Using the JK2 Connector
This is the start of a tutorial on using the JK2 Connector. See also the [TomcatFAQ/ModJK2OnRedHat| Tomcat FAQ on building mod_jk2 for { { { RedHat } } } Linux].
See also HowToRedhat8JK2 for configuring redhat's Apache with a mod_jk2 binary and Tomcat 4.1
Quick start for linux
This is just a quick start for people currently struggling with mod_jk2 and multiple hosts. It is a working configuration. My real content for this page will come in another week or so. But please feel free to collaborate on this page now! 
This is working on { { { RedHat } } } Linux. I use Unix Domain sockets because they eliminate the need to manage the list of IP ports. [One remaining task is to eliminate the need for the shutdown port. The shutdown command can be sent via AJP13, but the code from { { { StopTomcat } } } (in Tomcat v3.3) needs to be ported to use the connector classes.]
Layout
See RUNNING.txt for how to use CATALINA_BASE and CATALINA_HOME.
For each virtual host that will have its own JVM (shared JVM will be discussed later), setup a layout like:
site/ ${CATALINA_BASE}
- conf/ logs/ ${Host.appBase}/ROOT/ ${Host.appBase}/ROOT/web-inf/classes/ ${Host.appBase}/ROOT/web-inf/lib/ temp/ work/
This is just a basic description for this example. There are other options for placement of the site content.
Starting and Stopping
{{{ start: su --login user --command="export CATALINA_BASE=path; export JAVA_HOME=/usr/local/java; export JAVA_OPT=-server; /usr/local/tomcat-4/bin/startup.sh"
stop: su --login user --command="export CATALINA_BASE=path; export JAVA_HOME=/usr/local/java; export JAVA_OPT=-server; /usr/local/tomcat-4/bin/shutdown.sh" }}}
I use a { { { SysVInit } } } script that manages this cleanly for many sites. The user should be in the same group as the apache web server process.
Connector {{{ { { { <Connector className="org.apache.coyote.tomcat4.CoyoteConnector" } } }
port="0" minProcessors="5" maxProcessors="75" enableLookups="true" redirectPort="8443" acceptCount="10" debug="0" connectionTimeout="0" { { { useURIValidationHack="false" protocolHandlerClassName="org.apache.jk.server.JkCoyoteHandler"/> } } } }}}
Note that the port is set to zero. We're using UNIX domain sockets in this example, and we don't want the connector to open a port.
jk2.properties:
{{{ handler.list=apr,channelUnix,request
{ { { apr.NativeSo=/etc/httpd/modules/jkjni.so } } } channelUnix.file=${jkHome}/work/jk2.socket }}}
conf/work2er.properties:
{{{logger
- level=DEBUG [config:] file=${serverRoot}/conf/workers2.properties debug=0 debugEnv=0 [shm:] info=Scoreboard. Required for reconfiguration and status with multiprocess servers file=${serverRoot}/logs/jk2.shm size=1000000 debug=0 disabled=0 [workerEnv:] info=Global server options timing=1 debug=0
[channel.un:workerName] info=AF_UNIX socket connecting to "host" file=/catalina_base/work/jk2.socket debug=0
... repeat the above for each worker ... }}}
NOTE: You must make sure that the group owning the work/ directory is the same as the Group directive in httpd.conf. Issue the following:
{{{ chgrp group work
- chmod g+s work }}}
If you have already tried tomcat before doing this, then also issue: chgrp group jk2.socket
conf.d/jk2.conf:
{ { { LoadModule jk2_module modules/mod_jk2.so } } }
httpd.conf
{{{ # This sends all resource requests to tomcat
{ { { <VirtualHost ...> } } } { { { ServerName } } } vhost { { { DirectoryIndex } } } index.jsp index.html { { { JkSet } } } uri:vhost/*.group ajp13:{ { { workerName } } } # Alternative mapping mechanisms # 1. Place this in workers2.properties
# [uri:vhost/] # group=ajp13:workerName # # 2. This is the same as above, but in httpd.conf # { { { JkSet } } } uri:vhost/*.group ajp13:workerName # # 3. This does the same thing, but with mapping inside httpd # NOTE: this is currently broken for virtual hosts #<Location "/*"> # { { { JkUriSet } } } group ajp13:{ { { workerName } } } #{ { { </Location> } } } # # If you have a { { { ServerAlias } } }, methods #1 and #2 # require entries for each alias.
