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https://issues.apache.org/jira/browse/IGNITE-11687?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16818481#comment-16818481
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Andrey Gura commented on IGNITE-11687:
--------------------------------------
[~agoncharuk] I've investigated the problem deeper. While code snippet pointed
by you is incorrect and must be fixed it never executes by test because MMAP
mode is switched on by default. I think that
{{FileWriteHandleImpl#addRecord()}} method is root of the problem. See the
following code snippet:
{code:java}
fillBuffer(buf, rec);
if (mmap) {
// written field must grow only, but segment with
greater position can be serialized
// earlier than segment with smaller position.
while (true) {
long written0 = written;
if (seg.position() > written0) {
if (WRITTEN_UPD.compareAndSet(this, written0,
seg.position()))
break;
}
else
break;
}
}
return ptr;
{code}
WAL iterator on {{wal.replay()}} call gets {{hnd.written}} field value while
some previous WAL record before this position is still not fully serialized.
What do you think?
> Concurrent WAL replay & log may fail with CRC error on read
> -----------------------------------------------------------
>
> Key: IGNITE-11687
> URL: https://issues.apache.org/jira/browse/IGNITE-11687
> Project: Ignite
> Issue Type: Bug
> Reporter: Alexey Goncharuk
> Assignee: Andrey Gura
> Priority: Critical
> Fix For: 2.8
>
> Time Spent: 10m
> Remaining Estimate: 0h
>
> The cause is the way {{end}} is calculated for WAL iterator:
> {code}
> if (hnd != null)
> end = hnd.position();
> {code}
> {code}
> @Override public FileWALPointer position() {
> lock.lock();
> try {
> return new FileWALPointer(getSegmentId(), (int)written, 0);
> }
> finally {
> lock.unlock();
> }
> }
> {code}
> Consider a partially written entry. In this case, {{written}} has been
> already updated, concurrent WAL replay will attempt to read the incompletely
> written record and since {{end}} is not null, iterator will fail with CRC
> error.
> The issue may be rarely reproduced by {{IgniteWalSerializerVersionTest}}
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