Django application deployment in kubernetes

To get started with kubernetes in local environment use Microk8s. Go through the microk8s setup documentation and setup it.

Adding alias to "microk8s.kubectl" to "k8s"

Open ~/.bashrc and below line at the end of the file.

alias k8s="microk8s.kubectl"

Now, clone this repo using below commands

git clone [email protected]:AnjaneyuluBatta505/kubernetes_django.git

Let's start the deployment of the django application and other apps like redis, postgres, flower, etc.

Setting up postgres service

In the postgres we have 4 yaml configuration files.

1. secrets.yaml - Useful when using secret env vaibles in the apps
2. volume.yaml - Persistent Volume for Postgres database
3. volume_claim.yaml - This claim lets our deployment application store its data in an external location, so that if one of the application’s containers fails, it can be replaced with a new container and continue accessing its data stored externally, as though an outage never occurred.
4. deployment.yaml - Deployment to start the application containers
5. service.yaml - Allows other apps to comminicate with it's related deployment(i.e pods/containers)

Now, create above objects in kubernetes using below commands

k8s apply -f kubernetes/postgres/secrets.yaml
k8s apply -f kubernetes/postgres/volume.yaml
k8s apply -f kubernetes/postgres/volume_claim.yaml
k8s apply -f kubernetes/postgres/deployment.yaml
k8s apply -f kubernetes/postgres/service.yaml

We have successfully created the postgres service in k8s(i.e kubernetes cluster).

Setting up redis service

In the redis we have 2 yaml configuration files. To setup the redis service in k8s execute the below commands

k8s apply -f kubernetes/redis/deployment.yaml
k8s apply -f kubernetes/redis/service.yaml

Setting up django app

In django app we have 3 yaml configuration files. To setup the django app in k8s execute the below commands

k8s apply -f kubernetes/django/job-migration.yaml
k8s apply -f kubernetes/django/deployment.yaml
k8s apply -f kubernetes/django/service.yaml

Setting up celery app

In celery app we have 2 yaml configuration files. To setup the django app in k8s execute the below commands

k8s apply -f kubernetes/celery/beat-deployment.yaml
k8s apply -f kubernetes/celery/worker-deployment.yaml

Setting up flower app

In flower app we have 2 yaml configuration files. To setup the django app in k8s execute the below commands

k8s apply -f kubernetes/flower/deployment.yaml
k8s apply -f kubernetes/flower/service.yaml

How to debug the pods for errors if any failures occurs ?

$ k8s get po
NAME                             READY   STATUS      RESTARTS   AGE
celery-beat-75b5f954-m2pzj       1/1     Running     0          64m
celery-worker-56fc7b88f5-shd87   1/1     Running     0          61m
django-688f76f576-kt4h6          1/1     Error       0          60m
django-migrations-mhng7          0/1     Completed   0          59m
flower-77bf99c799-9drnp          1/1     Running     87         20h
postgres-76dc76ffbb-hzmdc        1/1     Running     2          23h
redis-76f6f4857b-srxlw           1/1     Running     1          20h

We can debug the pod failure using command k8s logs <pod name>. Sometimes k8s describe <name of k8s object>

To access the django app in our local browser

$ k8s get svc
NAME               TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)          AGE
django-service     NodePort    10.152.183.146   <none>        8000:32693/TCP   21h
flower-service     NodePort    10.152.183.170   <none>        5555:30675/TCP   21h
kubernetes         ClusterIP   10.152.183.1     <none>        443/TCP          25h
postgres-service   ClusterIP   10.152.183.151   <none>        5432/TCP         24h
redis-service      ClusterIP   10.152.183.89    <none>        6379/TCP         21h

Visit url "10.152.183.146:8000" (i.e CLUSTER-IP:PORT). It's just for testing.

References:

1. https://microk8s.io/docs/
2. https://kubernetes.io/docs/home/
3. https://medium.com/edureka/what-is-kubernetes-container-orchestration-tool-d972741550f6