Sarwar Kamal's Blog

About Load Balancing Loadbalancing is a useful mechanism to distribute incoming traffic around several capable Virtual Private servers. By apportioning the processing mechanism to several machines, redundancy is provided to the application -- ensuring fault tolerance and heightened stability. The Round Robin algorithm for load balancing sends visitors to one of a set of IPs. At its most basic level Round Robin, which is fairly easy to implement, distributes server load without implementing considering more nuanced factors like server response time and the visitors’ geographic region. Setup The steps in this tutorial require the user to have root privileges on your VPS. Prior to setting up nginx loadbalancing, you should have nginx installed on your VPS. You can install it quickly with apt-get: sudo apt-get install nginx Upstream Module In order to set up a round robin load balancer, we will need to use the nginx upstream module. We will incorporate the conf...

Session affinity/Sticky Session   Session affinity overrides the load-balancing algorithm by directing all requests in a session to a specific tomcat server. So when we setup the session affinity our problem will solved. But how to setup because session values are random value. We need to generate the session value some how identify the which tomcat generate response. Step 1: Tomcat configuration file (conf/server.xml) contain  <Engine> tag have jvmRoute property for this purpose. So edit the config file and update the <Engine > tag like this <Engine name="Catalina" defaultHost="localhost“ jvmRoute=“tomcat1” > Here tomcat1 is worker name of this tomcat. check the workers.properties file in last post .  Change this line to all tomcat instances  conf/server.xml file and change the jvmRoute value according to workers name and restart the tomcat instances. Now all tomcat generate the session-id pattern...

We already see how to run multiple tomcat instance in a single machine in my previous blog ( http://kmlsarwar.blogspot.com/2014/08/multiple-tomcat-instances-on-single.html ). In this post we will see how to configure load balancing with mod_jk and Apache on Ubuntu. Suppose we have two hosts, node1 and node2 . Node1 runs an Apache and a Tomcat instance. On node2 we’ve got another Tomcat. A browser will connect to the host that’s running the Apache. Since the load on a single server running a web application can be pretty severe, we’re going to share the burden of serving servlets with multiple hosts (in our case two hosts). And we’re going to make mod_jk to do that for us. Steps to Implement Virtual Host/Loadbalancer Concept in this Scenario: Install Apache httpd Web Server  Install mod_jk connector  Configure JK Connector  Configure Apache httpd server, apply loadbalancer concepts Step One—Install Apache We can install Apache web ser...