Skip to main content

Load Balancing and Clustering Tomcat

There are two ways of Clustering applications on Tomcat
1. Sticky Session
User request will always goes to same tomcat instance
2. Session Replication
User request can go to any tomcat in cluster and his session is copied on entire cluster

There are pros and cons of both approach, however i'll update this blog later on those.

Lets get started for Sticky Session based clustering and load balancing.

Use-Case
Setting up two tomcat along with apache on same windows machine.

Pre-requirements
1. install Apche 2.x
2. download tomcat 5.x /6.x and make an extra copy

Steps 1. open httpd.conf from apache_home/conf/ and add these lines at the end

BalancerMember ajp://localhost:8009/ route=tomcatA
BalancerMember ajp://localhost:8010/ route=tomcatB

ProxyPass balancer://mycluster/ stickysession=JSESSIONID

SetHandler balancer-manager
Order Deny,Allow
Deny from all
Allow from localhost

Step 2.

uncomment the following four lines

LoadModule proxy_module modules/mod_proxy.so
LoadModule proxy_ajp_module modules/mod_proxy_ajp.so
LoadModule proxy_balancer_module modules/mod_proxy_balancer.so
LoadModule status_module modules/mod_status.so

Step 3.

open tomcat_home_1/conf/server.xml and add jvmRoute="tomcatA" to the following line

Engine name="Catalina" defaultHost="localhost"

so it should look like this
Engine name="Catalina" defaultHost="localhost" jvmRoute="tomcatA"
Step 4.

open tomcat_home_2/conf/server.xml and add jvmRoute="tomcatB" to the following line

Engine name="Catalina" defaultHost="localhost"

so it should look like this
Engine name="Catalina" defaultHost="localhost" jvmRoute="tomcatB

also change the following port nos


Server port="8006" shutdown="SHUTDOWN"

Connector port="8081" protocol="HTTP/1.1"
connectionTimeout="20000"
redirectPort="8444"

Connector port="8010" protocol="AJP/1.3" redirectPort="8444"

Thats It!

start apache, tomcatA, tomcatB and

navigate to http://localhost/
also checkout balancer-manager
http://localhost/balancer-manager

for more configuration and understanding checkout the following link




Comments

Post a Comment

Popular posts from this blog

JPA 2 new feature @ElementCollection explained

@ElementCollection is new annotation introduced in JPA 2.0, This will help us get rid of One-Many and Many-One shitty syntax. Example 1: Stores list of Strings in an Entity @Entity public class Users implements Serializable {     private static final long serialVersionUID = 1L;     @Id     @GeneratedValue(strategy = GenerationType.AUTO)     private Long id;     @ElementCollection     private List<String> certifications = new ArrayList <String> ();     public Long getId() {         return id;     }     public void setId(Long id) {         this.id = id;     }     public List <String> getCertifications() {         return certifications;     }     public void setCertifications(List <String> certifications) {         this.certifications = certifications;     } .. }         Users u = new Users();         u.getCertifications().add("Sun Certified Java Programmer");         em.persist(u); Generated Tables    Users    Co
21 comments
Read more

Reuse JPA Entities as DTO

Note : Major design advantages of JPA Entities are they can detached and used across tiers and networks and later can by merged. Checkout this new way of querying entities in JPA 2.0 String ql = " SELECT new prepclass2.Employee (e.firstname, e.lastname) FROM Employee e "; List<Employee> dtos = em.createQuery(ql).getResultList(); The above query loads all Employee entities but with subset of data i.e. firstname, lastname. Employee entity looks like this. @Entity @Table(name="emp") public class Employee implements Serializable {     private static final long serialVersionUID = 1L;     @Id     @GeneratedValue(strategy = GenerationType.AUTO)     private Long id;     @Column     private String firstname;     @Column     private String lastname;     @Column     private String username;     @Column     private String street;     @Column     private String city;     @Column     private String state;     @Column     private String zipc
11 comments
Read more

Validating CSV Files

What is CsvValidator ?   A Java framework which validates any CSV files something similar to XML validation using XSD. Why should I use this ?   You don't have to use this and in fact its easy to write something your own and also checkout its source code for reference. Why did I write this ?   Some of our projects integrate with third party application which exchanges information in CSV files so I thought of writing a generic validator which can be hooked in multiple projects or can be used by QA for integration testing. What is the license clause ?   GNU GPL v2 Are there any JUnit test cases for me checkout ?  Yes,  source How to integrate in my existing project ? Just add the Jar which can be downloaded from here  CsvValidator.jar  and you are good. Instantiate  CsvValidator c onstructor which takes these 3 arguements          // filename is the the file to be validated and here is a  sample         // list - defines all the fields in the above csv file ( a
7 comments
Read more