71. Spring Cloud Zookeeper and Service Registry

Spring Cloud Zookeeper implements the ServiceRegistry interface allowing developers to register arbitrary service in a programmatic way.

The ServiceInstanceRegistration class offers a builder() method to create a Registration object that can be used by the ServiceRegistry .

@Autowired
private ZookeeperServiceRegistry serviceRegistry;

public void registerThings() {
    ZookeeperRegistration registration = ServiceInstanceRegistration.builder()
            .defaultUriSpec()
            .address("anyUrl")
            .port(10)
            .name("/a/b/c/d/anotherservice")
            .build();
    this.serviceRegistry.register(registration);
}

71.1 Instance Status

Netflix Eureka supports having instances registered with the server that are OUT_OF_SERVICE and not returned as active service instances. This is very useful for behaviors such as blue/green deployments. The Curator Service Discovery recipe does not support this behavior. Taking advantage of the flexible payload has let Spring Cloud Zookeeper implement OUT_OF_SERVICE by updating some specific metadata and then filtering on that metadata in the Ribbon ZookeeperServerList . The ZookeeperServerList filters out all non-null instance statuses that do not equal UP . If the instance status field is empty, it is considered UP for backwards compatibility. To change the status of an instance POST OUT_OF_SERVICE to the ServiceRegistry instance status actuator endpoint.

----
$ echo -n OUT_OF_SERVICE | http POST http://localhost:8081/service-registry/instance-status
----

NOTE: The above example uses the `http` command from https://httpie.org