Recently my instances have been exhibiting some really strange
behavior. A couple times a day an instance will simply stop
responding to requests for a period of time ranging from a minute to
ten minutes. During this period, top claims the instance is using
2.4% or so of processor. Other instances on the same server continue
running just fine.
If I issue a kill -QUIT to get a thread dump, I get nothing.... Until
the instance decides to wake up from whatever dreaming it's been
doing, several minutes later. At that moment I get the thread dump,
and the instance logs all of the requests that it should have
received during that period, with NSLog timestamps at the moment of
re-awakening. Monitor records this as a death, but once the instance
comes back it goes back to properly handling requests.
At first I suspected a deadlocking issue, but running with concurrent
request handling off doesn't make the weirdness go away. Also, the
eventual thread dump doesn't show any deadlocks. (And, what kind of
deadlock eventually works itself out?) What really makes me curious
is that the adaptor apparently doesn't notice that the requests
aren't being handled and continues to send them to the instance.
Receive timeout is 60 seconds, all other settings are default.
WebObjects 5.3.3, deployed on Intel Xserves running Mac OS X Server
10.4.10 and 10.4.11. We're using an ERXRemoteSynchronizer-derived
change notification system over JMS (openjms-0.7.7-beta-1 running on
a different box), and a couple of memcached daemons on another box.
(We tried various configurations using jgroups via UDP and/or TCP but
it seemed to make the problem worse.)
Any insight is greatly appreciated!
--
WireHose: Smart metadata and personalization for WebObjects.
http://wirehose.com/
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