what difference between KubernetesClient and OpenshiftClient in fabric8 - fabric8

Question

I am learning fabric8,
When I use KubernetesClient, it can access pods and return res
KubernetesClient k8sClient = new DefaultKubernetesClient();
try {
PodList podList = k8sClient.pods().inNamespace("myns").list();
logger.info("There are {} }pods in myns namespace.", podList.getItems().size());
} catch (KubernetesClientException exception) {
logger.info("error: {}", exception.getMessage());
}
When I use openshiftClient, it failed to return any results and no any errors.
OpenShiftClient openshiftClient = new DefaultOpenShiftClient();
try {
PodList podList = openshiftClient.pods().inNamespace("myns").list();
logger.info("There are {} }pods in myns namespace.", podList.getItems().size());
} catch (KubernetesClientException exception) {
logger.info("error: {}", exception.getMessage());
}
I am curious what difference between KubernetesClient and OpenshiftClient. In fact my cluster is a OpenShift 4.7.32, my fabbric8 version is
implementation group: 'io.fabric8', name: 'kubernetes-client', version: '5.8.0'
implementation group: 'io.fabric8', name: 'kubernetes-api', version: '3.0.12'
Any ideas for that?

Answer 1

KubernetesClient is the base of all clients provided by Fabric8. It is most popular module among all provided modules and is used when user only needs to access Kubernetes native resources (For example, Deployment, Pod, Service etc) or Custom Resources (via Fabric8 KubernetesClient CustomResource API). For most cases, you'd only need to manage basic Kubernetes Resources and would only need KubernetesClient, which is available via this dependency:
<dependency>
<groupId>io.fabric8</groupId>
<artifactId>kubernetes-client</artifactId>
<version>5.9.0</version>
</dependency>
OpenShiftClient is specific to Red Hat OpenShift container platform. It is a superset of KubernetesClient which means you get all the functionality of KubernetesClient along with some additional support of OpenShift specific API groups. Some examples of these are:
DeploymentConfig openshiftClient.deploymentConfigs()
Route openshiftClient.routes()
BuildConfig openshiftClient.buildConfigs()
ImageStream openshiftClient.imageStreams()
Project openshiftClient.projects()
Template openshiftClient.templates()
If you would not have been using OpenShiftClient, you would be accessing these resources via Fabric8 KubernetesClient Generic API. with OpenShiftClient, you get model classes and DSL support for these OpenShift specific resources. You can have a look at OpenShiftClient interface to see all the additional DSL endpoints provided. You can access this via the openshift-client module:
<dependency>
<groupId>io.fabric8</groupId>
<artifactId>openshift-client</artifactId>
<version>5.9.0</version>
</dependency>
I tried reproducing your issue by trying out your code on Red Hat OpenShift Developer Sandbox by running these code samples on OpenShiftCluster:
KubernetesClient:
public static void main(String[] args) {
try (KubernetesClient k8sClient = new DefaultKubernetesClient()) {
PodList podList = k8sClient.pods().inNamespace("rokumar-dev").list();
logger.info("There are {} pods in myns namespace.", podList.getItems().size());
} catch (KubernetesClientException exception) {
logger.info("error: {}", exception.getMessage());
}
}
OpenShiftClient:
public static void main(String[] args) {
try (OpenShiftClient k8sClient = new DefaultOpenShiftClient()) {
PodList podList = k8sClient.pods().inNamespace("rokumar-dev").list();
logger.info("There are {} pods in myns namespace.", podList.getItems().size());
} catch (KubernetesClientException exception) {
logger.info("error: {}", exception.getMessage());
}
}
However, it gives same result for me in both cases. I see you're using kubernetes-api(which is using quite old version of Fabric8 OpenShift Client(see code here)). This module is marked deprecated and is no longer maintained. I think if you run this code with openshift-client dependency it should work