On Wed, Jun 26, 2013 at 12:16 AM, aaron morton <aa...@thelastpickle.com>wrote:
> 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. >>> >> You need to re-write the sstables on disk using nodetool upgradesstables. > Otherwise only the new tables with have the 0.1 setting. > > I will try increasing the value to 0.7 and report my results. >>> >> No need to, it will probably be something like "Oh no, really, what, how, > please make it stop" :) > 0.7 will mean reads will hit most / all of the SSTables for the CF. > Changing the bloom_filter_fp_chance to 0.7 did seem to correct the problem in short run. I do not see the out of heap errors but I am taking a bit of a performance hit. Planning to run some more tests, also my BloomFilterFalseRatio is 0.8367977262013025 this was the reason behind bumping bloom_filter_fp_chance. > > I covered a high row situation in on of my talks at the summit this month, > the slide deck is here > http://www.slideshare.net/aaronmorton/cassandra-sf-2013-in-case-of-emergency-break-glass > and > the videos will soon be up at Planet Cassandra. > This was/is extremely helpful Aaron, cannot thank you enough for sharing this with the community, eagerly looking forward for the video. > > Rebuild the sstables, then reduce the index_interval if you still need to > reduce mem pressure. > > Cheers > > > ----------------- > Aaron Morton > Freelance Cassandra Consultant > New Zealand > > @aaronmorton > http://www.thelastpickle.com > > > On 22/06/2013, at 1:17 PM, sankalp kohli <kohlisank...@gmail.com> wrote: > > I will take a heap dump and see whats in there rather than guessing. > > > On Fri, Jun 21, 2013 at 4:12 PM, Bryan Talbot <btal...@aeriagames.com>wrote: > >> 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. >> >> -Bryan >> >> >> >> On Fri, Jun 21, 2013 at 5:58 AM, srmore <comom...@gmail.com> wrote: >> >>> >>> On Fri, Jun 21, 2013 at 2:53 AM, aaron morton >>> <aa...@thelastpickle.com>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. >>> >>> Cheers >>>> >>>> ----------------- >>>> Aaron Morton >>>> Freelance Cassandra Consultant >>>> New Zealand >>>> >>>> @aaronmorton >>>> http://www.thelastpickle.com >>>> >>>> On 20/06/2013, at 6:36 AM, Wei Zhu <wz1...@yahoo.com> 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 >>>> >>>> -Wei >>>> >>>> ------------------------------ >>>> *From: *"Robert Coli" <rc...@eventbrite.com> >>>> *To: *user@cassandra.apache.org >>>> *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 <comom...@gmail.com> 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. >>>> >>>> =Rob >>>> >>>> >>>> >>> >> > >
