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https://issues.apache.org/jira/browse/CASSANDRA-7361?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14020822#comment-14020822
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Benedict commented on CASSANDRA-7361:
-------------------------------------
As I attempted to clarify, there is not insignificant on-heap overhead
associated with even the off-heap row cache. Nowhere is it indicated that this
is designed to free you from heap limitations, only that it reduces the heap
burden. If your rows are small (<100 bytes) you will find that the on-heap
overhead is in fact *larger* than the data stored offheap. So the offheap limit
you place on the data should be determined by the size of the rows it will
typically cache. It is likely the documentation should be improved here, and it
may be worth emailing d...@datastax.com with this suggestion; it is also
possible a different "improvement" ticket could be filed asking to support a
configurable limit to the on-heap overhead as well as the off-heap data,
however this would not be prioritized highly at the moment since tuning your
off-heap limit correctly would suffice to ensure correct behaviour.
> Cassandra locks up in full GC when you assign the entire heap to row cache
> --------------------------------------------------------------------------
>
> Key: CASSANDRA-7361
> URL: https://issues.apache.org/jira/browse/CASSANDRA-7361
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Environment: Ubuntu, RedHat, JDK 1.7
> Reporter: Jacek Furmankiewicz
> Priority: Minor
> Attachments: histogram.png, leaks_report.png, top_consumers.png
>
>
> We have a long running batch load process, which runs for many hours.
> Massive amount of writes, in large mutation batches (we increase the thrift
> frame size to 45 MB).
> Everything goes well, but after about 3 hrs of processing everything locks
> up. We start getting NoHostsAvailable exceptions on the Java application side
> (with Astyanax as our driver), eventually socket timeouts.
> Looking at Cassandra, we can see that it is using nearly the full 8GB of heap
> and unable to free it. It spends most of its time in full GC, but the amount
> of memory does not go down.
> Here is a long sample from jstat to show this over an extended time period
> e.g.
> http://aep.appspot.com/display/NqqEagzGRLO_pCP2q8hZtitnuVU/
> This continues even after we shut down our app. Nothing is connected to
> Cassandra any more, yet it is still stuck in full GC and cannot free up
> memory.
> Running nodetool tpstats shows that nothing is pending, all seems OK:
> {quote}
> Pool Name Active Pending Completed Blocked All
> time blocked
> ReadStage 0 0 69555935 0
> 0
> RequestResponseStage 0 0 0 0
> 0
> MutationStage 0 0 73123690 0
> 0
> ReadRepairStage 0 0 0 0
> 0
> ReplicateOnWriteStage 0 0 0 0
> 0
> GossipStage 0 0 0 0
> 0
> CacheCleanupExecutor 0 0 0 0
> 0
> MigrationStage 0 0 46 0
> 0
> MemoryMeter 0 0 1125 0
> 0
> FlushWriter 0 0 824 0
> 30
> ValidationExecutor 0 0 0 0
> 0
> InternalResponseStage 0 0 23 0
> 0
> AntiEntropyStage 0 0 0 0
> 0
> MemtablePostFlusher 0 0 1783 0
> 0
> MiscStage 0 0 0 0
> 0
> PendingRangeCalculator 0 0 1 0
> 0
> CompactionExecutor 0 0 74330 0
> 0
> commitlog_archiver 0 0 0 0
> 0
> HintedHandoff 0 0 0 0
> 0
> Message type Dropped
> RANGE_SLICE 0
> READ_REPAIR 0
> PAGED_RANGE 0
> BINARY 0
> READ 585
> MUTATION 75775
> _TRACE 0
> REQUEST_RESPONSE 0
> COUNTER_MUTATION 0
> {quote}
> We had this happen on 2 separate boxes, one with 2.0.6, the other with 2.0.8.
> Right now this is a total blocker for us. We are unable to process the
> customer data and have to abort in the middle of large processing.
> This is a new customer, so we did not have a chance to see if this occurred
> with 1.1 or 1.2 in the past (we moved to 2.0 recently).
> We have the Cassandra process still running, pls let us know if there is
> anything else we could run to give you more insight.
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