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From William Oberman <ober...@civicscience.com>
Subject Re: normal thread counts?
Date Tue, 30 Apr 2013 14:18:39 GMT
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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