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https://issues.apache.org/jira/browse/HBASE-810?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12623692#action_12623692
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Jean-Daniel Cryans commented on HBASE-810:
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{quote}
It appears as if a region is splitting, any outstanding scanners either need to
finish scanning the region (blocking the split) or the scanners need to be
notified that a split is going to happen and they need to wait and recalibrate.
{quote}
This is also what I think we should do but like I said on IRC, we don't
currently have a way to communicate from the region server to the scanner.
Suppose the user code did a next() and while processing the info the split
happens (and it will finally try to insert something but won't be able to since
the split is blocking). What we need is an handle to the scanner to tell it to
"close" itself and wait.
> Prevent temporary deadlocks when, during a scan with write operations, the
> region splits
> ----------------------------------------------------------------------------------------
>
> Key: HBASE-810
> URL: https://issues.apache.org/jira/browse/HBASE-810
> Project: Hadoop HBase
> Issue Type: Bug
> Affects Versions: 0.2.0
> Reporter: Jean-Daniel Cryans
> Priority: Blocker
> Fix For: 0.2.1, 0.3.0
>
>
> HBASE-804 was not about the good problem, this one is. Anyone that iterates
> through the results of a scanner and that rewrites data back into the row at
> each iteration will hit a UnknownScannerException if a split occurs. See the
> stack in the referred jira. Timeline :
> Split occurs, acquires a write lock and waits for scanners to finish
> The scanner in the custom code iterates and writes data until the write is
> blocked by the lock
> deadlock
> The scanner timeouts thus the region splits but the USE will be thrown when
> next() is called
> Inside a Map, the task will simply be retried when the first one fails.
> Elsewhere, it becomes more complicated.
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