snapshotDiff, more work need to be done 
> for this file, e,g,, metadataEquals method will be called, even if there is 
> no modification is made (thus not recorded to snapshotDiff). This can cause 
> snapshotDiff to slow down quite a lot when there are a lot of files to be 
> examined.
> This jira is to provide an option to skip capturing accessTime only change to 
> snapshot. Thus snapshotDiff can be done faster.
> When accessTime of a file changed, if there is other modification to the 
> file, the access time will still be captured in snapshot.
> Sometimes we want accessTime be captured to snapshot, such that when 
> restoring from the snapshot, we know the accessTime of this snapshot. So this 
> new feature is optional, and is controlled by a config property.
> Worth to mention is, how accurately the acessTime is captured is dependent on 
> the following config that has default value of 1 hour, which means new access 
> within an hour of previous access will not be captured.
> {code}
> public static final String  DFS_NAMENODE_ACCESSTIME_PRECISION_KEY =
>       
> HdfsClientConfigKeys.DeprecatedKeys.DFS_NAMENODE_ACCESSTIME_PRECISION_KEY;
> public static final long    DFS_NAMENODE_ACCESSTIME_PRECISION_DEFAULT = 
> 3600000;
> {code}
> .



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