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From aaron morton <aa...@thelastpickle.com>
Subject Re: normal thread counts?
Date Tue, 30 Apr 2013 21:34:36 GMT
The issue below could result in abandoned threads under high contention, so we'll get that
fixed. 

But we are not sure how/why it would be called so many times. If you could provide a full
list of threads and the output from nodetool gossipinfo that would help. 

Cheers

-----------------
Aaron Morton
Freelance Cassandra Consultant
New Zealand

@aaronmorton
http://www.thelastpickle.com

On 1/05/2013, at 8:34 AM, aaron morton <aaron@thelastpickle.com> wrote:

>>  Many many many of the threads are trying to talk to IPs that aren't in the cluster
(I assume they are the IP's of dead hosts). 
> Are these IP's from before the upgrade ? Are they IP's you expect to see ? 
> 
> Cross reference them with the output from nodetool gossipinfo to see why the node thinks
they should be used. 
> Could you provide a list of the thread names ? 
> 
> One way to remove those IPs that may be to rolling restart with -Dcassandra.load_ring_state=false
i the JVM opts at the bottom of cassandra-env.sh
> 
> The OutboundTcpConnection threads are created in pairs by the OutboundTcpConnectionPool,
which is created here https://github.com/apache/cassandra/blob/trunk/src/java/org/apache/cassandra/net/MessagingService.java#L502
The threads are created in the OutboundTcpConnectionPool constructor checking to see if this
could be the source of the leak. 
> 
> Cheers
> 
> -----------------
> Aaron Morton
> Freelance Cassandra Consultant
> New Zealand
> 
> @aaronmorton
> http://www.thelastpickle.com
> 
> On 1/05/2013, at 2:18 AM, William Oberman <oberman@civicscience.com> wrote:
> 
>> I use phpcassa.
>> 
>> I did a thread dump.  99% of the threads look very similar (I'm using 1.1.9 in terms
of matching source lines).  The thread names are all like this: "WRITE-/10.x.y.z".  There
are a LOT of duplicates (in terms of the same IP).  Many many many of the threads are trying
to talk to IPs that aren't in the cluster (I assume they are the IP's of dead hosts).  The
stack trace is basically the same for them all, attached at the bottom.   
>> 
>> There is a lot of things I could talk about in terms of my situation, but what I
think might be pertinent to this thread: I hit a "tipping point" recently and upgraded a 9
node cluster from AWS m1.large to m1.xlarge (rolling, one at a time).  7 of the 9 upgraded
fine and work great.  2 of the 9 keep struggling.  I've replaced them many times now, each
time using this process:
>> http://www.datastax.com/docs/1.1/cluster_management#replacing-a-dead-node
>> And even this morning the only two nodes with a high number of threads are those
two (yet again).  And at some point they'll OOM.
>> 
>> Seems like there is something about my cluster (caused by the recent upgrade?) that
causes a thread leak on OutboundTcpConnection   But I don't know how to escape from the trap.
 Any ideas?
>> 
>> 
>> --------
>>   stackTrace = [ { 
>>     className = sun.misc.Unsafe;
>>     fileName = Unsafe.java;
>>     lineNumber = -2;
>>     methodName = park;
>>     nativeMethod = true;
>>    }, { 
>>     className = java.util.concurrent.locks.LockSupport;
>>     fileName = LockSupport.java;
>>     lineNumber = 158;
>>     methodName = park;
>>     nativeMethod = false;
>>    }, { 
>>     className = java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject;
>>     fileName = AbstractQueuedSynchronizer.java;
>>     lineNumber = 1987;
>>     methodName = await;
>>     nativeMethod = false;
>>    }, { 
>>     className = java.util.concurrent.LinkedBlockingQueue;
>>     fileName = LinkedBlockingQueue.java;
>>     lineNumber = 399;
>>     methodName = take;
>>     nativeMethod = false;
>>    }, { 
>>     className = org.apache.cassandra.net.OutboundTcpConnection;
>>     fileName = OutboundTcpConnection.java;
>>     lineNumber = 104;
>>     methodName = run;
>>     nativeMethod = false;
>>    } ];
>> ----------
>> 
>> 
>> 
>> 
>> On Mon, Apr 29, 2013 at 4:31 PM, aaron morton <aaron@thelastpickle.com> wrote:
>>>  I used JMX to check current number of threads in a production cassandra machine,
and it was ~27,000.
>> That does not sound too good. 
>> 
>> My first guess would be lots of client connections. What client are you using, does
it do connection pooling ?
>> See the comments in cassandra.yaml around rpc_server_type, the default uses sync
uses one thread per connection, you may be better with HSHA. But if your app is leaking connection
you should probably deal with that first. 
>> 
>> Cheers
>> 
>> -----------------
>> Aaron Morton
>> Freelance Cassandra Consultant
>> New Zealand
>> 
>> @aaronmorton
>> http://www.thelastpickle.com
>> 
>> On 30/04/2013, at 3:07 AM, William Oberman <oberman@civicscience.com> wrote:
>> 
>>> Hi,
>>> 
>>> I'm having some issues.  I keep getting:
>>> ------------
>>> ERROR [GossipStage:1] 2013-04-28 07:48:48,876 AbstractCassandraDaemon.java (line
135) Exception in thread Thread[GossipStage:1,5,main]
>>> java.lang.OutOfMemoryError: unable to create new native thread
>>> --------------
>>> after a day or two of runtime.  I've checked and my system settings seem acceptable:
>>> memlock=unlimited
>>> nofiles=100000
>>> nproc=122944
>>> 
>>> I've messed with heap sizes from 6-12GB (15 physical, m1.xlarge in AWS), and
I keep OOM'ing with the above error.
>>> 
>>> I've found some (what seem to me) to be obscure references to the stack size
interacting with # of threads.  If I'm understanding it correctly, to reason about Java mem
usage I have to think of OS + Heap as being locked down, and the stack gets the "leftovers"
of physical memory and each thread gets a stack.
>>> 
>>> For me, the system ulimit setting on stack is 10240k (no idea if java sees or
respects this setting).  My -Xss for cassandra is the default (I hope, don't remember messing
with it) of 180k.  I used JMX to check current number of threads in a production cassandra
machine, and it was ~27,000.  Is that a normal thread count?  Could my OOM be related to stack
+ number of threads, or am I overlooking something more simple?
>>> 
>>> will
>>> 
>> 
>> 
>> 
>> 
>> 
> 


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