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From "Hudson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-12130) Optimizing permission check for getContentSummary
Date Fri, 14 Jul 2017 21:00:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-12130?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16088051#comment-16088051

Hudson commented on HDFS-12130:

SUCCESS: Integrated in Jenkins build Hadoop-trunk-Commit #12009 (See [https://builds.apache.org/job/Hadoop-trunk-Commit/12009/])
HDFS-12130. Optimizing permission check for getContentSummary. (szetszwo: rev a29fe100b3c671954b759add5923a2b44af9e6a4)
* (edit) hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/Snapshot.java
* (edit) hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/INodeDirectory.java
* (edit) hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/ContentSummaryComputationContext.java
* (edit) hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/DirectorySnapshottableFeature.java
* (edit) hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockCollection.java
* (edit) hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/DirectoryWithQuotaFeature.java
* (edit) hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirStatAndListingOp.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/server/namenode/snapshot/DirectoryWithSnapshotFeature.java
* (edit) hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSPermissionChecker.java
* (edit) hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/INodeReference.java
* (add) hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestGetContentSummaryWithPermission.java

> Optimizing permission check for getContentSummary
> -------------------------------------------------
>                 Key: HDFS-12130
>                 URL: https://issues.apache.org/jira/browse/HDFS-12130
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: namenode
>            Reporter: Chen Liang
>            Assignee: Chen Liang
>             Fix For: 2.9.0, 3.0.0-beta1
>         Attachments: HDFS-12130.001.patch, HDFS-12130.002.patch, HDFS-12130.003.patch
> Currently, {{getContentSummary}} takes two phases to complete:
> - phase1. check the permission of the entire subtree. If any subdirectory does not have
{{READ_EXECUTE}}, an access control exception is thrown and {{getContentSummary}} terminates
here (unless it's super user).
> - phase2. If phase1 passed, it will then traverse the entire tree recursively to get
the actual content summary.
> An issue is, both phases currently hold the fs lock.
> Phase 2 has already been written that, it will yield the fs lock over time, such that
it does not block other operations for too long. However phase 1 does not yield. Meaning it's
possible that the permission check phase still blocks things for long time.
> One fix is to add lock yield to phase 1. But a simpler fix is to merge phase 1 into phase
2. Namely, instead of doing a full traversal for permission check first, we start with phase
2 directly, but for each directory, before obtaining its summary, check its permission first.
This way we take advantage of existing lock yield in phase 2 code and still able to check
permission and terminate on access exception.
> Thanks [~szetszwo] for the offline discussions!

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