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From "Konstantin Shvachko (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-10843) Quota Feature Cached Size != Computed Size When Block Committed But Not Completed
Date Fri, 09 Sep 2016 01:02:20 GMT

    [ https://issues.apache.org/jira/browse/HDFS-10843?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15475512#comment-15475512

Konstantin Shvachko commented on HDFS-10843:

Hey Erik, looks like you are fixing two issues here. One about updating space cache value
after completing the block, and another that {{setReplication()}} incorrectly updates space
for UC files. Both good finds, great!
# Your idea to place space update logic in a single place, inside {{completeBlock()}}, is
good. I would suggest implementing it a bit differently. I would move the part of {{FSN.commitOrCompleteLastBlock()}}
related to {{// Adjust disk space consumption if required}} to {{FSDirectory}} as a new method
{{adjustSpaceConsumed(fileINode, iip, commitBlock)}}. Then you can call it from {{completeBlock()}},
which should take {{FSDirectory}} as a parameter. Better not to change {{Namespace}} interface.
# The tests looks good. I see you shutting down 3 DNs in the new test. Which may affect old
tests if they are executed after the new ones. I did not check but worth verifying.
# Also {{Answer}} should be used with a generic parameter {{Answer<Object>}}.

> Quota Feature Cached Size != Computed Size When Block Committed But Not Completed
> ---------------------------------------------------------------------------------
>                 Key: HDFS-10843
>                 URL: https://issues.apache.org/jira/browse/HDFS-10843
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: hdfs, namenode
>    Affects Versions: 2.6.0
>            Reporter: Erik Krogen
>            Assignee: Erik Krogen
>         Attachments: HDFS-10843.000.patch, HDFS-10843.001.patch
> Currently when a block has been committed but has not yet been completed, the cached
size (used for the quota feature) of the directory containing that block differs from the
computed size. This results in log messages of the following form:
> bq. ERROR namenode.NameNode (DirectoryWithQuotaFeature.java:checkStoragespace(141)) -
BUG: Inconsistent storagespace for directory /TestQuotaUpdate. Cached = 512 != Computed =
> When a block is initially started under construction, the used space is conservatively
set to a full block. When the block is committed, the cached size is updated to the final
size of the block. However, the calculation of the computed size uses the full block size
until the block is completed, so in the period where the block is committed but not completed
they disagree. To fix this we need to decide which is correct and fix the other to match.
It seems to me that the cached size is correct since once the block is committed its size
will not change. 
> This can be reproduced using the following steps:
> - Create a directory with a quota
> - Start writing to a file within this directory
> - Prevent all datanodes to which the file is written from communicating the corresponding
BlockReceivedAndDeletedRequestProto to the NN temporarily (i.e. simulate a transient network
> - During this time, call DistributedFileSystem.getContentSummary() on the directory with
the quota

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