138. Ribbon discovery in Kubernetes

Spring Cloud client applications calling a microservice should be interested on relying on a client load-balancing feature in order to automatically discover at which endpoint(s) it can reach a given service. This mechanism has been implemented within the [spring-cloud-kubernetes-ribbon](spring-cloud-kubernetes-ribbon/pom.xml) project where a Kubernetes client will populate a Ribbon ServerList containing information about such endpoints.

The implementation is part of the following starter that you can use by adding its dependency to your pom file:

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-kubernetes-ribbon</artifactId>
    <version>${latest.version}</version>
</dependency>

When the list of the endpoints is populated, the Kubernetes client will search the registered endpoints living in the current namespace/project matching the service name defined using the Ribbon Client annotation:

@RibbonClient(name = "name-service")

You can configure Ribbon’s behavior by providing properties in your application.properties (via your application’s dedicated ConfigMap) using the following format: <name of your service>.ribbon.<Ribbon configuration key> where:

Additionally, the spring-cloud-kubernetes-ribbon project defines two additional configuration keys to further control how Ribbon interacts with Kubernetes. In particular, if an endpoint defines multiple ports, the default behavior is to use the first one found. To select more specifically which port to use, in a multi-port service, use the PortName key. If you want to specify in which Kubernetes' namespace the target service should be looked up, use the KubernetesNamespace key, remembering in both instances to prefix these keys with your service name and ribbon prefix as specified above.

Examples that are using this module for ribbon discovery are:

Note: The Ribbon discovery client can be disabled by setting this key within the application properties file spring.cloud.kubernetes.ribbon.enabled=false.