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https://issues.apache.org/jira/browse/TEZ-1867?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14254147#comment-14254147
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Bikas Saha commented on TEZ-1867:
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There is no need for a DrainDispatcher because the sending entities still use
the Dispatcher interface and so the real impl does not matter for them. The
DrainDispatcher is meant for unit tests and the existing one from YARN is fine.
I will add a check the the same event is not present in both kinds of handling.
We should not be depending on any ordering in the processing of events other
than the sending order for the same entity. ie. if entity A sends events (1 and
then 2) to entity B then entity B should see the events in the same order (1
and then 2). Events from other entities B or to other entities C should not
depend on ordering relative to other components. If we have such cases then we
should fix them as they come up after we move all event processing off the
central dispatcher. The design is expected to be decoupled but the current
single thread model may have led to inadvertent ordering behavior. We should
work our way out of this in 0.7.
> Create new central dispatcher for Tez AM
> ----------------------------------------
>
> Key: TEZ-1867
> URL: https://issues.apache.org/jira/browse/TEZ-1867
> Project: Apache Tez
> Issue Type: Improvement
> Reporter: Bikas Saha
> Assignee: Bikas Saha
> Attachments: TEZ-1867.1.patch
>
>
> The dispatcher should be able to federate events across multiple event
> specific dispatchers for AM control plane scalability. Add dispatcher
> specific thread names for easier debugging.
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