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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-16095) Add priority to TableDescriptor and priority region open thread pool
Date Wed, 20 Jul 2016 05:50:20 GMT

    [ https://issues.apache.org/jira/browse/HBASE-16095?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15385397#comment-15385397
] 

stack commented on HBASE-16095:
-------------------------------

bq. However, one complication with HBASE-16209 or similar solutions is that we do not know
which index regions we will depend on unless we start the recover and compute all the index
updates from the recovered WAL edits from the data table updates and find the regions that
these updates belong to. 

So it is worse than one region depending on another; rather, a whole table has to be up first.

I'd be ok w/ this in branch-1 as a hack to get over support burden imposed by a deployed dodgy
secondary index implementation. I don't think we should commit to branch-2 though. That should
be time enough to get off this misbehavior.

On some user tables being able to be opened before others, won't this always be sloppy when
regionserver-determined? One slow regionserver would for sure mess up any x-server expectation
and put a nail in an index table being up before any data region tries to open.

> 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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