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https://issues.apache.org/jira/browse/SAMZA-1454?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16219776#comment-16219776
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ASF GitHub Bot commented on SAMZA-1454:
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Github user asfgit closed the pull request at:
https://github.com/apache/samza/pull/324
> Globally unique and user settable IDs for stateful operators
> ------------------------------------------------------------
>
> Key: SAMZA-1454
> URL: https://issues.apache.org/jira/browse/SAMZA-1454
> Project: Samza
> Issue Type: Bug
> Reporter: Prateek Maheshwari
> Assignee: Prateek Maheshwari
> Fix For: 0.14.0
>
>
> Operators in the the High Level API need globally unique IDs so that we can:
> 1. Create intermediate topics (e.g. for partitionBy).
> 2. Create operator state stores and their changelog topics.
> 3. Start processing from particular points in the DAG (multi-stage).
> Ideally, a particular operator's ID should be:
> 1. The same across job restarts with no code changes.
> 2. The same despite functionality preserving changes in topology (e.g.
> splitting a map into two maps).
> 3. Different if the semantics of an operator change without a change in
> topology (e.g. a change in the map function logic).
> 1 is satisfied by a topology based ID, but 2 & 3 are difficult for the
> framework to determine automatically. All three are required to ensure
> correctness of durable intermediate state in the DAG across restarts with
> code changes. In other words, users need to be able handle the following
> scenarios:
> 1. If they make a code change that preserves the topology but changes the
> semantics, they should be able to indicate that the downstream stateful
> operators are now semantically different than before and the previous state
> should be invalidated.
> 2. If they make a code change that changes the topology but preserves the
> semantics, they should be able to indicate that the downstream stateful
> operators are still the same as earlier and the previous state should be
> reused.
> To support these two scenarios, we will allow (and recommend) users to
> provide a custom ID for stateful operators (partitionBy, window and join
> operators) that's unique in the DAG. We will use this ID as part of the name
> for any durable state (streams, stores, changelogs) associated with the
> operator. Whenever users make a code change that changes the topology or
> semantics of the application, they should identify any affected operators
> downstream of the change and change or preserve their operator names
> accordingly.
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