[jira] [Commented] (IGNITE-8020) Rebalancing for persistent caches should transfer file store over network instead of using existing supply/demand protocol

["Ilya Lantukh (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/IGNITE-8020?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16409522#comment-16409522 ] 

Ilya Lantukh commented on IGNITE-8020:
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This ticket is still a draft. Everybody is welcome to suggest ideas or pay attention on potential problems.

> Rebalancing for persistent caches should transfer file store over network instead of using existing supply/demand protocol
> --------------------------------------------------------------------------------------------------------------------------
>
>                 Key: IGNITE-8020
>                 URL: https://issues.apache.org/jira/browse/IGNITE-8020
>             Project: Ignite
>          Issue Type: Improvement
>          Components: persistence
>            Reporter: Ilya Lantukh
>            Assignee: Ilya Lantukh
>            Priority: Major
>
> Existing rebalancing protocol is suitable for in-memory data storage, but for data persisted in files it is sub-optimal and requires a lot of unnecessary steps. Efforts to optimize it led to necessity to completely rework the protocol - instead of sending batches (SupplyMessages) with cache entries it is possible to send data files directly.
> The algorithm should look like this:
> 1. Demander node sends requests with required partition IDs (like now)
> 2. Supplier node receives request and performs a checkpoint.
> 3. After checkpoint is done, supplier sends files with demanded partitions using low-level NIO API.
> 4. During steps 2-3, demander node should work in special mode - it should temporary store all incoming updates in such way that they can be quickly applied later.
> 5. After files are transferred, demander applies updates stored at step 4.
> The tricky part here is to switch work modes of demander node avoiding all possible race conditions. Also, the aforementioned algorithm should be extended to transfer or rebuild query indexes.



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