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https://issues.apache.org/jira/browse/HDFS-2627?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13162017#comment-13162017
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Todd Lipcon commented on HDFS-2627:
-----------------------------------
BTW, this implementation corresponds to section 9.1.2 "solution 2" of the
[design
doc|https://issues.apache.org/jira/secure/attachment/12480489/NameNode+HA_v2_1.pdf].
Instead of using an arbitrary sequence number, we're simply reusing the txnid,
which we already know will be bumped on any successful failover, since the new
active always starts a new log segment.
> HA: determine DN's view of which NN is active based on heartbeat responses
> --------------------------------------------------------------------------
>
> Key: HDFS-2627
> URL: https://issues.apache.org/jira/browse/HDFS-2627
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: data-node, ha, name-node
> Affects Versions: HA branch (HDFS-1623)
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Attachments: hdfs-2627-v1.txt
>
>
> This is the first part of the design described in [this
> comment|https://issues.apache.org/jira/browse/HDFS-1972?focusedCommentId=13160601&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13160601]
> in HDFS-1972. When the DNs start, they should not consider either of the NNs
> in a block pool to be the active one. Rather, the NNs should include their HA
> state as part of the heartbeat response to the DN, and the DN will believe
> whichever NN claims to be active at a higher transaction ID.
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