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From Joshua Galbraith <jgalbra...@newrelic.com.INVALID>
Subject Re: Too many Cassandra threads waiting!!!
Date Fri, 03 Aug 2018 02:57:52 GMT
Renoy,

Out of curiosity, which kernel version are your nodes running?

You may find this old message on the mailing list helpful:
http://mail-archives.apache.org/mod_mbox/cassandra-user/201602.mbox/%3CCAA=6J0-0VabfAn3DJfatOxyJwwEHpdiE67v2wm_u5KAqOrOqnA@mail.gmail.com%3E

On Wed, Aug 1, 2018 at 5:38 PM, Elliott Sims <elliott@backblaze.com> wrote:

> You might have more luck trying to analyze at the Java level, either via a
> (Java) stack dump and the "ttop" tool from Swiss Java Knife, or Cassandra
> tools like "nodetool tpstats"
>
> On Wed, Aug 1, 2018 at 2:08 AM, nokia ceph <nokiacephusers@gmail.com>
> wrote:
>
>> Hi,
>>
>> i'm having a 5 node cluster with cassandra 3.0.13.
>>
>> i could see the cassandra process has too many threads.
>>
>> *# pstree -p `pgrep java` | wc -l*
>> *453*
>>
>> And almost all of those threads are in *sleeping* state and wait at
>> *# cat  /proc/166022/task/1698913/wchan*
>> *futex_wait_queue_me*
>>
>> Some more info:
>> *# strace -e trace=all -p 166022*
>> *strace: Process 166022 attached*
>> *futex(0x7efc24aeb9d0, FUTEX_WAIT, 166023, NULL*
>>
>> # cat /proc/166022/stack
>> [<ffffffff810f5126>] futex_wait_queue_me+0xc6/0x130
>> [<ffffffff810f5deb>] futex_wait+0x17b/0x280
>> [<ffffffff810f7b26>] do_futex+0x106/0x5a0
>> [<ffffffff810f8040>] SyS_futex+0x80/0x180
>> [<ffffffff816b4fc9>] system_call_fastpath+0x16/0x1b
>> [<ffffffffffffffff>] 0xffffffffffffffff
>>
>>
>> What is the reason cassandra is having these many threads? is it the
>> normal behavior of cassandra?  Is there a way to reduce this thread count?
>> will there be any performance impact because of this (our platform experts
>> suspects so)?
>>
>> Regards,
>> Renoy  Paulose
>>
>>
>


-- 
*Joshua Galbraith *| Lead Software Engineer | New Relic

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