[jira] [Updated] (IGNITE-5821) Implement fuzzy checkpoints

["Alexey Goncharuk (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IGNITE-5821?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Alexey Goncharuk updated IGNITE-5821:
-------------------------------------
    Fix Version/s:     (was: 2.5)

> Implement fuzzy checkpoints
> ---------------------------
>
>                 Key: IGNITE-5821
>                 URL: https://issues.apache.org/jira/browse/IGNITE-5821
>             Project: Ignite
>          Issue Type: New Feature
>          Components: persistence
>    Affects Versions: 2.1
>            Reporter: Alexey Goncharuk
>            Priority: Major
>
> Currently, we are able to run only sharp checkpoints (all committed transactions are in the checkpoint, all non-committed are not included, all data structures are fully consistent).
> This has the following disadvantages:
> 1) All transactions are blocked for the markCheckpointBegin call
> 2) We have an additional overhead for checkpoint COW buffer
> 3) If checkpoint buffer is exhausted, we block all transactions and synchronously wait for the checkpoint to be finished.
> There is a technique called fuzzy checkpoints:
> 1) We keep a WAL LSN in every dirty page
> 2) When a page is being flushed to disk, we sync WAL up to the LSN
> 3) We maintain checkpoint low watermark so that WAL does not grow indefinitely
> 4) WAL logging is changed in a way that does not allow data structures updates to be mixed in WAL
> 5) The recovery procedure is changed to apply all physical deltas up to the end of WAL and have consistent memory state, then logical records revert all non-committed transactions



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