[users@httpd] Apache hung due to a lot of threads in "("W") Sending Reply " status

["Yu-Yuan, Zhang (Peter, SM CORD Agile)" <zh...@hp.com>]

Hello All,

We are using Apache/2.2.22 (Win32) mod_jk/1.2.32 to connect to JBoss Application server 4.2.0. (All servers are on Windows, so the MPM user winnt module)
After running sometime (it's random, hours or days) the Apache server will become slow and have high latency when user send request to it. This usually happened at peak hour when a lot of users are using the system.
When checking the status of Apache server, we can find few idle workers left, sometimes even 0 idle workers left.
And a lot of "W" (Sending Reply) on the Scoreboard. And the values of SS( Seconds since beginning of most recent request ) are from 0 second to 70 seconds or so (no very long SS value for each "W" request).
Does anyone happen to have such experience on this?

Below is the sample configuration, we almost used default configuration for Apache and  JBoss.

1. Configure worker nodes in mod_jk:
# Define list of workers that will be used
# for mapping requests
worker.list=loadbalancer,status

# Define Node1
# modify the host as your host IP or DNS name.
worker.node1.port=8009
worker.node1.host=node1.mydomain.com
worker.node1.type=ajp13
worker.node1.lbfactor=1
worker.node1.cachesize=10

# Define Node2
# modify the host as your host IP or DNS name.
worker.node2.port=8009
worker.node2.host= node2.mydomain.com
worker.node2.type=ajp13
worker.node2.lbfactor=1
worker.node2.cachesize=10

# Load-balancing behaviour
worker.loadbalancer.type=lb
worker.loadbalancer.balance_workers=node1,node2
worker.loadbalancer.sticky_session=1
#worker.list=loadbalancer

# Status worker for managing load balancer
worker.status.type=status

2. Configuring JBoss to work with mod_jk
<Connector protocol="AJP/1.3" port="8009" address="${jboss.bind.address}"
   redirectPort="8443" />



httpd-mpm.conf configuration:
<IfModule mpm_winnt_module>
    ThreadsPerChild      900
    MaxRequestsPerChild  10000
    ThreadLimit 900
</IfModule>



Any help would appreciate.
Thanks.