[jira] [Assigned] (IGNITE-13137) WAL reservation may failed even though the required segment is available

["Vyacheslav Koptilin (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IGNITE-13137?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Vyacheslav Koptilin reassigned IGNITE-13137:
--------------------------------------------

    Assignee: Vyacheslav Koptilin

> WAL reservation may failed even though the required segment is available
> ------------------------------------------------------------------------
>
>                 Key: IGNITE-13137
>                 URL: https://issues.apache.org/jira/browse/IGNITE-13137
>             Project: Ignite
>          Issue Type: Bug
>          Components: persistence
>    Affects Versions: 2.8
>            Reporter: Vyacheslav Koptilin
>            Assignee: Vyacheslav Koptilin
>            Priority: Major
>
> It seems there is a race in {{FileWriteAheadLogManager}} that may lead to the inability to reserve a WAL segment. 
>  Let's consider the following scenario:
>   - log WAL record that requires a rollover of the current segment.
>   - archiver is moving the WAL file to an archive folder
>   - trying to reserve this segment
> {code:java}
> @Override public boolean reserve(WALPointer start) {
>     ...
>     segmentAware.reserve(((FileWALPointer)start).index());
>     if (!hasIndex(((FileWALPointer)start).index())) {          <-- hasIndex returns false
>         segmentAware.release(((FileWALPointer)start).index());
>         return false;
>     }
>     ...
> }
> private boolean hasIndex(long absIdx) {
>     ...
>     boolean inArchive = new File(walArchiveDir, segmentName).exists() ||
>         new File(walArchiveDir, zipSegmentName).exists();
>     if (inArchive)    <-- At this point, the required WAL segment is not moved yet, so inArchive == false
>         return true;
>     if (absIdx <= lastArchivedIndex()) <-- lastArchivedIndex() scans archive directory and finds a new WAL segment,
>         return false;                  <-- and absIdx == lastArchivedIndex!
>     FileWriteHandle cur = currHnd;
>     return cur != null && cur.getSegmentId() >= absIdx;
> }
> {code}
> Besides this race, it seems to me, the behavior of WAL reservation should be improved in a case when the required segment is already reserved/locked. In that particular case, we don't need to check WAL archive directory at all.
>  



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