$ mkdir -p $HOME/projects/memcached-operator
Java-based Operator SDK is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process. For more information about the support scope of Red Hat Technology Preview features, see Technology Preview Features Support Scope. |
Operator developers can take advantage of Java programming language support in the Operator SDK to build an example Java-based Operator for Memcached, a distributed key-value store, and manage its lifecycle.
The Red Hat-supported version of the Operator SDK CLI tool, including the related scaffolding and testing tools for Operator projects, is deprecated and is planned to be removed in a future release of OpenShift Container Platform. Red Hat will provide bug fixes and support for this feature during the current release lifecycle, but this feature will no longer receive enhancements and will be removed from future OpenShift Container Platform releases. The Red Hat-supported version of the Operator SDK is not recommended for creating new Operator projects. Operator authors with existing Operator projects can use the version of the Operator SDK CLI tool released with OpenShift Container Platform 4.17 to maintain their projects and create Operator releases targeting newer versions of OpenShift Container Platform. The following related base images for Operator projects are not deprecated. The runtime functionality and configuration APIs for these base images are still supported for bug fixes and for addressing CVEs.
For the most recent list of major functionality that has been deprecated or removed within OpenShift Container Platform, refer to the Deprecated and removed features section of the OpenShift Container Platform release notes. For information about the unsupported, community-maintained, version of the Operator SDK, see Operator SDK (Operator Framework). |
This process is accomplished using two centerpieces of the Operator Framework:
The operator-sdk
CLI tool and java-operator-sdk
library API
Installation, upgrade, and role-based access control (RBAC) of Operators on a cluster
This tutorial goes into greater detail than Getting started with Operator SDK for Java-based Operators. |
Operator SDK CLI installed
OpenShift CLI (oc
) 4.17+ installed
Java 11+
Maven 3.6.3+
Logged into an OpenShift Container Platform 4.17 cluster with oc
with an account that has cluster-admin
permissions
To allow the cluster to pull the image, the repository where you push your image must be set as public, or you must configure an image pull secret
Use the Operator SDK CLI to create a project called memcached-operator
.
Create a directory for the project:
$ mkdir -p $HOME/projects/memcached-operator
Change to the directory:
$ cd $HOME/projects/memcached-operator
Run the operator-sdk init
command
with the quarkus
plugin
to initialize the project:
$ operator-sdk init \
--plugins=quarkus \
--domain=example.com \
--project-name=memcached-operator
Among the files generated by the operator-sdk init
command is a Kubebuilder PROJECT
file. Subsequent operator-sdk
commands, as well as help
output, that are run from the project root read this file and are aware that the project type is Java. For example:
domain: example.com
layout:
- quarkus.javaoperatorsdk.io/v1-alpha
projectName: memcached-operator
version: "3"
Use the Operator SDK CLI to create a custom resource definition (CRD) API and controller.
Run the following command to create an API:
$ operator-sdk create api \
--plugins=quarkus \(1)
--group=cache \(2)
--version=v1 \(3)
--kind=Memcached (4)
1 | Set the plugin flag to quarkus . |
2 | Set the group flag to cache . |
3 | Set the version flag to v1 . |
4 | Set the kind flag to Memcached . |
Run the tree
command to view the file structure:
$ tree
.
├── Makefile
├── PROJECT
├── pom.xml
└── src
└── main
├── java
│ └── com
│ └── example
│ ├── Memcached.java
│ ├── MemcachedReconciler.java
│ ├── MemcachedSpec.java
│ └── MemcachedStatus.java
└── resources
└── application.properties
6 directories, 8 files
Define the API for the Memcached
custom resource (CR).
Edit the following files that were generated as part of the create api
process:
Update the following attributes in the MemcachedSpec.java
file to define the desired state of the Memcached
CR:
public class MemcachedSpec {
private Integer size;
public Integer getSize() {
return size;
}
public void setSize(Integer size) {
this.size = size;
}
}
Update the following attributes in the MemcachedStatus.java
file to define the observed state of the Memcached
CR:
The example below illustrates a Node status field. It is recommended that you use typical status properties in practice. |
import java.util.ArrayList;
import java.util.List;
public class MemcachedStatus {
// Add Status information here
// Nodes are the names of the memcached pods
private List<String> nodes;
public List<String> getNodes() {
if (nodes == null) {
nodes = new ArrayList<>();
}
return nodes;
}
public void setNodes(List<String> nodes) {
this.nodes = nodes;
}
}
Update the Memcached.java
file to define the Schema for Memcached APIs that extends to both MemcachedSpec.java
and MemcachedStatus.java
files.
