Another day, another lab, this time something with k8s. I haven’t done anything with it, just some hello-world examples and the ocassional ranting of “we don’t need this here”. First I started with a simple python service (forget the bad code, we’ll fix it later)
from flask import Flask
import socket
app = Flask(__name__)
@app.route('/')
def hello():
docker_short_id = socket.gethostname()
return 'Hello, World! ' + docker_short_id
if __name__ == '__main__':
app.run(debug=True, host='0.0.0.0')
To expose the (flask) service with docker I had to add app.run(host='0.0.0.0')
Dockerfile:
FROM alpine:3.14
RUN apk add python3
RUN apk add py3-pip
RUN pip3 install flask
WORKDIR /opt/hello
ENV FLASK_APP=hello
ENV FLASK_ENV=development
CMD ["flask", "run", "--host=0.0.0.0"]
EXPOSE 5000
And a Makefile
build:
docker build -t k8s-lab .
run:
docker run -it -p 5000:5000 k8s-lab
shell:
docker run -it -p 5000:5000 k8s-lab /bin/sh
For initial tests, I’m going with minikube
curl -LO https://storage.googleapis.com/minikube/releases/latest/minikube-linux-amd64
sudo install minikube-linux-amd64 /usr/local/bin/minikube
minikube kubectl -- get po -A
alias kubectl="minikube kubectl --"
Then, read some docs and finish the Learn Kubernetes Basic Tutorial
I also had to point the docker daemon to the minikube internal registry (and build the image again)
> minikube docker-env
export DOCKER_TLS_VERIFY="1"
export DOCKER_HOST="tcp://172.17.0.2:2376"
export DOCKER_CERT_PATH="/home/user/.minikube/certs"
export MINIKUBE_ACTIVE_DOCKERD="minikube"
# To point your shell to minikube’s docker-daemon, run:
# eval $(minikube -p minikube docker-env)
Finally, the deployment file (hello.yaml):
apiVersion: apps/v1
kind: Deployment
metadata:
name: k8s-lab-deployment
labels:
app: k8s-lab
spec:
replicas: 3
selector:
matchLabels:
app: k8s-lab
template:
metadata:
labels:
app: k8s-lab
spec:
containers:
- name: k8s-lab
image: k8s-lab:1
ports:
- containerPort: 80
Create and tag a new build (because we’re using minikube’s registry), start the deployment and create a service
make build
docker tag k8s-lab k8s-lab:1
kubectl apply -f hello.yaml
kubectl expose deployment k8s-lab --type=LoadBalancer --port=5000