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From "Ashu Pachauri (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-16138) Cannot open regions after non-graceful shutdown due to deadlock with Replication Table
Date Wed, 29 Jun 2016 21:30:11 GMT

    [ https://issues.apache.org/jira/browse/HBASE-16138?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15355826#comment-15355826
] 

Ashu Pachauri commented on HBASE-16138:
---------------------------------------

1. It does not seem tidy, we are anyway looking to get rid of this and will come with it's
own set of complications and bugs.
2. Sounds like a good option. We can have TableBasedGroupingProvider which basically extends
RegionGroupingProvider, always opens at least two WALs, one for system tables and other(s)
based on number of WAL groups the admin specifies. Another idea is to have one WAL group for
tables that need replication and other for ones that don't. Our current WAL mechanism is not
very intelligent as far as replication is concerned. WALEntryFilter is a suboptimal way of
solving the issue of not even reading WALs in ReplicationSource for Tables/CFs you don't need
to replicate.
3. I think it can potentially cause data loss in replication.

> Cannot open regions after non-graceful shutdown due to deadlock with Replication Table
> --------------------------------------------------------------------------------------
>
>                 Key: HBASE-16138
>                 URL: https://issues.apache.org/jira/browse/HBASE-16138
>             Project: HBase
>          Issue Type: Sub-task
>          Components: Replication
>            Reporter: Joseph
>            Assignee: Joseph
>            Priority: Critical
>
> If we shutdown an entire HBase cluster and attempt to start it back up, we have to run
the WAL pre-log roll that occurs before opening up a region. Yet this pre-log roll must record
the new WAL inside of ReplicationQueues. This method call ends up blocking on TableBasedReplicationQueues.getOrBlockOnReplicationTable(),
because the Replication Table is not up yet. And we cannot assign the Replication Table because
we cannot open any regions. This ends up deadlocking the entire cluster whenever we lose Replication
Table availability. 
> There are a few options that we can do, but none of them seem very good:
> 1. Depend on Zookeeper-based Replication until the Replication Table becomes available
> 2. Have a separate WAL for System Tables that does not perform any replication (see discussion
 at HBASE-14623)
> 3. Record the WAL log in the ReplicationQueue asynchronously (don't block opening a region
on this event), which could lead to inconsistent Replication state
> The stacktrace:
>         org.apache.hadoop.hbase.replication.regionserver.ReplicationSourceManager.recordLog(ReplicationSourceManager.java:376)
>         org.apache.hadoop.hbase.replication.regionserver.ReplicationSourceManager.preLogRoll(ReplicationSourceManager.java:348)
>         org.apache.hadoop.hbase.replication.regionserver.Replication.preLogRoll(Replication.java:370)
>         org.apache.hadoop.hbase.regionserver.wal.FSHLog.tellListenersAboutPreLogRoll(FSHLog.java:637)
>         org.apache.hadoop.hbase.regionserver.wal.FSHLog.rollWriter(FSHLog.java:701)
>         org.apache.hadoop.hbase.regionserver.wal.FSHLog.rollWriter(FSHLog.java:600)
>         org.apache.hadoop.hbase.regionserver.wal.FSHLog.<init>(FSHLog.java:533)
>         org.apache.hadoop.hbase.wal.DefaultWALProvider.getWAL(DefaultWALProvider.java:132)
>         org.apache.hadoop.hbase.wal.RegionGroupingProvider.getWAL(RegionGroupingProvider.java:186)
>         org.apache.hadoop.hbase.wal.RegionGroupingProvider.getWAL(RegionGroupingProvider.java:197)
>         org.apache.hadoop.hbase.wal.WALFactory.getWAL(WALFactory.java:240)
>         org.apache.hadoop.hbase.regionserver.HRegionServer.getWAL(HRegionServer.java:1883)
>         org.apache.hadoop.hbase.regionserver.handler.OpenRegionHandler.openRegion(OpenRegionHandler.java:363)
>         org.apache.hadoop.hbase.regionserver.handler.OpenRegionHandler.process(OpenRegionHandler.java:129)
>         org.apache.hadoop.hbase.executor.EventHandler.run(EventHandler.java:129)
>         java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
>         java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
>         java.lang.Thread.run(Thread.java:745)
> Does anyone have any suggestions/ideas/feedback?



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