Kubernetes Client
Quarkus includes the kubernetes-client
extension which enables the use of the Fabric8 Kubernetes Client
in native mode while also making it easier to work with.
Having a Kubernetes Client extension in Quarkus is very useful in order to unlock the power of Kubernetes Operators. Kubernetes Operators are quickly emerging as a new class of Cloud Native applications. These applications essentially watch the Kubernetes API and react to changes on various resources and can be used to manage the lifecycle of all kinds of complex systems like databases, messaging systems and much more. Being able to write such operators in Java with the very low footprint that native images provide is a great match.
Configuration
Once you have your Quarkus project configured you can add the kubernetes-client
extension
to your project by running the following command in your project base directory.
quarkus extension add kubernetes-client
./mvnw quarkus:add-extension -Dextensions='kubernetes-client'
./gradlew addExtension --extensions='kubernetes-client'
This will add the following to your build file:
<dependency>
<groupId>io.quarkus</groupId>
<artifactId>quarkus-kubernetes-client</artifactId>
</dependency>
implementation("io.quarkus:quarkus-kubernetes-client")
Usage
Quarkus configures a Bean of type KubernetesClient
which can be injected into application code using the well known CDI methods.
This client can be configured using various properties as can be seen in the following example:
quarkus.kubernetes-client.trust-certs=false
quarkus.kubernetes-client.namespace=default
Note that the full list of properties is available in the Dev Services section of the configuration reference.
In dev mode and when running tests, Dev Services for Kubernetes automatically starts a Kubernetes API server.
Customizing and overriding
Quarkus provides multiple integration points for influencing the Kubernetes Client provided as a CDI bean.
Kubernetes Client Config customization
The first integration point is the use of the io.quarkus.kubernetes.client.KubernetesConfigCustomizer
interface. When such a bean exists,
it allows for arbitrary customizations of the io.fabric8.kubernetes.client.Config
created by Quarkus (which takes into account the quarkus.kubernetes-client.*
properties).
Alternatively, application code can override the io.fabric8.kubernetes.client.Config
or even the io.fabric8.kubernetes.client.KubernetesClient
bean (which are
normally provided by the extension) by simply declaring custom versions of those beans.
An example of this can be seen in the following snippet:
@Singleton
public class KubernetesClientProducer {
@Produces
public KubernetesClient kubernetesClient() {
// here you would create a custom client
return new DefaultKubernetesClient();
}
}
Kubernetes Client ObjectMapper customization
The Fabric8 Kubernetes Client uses its own ObjectMapper
instance for serialization and deserialization of Kubernetes resources.
This mapper is provided to the client through a KubernetesSerialization
instance that’s injected into
the KubernetesClient
bean.
If for some reason you must customize the default ObjectMapper
bean provided by this extension and used by the Kubernetes Client, you can do so by declaring a bean that implements the KubernetesClientObjectMapperCustomizer
interface.
The following code snippet contains an example of a KubernetesClientObjectMapperCustomizer
to set the ObjectMapper
locale:
@Singleton
public static class Customizer implements KubernetesClientObjectMapperCustomizer {
@Override
public void customize(ObjectMapper objectMapper) {
objectMapper.setLocale(Locale.ROOT);
}
}
Furthermore, if you must replace the default ObjectMapper
bean used by the Kubernetes Client that the extension creates automatically, you can do so by declaring a bean of type @KubernetesClientObjectMapper
.
The following code snippet shows how you can declare this bean:
@Singleton
public class KubernetesObjectMapperProducer {
@KubernetesClientObjectMapper
@Singleton
@Produces
public ObjectMapper kubernetesClientObjectMapper() {
return new ObjectMapper();
}
}
The static io.fabric8.kubernetes.client.utils.Serialization utils class is deprecated and should not be used.
Access to Serialization.jsonMapper() should be replaced by the usage of @KubernetesClientObjectMapperCustomizer` declared beans.
|
Testing
To make testing against a mock Kubernetes API extremely simple, Quarkus provides the WithKubernetesTestServer
annotation which automatically launches
a mock of the Kubernetes API server and sets the proper environment variables needed so that the Kubernetes Client configures itself to use said mock.
