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Deploying Flask applications using kube-downscaler

In this tutorial we will show how to deploy Kube-downscaler and test with sample application.

What is Kube-downscaler?

Please check kube-downscaler for a detailed explanation.

Production Status

The current version of downscaler is 0.5.

Architecture

The diagram below depicts how a Downscaler agent control applications. