Hi,
We're using apache httpd 2.2 with mod_proxy / mod_proxy_ajp as
frontend for our Glassfish Java Application Server. We have multiple
(four) ProxyPass rules in our virtual host configuration to forward
different URIs to Glassfish, while other static content is served by
apache directly.
Our apache configuration:
- MPM worker
- MaxClients 100
- 25 threads per child process
As the traffic on our website is growing we need to scale the number
of parallel connections up. However when we did this, we ran into
problems with too many glassfish worker threads being forked until we
eventually hit the limit of 250 threads. Wondering what this might
mean, I used the following command to watch the number of connections
between glassfish and apache:
netstat -nap | grep VERBUNDEN | grep 8009 | grep apache2 | awk -F' '
'{print $7}' | sort | uniq -c
(VERBUNDEN is german for CONNECTED).
And to our surprise we discovered that some apache child processes
hold more than 25 connections to the backend server:
29 18146/apache2
35 18188/apache2
23 18455/apache2
And it seems that some of these connections are "dead", i.e. they are
no longer used for forwarding requests to glassfish.
So I have a number of questions:
1. Is it true that each ProxyPass rule uses its own connection pool to
the backend? And if so, is there a way to unify this so that only one
connection pool is used per child?
2. When an apache thread is in "K" (keepalive) status, does it still
block backend connections from the pool ?
3. How long does apache keep idle connections to the backend before
they are closed?
4. Is there a way to make apache show the status of its AJP backend
connections, similar to the mod_status page ?
I am looking forward to your insightful replies!
Cheers
Bastian
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