@Version("v1")
@Group("cache.example.com")
public class Memcached extends CustomResource<MemcachedSpec, MemcachedStatus> implements Namespaced {}
After the API is defined with MemcachedSpec
and MemcachedStatus
files, you can generate CRD manifests.
Run the following command from the memcached-operator
directory to generate the CRD:
$ mvn clean install
Verify the contents of the CRD in the target/kubernetes/memcacheds.cache.example.com-v1.yml
file as shown in the following example:
$ cat target/kubernetes/memcacheds.cache.example.com-v1.yaml
# Generated by Fabric8 CRDGenerator, manual edits might get overwritten!
apiVersion: apiextensions.k8s.io/v1
kind: CustomResourceDefinition
metadata:
name: memcacheds.cache.example.com
spec:
group: cache.example.com
names:
kind: Memcached
plural: memcacheds
singular: memcached
scope: Namespaced
versions:
- name: v1
schema:
openAPIV3Schema:
properties:
spec:
properties:
size:
type: integer
type: object
status:
properties:
nodes:
items:
type: string
type: array
type: object
type: object
served: true
storage: true
subresources:
status: {}
After creating a new API and controller, you can implement the controller logic.
Append the following dependency to the pom.xml
file:
<dependency>
<groupId>commons-collections</groupId>
<artifactId>commons-collections</artifactId>
<version>3.2.2</version>
</dependency>
For this example, replace the generated controller file MemcachedReconciler.java
with following example implementation:
MemcachedReconciler.java
package com.example;
import io.fabric8.kubernetes.client.KubernetesClient;
import io.javaoperatorsdk.operator.api.reconciler.Context;
import io.javaoperatorsdk.operator.api.reconciler.Reconciler;
import io.javaoperatorsdk.operator.api.reconciler.UpdateControl;
import io.fabric8.kubernetes.api.model.ContainerBuilder;
import io.fabric8.kubernetes.api.model.ContainerPortBuilder;
import io.fabric8.kubernetes.api.model.LabelSelectorBuilder;
import io.fabric8.kubernetes.api.model.ObjectMetaBuilder;
import io.fabric8.kubernetes.api.model.OwnerReferenceBuilder;
import io.fabric8.kubernetes.api.model.Pod;
import io.fabric8.kubernetes.api.model.PodSpecBuilder;
import io.fabric8.kubernetes.api.model.PodTemplateSpecBuilder;
import io.fabric8.kubernetes.api.model.apps.Deployment;
import io.fabric8.kubernetes.api.model.apps.DeploymentBuilder;
import io.fabric8.kubernetes.api.model.apps.DeploymentSpecBuilder;
import org.apache.commons.collections.CollectionUtils;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
public class MemcachedReconciler implements Reconciler<Memcached> {
private final KubernetesClient client;
public MemcachedReconciler(KubernetesClient client) {
this.client = client;
}
// TODO Fill in the rest of the reconciler
@Override
public UpdateControl<Memcached> reconcile(
Memcached resource, Context context) {
// TODO: fill in logic
Deployment deployment = client.apps()
.deployments()
.inNamespace(resource.getMetadata().getNamespace())
.withName(resource.getMetadata().getName())
.get();
if (deployment == null) {
Deployment newDeployment = createMemcachedDeployment(resource);
client.apps().deployments().create(newDeployment);
return UpdateControl.noUpdate();
}
int currentReplicas = deployment.getSpec().getReplicas();
int requiredReplicas = resource.getSpec().getSize();
if (currentReplicas != requiredReplicas) {
deployment.getSpec().setReplicas(requiredReplicas);
client.apps().deployments().createOrReplace(deployment);
return UpdateControl.noUpdate();
}
List<Pod> pods = client.pods()
.inNamespace(resource.getMetadata().getNamespace())
.withLabels(labelsForMemcached(resource))
.list()
.getItems();
List<String> podNames =
pods.stream().map(p -> p.getMetadata().getName()).collect(Collectors.toList());
if (resource.getStatus() == null
|| !CollectionUtils.isEqualCollection(podNames, resource.getStatus().getNodes())) {
if (resource.getStatus() == null) resource.setStatus(new MemcachedStatus());
resource.getStatus().setNodes(podNames);
return UpdateControl.updateResource(resource);
}
return UpdateControl.noUpdate();
}
private Map<String, String> labelsForMemcached(Memcached m) {
Map<String, String> labels = new HashMap<>();
labels.put("app", "memcached");
labels.put("memcached_cr", m.getMetadata().getName());
return labels;
}
private Deployment createMemcachedDeployment(Memcached m) {
Deployment deployment = new DeploymentBuilder()
.withMetadata(
new ObjectMetaBuilder()
.withName(m.getMetadata().getName())
.withNamespace(m.getMetadata().getNamespace())
.build())
.withSpec(
new DeploymentSpecBuilder()
.withReplicas(m.getSpec().getSize())
.withSelector(
new LabelSelectorBuilder().withMatchLabels(labelsForMemcached(m)).build())
.withTemplate(
