Running multiple Tomcat instances on one server

奥德赛F9

　　Here's a brief step by step guide
to running more than one instance of Tomcat on a single machine.

Step 1: Install the Tomcat files
　　Download Tomcat 4.1
or 5.5
, and
unzip it into an appropriate directory. I usually put it in /usr/local,
so it ends up in a directory called /usr/local/apache-tomcat-5.5.17
(5.5.17 being the current version as of this writing), and make a
symlink named /usr/local/tomcat to that directory. When later versions
come out, I can unzip them and relink, leaving the older version in case
things don't work out (which rarely if ever happens, but I'm paranoid).

Step 2: Make directories for each instance
　　For each instance of Tomcat you're going to run, you'll need a
directory that will be CATALINA_HOME
. For example, you might
make them /var/tomcat/serverA
and /var/tomcat/serverB
.

　　In each of these directories you need the following subdirectories:
conf, logs, temp, webapps, and work.
　　Put a server.xml and web.xml file in the conf directory. You can get
these from the conf directory of the directory where you put the tomcat
installation files, although of course you should tighten up your
server.xml a bit.
　　The webapps directory is where you'll put the web applications you
want to run on the particular instance of Tomcat.
　　I like to have the Tomcat manager webapp installed on each instance,
so I can play with the webapps, and see how many active sessions there
are. See my instructions for configuring
the Tomcat manager webapp
.

Step 3: Configure the ports and/or addresses for each instance
　　Tomcat listens to at least two network ports, one for the shutdown
command, and one or more for accepting requests. Two instances of Tomcat
can't listen to the same port number on the same IP address, so you
will need to edit your server.xml files to change the ports they listen
to.
　　The first port to look at is the shutdown port. This is used by the
command line shutdown script (actually, but the Java code it runs) to
tell the Tomcat instance to shut itself down. This port is defined at
the top of the server.xml file for the instance.

<Server port="8001" shutdown="_SHUTDOWN_COMMAND_" debug="0">

　　
Make sure each instance uses a different port value. The port value will
normally need to be higher than 1024, and shouldn't conflict with any
other network service running on the same system. The shutdown string is
the value that is sent to shut the server down. Note that Tomcat won't
accept shutdown commands that come from other machines.
　　Unlike the other ports Tomcat listens to, the shutdown port can't be
configured to listen to its port on a different IP address. It always
listens on 127.0.0.1.
　　The other ports Tomcat listens to are configured with the
<Connector> elements, for instance the HTTP or JK listeners. The port
attribute configures which port to listen to. Setting this to a
different value on the different Tomcat instances on a machine will
avoid conflict.
　　Of course, you'll need to configure whatever connects to that
Connector to use the different port. If a web server is used as the
front end using mod_jk, mod_proxy, or the like, then this is simple
enough - change your web server's configuration.
　　In some cases you may not want to do this, for instance you may not
want to use a port other than 8080 for HTTP connectors. If you want all
of your Tomcat intances to use the same port number, you'll need to use
different IP addresses. The server system must be configured with
multiple IP addresses, and the address
attribute of the
<Connector> element for each Tomcat instance will be set to the
appropriate IP address.

Step 4: Startup
　　Startup scripts are a whole other topic, but here's the brief
rundown. The main different from running a single Tomcat instance is you
need to set CATALINA_BASE to the directory you set up for the
particular instance you want to start (or stop). Here's a typical
startup routine:

JAVA_HOME=/usr/java
JAVA_OPTS="-Xmx800m -Xms800m"
CATALINA_HOME=/usr/local/tomcat
CATALINA_BASE=/var/tomcat/serverA
export JAVA_HOME JAVA_OPTS CATALINA_HOME CATALINA_BASE
$CATALINA_HOME/bin/catalina.sh start




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