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https://issues.apache.org/jira/browse/SOLR-15052?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17250298#comment-17250298
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Ishan Chattopadhyaya commented on SOLR-15052:
---------------------------------------------

bq. Have you considered placing the children in a new replica_states znode 
instead of using the state.json znode?
Yes, we did discuss it internally. We decided to go with current approach to 
minimize code changes. Conceptually, there's no difference between both 
approaches.

> Reducing overseer bottlenecks using per-replica states
> ------------------------------------------------------
>
>                 Key: SOLR-15052
>                 URL: https://issues.apache.org/jira/browse/SOLR-15052
>             Project: Solr
>          Issue Type: Bug
>      Security Level: Public(Default Security Level. Issues are Public) 
>            Reporter: Ishan Chattopadhyaya
>            Priority: Major
>         Attachments: per-replica-states-gcp.pdf
>
>          Time Spent: 20m
>  Remaining Estimate: 0h
>
> This work has the same goal as SOLR-13951, that is to reduce overseer 
> bottlenecks by avoiding replica state updates from going to the state.json 
> via the overseer. However, the approach taken here is different from 
> SOLR-13951 and hence this work supercedes that work.
> The design proposed is here: 
> https://docs.google.com/document/d/1xdxpzUNmTZbk0vTMZqfen9R3ArdHokLITdiISBxCFUg/edit
> Briefly,
> # Every replica's state will be in a separate znode nested under the 
> state.json. It has the name that encodes the replica name, state, leadership 
> status.
> # An additional children watcher to be set on state.json for state changes.
> # Upon a state change, a ZK multi-op to delete the previous znode and add a 
> new znode with new state.
> Differences between this and SOLR-13951,
> # In SOLR-13951, we planned to leverage shard terms for per shard states.
> # As a consequence, the code changes required for SOLR-13951 were massive (we 
> needed a shard state provider abstraction and introduce it everywhere in the 
> codebase).
> # This approach is a drastically simpler change and design.
> Credits for this design and the PR is due to [~noble.paul]. 
> [~markrmil...@gmail.com], [~noble.paul] and I have collaborated on this 
> effort. The reference branch takes a conceptually similar (but not identical) 
> approach.
> I shall attach a PR and performance benchmarks shortly.



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