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PodSet Operator

An example of Kubernetes Operator built with the Operator SDK.

This PodSet operator takes care of scaling up and down pods that run a sleep 3600 command in a busybox image. Nothing really fancy, but the point is to:

  • see how the CRD and operator controller can be defined, packaged and deployed

  • demonstrate the logic of reconcialation when a custom resource changes, or when pods are added or removed by a user

Requirements

  • go 1.13

  • operator-sdk 0.12.0

  • a connection to an OpenShift or Kubernetes cluster

Building and deploying

Before deploying the operator, we need to create the Custom Resource Definitions, which (as their name suggests) define the custom resources we will manage with this operator, and we also need to configure the Service Account along with its role and role binding.

The commands below use the oc CLI which is the equivalent of kubectl for OpenShift.

# create a project/namespace for the Service Account and the operator controller
$ oc new-project podset-operator-test
Now using project "podset-operator-test" on server ...

# Create the CRDs
$ oc create -f deploy/crds/app.example.com_podsets_crd.yaml
customresourcedefinition.apiextensions.k8s.io/podsets.app.example.com created

# create the Service Account
$ oc create -f deploy/service_account.yaml
serviceaccount/podset-operator created

# apply the role and role binding to the service account
$ oc create -f deploy/role.yaml
role.rbac.authorization.k8s.io/podset-operator created

$ oc create -f deploy/role_binding.yaml
rolebinding.rbac.authorization.k8s.io/podset-operator created

Testing the operator

The Operator SDK provides a command to run the operator controller locally (ie, on the developer’s machine). In this mode, the operator controller will use the cluster’s external API to create, list, update, delete and watch the resources in the namespace.

$ operator-sdk up local --namespace podset-operator-test
INFO[0000] Running the operator locally.
INFO[0000] Using namespace podset-operator-test.
{"level":"info","ts":1573804940.828196,"logger":"cmd","caller":"manager/main.go:26","msg":"Go Version: go1.13.4"}
{"level":"info","ts":1573804940.828258,"logger":"cmd","caller":"manager/main.go:27","msg":"Go OS/Arch: darwin/amd64"}
...

in a separate terminal session, we can use the custom resource example to see how the operator controller reacts:

# create a custom PodSet resource to obtain 3 pods
$ oc create -f deploy/crds/app.example.com_podsets_cr.yaml
podset.app.example.com/example-podset created

# after checking the operator controller logs...
$ oc get pods
NAME                      READY   STATUS    RESTARTS   AGE
example-podset-pod46ttq   1/1     Running   0          2m19s
example-podset-pod885mx   1/1     Running   0          2m20s
example-podset-podtqdzs   1/1     Running   0          2m19s

License

This project is available under the Apache License, Version 2.0.