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From Jake Luciani <jak...@gmail.com>
Subject Re: Why does cassandra PoolingSegmentedFile recycle the RandomAccessReader?
Date Mon, 15 Jul 2013 14:08:26 GMT
Take a look at https://issues.apache.org/jira/browse/CASSANDRA-5661


On Mon, Jul 15, 2013 at 4:18 AM, sulong <sulong1984@gmail.com> wrote:

> Thanks for your help. Yes, I will try to increase the sstable size. I hope
> it can save me.
>
> 9000 SSTableReader x 10 RandomAccessReader x 64Kb = 5.6G memory. If there
> is only one RandomAccessReader, the memory will be 9000 * 1 * 64Kb = 0.56G
> . Looks great. But I think it must be reasonable to recycle the
> RandomAccessReader.
>
>
> On Mon, Jul 15, 2013 at 4:02 PM, Janne Jalkanen <janne.jalkanen@ecyrd.com>wrote:
>
>>
>> I had exactly the same problem, so I increased the sstable size (from 5
>> to 50 MB - the default 5MB is most certainly too low for serious usecases).
>>  Now the number of SSTableReader objects is manageable, and my heap is
>> happier.
>>
>> Note that for immediate effect I stopped the node, removed the *.json
>> files and restarted - which put all SSTables to L0, which meant a weekend
>> full of compactions… Would be really cool if there was a way to
>> automatically drop all LCS SSTables one level down to make them compact
>> earlier without avoiding the
>> "OMG-must-compact-everything-aargh-my-L0-is-full" -effect of removing the
>> JSON file.
>>
>> /Janne
>>
>> On 15 Jul 2013, at 10:48, sulong <sulong1984@gmail.com> wrote:
>>
>> > Why does cassandra PoolingSegmentedFile recycle the RandomAccessReader?
>> The RandomAccessReader objects consums too much memory.
>> >
>> > I have a cluster of 4 nodes. Every node's cassandra jvm has 8G heap.
>> The cassandra's memory is full after about one month, so I have to restart
>> the 4 nodes every month.
>> >
>> > I have 100G data on every node, with LevedCompactionStrategy and 10M
>> sstable size, so there are more than 10000 sstable files. By looking
>> through the heap dump file, I see there are more than 9000 SSTableReader
>> objects in memory, which references lots of  RandomAccessReader objects.
>> The memory is consumed by these RandomAccessReader objects.
>> >
>> > I see the PoolingSegementedFile has a recycle method, which puts the
>> RandomAccessReader to a queue. Looks like the Queue always grow until the
>> sstable is compacted.  Is there any way to stop the RandomAccessReader
>> recycling? Or, set a limit to the recycled RandomAccessReader's number?
>> >
>> >
>>
>>
>


-- 
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