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https://issues.apache.org/jira/browse/HDFS-1994?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Todd Lipcon resolved HDFS-1994.
-------------------------------
Resolution: Fixed
Hadoop Flags: [Reviewed]
Fixed the nits and committed to branch.
Unfortunately Mockito doesn't provide that Answer implementation, but I based
that implementation on a suggestion I found on the Mockito bugtracker.
> Fix race conditions when running two rapidly checkpointing 2NNs
> ---------------------------------------------------------------
>
> Key: HDFS-1994
> URL: https://issues.apache.org/jira/browse/HDFS-1994
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: name-node
> Affects Versions: Edit log branch (HDFS-1073)
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Fix For: Edit log branch (HDFS-1073)
>
> Attachments: hdfs-1994.txt, hdfs-1994.txt
>
>
> HDFS-1984 added the ability to run two secondary namenodes at the same time.
> However, there were two races I found when stress testing this (by running
> two NNs each checkpointing in a tight loop with no sleep):
> 1) the writing of the seen_txid file was not atomic, so it was at some points
> reading an empty file
> 2) it was possible for two checkpointers to try to take a checkpoint at the
> same transaction ID, which would cause the two image downloads to collide and
> fail
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