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From Aaron Morton <>
Subject Re: Re: Cassandra 0.7 beta 3 outOfMemory (OOM)
Date Sun, 05 Dec 2010 20:29:10 GMT
I remember you have 2 CF's but what are the settings for: 

- memtable_flush_after_mins
- memtable_throughput_in_mb
- memtable_operations_in_millions
- keys_cached
- rows_cached

- in_memory_compaction_limit_in_mb

Can you do the JVM Heap Calculation here and see what it says

What Consistency Level are you writing at? (Checking  it's not Zero) 

When you talk about 200 inserts per second is that storing 200 documents through lucandra
or 200 request to cassandra. If it's the first option I would assume that would generate a
lot more actual requests into cassandra. Open up jconsole and take a look at the WriteCount
settings for the CF's

You could also try setting the compaction thresholds to 0 to disable compaction while you
are pushing this data in. Then use node tool to compact and turn the settings back to normal.
See cassandra.yam for more info.

I would have thought you could get the writes through with the setup you've described so far
(even though a single 32bit node is unusual). The best advice is to turn all the settings
down (e.g. caches off, mtable flush 64MB, compaction disabled) and if it still fails try:

- checking your IO stats, not sure on windows but JConsole has some IO stats. If your IO cannot
keep up then your server is not fast enough for your client load.
- reducing the client load

Hope that helps. 

On 04 Dec, 2010,at 05:23 AM, Max <> wrote:


we increased heap space to 3 GB (with JRocket VM under 32-bit Win with 
but under "heavy" inserts Cassandra is still crashing with OutOfMemory 
error after a GC storm.

It sounds very similar to

In our insert-tests the average heap usage is slowly growing up to the 
3 GB border (jconsole monitor over 50 min and the CompactionManger queue is 
also constantly growing up to about 50 jobs pending.

We tried to decrease CF memtable threshold but after about half a 
million inserts it's over.

- Cassandra 0.7.0 beta 3
- Single Node
- about 200 inserts/s ~500byte - 1 kb

Is there no other possibility instead of slowing down inserts/s ?

What could be an indicator to see if a node works stable with this 
amount of inserts?

Thank you for your answer,

Aaron Morton <>:

> Sounds like you need to increase the Heap size and/or reduce the 
> memtable_throughput_in_mb and/or turn off the internal caches. 
> Normally the binary memtable thresholds only apply to bulk load 
> operations and it's the per CF memtable_* settings you want to 
> change. I'm not familiar with lucandra though. 
> See the section on JVM Heap Size here 
> Bottom line is you will need more JVM heap memory.
> Hope that helps.
> Aaron
> On 29 Nov, 2010,at 10:28 PM, wrote:
> Hi community,
> during my tests i had several OOM crashes.
> Getting some hints to find out the problem would be nice.
> First cassandra crashes after about 45 min insert test script.
> During the following tests time to OOM was shorter until it started to crash
> even in "idle" mode.
> Here the facts:
> - cassandra 0.7 beta 3
> - using lucandra to index about 3 million files ~1kb data
> - inserting with one client to one cassandra node with about 200 files/s
> - cassandra data files for this keyspace grow up to about 20 GB
> - the keyspace only contains the two lucandra specific CFs
> Cluster:
> - cassandra single node on windows 32bit, Xeon 2,5 Ghz, 4GB RAM
> - java jre 1.6.0_22
> - heap space first 1GB, later increased to 1,3 GB
> Cassandra.yaml:
> default + reduced "binary_memtable_throughput_in_mb" to 128
> CFs:
> default + reduced
> min_compaction_threshold: 4
> max_compaction_threshold: 8
> I think the problem appears always during compaction,
> and perhaps it is a result of large rows (some about 170mb).
> Are there more options we could use to work with few memory?
> Is it a problem of compaction?
> And how to avoid?
> Slower inserts? More memory?
> Even fewer memtable_throuput or in_memory_compaction_limit?
> Continuous manual major comapction?
> I've read
> - row_size should be fixed since 0.7 and 200mb is still far away from 2gb
> - only key cache is used a little bit 3600/20000
> - after a lot of writes cassandra crashes even in idle mode
> - memtablesize was reduced and there are only 2 CFs
> Several heapdumps in MAT show 60-99% heapusage of compaction thread.

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