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From Bill Davidson <>
Subject Confused by mpm/mod_jk
Date Mon, 11 May 2009 21:15:19 GMT
I'm trying to understand mpm_worker MaxCLients and it's relationship
with mod_jk connection_pool_size.

Here's what I've got at the moment:

OS: Red Hat 5.2 Server
httpd: 2.2.11
tomcat-connector: 1.2.28
tomcat: 6.0.18
Java: 1.6.0_13


ListenBacklog      2048
<IfModule mpm_worker_module>
    StartServers          2
    MaxClients          256
    MinSpareThreads      25
    MaxSpareThreads      75
    ThreadsPerChild      32
    MaxRequestsPerChild   0



<Connector port="8009"
               maxThreads="150" />

Also, I've added these to /etc/sysctl.conf

# increase the maximum number of TCP connections.
net.core.somaxconn = 2048
net.core.netdev_max_backlog = 1024

I've got three separate boxes running their own httpd/Tomcat, load
balanced with LVS so total connections is actually 3x of what is
indicated above.

I'm feeling like MaxClients is a bit low, but I can't seem to satisfactorily
articulate why.  I'm going to be hit with a traffic storm (many thousands
of simultaneous connection attempts in a few minutes) in a few days, and
I'm thinking I should make sure I've got this right.  I went through it 
8-10 months ago but that was long before I put these systems into
production.  I probably should have gone through it again a month ago but
didn't think to.

I'm also contemplating increasing connection_pool_size & maxThreads
(I'm pretty sure those have to be equal) since my database can handle
up to 1000 simultaneous connections and as it is, I've got a maximum
of 3*150=450 Tomcat threads that can access it at any given time.

Any useful advice on this would be appreciated.

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