{"id":211,"date":"2016-01-17T22:47:17","date_gmt":"2016-01-17T20:47:17","guid":{"rendered":"http:\/\/www.systemcodegeeks.com\/?p=211"},"modified":"2016-01-17T22:47:17","modified_gmt":"2016-01-17T20:47:17","slug":"set-tomcat-apache-mod_jk-cluster","status":"publish","type":"post","link":"https:\/\/www.systemcodegeeks.com\/web-servers\/apache\/set-tomcat-apache-mod_jk-cluster\/","title":{"rendered":"Set up Tomcat, Apache and mod_jk cluster"},"content":{"rendered":"

In this article I will go through a common set-up for a small production environment. A single tier, load balanced application server cluster.<\/p>\n

Overview<\/h2>\n

A high level overview of what we will be doing.<\/p>\n

    \n
  1. Downloading and installing Apache HTTP server and mod_jk<\/li>\n
  2. Downloading Tomcat<\/li>\n
  3. Downloading Java<\/li>\n
  4. Configuring two local Tomcat servers<\/li>\n
  5. Clustering the two Tomcat servers<\/li>\n
  6. Configuring Apache to use mod_jk to forward request to Tomcat<\/li>\n
  7. Deploying application to Tomcat server that tests our set-up<\/li>\n<\/ol>\n

    Introduction<\/h2>\n

    What is Apache?<\/h4>\n

    Apache is an HTTP server.<\/p>\n

    What is mod_jk?<\/h4>\n

    It is an Apache module that allows AJP communication<\/a> between Apache and a back end application server like Tomcat.<\/p>\n

    I am running this on Ubuntu 14.04LTS installed on a dual boot PC with Windows 7.<\/p>\n

    \"screenshot-from-2015-02-28-173928\"<\/a><\/p>\n

    Download Apache2<\/h4>\n

    We are going to use Ubuntu\u2019s APT package maintenance system to obtain and install Apache2.<\/p>\n

    sudo apt-get install apache2<\/pre>\n
    This will install in \/etc\/apache2<\/p>\n
    Download and install mod_jk<\/h4>\n
    The mod_jk module is not included in the Apache2 download so must be obtained and installed separately. The installation requires that the mod_jk module is visible to Apache and configured to ensure that Apache knows where to look for it and what to do with the requests you want to proxy.<\/p>\n
    sudo apt-get install libapache2-mod-jk<\/pre>\n
    This will install in \/etc\/libapache2-mod-jk also two files have been added to the \/etc\/apache2\/mods-available folder.<\/p>\n
    Downloading and installing Tomcat 8<\/h4>\n
    At the time of writing this Tomcat 8 does not have a package in APT so you must download the binaries from the tomcat website.<\/p>\n
    http:\/\/tomcat.apache.org\/download-80.cgi<\/a> select the appropriate binary distribution and extract it as follows.<\/p>\n
    tar xvzf apache-tomcat-8.0.5.tar.gz<\/pre>\n
    We need two copies of the Tomcat server to be load balanced. I created two directories in the \/opt\/ location: \/opt\/tomcat-server1\/ and \/opt\/tomcat-server2\/ and copied tomcat into each one.<\/p>\n
    Download and install Java<\/h4>\n
    Download Java from APT as follows:<\/p>\n
    apt-get install openjdk-7-jdk<\/pre>\n
    and set JAVA_HOME in .bashrc<\/p>\n
    vim ~\/.bashrc<\/pre>\n
    export JAVA_HOME=\/usr\/lib\/jvm\/java-7-openjdk-amd64<\/pre>\n
    Configure two local Tomcat servers<\/h4>\n
    We will edit only the server.xml of the server2 installation of tomcat. We need to change port numbers to avoid conflicts.<\/p>\n
    We change the following:<\/p>\n
    <Server port=\"9005\" shutdown=\"SHUTDOWN\"><\/pre>\n
    <Connector port=\"9009\" protocol=\"AJP\/1.3\" redirectPort=\"9443\"\/><\/pre>\n
    and comment out the HTTP Connector as we only want the web application to be accessible through the load balancer.<\/p>\n
    Here is my server2 Tomcat server.xml configuration<\/a>.<\/p>\n
    Configure mod_jk<\/h4>\n
    Load balancing is configured in the workers.properties file, located \/etc\/libapache2-mod-jk\/ where workers represent actual or virtual workers.We will define two actual workers and two virtual workers which map to the Tomcat servers. In the worker.list<\/strong> property I have defined two virtual workers: status<\/strong> and loadbalancer<\/strong>, I will refer to these later in the Apache configuration.<\/p>\n
    Workers for each server have been defined using values for the server.xml<\/strong> configuration files. I used the port values for the AJP connectors and I have included an lbfactor<\/strong> that sets the preference that the load balancer will show for that server.<\/p>\n
    Finally we define the virtual workers. The loadbalancer<\/strong> worker is set to type lb<\/strong> and set the workers that represent the Tomcat servers in the balancer_workers<\/strong> properties. The status only needs to be set to type status.<\/p>\n
    worker.list=loadbalancer,status \r\n\r\nworker.server1.port=8009\r\nworker.server1.host=localhost\r\nworker.server1.type=ajp13 \r\n\r\nworker.server2.port=9009\r\nworker.server2.host=localhost\r\nworker.server2.type=ajp13 \r\n\r\nworker.server1.lbfactor=1\r\nworker.server2.lbfactor=1 \r\n\r\nworker.loadbalancer.type=lb\r\nworker.loadbalancer.balance_workers=server1,server2 \r\n\r\nworker.status.type=status<\/pre>\n
    Ensure that you remove any other worker configuration that are not being used.<\/p>\n
    Configure Apache Web Server to forward requests<\/h4>\n
    You will need to add the following to the Apache configurations located in etc\/apache2\/sites-enabled\/000-default.conf<\/p>\n
    JkMount \/status status\r\nJkMount \/* loadbalancer<\/pre>\n
    Verify the installation<\/h4>\n
    To test that all has been configured correctly we need to deploy an application. A sample application that has been used for years to test such configurations is called the ClusterJSP sample application. You can find it by googling in or from the JBoss site<\/a>.<\/p>\n
    Now deploy the war to the webapps folder on both servers and start each server using the start-up script \/opt\/tomcat-server1\/bin\/startup.sh.<\/p>\n
    Go to http:\/\/localhost\/clusterjsp\/HaJsp.jsp<\/a> and you should see the page show HttpSession information.<\/p>\n
    \"screenshot-from-2015-02-28-123654\"<\/a><\/p>\n
    Now lets look at the mod_jk status page: http:\/\/localhost\/status<\/a>. You will see that this page shows information about the load balancer workers and the workers it is balancing.<\/p>\n
    \"screenshot-from-2015-02-28-164329\"<\/a><\/p>\n
    If everything is working you will see the worker error state show OK or OK\/IDLE if they are not currently balancing load.<\/p>\n
    Things to try out<\/h4>\n
    Enable sticky sessions: Configure jvmRoute<\/strong> in the server.xml<\/strong> configuration.<\/p>\n
    Further reading<\/h4>\n