new PodTemplateSpecBuilder()
.withMetadata(
new ObjectMetaBuilder().withLabels(labelsForMemcached(m)).build())
.withSpec(
new PodSpecBuilder()
.withContainers(
new ContainerBuilder()
.withImage("memcached:1.4.36-alpine")
.withName("memcached")
.withCommand("memcached", "-m=64", "-o", "modern", "-v")
.withPorts(
new ContainerPortBuilder()
.withContainerPort(11211)
.withName("memcached")
.build())
.build())
.build())
.build())
.build())
.build();
deployment.addOwnerReference(m);
return deployment;
}
}
The example controller runs the following reconciliation logic for each Memcached
custom resource (CR):
Creates a Memcached deployment if it does not exist.
Ensures that the deployment size matches the size specified by the Memcached
CR spec.
Updates the Memcached
CR status with the names of the memcached
pods.
The next subsections explain how the controller in the example implementation watches resources and how the reconcile loop is triggered. You can skip these subsections to go directly to Running the Operator.
Every controller has a reconciler object with a Reconcile()
method that implements the reconcile loop. The reconcile loop is passed the Deployment
argument, as shown in the following example:
Deployment deployment = client.apps()
.deployments()
.inNamespace(resource.getMetadata().getNamespace())
.withName(resource.getMetadata().getName())
.get();
As shown in the following example, if the Deployment
is null
, the deployment needs to be created. After you create the Deployment
, you can determine if reconciliation is necessary. If there is no need of reconciliation, return the value of UpdateControl.noUpdate()
, otherwise, return the value of `UpdateControl.updateStatus(resource):
if (deployment == null) {
Deployment newDeployment = createMemcachedDeployment(resource);
client.apps().deployments().create(newDeployment);
return UpdateControl.noUpdate();
}
After getting the Deployment
, get the current and required replicas, as shown in the following example:
int currentReplicas = deployment.getSpec().getReplicas();
int requiredReplicas = resource.getSpec().getSize();
If currentReplicas
does not match the requiredReplicas
, you must update the Deployment
, as shown in the following example:
if (currentReplicas != requiredReplicas) {
deployment.getSpec().setReplicas(requiredReplicas);
client.apps().deployments().createOrReplace(deployment);
return UpdateControl.noUpdate();
}
The following example shows how to obtain the list of pods and their names:
List<Pod> pods = client.pods()
.inNamespace(resource.getMetadata().getNamespace())
.withLabels(labelsForMemcached(resource))
.list()
.getItems();
List<String> podNames =
pods.stream().map(p -> p.getMetadata().getName()).collect(Collectors.toList());
Check if resources were created and verify podnames with the Memcached resources. If a mismatch exists in either of these conditions, perform a reconciliation as shown in the following example:
if (resource.getStatus() == null
|| !CollectionUtils.isEqualCollection(podNames, resource.getStatus().getNodes())) {
if (resource.getStatus() == null) resource.setStatus(new MemcachedStatus());
resource.getStatus().setNodes(podNames);
return UpdateControl.updateResource(resource);
}
labelsForMemcached
labelsForMemcached
is a utility to return a map of the labels to attach to the resources:
private Map<String, String> labelsForMemcached(Memcached m) {
Map<String, String> labels = new HashMap<>();
labels.put("app", "memcached");
labels.put("memcached_cr", m.getMetadata().getName());
return labels;
}
createMemcachedDeployment
The createMemcachedDeployment
method uses the fabric8 DeploymentBuilder
class:
private Deployment createMemcachedDeployment(Memcached m) {
Deployment deployment = new DeploymentBuilder()
.withMetadata(
new ObjectMetaBuilder()
.withName(m.getMetadata().getName())
.withNamespace(m.getMetadata().getNamespace())
.build())
.withSpec(
new DeploymentSpecBuilder()
.withReplicas(m.getSpec().getSize())
.withSelector(
new LabelSelectorBuilder().withMatchLabels(labelsForMemcached(m)).build())
.withTemplate(
new PodTemplateSpecBuilder()
.withMetadata(
new ObjectMetaBuilder().withLabels(labelsForMemcached(m)).build())
.withSpec(
new PodSpecBuilder()
.withContainers(
new ContainerBuilder()
.withImage("memcached:1.4.36-alpine")
.withName("memcached")
.withCommand("memcached", "-m=64", "-o", "modern", "-v")
.withPorts(
new ContainerPortBuilder()
.withContainerPort(11211)
.withName("memcached")
.build())
.build())
.build())
.build())
.build())
.build();
deployment.addOwnerReference(m);
return deployment;
}
There are three ways you can use the Operator SDK CLI to build and run your Operator:
Run locally outside the cluster as a Go program.
