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https://issues.apache.org/jira/browse/CASSANDRA-7401?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14034693#comment-14034693
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Aleksey Yeschenko commented on CASSANDRA-7401:
----------------------------------------------
Committed in 9afc2097ef8e806b9916e623815202b0f43d1cfc
(https://github.com/apache/cassandra/commit/9afc2097ef8e806b9916e623815202b0f43d1cfc)
(replaced < with <=).
bq. Looks related to the "start new memtable w/ the old memtable's liveRatio"
thing we were talking about.
It's not, at least directly it isn't.
bq. is it possible that addAndGet in resolve() increases by 0 in some cases?
Apparently yes, it is - when the CF has no cells in it, no range tombstones,
and isn't top-level marked for deletion.
I have NO idea where that CF originated from, and don't even know where to
start looking. If you find out - let us know.
> Memtable.maybeUpdateLiveRatio goes into an endless loop when
> currentOperations is zero
> --------------------------------------------------------------------------------------
>
> Key: CASSANDRA-7401
> URL: https://issues.apache.org/jira/browse/CASSANDRA-7401
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Reporter: Christian Spriegel
> Assignee: Aleksey Yeschenko
> Fix For: 2.0.9
>
> Attachments: MemtableFixV1.patch
>
>
> Hi,
> I was describing an error the other day on the mailing list, where the
> MemoryMeter would go into an endless loop. This happened multiple times last
> week, unfortunetaly I cannot reproduce it at the moment.
> The whole cassandra server got unresponsive and logged about 7000k messages
> per second into the log:
> {quote}
> ...
> INFO [MemoryMeter:1] 2014-06-14 19:24:09,488 Memtable.java (line 481)
> CFS(Keyspace='MDS', ColumnFamily='ResponsePortal') liveRatio is 64.0
> (just-counted was 64.0). calculation took 0ms for 0 cells
> ...
> {quote}
> The cause for this seems to be Memtable.maybeUpdateLiveRatio(), which cannot
> handle currentOperations (and liveRatioComputedAt) to be zero. The loop will
> iterate endlessly:
> {code}
> ...
> if (operations < 2 * last) // does never break when zero: 0 < 0
> is not true
> break;
> ...
> {code}
> One thing I cannot explain: How can the operationcount be zero when
> maybeUpdateLiveRatio() gets called?
> is it possible that addAndGet in resolve() increases by 0 in some cases?
> {code}
> currentOperations.addAndGet(cf.getColumnCount() + (cf.isMarkedForDelete() ? 1
> : 0) + cf.deletionInfo().rangeCount()); // can this be zero?
> {code}
> Nevertheless, the attached patch fixes the endless loop. Feel free to
> reassign this ticket or create a followup ticket if currentOperations should
> not be zero.
> kind regards,
> Christian
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