Tests can inject the mock server and set it up in any way necessary for the particular testing using the @KubernetesTestServer
annotation.
Let’s assume we have a REST endpoint defined like so:
@Path("/pod")
public class Pods {
private final KubernetesClient kubernetesClient;
public Pods(KubernetesClient kubernetesClient) {
this.kubernetesClient = kubernetesClient;
}
@GET
@Path("/{namespace}")
public List<Pod> pods(String namespace) {
return kubernetesClient.pods().inNamespace(namespace).list().getItems();
}
}
We could write a test for this endpoint very easily like so:
// you can even configure aspects like crud, https and port on this annotation
@WithKubernetesTestServer
@QuarkusTest
public class KubernetesClientTest {
@KubernetesTestServer
KubernetesServer mockServer;
@Inject
KubernetesClient client;
@BeforeEach
public void before() {
final Pod pod1 = new PodBuilder().withNewMetadata().withName("pod1").withNamespace("test").and().build();
final Pod pod2 = new PodBuilder().withNewMetadata().withName("pod2").withNamespace("test").and().build();
// Set up Kubernetes so that our "pretend" pods are created
client.pods().resource(pod1).create();
client.pods().resource(pod2).create();
}
@Test
public void testInteractionWithAPIServer() {
RestAssured.when().get("/pod/test").then()
.body("size()", is(2));
}
}
Note that to take advantage of these features, the quarkus-test-kubernetes-client
dependency needs to be added, for example like so:
<dependency>
<groupId>io.quarkus</groupId>
<artifactId>quarkus-test-kubernetes-client</artifactId>
<scope>test</scope>
</dependency>
testImplementation("io.quarkus:quarkus-test-kubernetes-client")
By default, the mock server will be in CRUD mode, so you have to use the client to build your state before your application can retrieve it, but you can also set it up in non-CRUD mode and mock all HTTP requests made to Kubernetes:
// you can even configure aspects like crud, https and port on this annotation
@WithKubernetesTestServer(crud = false)
@QuarkusTest
public class KubernetesClientTest {
@KubernetesTestServer
KubernetesServer mockServer;
@BeforeEach
public void before() {
final Pod pod1 = new PodBuilder().withNewMetadata().withName("pod1").withNamespace("test").and().build();
final Pod pod2 = new PodBuilder().withNewMetadata().withName("pod2").withNamespace("test").and().build();
// Mock any HTTP request to Kubernetes pods so that our pods are returned
mockServer.expect().get().withPath("/api/v1/namespaces/test/pods")
.andReturn(200,
new PodListBuilder().withNewMetadata().withResourceVersion("1").endMetadata().withItems(pod1, pod2)
.build())
.always();
}
@Test
public void testInteractionWithAPIServer() {
RestAssured.when().get("/pod/test").then()
.body("size()", is(2));
}
}
You can also use the setup
attribute on the @WithKubernetesTestServer
annotation to provide a class that will configure the KubernetesServer
instance:
@WithKubernetesTestServer(setup = MyTest.Setup.class)
@QuarkusTest
public class MyTest {
public static class Setup implements Consumer<KubernetesServer> {
@Override
public void accept(KubernetesServer server) {
server.expect().get().withPath("/api/v1/namespaces/test/pods")
.andReturn(200, new PodList()).always();
}
}
// tests
}
Alternately, you can create an extension of the KubernetesServerTestResource
class to ensure all your @QuarkusTest
enabled test classes share the same mock server setup via the QuarkusTestResource
annotation:
public class CustomKubernetesMockServerTestResource extends KubernetesServerTestResource {
@Override
protected void configureServer() {
super.configureServer();
server.expect().get().withPath("/api/v1/namespaces/test/pods")
.andReturn(200, new PodList()).always();
}
}
and use this in your other test classes as follows:
@QuarkusTestResource(CustomKubernetesMockServerTestResource.class)
@QuarkusTest
public class KubernetesClientTest {
//tests will now use the configured server...
}
Note on implementing or extending generic types
Due to the restrictions imposed by GraalVM, extra care needs to be taken when implementing or extending generic types provided by the client if the application is intended to work in native mode.