Run as a deployment on the cluster.
Bundle your Operator and use Operator Lifecycle Manager (OLM) to deploy on the cluster.
You can run your Operator project as a Go program outside of the cluster. This is useful for development purposes to speed up deployment and testing.
Run the following command to compile the Operator:
$ mvn clean install
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 11.193 s
[INFO] Finished at: 2021-05-26T12:16:54-04:00
[INFO] ------------------------------------------------------------------------
Run the following command to install the CRD to the default namespace:
$ oc apply -f target/kubernetes/memcacheds.cache.example.com-v1.yml
customresourcedefinition.apiextensions.k8s.io/memcacheds.cache.example.com created
Create a file called rbac.yaml
as shown in the following example:
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
name: memcached-operator-admin
subjects:
- kind: ServiceAccount
name: memcached-quarkus-operator-operator
namespace: <operator_namespace>
roleRef:
kind: ClusterRole
name: cluster-admin
apiGroup: ""
Run the following command to grant cluster-admin
privileges to the memcached-quarkus-operator-operator
by applying the rbac.yaml
file:
$ oc apply -f rbac.yaml
Enter the following command to run the Operator:
$ java -jar target/quarkus-app/quarkus-run.jar
The |
Apply the memcached-sample.yaml
file with the following command:
$ kubectl apply -f memcached-sample.yaml
memcached.cache.example.com/memcached-sample created
Run the following command to confirm that the pod has started:
$ oc get all
NAME READY STATUS RESTARTS AGE
pod/memcached-sample-6c765df685-mfqnz 1/1 Running 0 18s
You can run your Operator project as a deployment on your cluster.
Run the following make
commands to build and push the Operator image. Modify the IMG
argument in the following steps to reference a repository that you have access to. You can obtain an account for storing containers at repository sites such as Quay.io.
Build the image:
$ make docker-build IMG=<registry>/<user>/<image_name>:<tag>
The Dockerfile generated by the SDK for the Operator explicitly references |
Push the image to a repository:
$ make docker-push IMG=<registry>/<user>/<image_name>:<tag>
The name and tag of the image, for example |
Run the following command to install the CRD to the default namespace:
$ oc apply -f target/kubernetes/memcacheds.cache.example.com-v1.yml
customresourcedefinition.apiextensions.k8s.io/memcacheds.cache.example.com created
Create a file called rbac.yaml
as shown in the following example:
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
name: memcached-operator-admin
subjects:
- kind: ServiceAccount
name: memcached-quarkus-operator-operator
namespace: <operator_namespace>
roleRef:
kind: ClusterRole
name: cluster-admin
apiGroup: ""
The |
Run the following command to deploy the Operator:
$ make deploy IMG=<registry>/<user>/<image_name>:<tag>
Run the following command to grant cluster-admin
privileges to the memcached-quarkus-operator-operator
by applying the rbac.yaml
file created in a previous step:
$ oc apply -f rbac.yaml
Run the following command to verify that the Operator is running:
$ oc get all -n default
NAME READY UP-TO-DATE AVAILABLE AGE
pod/memcached-quarkus-operator-operator-7db86ccf58-k4mlm 0/1 Running 0 18s
Run the following command to apply the memcached-sample.yaml
and create the memcached-sample
pod:
$ oc apply -f memcached-sample.yaml
memcached.cache.example.com/memcached-sample created
Run the following command to confirm the pods have started:
$ oc get all
NAME READY STATUS RESTARTS AGE
pod/memcached-quarkus-operator-operator-7b766f4896-kxnzt 1/1 Running 1 79s
pod/memcached-sample-6c765df685-mfqnz 1/1 Running 0 18s
The Operator bundle format is the default packaging method for Operator SDK and Operator Lifecycle Manager (OLM). You can get your Operator ready for use on OLM by using the Operator SDK to build and push your Operator project as a bundle image.
