user-op

This is a simple example of a Kubernetes operator written in Go. The sole purpose of this operator is to add a user in a Database table called users

Description

The milestones of this project are:

• Create a Custom Resource Definition (CRD) for the user in order to create CRs (e.g. User CR)
• Create a database table called users in a PostgreSQL database. The database should be installed via Helm.
• Add logic in the controller to add a user in the users table when a User CR is created (use port-forwarding to connect to the database)
• Fix issue with concurrent updates (e.g. "...the object has been modified; please apply your changes to the latest version and try again"..."")
• Update controller to read connection details from environment variables
• Deploy the controller to a Kubernetes cluster via Helm and connect it with the PostgreSQL database
• Add a second controller that will take care of creating a PostgresSQL Database

Getting Started

You’ll need a Kubernetes cluster to run against. You can use KIND to get a local cluster for testing, or run against a remote cluster. Note: Your controller will automatically use the current context in your kubeconfig file (i.e. whatever cluster kubectl cluster-info shows).

Running on the cluster

1. Install Instances of Custom Resources:

kubectl apply -k config/samples/

2. Build and push your image to the location specified by IMG:

make docker-build docker-push IMG=<some-registry>/user-op:tag

3. Deploy the controller to the cluster with the image specified by IMG:

make deploy IMG=<some-registry>/user-op:tag

Uninstall CRDs

To delete the CRDs from the cluster:

make uninstall

Undeploy controller

UnDeploy the controller from the cluster:

make undeploy

Contributing

How it works

This project aims to follow the Kubernetes Operator pattern.

It uses Controllers, which provide a reconcile function responsible for synchronizing resources until the desired state is reached on the cluster.

Test It Out

1. Have a Kubernetes cluster running. For local testing you can use KIND

kind create cluster -n user-op

2. Install the DB helm chart

make install-db

3. Connect to the DB

kubectl port-forward --namespace default svc/my-db-postgresql 25432:5432
# authernticate with user-op user
PGPASSWORD=user-op-pretest psql --host 127.0.0.1 -U user-op -d user-db -p 25432

# OR authenticate with postgres user
PGPASSWORD=pg-pretest psql --host 127.0.0.1 -U postgres -d user-db -p 25432

4. Install the CRDs into the cluster:

make install

5. Run your controller (this will run in the foreground, so switch to a new terminal if you want to leave it running):

make run

NOTE: You can also run this in one step by running: make install run

6. Create a User CR:

kubectl apply -f config/samples/user.yaml 

7. List resourceds

watch "kubectl get all,configmap,secrets,pv,pvc"

8. Cleanup

# uninstall PostgreSQL DB
make uninstall-db

Modifying the API definitions

If you are editing the API definitions, generate the manifests such as CRs or CRDs using:

make manifests

NOTE: Run make --help for more information on all potential make targets

More information can be found via the Kubebuilder Documentation

License

Copyright 2024.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.