Ramki Technical Blog

Hi this second part of the  Tomcat Clustering Series . In my first part we discuss about how to setup simple load balancer. and we seen how load balancer distribute the request to tomcat instance in round robin fashion. [Check the video below for better understanding] In this post we discuss about what is the problem is occur in simple load balancer when we introduce sessions in our web application. and we will see how to resolve this issue. Its continuation of my first part of this series. so kindly go read my first part then continue here. How Session works in Servlet/Tomcat?        Before going into problem, let see the session management in Tomcat . If any if the page/servlet create the session then Tomcat create the Session Object and attached into group of session (HashMap kind structure) and that session can identify using session-id, its just random number generated through any one of the hash algorithm. then respond to client with cookie header field. That cookie

I am going to start new series of posts about Tomcat clustering . In this first post we will see what is problem in normal deployment in only single machine, what is clustering and why is necessary and how to setup the simple load balancer with Apache httpd web server + Tomcat server cluster. [Check the video for better understanding] Why need Clustering? (Tomcat Clustering)            In normal production servers are running in single machine. If that's machine may be failed due to crashed or hardware defects or OutOfMemory exception then  our site can't access by anybody. so how to solve this problem? . to add more tomcat machine to collectively (group/cluster) run as a production server. (oppose of single machine). Each tomcat has deployed the same web application. so any tomcat can process the client request. If one tomcat is failed, then other tomcat in the cluster to proceeds the request. Here one big problem is arrive. each tomcat instances are running in de