camel load balancer EIP

Camel With Load Balancer EIP with simple steps.


In this tutorial we learn about load balancer EIP in camel.In load balancer EIP ,workload is divided among resources to utilize it effectively.When we use load balancer then we need to select strategy which decides how resources should be distributed,in our example we are using round robin strategy.

Example

In our example we will send a message to queue and from router we will define load balancer that will send message to two queue in round robin fashion so at the end we will get messages distributed among two queues.

  • In eclipse go to MyFirstCamelProject that we created in earlier page and right click on src/main/java to create package.New -> package



  • Give any name for example com.preparationforinterview and click on Finish



  • Right click on package and create a java class for example MyRoute.



  • Add following dependency in pom.xml file.you can use any latest version.

  •  	
    <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>MyFirstCamelProject</groupId>
    	<artifactId>MyFirstCamelProject</artifactId>
    	<version>0.0.1-SNAPSHOT</version>
    	<dependencies>
    		<dependency>
    			<groupId>org.apache.camel</groupId>
    			<artifactId>camel-test</artifactId>
    			<version>2.5.0</version>
    			<scope>test</scope>
    		</dependency>
    		<dependency>
    			<groupId>junit</groupId>
    			<artifactId>junit</artifactId>
    			<version>4.8.1</version>
    			<scope>test</scope>
    		</dependency>
    	</dependencies>
    </project>
    
  • Run mvn:install from command prompt or if you are using Eclipse right click on pom.xml and run mvn install.It will download camel jars

  • Copy below code in MyRoute.

  •  	
    package com.preparationforinterview;
    
    import org.apache.camel.builder.RouteBuilder;
    
    public class MyRoute extends RouteBuilder {
    
    	@Override
    	public void configure() throws Exception {
    		from("direct:start").log("Sending ").loadBalance().roundRobin()
    				.to("direct:first").to("direct:second");
    
    		from("direct:first").log("First endpoint received: ").to(
    				"mock:first");
    		from("direct:second").log("Second endpoint received: ").to(
    				"mock:second");
    
    	}
    
    }
    

    Explain

    To create a route in camel we need to extend RouteBuilder class and override configure method.In configure method we define our route.In above route we are accepting message from in memory route and logging it to see the content of the message.After that we are calling loadBalance with roundRobin which distribute messages to direct:first and direct:second.First message will go to direct:first and second will go to direct:second and again third will go to direct:first and so on.

    To test above load balancer we will create one class LoadBalancerTest.java.



  • At the end we will have following structure


  • Copy below code in LoadBalancerTest.java.

  •  	
    package com.preparationforinterview;
    
    import org.apache.camel.builder.RouteBuilder;
    import org.apache.camel.test.junit4.CamelTestSupport;
    import org.junit.Test;
    
    public class LoadBalancerTest extends CamelTestSupport {
    	@Override
    	protected RouteBuilder createRouteBuilder() throws Exception {
    		return new MyRoute();
    	}
    
    	@Test
    	public void testSplitterEIP() throws Exception {
    		
    	 String message1 = "Hello, I am preparaing from PreparationforInterview.com";
    	 String message2 = "I have prepared from preparationforinterview.com"; 
    
    		getMockEndpoint("mock:first").expectedMessageCount(2);
    		getMockEndpoint("mock:second").expectedMessageCount(2);
    		
    		getMockEndpoint("mock:first").expectedBodiesReceived(message1,message2);
    		getMockEndpoint("mock:second").expectedBodiesReceived(message1,message2);
    
    		template.sendBody("direct:start",message1);
    		template.sendBody("direct:start",message1);
    		template.sendBody("direct:start",message2);
    		template.sendBody("direct:start",message2);
    		assertMockEndpointsSatisfied();
    
    	}
    }
    

    Explain

    To get camel test kit advantage we need to extend CamelTestSupport.CamelTestSupport class is wrapped on Junit.When we extend CamelTestSupport then we need to override one method createRouteBuilder.In that method create an object of route class.In our case we have done MyRoute.To test router we created method annotated with @Test. In that method we are getting mock endpoint and we have set expectation for example Expected expectedBodiesReceived and expectedMessageCount.After expectation has been set,we are sending message to direct:start queue.To Test execution with our result we fire assertion.template, we get from CamelTestSupport.

    To check the output right click on LoadBalancerTest.java and run it.It will pass test case and we will get following output.


    To run the program from command prompt,open command prompt and go to project location and run below command.
    mvn compile exec:java -Dexec.mainClass=com.preparationforinterview.LoadBalancerTest

Download source code

Camel With Load Balancer EIP



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