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From "Weiwei Yang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-11886) Ozone : Optimize putKey operation to be async and consensus
Date Fri, 28 Jul 2017 16:49:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-11886?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16105292#comment-16105292
] 

Weiwei Yang commented on HDFS-11886:
------------------------------------

For the record, since HDFS-11984 is resolved. We will need to make sure key creation time
and modification time get updated during {{commit key}} phase, instead of {{creating key}}
phase. A work that needs to keep in mind :).

> Ozone : Optimize putKey operation to be async and consensus
> -----------------------------------------------------------
>
>                 Key: HDFS-11886
>                 URL: https://issues.apache.org/jira/browse/HDFS-11886
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: ozone
>            Reporter: Chen Liang
>            Assignee: Weiwei Yang
>         Attachments: design-notes-putkey.pdf
>
>
> Ozone's putKey operations involve a couple steps:
> 1. KSM calls allocateBlock to SCM, writes this info to KSM's local metastore
> 2. allocatedBlock gets returned to client, client checks to see if container needs to
be created on datanode, if yes, create the container
> 3. writes the data to container.
> it is possible that 1 succeeded, but 2 or 3 failed, in this case there will be an entry
in KSM's local metastore, but the key is actually nowhere to be found. We need to revert 1
is 2 or 3 failed in this case. 
> To resolve this, we need at least two things to be implemented first.
> 1. We need deleteKey() to be added KSM first. 
> 2. We also need container reports to be implemented first such that SCM can track whether
the container is actually added.



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