This repository contains code and notes to get a sample Django application running on a Kubernetes cluster. It is meant to go along with a blog post describing this in some detail.

1. Install Docker.

2. Take a look at and get a feel for the example application used in this repository. It is a simple blog application built by following the excellent Django Girls Tutorial.

3. Setup a cluster managed by Kubernetes. The effort required to do this can be substantial, so one easy way to get started is to sign up (for free) on Google Cloud Platform and use a managed version of Kubernetes called Google Container Engine (GKE).

   First, we set some basic configuration.

   gcloud config set project $GCP_PROJECT
   gcloud config set compute/zone us-central1-b
   

   Then we create the cluster itself.

   gcloud container clusters create demo
   gcloud container clusters list
   

   Finally, we configure kubectl to talk to the cluster.

   gcloud container clusters get-credentials demo
   kubectl get nodes
   

4. Setup a persistent store for the database. In this example we're going to be using Persistent Disks from Google Cloud Platform.

   Create a disk and format it (using an instance that's temporarily created just for this purpose).

   gcloud compute disks create pg-data-disk --size 50GB
   gcloud compute instances create pg-disk-formatter
   gcloud compute instances attach-disk pg-disk-formatter --disk pg-data-disk
   gcloud compute config-ssh
   ssh pg-disk-formatter.$GCP_PROJECT
       sudo mkfs.ext4 -F /dev/sdb
       exit
   gcloud compute instances detach-disk pg-disk-formatter --disk pg-data-disk
   gcloud compute instances delete pg-disk-formatter
   

Build the container:

cd containers/database
docker build -t hnarayanan/postgresql:9.5 .

You can check it out locally if you want:

docker run --name database -e POSTGRES_DB=app_db -e POSTGRES_PASSWORD=app_db_pw -e POSTGRES_USER=app_db_user -d hnarayanan/postgresql:9.5
# Echoes $PROCESS_ID to the screen
docker exec -i -t $PROCESS_ID bash

Push it to a repository:

For this project, we'll be using Docker Hub to host and deliver our containers. If you're interested in a private repository, you need to instead use something like Google Container Registry.

docker login
docker push hnarayanan/postgresql:9.5

Build the container:

cd containers/app
docker build -t hnarayanan/djangogirls-app:0.1 .

You can check it out locally if you want:

# docker run --name some-app --link some-postgres:postgres -d application-that-uses-postgres

Push it to a repository:

docker push hnarayanan/djangogirls-app:0.1

Even though our application only requires a single PostgreSQL instance running, we still run it under a (pod) replication controller. This way, we have a service that monitors our database pod and ensures that one instance is running even if something weird happens, such as the underlying node fails.

kubectl create -f kubernetes/database/persistent-volume.yaml
kubectl get pv
kubectl create -f kubernetes/database/persistent-volume-claim.yaml
kubectl get pvc

kubectl create -f kubernetes/database/replication-controller.yaml
kubectl get replicationcontrollers
kubectl get pods
kubectl describe pod <pod-id>
kubectl logs <pod-id>

kubectl create -f kubernetes/database/service.yaml
kubectl get services
kubectl describe services database

kubectl create -f replication-controller.yaml
kubectl create -f service.yaml

kubectl get pods
kubectl describe pod <pod-id>
kubectl logs <pod-id>

gsutil mb gs://django-kubernetes-assets
gsutil defacl set public-read gs://django-kubernetes-assets
cd django-k8s/containers/app
./manage.py collectstatic --noinput
gsutil -m cp -r static/* gs://django-kubernetes-assets

• scaling
• deleting one pod
• different versions, split by colour?
• monitoring UI

- Migrations
  kubectl exec <some_app_pod> -- python /app/manage.py migrate

- Secrets Resource
  echo mysecretpassword | base64
  <paste into secrets file>
  kubectl create -f kubernetes_configs/db_password.yaml

- PostgreSQL

  Disk
  gcloud compute disks create pg-data  --size 500GB