MOD_JK Installation and Configuration - Apache HTTPD and Tomcat

root@ mw-web01 # pwd
/tmp/tomcat-connectors-1.2.42-src/native/apache-2.0
root@ mw-web01 # ls -rlt
total 4960
-rw-r--r – 1 root bin 1335 Sep 13 2010 config.m4
-rw-r--r – 1 root bin 11019 Nov 14 2011 mod_jk.dsp
-rw-r--r – 1 root bin 6351 Nov 16 2011 NWGNUmakefile
-rw-r--r – 1 root bin 9541 Nov 16 2011 bldjk.qclsrc
-rw-r--r – 1 root bin 10350 Nov 16 2011 bldjk54.qclsrc
-rw-r--r – 1 root bin 6947 Mar 9 2012 Makefile.vc
-rw-r--r – 1 root bin 1434 Dec 20 2014 Makefile.apxs.in
-rw-r--r – 1 root bin 3068 Dec 20 2014 Makefile.in
-rw-r--r – 1 root bin 147853 Sep 22 2016 mod_jk.c
-rw-r--r – 1 root root 3328 Nov 6 14:37 Makefile
-rw-r--r – 1 root root 1622 Nov 6 14:37 Makefile.apxs
-rw-r--r – 1 root root 365288 Nov 6 14:49 mod_jk.o
-rw-r--r – 1 root root 270 Nov 6 14:49 mod_jk.lo
-rwxr-xr-x 1 root root 1553336 Nov 6 14:49 mod_jk.so
-rw-r--r – 1 root root 920 Nov 6 14:49 mod_jk.la
-rw-r--r – 1 root root 2917994 Nov 6 14:49 mod_jk.a

cp mod_jk.so /etc/httpd/modules

here is my directory listing of server_root /etc/httpd for your reference

root@ mw-web01 # ls -rlt
total 4
drwxr-xr-x. 2 root root 78 Oct 31 13:58 conf.d
drwxr-xr-x. 2 root root 4096 Oct 31 13:58 conf.modules.d
lrwxrwxrwx 1 root root 19 Oct 31 13:58 logs -> ../../var/log/httpd
lrwxrwxrwx 1 root root 29 Oct 31 13:58 modules -> ../../usr/lib64/httpd/modules
lrwxrwxrwx 1 root root 10 Oct 31 13:58 run -> /run/httpd
drwxr-xr-x. 2 root root 35 Nov 6 14:55 conf

 

Step7: Load the Module mod_jk.so

Now it is a time to load the module .SO file, we have just copied to the  modules directory

In an earlier version of apache if we want to Load any module we would use LoadModule directive in httpd.conf file.

But, in Apache2+ every configuration files are in a distinct directory and imported into httpd.conf using Include directive.

You can see there are multiple INCLUDES in httpd.conf

root@ mw-web01 # grep -i ^Include conf/httpd.conf
Include conf.modules.d/*.conf
Include sites-enabled/*
IncludeOptional conf.d/*.conf

and all the module related configurations are loaded from conf.modules.d directory

our LoadModule has to be put under /etc/httpd/conf.modules.d directory as a new file. This setup would help in categorizing and managing the modules effectively

here is the Snap of my conf.modules.d directory before adding a new file.

root@ mw-web01 # cd conf.modules.d
root@ mw-web01 # pwd
/etc/httpd/conf.modules.d
root@ mw-web01 # ls -rlt
total 32
-rw-r--r--. 1 root root 43 Aug 19 2014 10-wsgi.conf
-rw-r--r – 1 root root 451 Jul 26 04:43 01-cgi.conf
-rw-r--r – 1 root root 88 Jul 26 04:43 00-systemd.conf
-rw-r--r – 1 root root 957 Jul 26 04:43 00-proxy.conf
-rw-r--r – 1 root root 742 Jul 26 04:43 00-mpm.conf
-rw-r--r – 1 root root 41 Jul 26 04:43 00-lua.conf
-rw-r--r – 1 root root 139 Jul 26 04:43 00-dav.conf
-rw-r--r – 1 root root 3739 Jul 26 04:43 00-base.conf
root@ mw-web01 #

Now we need to Create a new file named mod_jk.conf and add the following lines

LoadModule jk_module "/etc/httpd/modules/mod_jk.so"

JkWorkersFile /etc/httpd/conf/workers.properties
JkLogFile /etc/httpd/logs/mod_jk.log

JkLogLevel info

JkLogStampFormat "[%a %b %d %H:%M:%S %Y]"
JkOptions +ForwardKeySize +ForwardURICompat -ForwardDirectories
JkRequestLogFormat "%w %V %T"

Here

JkWorkersFile is the file where we would be defining the application server details and nodes etc
JkLogFile is the log for the mod_jk, It is good to troubleshoot in case of issues

The other four directive's tasks could be easily interpreted by their very name

 

Step8: Creating Workers ( they are our minions!!)

We have defined theJkWorkersFile file name and location on the Step7 inside the mod_jk.conf file

Now Its a time to create a Workers file and define the application server (tomcat) details,  In my case I have tomcat servers running at following hostnames and ports  tc_node1.techolaf.com:8009 andtc_node2.techolaf.com:8009

Here 8009 is the AJP port number on the backend Tomcat Servers.

#Define the list of workers you have
worker.list=jkstatus,lb_router

# Set LOADBALANCER
worker.lb_router.type=lb
worker.jkstatus.type=status

# HERE is where you decide on how many Tomcat Server's there are in the cluster
worker.lb_router.balance_workers=tc-node1,tc-node2
worker.lb_router.sticky_session=1

# Set Worker

worker.tc-node1.port=8009
worker.tc-node1.host=tc_node1.techolaf.com
worker.tc-node1.type=ajp13
worker.tc-node1.lbfactor=1
worker.tc-node2.port=8009
worker.tc-node2.host=tc_node1.techolaf.com
worker.tc-node2.type=ajp13
worker.tc-node2.lbfactor=1

Note:*
mwitc-node1  is the worker name (member) here, there will be a dedicated worker for each application server node. Name of this worker should be matched to the JVM_Route parameter value in the back-end tomcat's server.xml file

 

Step8: Adding JVMRoute in server.xml

in the backend servers you need to add a jvmRoute parameter and the value of jvmRoute should be as same as the worker name mentioned in the workers.properties file.

Hostname	WorkerName	JvmRoute Value
tc_node1.techolaf.com	tc-node1	tc-node1
tc_node2.techolaf.com	tc-node2	tc-node2

<Engine name="Catalina" defaultHost="localhost" jvmRoute="tc-node1">

 

Step9: Update your Apache Virtual Host file and add JKMount

Update your virtual Host Configuration to enable URI forwarding

Now go back to your virtual host configuration file on the Apache webserver end based on your apache server configuration you can find the file in any of these paths

/etc/apache2/sites-enabled/<your-app-name>.conf
/etc/apache2/conf.d/<your-app-name>.conf

Now, it's time to configure apache to forward the requests to the application server

If the URI path aka context-root matches to a certain string. These Strings are basically referred to as Context-root (or) war file names in the tomcat end.

At the end of your virtual host file, add the below line