3. DiscoveryClient for Kubernetes

This project provides an implementation of Discovery Client for Kubernetes. This client lets you query Kubernetes endpoints (see services) by name. A service is typically exposed by the Kubernetes API server as a collection of endpoints that represent http and https addresses and that a client can access from a Spring Boot application running as a pod.spring-doc.cn

This is something that you get for free by adding the following dependency inside your project:spring-doc.cn

Fabric8 Kubernetes Clientspring-doc.cn

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-kubernetes-fabric8</artifactId>
</dependency>

Kubernetes Java Clientspring-doc.cn

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-kubernetes-client</artifactId>
</dependency>

To enable loading of the DiscoveryClient, add @EnableDiscoveryClient to the according configuration or application class, as the following example shows:spring-doc.cn

@SpringBootApplication
@EnableDiscoveryClient
public class Application {
  public static void main(String[] args) {
    SpringApplication.run(Application.class, args);
  }
}

Then you can inject the client in your code simply by autowiring it, as the following example shows:spring-doc.cn

@Autowired
private DiscoveryClient discoveryClient;

You can choose to enable DiscoveryClient from all namespaces by setting the following property in application.properties:spring-doc.cn

spring.cloud.kubernetes.discovery.all-namespaces=true

To discover service endpoint addresses that are not marked as "ready" by the kubernetes api server, you can set the following property in application.properties (default: false):spring-doc.cn

spring.cloud.kubernetes.discovery.include-not-ready-addresses=true
This might be useful when discovering services for monitoring purposes, and would enable inspecting the /health endpoint of not-ready service instances.

If your service exposes multiple ports, you will need to specify which port the DiscoveryClient should use. The DiscoveryClient will choose the port using the following logic.spring-doc.cn

  1. If the service has a label primary-port-name it will use the port with the name specified in the label’s value.spring-doc.cn

  2. If no label is present, then the port name specified in spring.cloud.kubernetes.discovery.primary-port-name will be used.spring-doc.cn

  3. If neither of the above are specified it will use the port named https.spring-doc.cn

  4. If none of the above conditions are met it will use the port named http.spring-doc.cn

  5. As a last resort it wil pick the first port in the list of ports.spring-doc.cn

The last option may result in non-deterministic behaviour. Please make sure to configure your service and/or application accordingly.

By default all of the ports and their names will be added to the metadata of the ServiceInstance.spring-doc.cn

If, for any reason, you need to disable the DiscoveryClient, you can set the following property in application.properties:spring-doc.cn

spring.cloud.kubernetes.discovery.enabled=false

Some Spring Cloud components use the DiscoveryClient in order to obtain information about the local service instance. For this to work, you need to align the Kubernetes service name with the spring.application.name property.spring-doc.cn

spring.application.name has no effect as far as the name registered for the application within Kubernetes

Spring Cloud Kubernetes can also watch the Kubernetes service catalog for changes and update the DiscoveryClient implementation accordingly. In order to enable this functionality you need to add @EnableScheduling on a configuration class in your application.spring-doc.cn