Kubernetes Service Discovery

Kubernetes has a built-in support for service discovery and load-balancing. However, you may need more flexibility to carefully select the service instance you want.

This page explains how Stork can use the Kubernetes API to handle the service discovery.

Dependency

First, you need to add the Stork Kubernetes Service Discovery provider:

<dependency>
    <groupId>io.smallrye.stork</groupId>
    <artifactId>stork-service-discovery-kubernetes</artifactId>
    <version>1.1.0</version>
</dependency>

A few words about server authentication.

Stork uses Fabric8 Kubernetes Client to access the Kubernetes resources, concretely the DefaultKubernetesClient implementation. It will try to read the ~/.kube/config file in your home directory and load information required for authenticating with the Kubernetes API server. If you are using DefaultKubernetesClient from inside a Pod, it will load ~/.kube/config from the ServiceAccount volume mounted inside the Pod. You can override this configuration if you want a more complex configuration.

Configuration

For each service expected to be exposed as Kubernetes Service, configure the lookup:

stork.my-service.service-discovery=kubernetes
stork.my-service.service-discovery.k8s-namespace=my-namespace

Stork looks for the Kubernetes Service with the given name (my-service in the previous example) in the specified namespace.

Instead of using the Kubernetes Service IP directly, and let Kubernetes handle the selection and balancing, Stork inspects the service and retrieves the list of pods providing the service. Then, it can select the instance.

Supported attributes are the following:

Attribute	Mandatory	Default Value	Description
k8s-host	No		The Kubernetes API host.
k8s-namespace	No		The namespace of the service. Use all to discover all namespaces.
application	No		The Eureka application Id; if not defined Stork service name will be used.
refresh-period	No	5M	Service discovery cache refresh period.
secure	No	false	Whether the communication should use a secure connection (e.g. HTTPS)