Nikolas Nikolaou wrote:
Hi. I've managed to connect the default CATALINA_HOME tomcat 8.0.15 with
apache2 using mod_jk but I can't find Info on how to connect to an Instance of
CATALINA_BASE. What changes would I need to make to the workers file as to the
location of tomcat_home.
Hi.
You may be looking at this from the wrong side, and that may be why you are
getting confused.
mod_jk is a connector, which allows to "connect" *one* front-end instance of Apache httpd,
with *one or multiple* back-end tomcat instances (which in mod_jk terminology, are called
"workers").
If one Apache2 front-end connects to multiple back-end Tomcat instances, then mod_jk can
act not only as a connector, but it can also act :
- as a switch, by forwarding requests to different Tomcats based on the request
URLs
- as a load-balancer, by forwarding requests to different Tomcats based on some
load-balancing algorithm
- or as both
Schematically :
Browser <-- HTTP --> Apache2 + mod_jk <-- AJP --> Tomcat1 + webapps
|--<-- AJP --> Tomcat2 + webapps
|--<-- AJP --> Tomcat3 + webapps
etc..
each of the above Tomcat's, would be known to mod_jk as a "worker", e.g.
Tomcat1 = worker1
Tomcat2 = worker2
Tomcat3 = worker3
etc..
mod_jk "talks to" a specific Tomcat worker using TCP/IP.
For that, mod_jk needs to know the IP address/port of that Tomcat worker, on which it is
listening for such requests (a).
Vice-versa, to accept requests from mod_jk and respond to them, each Tomcat instance needs
an "AJP Connector", set up to listen on a specific IP address/port combination (b).
(a) is configured in the Apache2/mod_jk "workers.properties" file, which is unique and
belongs to the unique mod_jk module in Apache2.
The syntax of the workers.properties file is explained here :
http://tomcat.apache.org/connectors-doc/generic_howto/workers.html
In this file, there should be one "worker" defined, for each back-end Tomcat instance you
wish to communicate with.
(b) is configured in each of the running Tomcat instances specifically, by a configuration
snippet like <Connector protocol="AJP.."
The syntax of this is explained here :
http://tomcat.apache.org/tomcat-8.0-doc/config/ajp.html
To allow mod_jk to communicate with a given running Tomcat instance, there must be a match
between
- the IP (or DNS name) and port that you indicate for a "worker-x" (a running Tomcat
instance) in the (single) Apache2 workers.properties file
- and the "listening IP/port" that you indicate in the AJP <Connector> entry in the
configuration of that Tomcat instance (in the "server.xml" configuration file that is in
that Tomcat's CATALINA_BASE directory.
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