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From Marcin Zajączkowski <>
Subject Re: Connections are not rejected (AJP 1.3) (Was: Re: Problem with backlog (AJP 1.3))
Date Wed, 17 Jan 2007 09:07:04 GMT
Marcin Zajączkowski wrote:
> Tracking down one problem I tried to get 503 error by reduction number 
> of parallel connections to Tomcat (Apache - mod_jk - (JBoss) - Tomcat) 
> to 10 (MaxThreads) and backlog to 1 (also tried with 10).
> Regarding to documentation for backlog: "Any requests received when the 
> queue is full will be refused". Unfortunately I wasn't able to get that 
> effect (connection waits until served) using prepared action which waits 
> for several seconds.

After review of source code I know that backlog isn't made internally by 
Tomcat, but is forwarded to listen() method in OS.

When maxThreads value is reached one more request hangs in a ThreadPool, 
but strange for me is that next requests pass through mod_jk which 
connect to and send it to Tomcat:

[debug] jk_open_socket::jk_connect.c (433): trying to connect socket 20 
[debug] jk_open_socket::jk_connect.c (459): socket 20 connected to
[debug] ajp_connect_to_endpoint::jk_ajp_common.c (847): Connected socket 
20 to (
[debug] ajp_connection_tcp_send_message::jk_ajp_common.c (893): sending 
to ajp13 pos=4 len=570 max=8192

I don't see any signs of those request in Tomcat log until some threads 
are freed (even after several minutes) and this request first waits in a 
ThreadPool and later is served by Tomcat.

I have DEBUG logs enabled for:
(something else could be useful?)

<Connector port="8009" address="${jboss.bind.address}"
   emptySessionPath="true" enableLookups="false" redirectPort="8443"
   maxThreads="10" acceptCount="1" connectionTimeout="5000" backlog="1"

Could somebody tell me why connections are accepted at a Tomcat/Jboss side?

> Is is possible to get 503 in described circumstances?

And why clients are received timeout (in spite of up 20 minutes delay)?

> I use JBoss 4.0.3SP1 with Tomcat 5.5 and Apache 2.2.3 with mod_jk 
> 1.2.20. Fedora Core 6.

Thanks for help

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