Operator SDK CLI installed on a development workstation
OpenShift CLI (oc
) v4.17+ installed
Operator project initialized by using the Operator SDK
Run the following make
commands in your Operator project directory to build and push your Operator image. Modify the IMG
argument in the following steps to reference a repository that you have access to. You can obtain an account for storing containers at repository sites such as Quay.io.
Build the image:
$ make docker-build IMG=<registry>/<user>/<operator_image_name>:<tag>
The Dockerfile generated by the SDK for the Operator explicitly references |
Push the image to a repository:
$ make docker-push IMG=<registry>/<user>/<operator_image_name>:<tag>
Create your Operator bundle manifest by running the make bundle
command, which invokes several commands, including the Operator SDK generate bundle
and bundle validate
subcommands:
$ make bundle IMG=<registry>/<user>/<operator_image_name>:<tag>
Bundle manifests for an Operator describe how to display, create, and manage an application. The make bundle
command creates the following files and directories in your Operator project:
A bundle manifests directory named bundle/manifests
that contains a ClusterServiceVersion
object
A bundle metadata directory named bundle/metadata
All custom resource definitions (CRDs) in a config/crd
directory
A Dockerfile bundle.Dockerfile
These files are then automatically validated by using operator-sdk bundle validate
to ensure the on-disk bundle representation is correct.
Build and push your bundle image by running the following commands. OLM consumes Operator bundles using an index image, which reference one or more bundle images.
Build the bundle image. Set BUNDLE_IMG
with the details for the registry, user namespace, and image tag where you intend to push the image:
$ make bundle-build BUNDLE_IMG=<registry>/<user>/<bundle_image_name>:<tag>
Push the bundle image:
$ docker push <registry>/<user>/<bundle_image_name>:<tag>
Operator Lifecycle Manager (OLM) helps you to install, update, and manage the lifecycle of Operators and their associated services on a Kubernetes cluster. OLM is installed by default on OpenShift Container Platform and runs as a Kubernetes extension so that you can use the web console and the OpenShift CLI (oc
) for all Operator lifecycle management functions without any additional tools.
The Operator bundle format is the default packaging method for Operator SDK and OLM. You can use the Operator SDK to quickly run a bundle image on OLM to ensure that it runs properly.
Operator SDK CLI installed on a development workstation
Operator bundle image built and pushed to a registry
OLM installed on a Kubernetes-based cluster (v1.16.0 or later if you use apiextensions.k8s.io/v1
CRDs, for example OpenShift Container Platform 4.17)
Logged in to the cluster with oc
using an account with cluster-admin
permissions
Enter the following command to run the Operator on the cluster:
$ operator-sdk run bundle \(1)
-n <namespace> \(2)
<registry>/<user>/<bundle_image_name>:<tag> (3)
1 | The run bundle command creates a valid file-based catalog and installs the Operator bundle on your cluster using OLM. |
2 | Optional: By default, the command installs the Operator in the currently active project in your ~/.kube/config file. You can add the -n flag to set a different namespace scope for the installation. |
3 | If you do not specify an image, the command uses quay.io/operator-framework/opm:latest as the default index image. If you specify an image, the command uses the bundle image itself as the index image. |
As of OpenShift Container Platform 4.11, the |
This command performs the following actions:
Create an index image referencing your bundle image. The index image is opaque and ephemeral, but accurately reflects how a bundle would be added to a catalog in production.
Create a catalog source that points to your new index image, which enables OperatorHub to discover your Operator.
Deploy your Operator to your cluster by creating an OperatorGroup
, Subscription
, InstallPlan
, and all other required resources, including RBAC.
See Project layout for Java-based Operators to learn about the directory structures created by the Operator SDK.
If a cluster-wide egress proxy is configured, cluster administrators can override the proxy settings or inject a custom CA certificate for specific Operators running on Operator Lifecycle Manager (OLM).