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https://issues.apache.org/jira/browse/BOOKKEEPER-685?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13769719#comment-13769719
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Sijie Guo commented on BOOKKEEPER-685:
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I can image how you use offset, but I still don't understand the benefits of
using offset.
for example, suppose GCThread is compacting entry log file X, which adding N
entries in entry log file Y and adding M entries in entry log file (Y+1). the
only benefit is that you could flush N entries using offset when entry logger
rotated from Y to Y+1. *but, you still could not flush M entries until entry
logger rotated from Y+1 to Y+2, which means you also could not delete entry log
file X at this point, right?* so if bookie crashed at this point, bookie will
still need to compact entry log file X again, both N and M entries. the new
flushed N entries don't help anything.
from the compaction perspective, I didn't see any difference between using
offset and just setting flushed after adding entry. so why not keep the
solution simpler and also keep solution consistent crossing 4.2.2 and 4.3.0?
I don't have strong preferences. you could use offset in 4.2.2 if you want.
> 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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