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https://issues.apache.org/jira/browse/HDFS-5924?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13907471#comment-13907471
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Brandon Li commented on HDFS-5924:
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{quote}This feature does not guarantee all client writes to continue across
restart. {quote}
Would it cause data loss? especially when the only one or more than one
datanode in the pipeline is shutting down for upgrade.
> 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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