Introduction
Creating a k8s cluster is a nice thing but it’s better to use it 🙂
Here is a simple tutorial where I demonstrate how to quickly code and test an app.
Code the application
For this example we’ll use a simple http server written in Python.
#!/usr/bin/python
from BaseHTTPServer import BaseHTTPRequestHandler,HTTPServer
PORT_NUMBER = 8080
#This class will handles any incoming request from
#the browser
class myHandler(BaseHTTPRequestHandler):
#Handler for the GET requests
def do_GET(self):
self.send_response(200)
self.send_header('Content-type','text/html')
self.end_headers()
# Send the html message
self.wfile.write("Hello World - This is http python node test app v1 !")
return
try:
#Create a web server and define the handler to manage the
#incoming request
server = HTTPServer(('', PORT_NUMBER), myHandler)
print 'Started httpserver on port ' , PORT_NUMBER
#Wait forever for incoming htto requests
server.serve_forever()
except KeyboardInterrupt:
print '^C received, shutting down the web server'
server.socket.close()
Source : http://www.acmesystems.it/python_httpd
Test your app
Now that we have our application we can test it locally
python httpython.py Started httpserver on port 8080
Result
curl http://localhost:8080 Hello World - This is http python node test app v1 !%
It works !
Create the container
Now in order to put our application on a kubernetes cluster we first need to create a container that contains our code.
Create the docker file
To create the container we define it in a Dockerfile
FROM python:2-onbuild EXPOSE 8080 COPY httpython.py . ENTRYPOINT [ "python", "./httpython.py" ]
FROM : specify the source image name. https://store.docker.com
EXPOSE : make the container listen on the specified port
COPY : copy file to destination (copy src dst)
ENTRYPOINT : specify the executable to be run we you start the container
Create a Requierment filetouch requirements.txt
touch requirements.txt
Build your docker container
docker build -t gcr.io/techfulab-testk8s-01/hello-py-node:v1 .
-t, –tag value Name and optionally a tag in the ‘name:tag’ format (default [])
Name your container with
- gcr.io = google container repo
- techfulab-testk8s-01 = Name of your project on GCP
- hello-py-node : name of the container
- v1 = version number/id
At the moment the container is build locally but this naming will help us later
Test locally
docker run -d -p 8080:8080 --name hello_tutorial gcr.io/techfulab-testk8s-01/hello-py-node:v1 ⇒ docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES e483b5998d71 gcr.io/techfulab-testk8s-01/hello-py-node:v3 "python ./httpython.p" 5 seconds ago Up 3 seconds 0.0.0.0:8080->8080/tcp hello_tutorial
Test with :
curl http://localhost:8080 Hello World - This is http python node test app v1 !%
It works !
Push to Google cloud registry
gcloud docker -- push gcr.io/techfulab-testk8s-01/hello-py-node:v1
Deploy your application on Kubernetes
Now that we have our application containerised and pushed to google container registry we can deploy it to kubernetes
Create namespace
kubectl create namespace "team-01"
Change your config to use this namespace (rather than puttin –namespace team-01 at the end of every command)
kubectl config get-contexts kubectl config set-context gke_techfulab-testk8s-01_europe-west1-d_techful-kops-cluster01 --namespace team-01
Deploy the application :
kubectl run hello-py-app --image=gcr.io/techfulab-testk8s-01/hello-py-node:v1 --port=8080 --replicas=2 --namespace team-01
Check status :
watch -n 1 kubectl get deployments watch -n 1 kubectl get pods
Expose it :
kubectl expose deployment hello-py-app --type="LoadBalancer"
Check status :
watch -n 1 kubectl get services
Retrieve the Public IP and :
watch -n 1 curl http://$PUBLIC_IP:8080
Modify your deployment – Change the number of replica
kubectl scale deployment hello-py-app --replicas=4
Modify your deployment – Edit the deployment file
kubectl edit deployment/hello-py-app
Modify your deployment -Update the version of your app
Edit the local code (httpython.py) and change the message to display
...
# Send the html message
self.wfile.write("Hello World - This is http python node test app v2 !")
return
...
Build a new version of the container
docker build -t gcr.io/techfulab-testk8s-01/hello-py-node:v2 .
Test it locally
docker run -d -p 8080:8080 --name hello_tutorial gcr.io/techfulab-testk8s-01/hello-py-node:v2
curl http://localhost:8080 Hello World - This is http python node test app v2 !%
Push to Google cloud registry
gcloud docker -- push gcr.io/techfulab-testk8s-01/hello-py-node:v2
Update the version deployed
kubectl set image deployment/hello-py-app hello-node=gcr.io/techfulab-testk8s-01/hello-py-node:v2
Rollback
kubectl set image deployment/hello-py-app hello-node=gcr.io/techfulab-testk8s-01/hello-py-node:v1
Delete your application
kubectl delete service,deployment hello-py-app
Documentation/sources :
https://kubernetes.io/docs/hellonode/#create-a-docker-container-image
https://kubernetes.io/docs/user-guide/kubectl/kubectl_run/
Kubernetes is a very new technology, it was release in stable version 1.0 in July 21, 2015. It’s today in version 1.4 with a very active community and a lot of enthusiasm from IT pro.