Essentially every implementation or extension of generic classes such as Watcher
, ResourceHandler
or CustomResource
needs to specify their associated Kubernetes model class (or, in the case of CustomResource
, regular Java types) at class definition time.
To better understand this, suppose we want to watch for changes to Kubernetes Pod
resources.
There are a couple ways to write such a Watcher
that are guaranteed to work in native:
client.pods().watch(new Watcher<Pod>() {
@Override
public void eventReceived(Action action, Pod pod) {
// do something
}
@Override
public void onClose(KubernetesClientException e) {
// do something
}
});
or
public class PodResourceWatcher implements Watcher<Pod> {
@Override
public void eventReceived(Action action, Pod pod) {
// do something
}
@Override
public void onClose(KubernetesClientException e) {
// do something
}
}
...
client.pods().watch(new PodResourceWatcher());
Note that defining the generic type via a class hierarchy similar to the following example will also work correctly:
public abstract class MyWatcher<S> implements Watcher<S> {
}
...
client.pods().watch(new MyWatcher<Pod>() {
@Override
public void eventReceived(Action action, Pod pod) {
// do something
}
});
The following example will not work in native mode because the generic type of watcher cannot be determined by looking at the class and method definitions thus making Quarkus unable to properly determine the Kubernetes model class for which reflection registration is needed: |
public class ResourceWatcher<T extends HasMetadata> implements Watcher<T> {
@Override
public void eventReceived(Action action, T resource) {
// do something
}
@Override
public void onClose(KubernetesClientException e) {
// do something
}
}
client.pods().watch(new ResourceWatcher<Pod>());
Note on using Elliptic Curve keys
Please note that if you would like to use Elliptic Curve keys with Kubernetes Client then adding a BouncyCastle PKIX dependency is required:
<dependency>
<groupId>org.bouncycastle</groupId>
<artifactId>bcpkix-jdk18on</artifactId>
</dependency>
implementation("org.bouncycastle:bcpkix-jdk18on")
Note that internally an org.bouncycastle.jce.provider.BouncyCastleProvider
provider will be registered if it has not already been registered.
You can have this provider registered as described in the BouncyCastle or BouncyCastle FIPS sections.
Access to the Kubernetes API
In many cases in order to access the Kubernetes API server a ServiceAccount
, Role
and RoleBinding
will be necessary.
An example that allows listing all pods could look something like this:
---
apiVersion: v1
kind: ServiceAccount
metadata:
name: <applicationName>
namespace: <namespace>
---
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
name: <applicationName>
namespace: <namespace>
rules:
- apiGroups: [""]
resources: ["pods"]
verbs: ["list"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
name: <applicationName>
namespace: <namespace>
roleRef:
kind: Role
name: <applicationName>
apiGroup: rbac.authorization.k8s.io
subjects:
- kind: ServiceAccount
name: <applicationName>
namespace: <namespace>
Replace <applicationName>
and <namespace>
with your values.
Have a look at Configure Service Accounts for Pods to get further information.
OpenShift Client
If the targeted Kubernetes cluster is an OpenShift cluster, it is possible to access it through
the openshift-client
extension, in a similar way. This leverages the dedicated fabric8
openshift client, and provides access to OpenShift
proprietary objects (e.g. Route
, ProjectRequest
, BuildConfig
…)
Note that the configuration properties are shared with the kubernetes-client
extension. In
particular, they have the same quarkus.kubernetes-client
prefix.
Add the extension with:
quarkus extension add openshift-client
./mvnw quarkus:add-extension -Dextensions='openshift-client'
./gradlew addExtension --extensions='openshift-client'
Note that openshift-client
extension has a dependency on the kubernetes-client
extension.
To use the client, inject an OpenShiftClient
instead of the KubernetesClient
:
@Inject
private OpenShiftClient openshiftClient;
If you need to override the default OpenShiftClient
, provide a producer such as:
@Singleton
public class OpenShiftClientProducer {
@Produces
public OpenShiftClient openshiftClient() {
// here you would create a custom client
return new DefaultOpenShiftClient();
}
}
Mock support is also provided in a similar fashion:
@QuarkusTestResource(OpenShiftMockServerTestResource.class)
@QuarkusTest
public class OpenShiftClientTest {
@MockServer
private OpenShiftMockServer mockServer;
...
