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https://issues.apache.org/jira/browse/HDFS-5924?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13907748#comment-13907748
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Brandon Li commented on HDFS-5924:
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{quote}This is no worse than the current behavior.{quote}
The application could experience much higher write failure rate during the
datanode upgrade. For example, all datanodes inaccessible in the pipeline is
more possible now. Shutting down a datanode after previous shutdown datanode is
up might be able to minimize the write failure but would increase the total
upgrade time.
Recall there was some discussion that, after datanode sends OOB, its shutdown
can be paused until the client agrees to let it go. I don't remember the reason
why not taking that approach.
> Utilize OOB upgrade message processing for writes
> -------------------------------------------------
>
> Key: HDFS-5924
> URL: https://issues.apache.org/jira/browse/HDFS-5924
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: datanode, ha, hdfs-client, namenode
> Reporter: Kihwal Lee
> Assignee: Kihwal Lee
> Attachments: HDFS-5924_RBW_RECOVERY.patch,
> HDFS-5924_RBW_RECOVERY.patch
>
>
> After HDFS-5585 and HDFS-5583, clients and datanodes can coordinate
> shutdown-restart in order to minimize failures or locality loss.
> In this jira, HDFS client is made aware of the restart OOB ack and perform
> special write pipeline recovery. Datanode is also modified to load marked RBW
> replicas as RBW instead of RWR as long as the restart did not take long.
> For clients, it considers doing this kind of recovery only when there is only
> one node left in the pipeline or the restarting node is a local datanode.
> For both clients and datanodes, the timeout or expiration is configurable,
> meaning this feature can be turned off by setting timeout variables to 0.
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