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https://issues.apache.org/jira/browse/HBASE-16095?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15385077#comment-15385077
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Enis Soztutar commented on HBASE-16095:
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bq. We already have priority region opening pool for meta (and closing). This
is another tier? For user tables and/or system tables?
Yes this tear is between meta and regular tables. HBase system table regions
and all regions of tables marked with high priority uses this tier.
> Add priority to TableDescriptor and priority region open thread pool
> --------------------------------------------------------------------
>
> Key: HBASE-16095
> URL: https://issues.apache.org/jira/browse/HBASE-16095
> Project: HBase
> Issue Type: Bug
> Reporter: Enis Soztutar
> Assignee: Enis Soztutar
> Fix For: 2.0.0, 1.3.0, 1.4.0, 0.98.21
>
> Attachments: HBASE-16095-0.98.patch, HBASE-16095-0.98.patch,
> hbase-16095_v0.patch, hbase-16095_v1.patch, hbase-16095_v2.patch,
> hbase-16095_v3.patch
>
>
> This is in the similar area with HBASE-15816, and also required with the
> current secondary indexing for Phoenix.
> The problem with P secondary indexes is that data table regions depend on
> index regions to be able to make progress. Possible distributed deadlocks can
> be prevented via custom RpcScheduler + RpcController configuration via
> HBASE-11048 and PHOENIX-938. However, region opening also has the same
> deadlock situation, because data region open has to replay the WAL edits to
> the index regions. There is only 1 thread pool to open regions with 3 workers
> by default. So if the cluster is recovering / restarting from scratch, the
> deadlock happens because some index regions cannot be opened due to them
> being in the same queue waiting for data regions to open (which waits for
> RPC'ing to index regions which is not open). This is reproduced in almost all
> Phoenix secondary index clusters (mutable table w/o transactions) that we
> see.
> The proposal is to have a "high priority" region opening thread pool, and
> have the HTD carry the relative priority of a table. This maybe useful for
> other "framework" level tables from Phoenix, Tephra, Trafodian, etc if they
> want some specific tables to become online faster.
> As a follow up patch, we can also take a look at how this priority
> information can be used by the rpc scheduler on the server side or rpc
> controller on the client side, so that we do not have to set priorities
> manually per-operation.
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