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https://issues.apache.org/jira/browse/BOOKKEEPER-685?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13769361#comment-13769361
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Ivan Kelly commented on BOOKKEEPER-685:
---------------------------------------
For 4.2 I was thinking of a solution like.
{code}
class EntryLogListener {
void onRotateEntryLog();
void onEntryLogFlush(int offset);
}
{code}
Then, when the scanner would implement only #onEntryLogFlush.
{code}
@Override
public void onEntryLogFlush(int flushedToOffset) {
for (Offset o : offsets) {
if (offset.getOffset() < offset) {
toFlush.add(o);
}
}
offsets.removeAll(toFlush);
for (Offset o : toFlush) {
ledgerCache.putEntryOffset(...);
}
}
{code}
Or the work could be done in other thread after setting a shared
flushedToOffset var. But in any case, this is how I was planning to use the
offset. Trunk can just use #checkpoint as you said. This interface is as
internals as they get in any case. It's not like we need to maintain any
compatibility between branches on it.
> Race in compaction algorithm from BOOKKEEPER-664
> ------------------------------------------------
>
> Key: BOOKKEEPER-685
> URL: https://issues.apache.org/jira/browse/BOOKKEEPER-685
> Project: Bookkeeper
> Issue Type: Bug
> Reporter: Ivan Kelly
> Priority: Blocker
> Fix For: 4.2.2
>
>
> I discovered a race in the algorithm when I was forward porting to trunk.
> 1) Thread1: flushed.set(false)
> 2) Thread2: onRotateEntryLog() // flushed.set(true)
> 3) Thread1: entryLogger addEntry L123-E456
> 4) Thread1: offsets > max, waits for flushed, flushed is true(as set in 2),
> L123-E456 updated in ledger cache
> 5) T2: L123 flushed out of ledger cache
> 6) Crash
> This will possible lose 1 entry. I've only reasoned this, not observed it,
> but it can happen.
> The fix is pretty easy. EntryLoggerListener should notify with the point
> offset in the entry log it has synced as far as.
>
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