Vyacheslav Koptilin created IGNITE-13137:
--------------------------------------------
Summary: 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
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, and absIdx == lastArchivedIndex!
return false;
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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