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From "Caldarale, Charles R" <Chuck.Caldar...@unisys.com>
Subject RE: Logging servlet time and connections
Date Thu, 23 Jul 2009 20:27:54 GMT
> From: Jess Holle [mailto:jessh@ptc.com]
> Subject: Re: Logging servlet time and connections
> 
> In this scenario once you exceed maxThread minus 2 simultaneous
> connections (there's a clear off by 2 error here somewhere) any
> additional simultaneous connections go into some sort of weird
> limbo, are never processed, and eventually time out.

That would be expected, since AJP connections are intended to be persistent.  Once the max
connections have been established, Tomcat gets no indication that more are needed, since that's
all handled by the TCP/IP stack, not Tomcat or the JVM.  The "weird limbo" is likely just
the normal TCP/IP accept queue.  (There's no timeout limit for that queue - the server is
expected to do accepts within a "reasonable" amount of time and get the connection requests
off the queue; TCP clients can specify a timeout for the request.)  It's extremely important
to have compatible configurations for Tomcat and httpd when using AJP.

> This is irrespective of the value of acceptCount used, which is simply
> ignored in this case!

It's not ignored - incoming requests that would exceed the acceptCount are refused; some server
TCP/IP stacks send an RST back when the accept queue is full, some just silently discard the
SYN.  Tomcat has no way of finding out that refusals happened.

 - Chuck


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