Pelops uses a single connection per operation from a pool that is backed by Apache Commons Pool (assuming you're using Cassandra 0.7).  I'm not saying it's perfect but it's NOT sharing a connection over multiple threads.

Dan Hendry mentioned that he sees these errors.  Is he also using Pelops?  From his comment about retrying I'd assume not...

Dan Washusen

On Thursday, 7 April 2011 at 7:39 PM, Héctor Izquierdo Seliva wrote:

El mié, 06-04-2011 a las 21:04 -0500, Jonathan Ellis escribió:
"out of sequence response" is thrift's way of saying "I got a response
for request Y when I expected request X."

my money is on using a single connection from multiple threads. don't do that.

I'm not using thrift directly, and my application is single thread, so I
guess this is Pelops fault somehow. Since I managed to tame memory
comsuption the problem has not appeared again, but it always happened
during a stop-the-world GC. Could it be that the message was sent
instead of being dropped by the server when the client assumed it had
timed out?