{ { { </VirtualHost> } } } # This sends only JSP page requests to tomcat
{ { { <VirtualHost ...> } } } { { { ServerName } } } vhost { { { DocumentRoot } } } /catalina_base/webapps/ROOT/ { { { DirectoryIndex } } } index.jsp index.html { { { JkSet } } } uri:vhost/*.jsp.group ajp13:{ { { workerName } } } { { { </VirtualHost> } } } }}}
<B>This is only a start. But hopefully it will help people already trying to get this working, and having problems. For the Windows users, and others using TCP/IP ports or other transports, sorry. TCP/IP ports will be in the next revision, or you can glean the workers2.properties and jk2.properties directives from the official JK2 documentation.</B>
FYI
September 3rd 2003 - gturcios
During the last two weeks I was unable to find a good example for configuring Apache 2.0.47, Tomcat 4.1.27 and mod_jk-2.0.42. After piecing together examples and ideas from multiple sources I was able to get these three components to work in a load balanced environment. Each Apache and Tomcat lives on a separate server.
Current Environment
{{{ 1 WSD (Load Balancer)
- 3 Apache servers (front-end) 3 Tomcat servers (back-end) The WSD DS Radware is set up with multiple farm addresses that point to the Apaches' primary and virtual interface IP addresses. Each Apache server is load balanced by the WSD using a weighted round-robin mechanism. Each Tomcat server is load balanced between the three Apache servers.
- WSD /|{ { { \ } } }
- / | { { { \ } } }
- Apache1 Apache2 Apache3
- /|\ /|\ /|{ { { \ } } }
- / | \ / | \ / | { { { \ } } }
Building and Configuring Apache
./configure --prefix=/usr/local/apache2 --enable-so --enable-vhost-alias
Copied mod_jk2.so to /usr/local/apache2/modules
Add the following lines to httpd.conf:
{{{ { { { LoadModule jk2_module modules/mod_jk2.so } } }
{ { { <IfModule mod_jk.c> } } }
{ { { JkWorkersFile } } } conf/workers2.properties
{ { { </IfModule> } } } }}}
(note from another author, I couldn't get apache1.3.28 to accept this, I had to use { { { JkSet config:file /usr/local/tomcat/conf/jk/workers2.properties } } })
{{{ # Default { { { DocumentRoot } } }
- #
{ { { DocumentRoot "/usr/local/apache2/htdocs" } } } <location "/*.jsp">
{ { { JkUriSet group loadbalancer } } }
</location> <location "/servlet/*">
{ { { JkUriSet group loadbalancer } } }
</location> <location "/test/*">
{ { { JkUriSet group loadbalancer } } }
</location> }}}
workers2.properties
{{{ # workers2.properties
- # # Tomcat shared memory component
["shm"]
- info=Scoreboard required for reconfiguration and status with multiprocess servers file=/usr/local/apache2/logs/jk2.shm size=1048576 debug=0 disabled=0 # Status worker [status:] info=Status worker, displays runtime informations [uri:/jkstatus/*] info=Display status information and checks the config file for changes. group=status: # Define Load Balancer worker [lb:loadbalancer] info=Default load balancer debug=0 # Define the loadbalancer group communication channel(s) [channel.socket:10.1.1.14:8009] port=8009 host=10.1.1.14 tomcatId=tomcat1 group=loadbalancer [channel.socket:10.1.1.15:8009] port=8009 host=10.1.1.15 tomcatId=tomcat2 group=loadbalancer [channel.socket:10.1.1.16:8009] port=8009 host=10.1.1.16 tomcatId=tomcat3 group=loadbalancer }}}
server.xml
Added jvmRoute="<unique tomcat id>" to the following line:
{{{ <!-- Define the top level container in our container hierarchy -->
<Engine jvmRoute="tomcat1" name="Standalone" defaultHost="localhost" debug="0"> }}}
This jvmRoute parameter uniquely identifies the Tomcat server to each Apache server and maintains a sticky session between the two during a user's session.
Hope this helps...