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https://issues.apache.org/jira/browse/PHOENIX-3072?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15474982#comment-15474982
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Lars Hofhansl commented on PHOENIX-3072:
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[~enis], [~jamestaylor], where are we with this? Push to 4.8.2?
> Deadlock on region opening with secondary index recovery
> --------------------------------------------------------
>
> Key: PHOENIX-3072
> URL: https://issues.apache.org/jira/browse/PHOENIX-3072
> Project: Phoenix
> Issue Type: Bug
> Reporter: Enis Soztutar
> Assignee: Enis Soztutar
> Fix For: 4.9.0, 4.8.1
>
> Attachments: phoenix-3072_v1.patch
>
>
> There is a distributed deadlock happening in clusters with some moderate
> number of regions for the data tables and secondary index tables and cluster
> and it is cluster restart or some large failure. We have seen this in a
> couple of production cases already.
> Opening of regions in hbase is performed by a thread pool with 3 threads by
> default. Every regionserver can open 3 regions at a time. However, opening
> data table regions has to write to multiple index regions during WAL
> recovery. All other region open requests are queued up in a single queue.
> This causes a deadlock, since the secondary index regions are also opened by
> the same thread pools that we do the work. So if there is greater number of
> data table regions then available number of region opening threads from
> regionservers, the secondary index region open requests just wait to be
> processed in the queue. Since these index regions are not open, the region
> opening of data table regions just block the region opening threads for a
> long time.
> One proposed fix is to use a different thread pool for opening regions of the
> secondary index tables so that we will not deadlock. See HBASE-16095 for the
> HBase-level fix. In Phoenix, we just have to set the priority for secondary
> index tables.
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