bloom_filter_fp_chance = 0.7 is probably way too large to be effective and you'll probably have issues compacting deleted rows and get poor read performance with a value that high.  I'd guess that anything larger than 0.1 might as well be 1.0.


On Fri, Jun 21, 2013 at 5:58 AM, srmore <> wrote:

On Fri, Jun 21, 2013 at 2:53 AM, aaron morton <> wrote:
> nodetool -h localhost flush didn't do much good.
Do you have 100's of millions of rows ?
If so see recent discussions about reducing the bloom_filter_fp_chance and index_sampling. 
Yes, I have 100's of millions of rows.

If this is an old schema you may be using the very old setting of 0.000744 which creates a lot of bloom filters. 

bloom_filter_fp_chance value that was changed from default to 0.1, looked at the filters and they are about 2.5G on disk and I have around 8G of heap.
I will try increasing the value to 0.7 and report my results.

It also appears to be a case of hard GC failure (as Rob mentioned) as the heap is never released, even after 24+ hours of idle time, the JVM needs to be restarted to reclaim the heap.

Aaron Morton
Freelance Cassandra Consultant
New Zealand


On 20/06/2013, at 6:36 AM, Wei Zhu <> wrote:

If you want, you can try to force the GC through Jconsole. Memory->Perform GC.

It theoretically triggers a full GC and when it will happen depends on the JVM


From: "Robert Coli" <>
Sent: Tuesday, June 18, 2013 10:43:13 AM
Subject: Re: Heap is not released and streaming hangs at 0%

On Tue, Jun 18, 2013 at 10:33 AM, srmore <> wrote:
> But then shouldn't JVM C G it eventually ? I can still see Cassandra alive
> and kicking but looks like the heap is locked up even after the traffic is
> long stopped.

No, when GC system fails this hard it is often a permanent failure
which requires a restart of the JVM.

> nodetool -h localhost flush didn't do much good.

This adds support to the idea that your heap is too full, and not full
of memtables.

You could try nodetool -h localhost invalidatekeycache, but that
probably will not free enough memory to help you.