[jira] [Commented] (IGNITE-5322) Improve WAL record/iterator structure

["Dmitriy Pavlov (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/IGNITE-5322?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16066476#comment-16066476 ] 

Dmitriy Pavlov commented on IGNITE-5322:
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Additionally Swich Segment record (and its WAL pointer) writting was fixed in IGNITE-5598.

> Improve WAL record/iterator structure
> -------------------------------------
>
>                 Key: IGNITE-5322
>                 URL: https://issues.apache.org/jira/browse/IGNITE-5322
>             Project: Ignite
>          Issue Type: Improvement
>          Components: cache
>    Affects Versions: 2.1
>            Reporter: Alexey Goncharuk
>            Assignee: Alexey Goncharuk
>              Labels: important
>             Fix For: 2.1
>
>
> Currently, we rely on the WAL files layout and zero-ing to make a decision when to stop the iteration.
> Instead, we should write a WAL Pointer to each record with it's position in the file. This will allow us to verify that we are reading a consistent records sequence and should also remove a requirement for zero-clean WAL segment.
> When iterating over the WAL, we should calculate expected next WAL pointer and check that read pointer is equal to the read. If we found a difference, this means that we encountered a stale segment and can stop the iteration.



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