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From "Tao Jie (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-15918) Namenode gets stuck when deleting large dir in trash
Date Fri, 09 Nov 2018 09:09:01 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-15918?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16681108#comment-16681108

Tao Jie commented on HADOOP-15918:

[~jojochuang] Thank you for your comments.
I updated the patch and moved this jira issue to HADOOP-COMMON.
I am still not satisfied with FileSystem#contentSummary(). The closest I could find is FileSystem#getQuotaUsage()
which would return number of objects in a directory. but quota is not enabled by default.
It is true that {{getContentSummary()}} is a heavy method in namenode since it will compute
usage of subdirs recursively while {{getQuotaUsage()}} just fetch usage information in  {{DirectoryWithQuotaFeature}}
of inode. However in the implementation of {{getContentSummary()}}, it will also get namespace
usage from {{DirectoryWithQuotaFeature}} in inode directly once its quota is set. So the performance
of {{getContentSummary()}} is not worse than {{getQuotaUsage()}}  approximately.

> Namenode gets stuck when deleting large dir in trash
> ----------------------------------------------------
>                 Key: HADOOP-15918
>                 URL: https://issues.apache.org/jira/browse/HADOOP-15918
>             Project: Hadoop Common
>          Issue Type: Improvement
>    Affects Versions: 2.8.2, 3.1.0
>            Reporter: Tao Jie
>            Assignee: Tao Jie
>            Priority: Major
>         Attachments: HADOOP-15918.001.patch, HDFS-13769.001.patch, HDFS-13769.002.patch,
HDFS-13769.003.patch, HDFS-13769.004.patch
> Similar to the situation discussed in HDFS-13671, Namenode gets stuck for a long time
when deleting trash dir with a large mount of data. We found log in namenode:
> {quote}
> 2018-06-08 20:00:59,042 INFO namenode.FSNamesystem (FSNamesystemLock.java:writeUnlock(252))
- FSNamesystem write lock held for 23018 ms via
> java.lang.Thread.getStackTrace(Thread.java:1552)
> org.apache.hadoop.util.StringUtils.getStackTrace(StringUtils.java:1033)
> org.apache.hadoop.hdfs.server.namenode.FSNamesystemLock.writeUnlock(FSNamesystemLock.java:254)
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.writeUnlock(FSNamesystem.java:1567)
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.delete(FSNamesystem.java:2820)
> org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.delete(NameNodeRpcServer.java:1047)
> {quote}
> One simple solution is to avoid deleting large data in one delete RPC call. We implement
a trashPolicy that divide the delete operation into several delete RPCs, and each single deletion
would not delete too many files.
> Any thought? [~linyiqun]

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