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https://issues.apache.org/jira/browse/IGNITE-18060?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Kirill Gusakov updated IGNITE-18060:
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Attachment: rebalance_redesign.md
> Prepare design and tickets breakdown for rebalance over replicas
> ----------------------------------------------------------------
>
> Key: IGNITE-18060
> URL: https://issues.apache.org/jira/browse/IGNITE-18060
> Project: Ignite
> Issue Type: New Feature
> Reporter: Alexander Lapin
> Assignee: Kirill Gusakov
> Priority: Major
> Labels: ignite-3
> Attachments: rebalance_redesign.md
>
>
> h3. Motivation
> Current rebalance design specified in
> {code:java}
> ignite-3/modules/table/tech-notes/rebalance.md {code}
> is a bit complicated. The good news is that it can be simplified using the
> following mechanics:
> * Meta storage over learners, meaning that every cluster node will have meta
> storage locally.
> * Rebalance over replicas, meaning that there will be useful abstraction of
> (at most) single actor in replication group, better known as primary replica.
> * Meta storage over version values, meaning that it'll be possible to
> eliminate the requirement of single-threaded meta storage watch, that, among
> other things, will also eliminate watch-redeployment procedure.
> All in all, given ticket is only about over replicas part. So, it's required
> to prototype and design new rebalance algorithm on top of at most single
> actor invariant. Among the key potential difficulties, I would highlight the
> following set:
> * Stale triggers. Primary replica that manages rebalance could still be
> notified about stale updates, that will required ms invokes over trigger
> revision.
> * It's required to take into consideration in-memory replicas switch logic.
> h3. Definition of Done
> * Either new design along with tickets breakdown for rebalance over replicas
> (at most single actor) is ready or list of substantial arguments that the use
> of replicas does not simplify the rebalancing algorithm is provided.
> * Proposed replica based logic should be simple, it's not worth to waste
> time for micro enhancements. In that case we should consider system table as
> an alternative.
> * Thus high level design of rebalance over system table is also expected.
> All in all we should compare whether it's easier to have (ms based, replica
> based) approach or implement system tables and build rebalance logic on top
> of it.
>
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