Christian Spriegel created CASSANDRA-7401:
---------------------------------------------
Summary: 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: Christian Spriegel
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
--
This message was sent by Atlassian JIRA
(v6.2#6252)