Or by using the @WithOpenShiftTestServer
similar to the @WithKubernetesTestServer
explained in the
previous section:
@WithOpenShiftTestServer
@QuarkusTest
public class OpenShiftClientTest {
@OpenShiftTestServer
private OpenShiftServer mockOpenShiftServer;
...
To use this feature, you have to add a dependency on quarkus-test-openshift-client
:
<dependency>
<groupId>io.quarkus</groupId>
<artifactId>quarkus-test-openshift-client</artifactId>
<scope>test</scope>
</dependency>
testImplementation("io.quarkus:quarkus-test-openshift-client")
Configuration Reference
Configuration property fixed at build time - All other configuration properties are overridable at runtime
Configuration property |
Type |
Default |
---|---|---|
Whether the client should trust a self-signed certificate if so presented by the API server Environment variable: Show more |
boolean |
|
URL of the Kubernetes API server Environment variable: Show more |
string |
|
Default namespace to use Environment variable: Show more |
string |
|
CA certificate file Environment variable: Show more |
string |
|
CA certificate data Environment variable: Show more |
string |
|
Client certificate file Environment variable: Show more |
string |
|
Client certificate data Environment variable: Show more |
string |
|
Client key file Environment variable: Show more |
string |
|
Client key data Environment variable: Show more |
string |
|
Client key algorithm Environment variable: Show more |
string |
|
Client key passphrase Environment variable: Show more |
string |
|
Kubernetes auth username Environment variable: Show more |
string |
|
Kubernetes auth password Environment variable: Show more |
string |
|
Kubernetes oauth token Environment variable: Show more |
string |
|
Watch reconnect interval Environment variable: Show more |
||
Maximum reconnect attempts in case of watch failure By default there is no limit to the number of reconnect attempts Environment variable: Show more |
int |
|
Maximum amount of time to wait for a connection with the API server to be established Environment variable: Show more |
||
Maximum amount of time to wait for a request to the API server to be completed Environment variable: Show more |
||
Maximum number of retry attempts for API requests that fail with an HTTP code of >= 500 Environment variable: Show more |
int |
|
Time interval between retry attempts for API requests that fail with an HTTP code of >= 500 Environment variable: Show more |
||
HTTP proxy used to access the Kubernetes API server Environment variable: Show more |
string |
|
HTTPS proxy used to access the Kubernetes API server Environment variable: Show more |
string |
|
Proxy username Environment variable: Show more |
string |
|
Proxy password Environment variable: Show more |
string |
|
IP addresses or hosts to exclude from proxying Environment variable: Show more |
list of string |
|
Enable the generation of the RBAC manifests. If enabled and no other role binding are provided using the properties Environment variable: Show more |
boolean |
|
Type |
Default |
|
If Dev Services for Kubernetes should be used. (default to true) If this is true and kubernetes client is not configured then a kubernetes cluster will be started and will be used. Environment variable: Show more |
boolean |
|
The kubernetes api server version to use. If not set, Dev Services for Kubernetes will use the latest supported version of the given flavor. see https://github.com/dajudge/kindcontainer/blob/master/k8s-versions.json Environment variable: Show more |
string |
|
The flavor to use (kind, k3s or api-only). Default to api-only. Environment variable: Show more |
|
|
By default, if a kubeconfig is found, Dev Services for Kubernetes will not start. Set this to true to override the kubeconfig config. Environment variable: Show more |
boolean |
|
Indicates if the Kubernetes cluster managed by Quarkus Dev Services is shared. When shared, Quarkus looks for running containers using label-based service discovery. If a matching container is found, it is used, and so a second one is not started. Otherwise, Dev Services for Kubernetes starts a new container. The discovery uses the Container sharing is only used in dev mode. Environment variable: Show more |
boolean |
|
The value of the This property is used when you need multiple shared Kubernetes clusters. Environment variable: Show more |
string |
|
Environment variables that are passed to the container. Environment variable: Show more |
Map<String,String> |
About the Duration format
To write duration values, use the standard You can also use a simplified format, starting with a number:
In other cases, the simplified format is translated to the
|