StickyLoadBalancerTest.java

package camelinaction;

import org.apache.camel.builder.RouteBuilder;
import org.apache.camel.component.mock.MockEndpoint;
import org.apache.camel.test.junit4.CamelTestSupport;
import org.junit.Test;

/**
 * Demonstrates how to use the Load Balancer EIP pattern.
 * <p/>
 * Using the sticky strategy.
 */
public class StickyLoadBalancerTest extends CamelTestSupport {

    @Test
    public void testLoadBalancer() throws Exception {
        // A should get the 1st and 4th message
        MockEndpoint a = getMockEndpoint("mock:a");
        a.expectedBodiesReceived("Hello", "Bye");

        // B should get the 2nd and 3rd message
        MockEndpoint b = getMockEndpoint("mock:b");
        b.expectedBodiesReceived("Camel rocks", "Cool");

        // send in 4 messages with id as correlation key
        // notice that the ids is not an exact number to pick the processor in order.
        // Camel will use the key to generate a hash value which is used for choosing the processor.
        // gold will pick A because its the first message
        // then silver will be bound to pick B as its the next
        template.sendBodyAndHeader("direct:start", "Hello", "type", "gold");
        template.sendBodyAndHeader("direct:start", "Camel rocks", "type", "silver");
        template.sendBodyAndHeader("direct:start", "Cool", "type", "silver");
        template.sendBodyAndHeader("direct:start", "Bye", "type", "gold");

        assertMockEndpointsSatisfied();
    }

    @Override
    protected RouteBuilder createRouteBuilder() throws Exception {
        return new RouteBuilder() {
            @Override
            public void configure() throws Exception {
                from("direct:start")
                    // use load balancer with sticky strategy
                    .loadBalance()
                        // sticky requires an expression parameter to be used
                        // for calculating the correlation key
                        .sticky(header("type"))
                        // this is the 2 processors which we will balance across
                        .to("seda:a").to("seda:b")
                    .end();

                // service A
                from("seda:a")
                    .log("A received: ${body}")
                    .to("mock:a");

                // service B
                from("seda:b")
                    .log("B received: ${body}")
                    .to("mock:b");
            }
        };
    }

}