[jira] [Commented] (SAMZA-1554) Host affinity in standalone.

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SAMZA-1554?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16426435#comment-16426435 ] 

ASF GitHub Bot commented on SAMZA-1554:
---------------------------------------

Github user shanthoosh closed the pull request at:

    https://github.com/apache/samza/pull/448


> Host affinity in standalone.
> ----------------------------
>
>                 Key: SAMZA-1554
>                 URL: https://issues.apache.org/jira/browse/SAMZA-1554
>             Project: Samza
>          Issue Type: New Feature
>            Reporter: Shanthoosh Venkataraman
>            Assignee: Shanthoosh Venkataraman
>            Priority: Major
>
> Samza framework enables its users to build stateful stream processing applications–that is, applications that remember information about past events in a local state(store), which will be then used to influence the processing of future events from the stream. Local state is a fundamental and enabling concept in stream processing which is required and essential to support a majority of common use cases such as stream-stream join, stream-table join, windowing etc.
> Local store of a task instance is backed up by an log compacted kafka topic referred to as change-log. When a task instance commits, incremental local task store updates are flushed to the kafka topic. When a task instance runs on a host that doesn’t have latest local store, it’s restored by replaying messages from the change-log stream. For large stateful jobs, this restoration phase takes longer time, thus preventing the application from starting up and processing events from the input streams. Host affinity is a feature that maintains stickiness between a task and physical host and offers best-effort guarantees that a task instance will be assigned to run on the same physical it had ran before. 
> This tracks the work required to accomplish this feature.



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