operator-workshop

README

operator-workshop

Slides

Workshop slides in PDF format.

• Operators and Custom Resource Definitions
• Exercise 1: REST API
• Exercise 2: Kubernetes client-go

Setup

During the workshop the operator we create will manage PostgreSQL databases. A Kubernetes deployment and service is provided to run PostgreSQL in Minikube.

Start a minikube.

minikube start --kubernetes-version 'v1.8.0'

Start a PostgreSQL instance inside Kubernetes.

kubectl apply -f ./manifest/postgresql.yaml

Running Example Solutions

First follow the steps in Setup.

There are three examples provided:

• solution1: is an example of the operator using Go http package.
• solution2: is an example of the operator using client-go package.
• solution3: is an example of the operator using operatorkit package.

Remote Mode

Remote mode means the operator runs outside the Kubernetes cluster and connects to the remote Kubernetes API.

name="solution1"
#name="solution2"
#name="solution3"

go run ./cmd/${name}/main.go \
    -postgresql.host="$(minikube ip)" \
    -postgresql.port="$(minikube service workshop-postgresql --format '{{.Port}}')" \
    -postgresql.user="postgres" \
    -postgresql.password="operator-workshop" \
    -kubernetes.incluster="false" \
    -kubernetes.server="https://$(minikube ip):8443" \
    -kubernetes.crt="$HOME/.minikube/apiserver.crt" \
    -kubernetes.key="$HOME/.minikube/apiserver.key" \
    -kubernetes.ca="$HOME/.minikube/ca.crt"

In-cluster Mode

The alternative, and most likely desired way to run the operator is the in-cluster mode. In that mode the operator connects to the Kubernetes API with credentials injected by the Kubernetes to the Pod.

Only solution2 and solution3 support this mode.

To run in in-cluster mode it is necessary to have a docker image in a registry visible by the cluster and then create a deployment. When using minikube you can reuse minikube's docker registry.

eval $(minikube docker-env)

name="solution2"
#name="solution3"

CGO_ENABLED=0 GOOS=linux go build -o operator-workshop ./cmd/${name}/main.go

docker build --tag operator-workshop .

kubectl apply -f ./manifest/operator.yaml

Working with the Operator

Creating an Example Custom Object

kubectl apply -f ./manifest/example_cro.yaml

List databases

List the PostgreSQL databases and their owners.

 kubectl exec  \
    $(kubectl get pod -l 'app=workshop-postgresql' -o jsonpath='{.items[0].metadata.name}') \
    -- psql -U postgres postgres -c "\list"

Delete PostgreSQL database

Delete the k8s resources.

kubectl delete -f ./manifest/postgresql.yaml

Connect to the database

kubectl exec -it \
    $(kubectl get pod -l 'app=workshop-postgresql' -o jsonpath='{.items[0].metadata.name}') \
    -- psql -U postgres postgres