Apache webserver integration with tomcat
How to integrate tomcat in apache webserver and load balance the requests to two tomcat instances.
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Configure the JK Module in httpd.conf
Download the mod_jk.so for apache website suitable for your apache installed and tomcat as well.
Edit the Apache server’s configuration file httpd.conf which is located in the /usr/apache2 /conf directory.
# Load mod_jk
#
LoadModule jk_module modules/mod_jk.so
#
# Configure mod_jk
#
JkWorkersFile conf/workers.properties
JkLogFile logs/mod_jk.log
JkLogLevel info
NOTE : You will need to change mod_jk.so to mod_jk.dll for Windows.
Below the “DocumentRoot” line, insert the following two lines:
JkMount /*.jsp loadbalancer
JkMount /servlet/* loadbalancer
Create the workers.properties file
Now we will create a file called workers.properties, and we will place it under /usr/apache2/conf. The workers.properties file tells Apache about the various Tomcat servers that are running, and on which port they are listening.
In my setup, I installed the two Tomcat servers in different directories, on the same machine as Apache. Feel free to put your Tomcat servers on different machines.
I made the first Tomcat server’s AJP13 connector listen on port 8801 instead of the default port which is 8009, and the second one listens on port 8802.
I have decided to name my tomcat servers tomcat1 and tomcat2.
Create the file exactly like this:
#
# workers.properties
#
# list the workers by name
worker.list=tomcat1, tomcat2, loadbalancer
# ————————
# First tomcat server
# ————————
worker.tomcat1.port=8801
worker.tomcat1.host=localhost
worker.tomcat1.type=ajp13
# Specify the size of the open connection cache.
#worker.tomcat1.cachesize
#
# Specifies the load balance factor when used with
# a load balancing worker.
# Note:
# —-> lbfactor must be > 0
# —-> Low lbfactor means less work done by the worker.
worker.tomcat1.lbfactor=100
# ————————
# Second tomcat server
# ————————
worker.tomcat2.port=8802
worker.tomcat2.host=localhost
worker.tomcat2.type=ajp13
# Specify the size of the open connection cache.
#worker.tomcat2.cachesize
#
# Specifies the load balance factor when used with
# a load balancing worker.
# Note:
# —-> lbfactor must be > 0
# —-> Low lbfactor means less work done by the worker.
worker.tomcat2.lbfactor=100
# ————————
# Load Balancer worker
# ————————
#
# The loadbalancer (type lb) worker performs weighted round-robin
# load balancing with sticky sessions.
# Note:
# —-> If a worker dies, the load balancer will check its state
# once in a while. Until then all work is redirected to peer
# worker.
worker.loadbalancer.type=lb
worker.loadbalancer.balanced_workers=tomcat1, tomcat2
#
# END workers.properties
#
That’s it, we’re done with Apache.
Install and Configure the Tomcat Servers
Now let’s suppose that Java 1.4.x is installed under /usr/local/jdk1.4.x/. Create two Tomcat 4.x servers and install them under /usr/local/:
tar fvxz jakarta-tomcat-4.x.tar.gz
mv jakarta-tomcat-4.x /usr/local/tomcat1
cp -R /usr/local/tomcat1 /usr/local/tomcat2
In both /usr/local/tomcat1 and /usr/local/tomcat2, the same files will be modified. I here by present the modifications made to the files contained in the /usr/local/tomcat1 directory tree structure. You should also apply the same changes to the corresponding files located under the /usr/local/tomcat2 directory tree structure.
Modify catalina.sh
We can set the JAVA_HOME and CATALINA_HOME envoirment variables directly in the catalina.sh file.
At line 32, before the “# —– Verify and Set Required Environment Variables ” line, insert the following two lines:
JAVA_HOME=/usr/local/jdk1.4 ; export JAVA_HOME
CATALINA_HOME=/usr/local/tomcat1 ; export CATALINA_HOME
(Set CATALINA_HOME to /usr/local/tomcat2 in /usr/local/tomcat2/conf/catalina.sh)
Modify conf/server.xml
Add a unique jvmRoute to the Catalina engine
Near line 100, replace:
<Engine defaultHost=”localhost” debug=”0″>
with:
<EnginejvmRoute=”tomcat1″name=”Standalone” defaultHost=”localhost” debug=”0″>
For tomcat2, put jvmRoute=”tomcat2″.
