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From Scott Tatum <>
Subject Restarting Tomcat w/o restarting Apache (with ajp13) works halfway
Date Mon, 09 Apr 2001 23:11:16 GMT
It is my understanding that, with ajp13, restarting Tomcat requires
restarting Apache. With ajp12, restarting Tomcat did not require
restarting Apache. I assume that this stems from the fact that, with
ajp12, a connection was made for each request, while with ajp13 the
connection between Tomcat and Apache stays open.

I have been experimenting with restarting Tomcat but not Apache under
ajp13. When I do a restart, I get 500 errors for a little while, but it
does eventually reconect.

My question is, will ajp13 ever be modified so that it will be possible
to restart Tomcat without having to restart Apache, and have the
connection reestablish itself within a couple of seconds at the most?

Being able to restart Tomcat without restarting Apache becomes very
important when using virtual hosts in a production environment.  Let's
say you have one machine running Apache+Tomcat. It serves 10 virtual
hosts, each with a critical production application (e.g. app1.domain,
app2.domain). Each virtual domain/application runs in its own JRE (i.e.
Tomcat instance). If there is a need to bring one application down, to
update code or make some kind of change, it means notifying all the
users of that application beforehand.

If you can restart Tomcat without restarting Apache, then that is all
you have to do. However, if you also have to restart Apache, then all 10
applications must be brought down! This means notifying users of all 10
applications and unnecessary downtime for critical applications.

One could argue that "critical application" means it needs to run on its
own Tomcat+Apache setup.. but doesn't this halfway defeat the purpose of
using virtual hosts and multiple Tomcat instances? This kind of
configuration is great for saving money and resources by grouping
applications together on a single server.

Should I post this request to the Tomcat developer list? I really am
desperate for this feature in ajp13. I don't know much about network
programming, but I'm hopeful there is some way to close the socket
connection gracefully when a shutdown of the Tomcat side is performed,
and send the Apache side back into waiting for a connection again. I
could just stick with ajp12, but I lose the increased speed and
stability. Plus, if I need to do SSL (which I need to do soon), I am in
big trouble. I'm wondering if anyone else feels the same way I do.


Scott Tatum |
Senior Applications Developer, Special Projects
WorldCom |

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