Getting started with Operator SDK for Go-based Operators

Getting started with Operator SDK for Go-based Operators

To demonstrate the basics of setting up and running a Go-based Operator using tools and libraries provided by the Operator SDK, Operator developers can build an example Go-based Operator for Memcached, a distributed key-value store, and deploy it to a cluster.

Prerequisites

Operator SDK CLI installed
OpenShift CLI (oc) v4.7+ installed
Logged into an OKD 4.7 cluster with oc with an account that has cluster-admin permissions
To allow the cluster pull the image, the repository where you push your image must be set as public, or you must configure an image pull secret.

Creating and deploying Go-based Operators

You can build and deploy a simple Go-based Operator for Memcached by using the Operator SDK.

Procedure

Create a project.
1. Create your project directory:
```
$ mkdir memcached-operator
```
2. Change into the project directory:
```
$ cd memcached-operator
```
3. Run the operator-sdk init command to initialize the project:
```
$ operator-sdk init \
    --domain=example.com \
    --repo=github.com/example-inc/memcached-operator
```
  The command uses the Go plug-in by default.
4. To enable your Go-based Operator to run on OKD, edit the config/manager/manager.yaml file and replace the following line:
```
runAsUser: 65532
```
  with:
```
runAsNonRoot: true
```
  This step is a temporary workaround required for Go-based Operators only. For more information, see BZ#1914406.

Create an API.

Create a simple Memcached API:

$ operator-sdk create api \
    --resource=true \
    --controller=true \
    --group cache \
    --version v1 \
    --kind Memcached

Build and push the Operator image.

Use the default Makefile targets to build and push your Operator. Set IMG with a pull spec for your image that uses a registry you can push to:
```
$ make docker-build docker-push IMG=<registry>/<user>/<image_name>:<tag>
```
Run the Operator.
1. Install the CRD:
```
$ make install
```
2. Deploy the project to the cluster. Set IMG to the image that you pushed:
```
$ make deploy IMG=<registry>/<user>/<image_name>:<tag>
```

Create a sample custom resource (CR).

Create a sample CR:

$ oc apply -f config/samples/cache_v1_memcached.yaml \
    -n memcached-operator-system

Watch for the CR to reconcile the Operator:

$ oc logs deployment.apps/memcached-operator-controller-manager \
    -c manager \
    -n memcached-operator-system

Clean up.

Run the following command to clean up the resources that have been created as part of this procedure:
```
$ make undeploy
```

Next steps

See Operator SDK tutorial for Go-based Operators for a more in-depth walkthrough on building a Go-based Operator.