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https://issues.apache.org/jira/browse/HDFS-2692?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13171377#comment-13171377
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Todd Lipcon commented on HDFS-2692:
-----------------------------------
Here's an explanation of the assertion failure - I'm able to trigger it
reliably from a test now:
- Namespace image exists with 1 block
- Active NN has some more blocks that have been written recently in an
in-progress edit log
- NN starts up in standby mode and reads the image during the normal startup.
It sets the safemode threshold to 1
- It receives block reports, but they are delayed because the highest gen-stamp
in the BR is higher than the GS from the namespace
- Active NN rolls edit log
- edit log tailer rolls forward edits, sees the file creations, and allows the
block reports through. The block reports call {{incrementSafeBlocks}} for each
of the blocks in the NS.
This causes an assertion failure because the number of safe blocks is greater
than the number of blocks indicated in SafeModeInfo during startup.
Trying to figure out the cleanest way to deal with this issue.
> HA: Bugs related to failover from/into safe-mode
> ------------------------------------------------
>
> Key: HDFS-2692
> URL: https://issues.apache.org/jira/browse/HDFS-2692
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: ha, name-node
> Affects Versions: HA branch (HDFS-1623)
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Priority: Critical
>
> In testing I saw an AssertionError come up several times when I was trying to
> do failover between two NNs where one or the other was in safe-mode. Need to
> write some unit tests to try to trigger this -- hunch is it has something to
> do with the treatment of "safe block count" while tailing edits in safemode.
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