Change the control port
At line 13, replace:
<Server port=”8005″
with:
<Server port=”8811″
For the tomcat2 server, replace port 8005 with 8812. This will prevent the two servers from conflicting.
Change the AJP13 port
At line 75, in the AJP 13 connector definition, replace:
port=”8009″
with:
port=”8801″
For the tomcat2 server, replace port 8009 with 8802.
Disable the standalone HTTP port
We don’t want or need our tomcat servers to directly respond to HTTP requests. So we comment out the Http Connector section between lines and 58 in the server.xml file.
Example:
<!– Define a non-SSL HTTP/1.1 Connector on port 8080 –>
<!–
<Connector className=”org.apache.catalina.connector.http.HttpConnector”
port=”8080″ minProcessors=”5″ maxProcessors=”75″
enableLookups=”true” redirectPort=”8443″
acceptCount=”10″ debug=”0″ connectionTimeout=”60000″/>
–>
NOTE: If you don’t comment this out, you will need to change the port numbers so they don’t conflict between tomcat instances.
Disable the WARP connector
At line 314, comment out the <Connector…WarpConnector…> tag.
Example:
<Service>
<!–
<Connector className=”org.apache.catalina.connector.warp.WarpConnector”
port=”8008″ minProcessors=”5″ maxProcessors=”75″
enableLookups=”true” appBase=”webapps”
acceptCount=”10″ debug=”0″/>
–>
Do not forget to do the same thing to tomcat2′s server.xml file.
NOTE: You might want to comment out the entire <Service> element. If so, make sure and remove the comments within it – XML doesn’t like comments within comments.
Create test JSP pages ( index.jsp )
Create a file named index.jsp and put it in the /usr/local/tomcat1/webapps/ROOT directory:
<html>
<body bgcolor=”green”>
<center>
<%= request.getSession().getId() %>
<h1>Tomcat 1</h1>
</body>
</html>
Create a file named index.jsp and put it in the /usr/local/tomcat2/webapps/ROOT directory:
<html>
<body bgcolor=”yellow”>
<center>
<%= request.getSession().getId() %>
<h1>Tomcat 2</h1>
</body>
</html>
Start Tomcat1, Tomcat2 and Apache
/usr/local/tomcat1/bin/startup.sh
/usr/local/tomcat2/bin/startup.sh
/usr/local/apache2/bin/apachectl start
Test your Installation
Now is the time to test your setup. First, verify that Apache serves static content.
Click on: http://localhost/ . You should see the default Apache index.html page.
Now test that tomcat (either Tomcat 1 or Tomcat 2) is serving Java Server Pages.
Click on: http://localhost/index.jsp
If you get a green page, the page was served by the tomcat1 server, and if you get a yellow page, it was served by the tomcat2 server.
Now test that session affinity – also known as sticky sessions – works within the load balancer. Hit the reload button of your web browser several times and verify that the index.jsp page you get is always received from the same tomcat server.
Configuring Private JVMs
If you don’t need load-balancing, but you are interested in configuring Apache/Tomcat for private Tomcat instances, you can add one of the following near the end of httpd.conf:
Name-based (1 IP address or NIC).
NameVirtualHost *
<VirtualHost *>
ServerName localhost1
JkMount /*.jsp tomcat1
JkMount /servlet/* tomcat1
</VirtualHost>
<VirtualHost *>
ServerName localhost2
JkMount /*.jsp tomcat2
JkMount /servlet/* tomcat2
</VirtualHost>
IP-based (different IP for each site).
# First Virtual Host.
#
<VirtualHost 172.16.19.56:80>
ServerName localhost
JkMount /*.jsp tomcat1
JkMount /servlet/* tomcat1
</VirtualHost>
# Second Virtual Host.
#
<VirtualHost 172.16.19.58:80>
ServerName localhost2
JkMount /*.jsp tomcat2
JkMount /servlet/* tomcat2
</VirtualHost>
Where the serverNames are fully-qualified host names in a DNS Server. More information can be found at http://httpd.apache.org/docs-2.0/vhosts/ .
NOTE:
When using SSL with multiple Virtual Hosts, you must use an ip-based configuration. This is because SSL requires you to configure a specific port (443), whereas name-based specifies all ports (*). You might the following error if you try to mix name-based virtual hosts with SSL.
[error] VirtualHost _default_:443 — mixing * ports and non-* ports with a NameVirtualHost address is not supported, proceeding with undefined result.
