code forum: Implementation of tomcat clustering

When first time i tried to cluster tomcat, found it very difficult. So after going through many many posts, i was able to finally get a cluster working.

That's when i decided to put all my efforts in a simple steps to follow guide

These steps are written keeping windows operating system in mind. For Linux and other OS, installation process differ slightly.

Types of clustering

1)-Horizontal Clustering

2)-Vertical Clustering

Steps to follow:

1- Download zip file for tomcat/don’t use direct installer as it doesn't contain “starup.bat” etc.

2- Unzip it and rename it to your convenience say tomcatA

3- Copy this unzipped folder (in our example I am calling it as tomactA) and make one copy of it and again rename it to your convenience say tomcatB

4-If u want third tomcat also in cluster then make one more copy and rename it to say tomcat, I will be using only two tomcats in this example.

5-now modify server.xml file in each tomcat, i.e. in our example in tomcatA and tomcat. The server.xml can be found in conf folder of tomcat.

6)-just modify the highlighted part as shown in server.xml below

tomcatA:

<Server port="8105" shutdown="SHUTDOWN">

<Listener className="org.apache.catalina.core.AprLifecycleListener" SSLEngine="on" />

<Listener className="org.apache.catalina.core.JasperListener" />

<Listener className="org.apache.catalina.mbeans.ServerLifecycleListener" />
<Listener className="org.apache.catalina.mbeans.GlobalResourcesLifecycleListener" />

<GlobalNamingResources>
    
    <Resource name="UserDatabase" auth="Container"
              type="org.apache.catalina.UserDatabase"
              description="User database that can be updated and saved"
              factory="org.apache.catalina.users.MemoryUserDatabaseFactory"
              pathname="conf/tomcat-users.xml" />
</GlobalNamingResources>

<Service name="Catalina">

    
    


    
    <Connector port="8081" protocol="HTTP/1.1"
               connectionTimeout="20000"
               redirectPort="8443" />

<Connector port="8109" protocol="AJP/1.3" redirectPort="8443" />

<Engine name="Catalina" defaultHost="localhost" jvmRoute="tomcatA">

<Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster"/>

<Realm className="org.apache.catalina.realm.UserDatabaseRealm"
             resourceName="UserDatabase"/>

<Host name="localhost" appBase="webapps"
            unpackWARs="true" autoDeploy="true"
            xmlValidation="false" xmlNamespaceAware="false">

</Host>
</Engine>
</Service>
</Server>

2 tomcatB:

<Service name="Catalina">

    
    


    
    <Connector port="8082" protocol="HTTP/1.1"
               connectionTimeout="20000"
               redirectPort="8443" />

<Connector port="8209" protocol="AJP/1.3" redirectPort="8443" />

</Host>
</Engine>
</Service>
</Server>

7) - To check whether both tomcat are working properly or not

1) - open terminal go to tomcat folder say d: /tomcatA/bin

Now run startup.bat

You will see the logs on terminal, saying server startup in xxx ms

2) Do the same for remaining tomcats.

One common error is message is CATLINA_HOME not defined properly, for clustering purpose we don’t need the variable defined. Therefore just open system variable and remove it from there.

8)-Now install Apche on your system, if u hasn’t done so then download it first.

9) - Now download” mod_jk” and copy it to modules folder of Apache.

10) - Rename the downloaded file to mod_jk.so (if some other name is given u can use that name also on configuration but I feel this more convenient)

11)-Now edit” httpd.conf file”, it can be found in Apache/conf folder

12) - Just add following code in that file

LoadModule jk_module modules/mod_jk.so
JkWorkersFile "C:\Apache\conf\workers.properties"
JkLogFile "logs/mod_jk.log"
JkLogLevel error
JkMount /cluster loadbalancer
JkMount /cluster/* loadbalancer

Points to note here

1)- if you have used any other name then mod_jk.so by skipping step 9 then add that name instead of “mod_jk.so” on first line of above code

2) - I am assuming you have installed Apache on C drive, if it’s in some different location then change the second line of code accordingly

13) - Now add “mod_jk.log” file in log folder of Apache, as some times Apache gives error if it is not present

14) - Now create “worker.properties” file in Apache/conf

15) –Add following content to the file

Vertical tomcat clustering this file like

workers.tomcat_home=/tomcatA
workers.java_home=$JAVA_HOME
ps=/
worker.list=tomcatA,tomcatB,loadbalancer

worker.tomcatA.port=8109
worker.tomcatA.host=localhost
worker.tomcatA.type=ajp13
worker.tomcatA.lbfactor=1

worker.tomcatB.port=8209
worker.tomcatB.host=localhost
worker.tomcatB.type=ajp13
worker.tomcatB.lbfactor=1

worker.loadbalancer.type=lb
worker.loadbalancer.balanced_workers=tomcatA,tomcatB
worker.loadbalancer.sticky_session=1

For horizontal tomcat clustering

workers.tomcat_home=/tomcatA
workers.java_home=$JAVA_HOME
ps=/
worker.list=tomcatA,tomcatB,tomcatC,loadbalancer

worker.tomcatA.port=8009
worker.tomcatA.host=192.168.1.1
worker.tomcatA.type=ajp13
worker.tomcatA.lbfactor=1

worker.tomcatB.port=8009
worker.tomcatB.host=192.168.1.2
worker.tomcatB.type=ajp13
worker.tomcatB.lbfactor=1

worker.loadbalancer.type=lb
worker.loadbalancer.balanced_workers=tomcatA,tomcatB
worker.loadbalancer.sticky_session=1

Points to note:

The sticky_session property specifies the cluster behavior for HTTP sessions. If you specifyworker.loadbalancer.sticky_session=0, each request will be load balanced between node1 and node2; i.e., different requests for the same session will go to different servers. But when a user opens a session on one server, it is always necessary to always forward this user's requests to the same server, as long as that server is available. This is called a "sticky session", as the client is always using the same server he reached on his first request. To enable session stickiness, you need to setworker.loadbalancer.sticky_session to 1.

16) - Now start Apache, you can do it by going in Apache/bin folder using terminal and then run httpd.exe

17) - Start both the tomcat as explained on step 7

18) - You have working cluster now, but we need to modify “web.xml” of any project in order to make it work in clustered environment, to achieve this just add following line in web.xml

Add <distributable /> in web.xml file

<?xml version="1.0" encoding="ISO-8859-1"?>

<web-app xmlns="http://java.sun.com/xml/ns/javaee"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
   version="2.5">
  <distributable />

</web-app>

code forum

Pages

Wednesday, August 3, 2011

Implementation of tomcat clustering

1 comment :