Camel and Spring Boot

Camel supports Spring Boot since Camel 2.15 but in the latest release we have improved Camel to make it a first class citizen of Spring Boot, some notables improvements available as of Camel 2.18 are:

  • spring boot starters

  • spring boot auto configuration

  • spring boot healt check

In Camel 2.19 we’ll furter improve the integration between Camel and Spring Boot and it will include support for Spring Cloud.

Meet Camel Spring Cloud

Spring Cloud [1] provides an implementation of some common pattern in distributed system like:

  • configuration management

  • service discovery

  • load balancing

The initial support for Spring Cloud in Camel leverages service discovery and load balancing to provide an implementation of the ServiceCall EIP [2] so that you can easilly call remote services with minimal efforts.

Let’s build a simple load balanced ServiceCall in OpenShift

I’ll show the relevant parts here, full code is available on github

Bill of materials

  • Minishift [3]

  • Apache Maven

  • Fabri8 Maven Plugin [4]

  • Spring Boot

  • Spring Cloud Commons

  • Spring Cloud Netflix

  • Spring Cloud Kubernetes

  • Apache Camel 2.19.0-SNAPSHOT

Spring Cloud Kubernetes is now part of Spring Cloud Incubator [5] but we are still using the version from fabric8io [6] to let the migration process to complete

Set up a simple REST Web Service

Thanks to Spring Boot, writing a simple REST Web Service is really trivial:

@RestController
public class ServiceController {
    @RequestMapping("/hello")
    public String hello() {
        return "Hello from " + System.getenv("POD_NAME");
    }
}

Now, let’s write a OpenShift descriptor to start two replicas of the Web Service we have created:

spec:
  replicas: 2
  template:
    spec:
      containers:
        -
          env:
          - name: SPRING_APPLICATION_NAME
            value: camel-cloud-svc
          - name: POD_NAME
            valueFrom:
              fieldRef:
                fieldPath: metadata.name

Thanks to the Fabric8 Maven Plugin, deploying our Web Service is a matter of a single command:

$ mvn fabric8:deploy

...

$ oc get pods
NAME                          READY     STATUS      RESTARTS   AGE
camel-cloud-svc-1-deploy      1/1       Running     0          27s
camel-cloud-svc-1-ojyy6       0/1       Running     0          24s
camel-cloud-svc-1-sbkbi       0/1       Running     0          24s
camel-cloud-svc-s2i-2-build   0/1       Completed   0          55s

If you looks at the endpoints you’ll see the internal addresses our Web Service is listening to and its name:

$ oc get endpoints
NAME              ENDPOINTS                         AGE
camel-cloud-svc   172.17.0.3:8080,172.17.0.5:8080   2m

Set up a simple Camel Route

Thanks to Spring Boot, Spring Cloud and Camel Spring Cloud writing a simple route that invokes the Web Services we have deployed above is really easy:

@Configuration
public class ConsumerConfiguration {
    @Bean
    public RouteBuilder routeBuilder() {
        return new RouteBuilder() {
            @Override
            public void configure() throws Exception {
                from("timer:service-call?period=1s")
                    .serviceCall("camel-cloud-svc/hello") (1)
                    .convertBodyTo(String.class)
                        .to("log:service.consumer?level=INFO&showAll=tru&multiline=true");
            }
        };
    }
}
1 The only thing you need to configure the Service Call EIP: the name of the service and its context path

Thanks to the Fabric8 Maven Plugin, running our Web Service Consumer is a matter of a single command:

$ mvn fabric8:run

...

[INFO] F8: 2016-12-21 17:35:25.473  INFO 1 --- [://service-call] service.consumer : Exchange[
[INFO] F8: , ExchangePattern: InOnly
[INFO] F8: , BodyType: String
[INFO] F8: , Body: Hello from camel-cloud-svc-1-sbkbi (1)
[INFO] F8: ]
[INFO] F8: 2016-12-21 17:35:25.563  INFO 1 --- [://service-call] service.consumer : Exchange[
[INFO] F8: , ExchangePattern: InOnly
[INFO] F8: , BodyType: String
[INFO] F8: , Body: Hello from camel-cloud-svc-1-ojyy6 (2)
[INFO] F8: ]
1 Web Service invoked on POD camel-cloud-svc-1-sbkbi
2 Web Service invoked on POD camel-cloud-svc-1-ojyy6

Wrap up

What’s happen under the hood ?

  1. Spring Cloud Kubernetes automatically creates a DiscoveryClient which is used to lookup services by name

  2. Spring Cloud Commons/Netflix automatically creates a LoadBalancerClient which leverages Netflix’s Ribbon for load balancing

  3. Camel Spring Cloud automatically configure the SerivceCall EIP to use the LoadBalancerClient created by Spring Cloud

This is a work in progress so things may change in the next future.
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