Apache Camel Load Balancer Pattern in Apache Camel using example

In previous tutorial we implemented the Dynamic Router EIP Pattern
In this tutorial we will implement the Load Balancer EIP.
For this tutorial we will be taking reference of the Apache Camel+ JMS tutorial we had implemented before. The Load Balancer Pattern allows you to delegate to one of a number of endpoints using a variety of different load balancing policies.

Apache Camel - Table of Contents
File Transfer Using Java DSL Apache Camel
Apache Camel Java DSL + Spring Integration Hello World Example
Apache Camel Exception Handling Using Simple Example
Apache Camel Redelivery policy using example
Integrate Apache Camel and ActiveMQ
EIP patterns using Apache Camel
Apache Camel Tutorial- Integrate Spring Boot+ Apache Camel
Apache Camel Tutorial- Integrate with MySQL DB using SQL query
Apache Camel + Spring + ActiveMQ + JBoss Fuse 
Apache Camel EIP - Splitter and Aggregator pattern
Apache Camel Unit Testing 
Apache Camel + Spring + Quartz Hello World Example 
Camel application deployment on JBoss Fuse 
Apache Camel + Apache CXF SOAP Webservices
Apache Camel + JAX-RS REST Webservice
Apache Camel + CXFRS REST Webservice 
Apache Camel Routing Slip EIP Pattern
Apache Camel Dynamic Router Pattern
Apache Camel Load Balancer EIP Pattern
Apache Camel Interceptors
Apache Camel + Kafka Hello World Example
Apache Camel - Marshalling/Unmarshalling XML/JSON Data Example
Calling and Consuming Webservices using Apache Camel
Apache Camel Tutorial - Send SMTP Email Using Gmail
Apache Camel Tutorial - SEDA component Hello World Example
Spring Boot + Apache Camel + RabbitMQ - Hello World Example
Apache Camel Tutorial - Idempotent Consumer using MemoryIdempotentRepository and FileIdempotentRepository
Spring Boot + Apache Camel JDBC component + MySQL - Hello World Example 
Spring Boot + Apache Camel SQL component + MySQL - Hello World Example
Spring Boot + Apache Camel SQL component + Transaction Management Example

Lets Begin

The load balancing pattern can be any of the following-

Policy	Description
Round Robin	The exchanges are selected from in a round robin fashion. This is a well known and classic policy, which spreads the load evenly.
Random	A random endpoint is selected for each exchange.
Sticky	Sticky load balancing using an Expression to calculate a correlation key to perform the sticky load balancing; rather like jsessionid in the web or JMSXGroupID in JMS.
Topic	Topic which sends to all destinations (rather like JMS Topics)
Failover	In case of failures the exchange will be tried on the next endpoint.
Weighted Round-Robin	The weighted load balancing policy allows you to specify a processing load distribution ratio for each server with respect to the others. In addition to the weight, endpoint selection is then further refined using round-robin distribution based on weight.
Weighted Random	The weighted load balancing policy allows you to specify a processing load distribution ratio for each server with respect to others.In addition to the weight, endpoint selection is then further refined using random distribution based on weight.
Custom	From Camel 2.8 onwards the preferred way of using a custom Load Balancer is to use this policy, instead of using the @deprecated ref attribute.
Circuit Breaker	Implements the Circuit Breaker pattern

In this tutorial we will be using the Round Robbin Load Balancer Pattern.
We will create Eclipse maven project as follows-


Our pom file will be as follows-

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.javainuse</groupId>
	<artifactId>camel-load-balancer</artifactId>
	<version>0.0.1-SNAPSHOT</version>

	<dependencies>
		<dependency>
			<groupId>org.apache.camel</groupId>
			<artifactId>camel-core</artifactId>
			<version>2.13.0</version>
		</dependency>
		<dependency>
			<groupId>org.apache.camel</groupId>
			<artifactId>camel-jms</artifactId>
			<version>2.14.1</version>
		</dependency>

		<dependency>
			<groupId>org.apache.activemq</groupId>
			<artifactId>activemq-camel</artifactId>
			<version>5.7.0</version>
		</dependency>

		<dependency>
			<groupId>org.apache.activemq</groupId>
			<artifactId>activemq-broker</artifactId>
			<version>5.10.1</version>
		</dependency>

		<dependency>
			<groupId>org.apache.activemq</groupId>
			<artifactId>activemq-client</artifactId>
			<version>5.10.1</version>
		</dependency>
		<dependency>
			<groupId>org.apache.activemq</groupId>
			<artifactId>activemq-pool</artifactId>
			<version>5.10.1</version>
		</dependency>
	</dependencies>
</project>

Define the route.

package com.javainuse;

import org.apache.camel.builder.RouteBuilder;

public class SimpleRouteBuilder extends RouteBuilder {

	@Override
	public void configure() throws Exception {
		from("file:C:/inbox?noop=true").split().tokenize("\n").loadBalance().roundRobin().to("jms:queue:javainuse1")
				.to("jms:queue:javainuse2").to("jms:queue:javainuse3");
	}
}

When Camel is started, it creates a CamelContext object that contains the definition of the Route to be started. Below we create default camel context and load the routes created in SimpleRouteBuilder.

package com.javainuse;

import javax.jms.ConnectionFactory;
import org.apache.activemq.ActiveMQConnectionFactory;
import org.apache.camel.CamelContext;
import org.apache.camel.component.jms.JmsComponent;
import org.apache.camel.impl.DefaultCamelContext;

public class MainApp {

    public static void main(String[] args) {
        SimpleRouteBuilder routeBuilder = new SimpleRouteBuilder();
        CamelContext ctx = new DefaultCamelContext();
        ConnectionFactory connectionFactory = new ActiveMQConnectionFactory("tcp://0.0.0.0:61616");
        //define the jms component
        ctx.addComponent("jms", JmsComponent.jmsComponentAutoAcknowledge(connectionFactory));
        try {
            ctx.addRoutes(routeBuilder);
            ctx.start();
            Thread.sleep(5 * 60 * 1000);
            ctx.stop();
        }
        catch (Exception e) {
            e.printStackTrace();
        }

    }
}

In C:/inbox folder we have a file with following content-

learn 
camel 
using 
javainuse

Next run the MainApp class as a java application. We can see that the above file contents get split and messages have been routed to different queues based on the Round Robbin Pattern.

Download Source Code

Download it - Apache Camel Load Balancer EIP Pattern

See Also
Spring Boot Hello World Application- Create simple controller and jsp view using Maven
Spring Boot Tutorial-Spring Data JPA
Spring Boot + Simple Security Configuration
Pagination using Spring Boot Simple Example
Spring Boot + ActiveMQ Hello world Example
Spring Boot + Swagger Example Hello World Example
Spring Boot + Swagger- Understanding the various Swagger Annotations
Spring Boot Main Menu
Spring Boot Interview Questions