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From "Ted Yu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-15001) Thread Safety issues in ReplicationSinkManager and HBaseInterClusterReplicationEndpoint
Date Thu, 17 Dec 2015 22:04:46 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15001?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15062937#comment-15062937

Ted Yu commented on HBASE-15001:

263	          LOG.warn("The number of edits replicated is different from the number received,"
264	              + " failing for now.");
Please note the two numbers in the above message so that the log is more useful for debugging.

Is it possible to reproduce, in a unit test, the race you outlined ?


> Thread Safety issues in ReplicationSinkManager and HBaseInterClusterReplicationEndpoint
> ---------------------------------------------------------------------------------------
>                 Key: HBASE-15001
>                 URL: https://issues.apache.org/jira/browse/HBASE-15001
>             Project: HBase
>          Issue Type: Bug
>          Components: Replication
>    Affects Versions: 2.0.0, 1.2.0, 1.3.0, 1.2.1
>            Reporter: Ashu Pachauri
>            Assignee: Ashu Pachauri
>            Priority: Critical
>         Attachments: HBASE-15001-V0.patch
> ReplicationSinkManager is not thread-safe. This can cause problems in HBaseInterClusterReplicationEndpoint,
 when the walprovider is multiwal. 
> For example: 
> 1. When multiple threads report bad sinks, the sink list can be non-empty but report
a negative size because the ArrayList itself is not thread-safe. 
> 2. HBaseInterClusterReplicationEndpoint depends on the number of sinks to batch edits
for shipping. However, it's quite possible that the following code makes it assume that there
are no batches to process (sink size is non-zero, but by the time we reach the "batching"
part, sink size becomes zero.)
> {code}
> if (replicationSinkMgr.getSinks().size() == 0) {
>     return false;
> }
> ...
> int n = Math.min(Math.min(this.maxThreads, entries.size()/100+1),
>                replicationSinkMgr.getSinks().size());
> {code}
> This is very dangerous, because, (incorrectly) assuming no batches to process based on
value of n, we can safely report that we replicated successfully, while we actually did not
replicate anything. 
> The idea is to make all operations in ReplicationSinkManager thread-safe and do a verification
on the size of replicated edits before we report success.

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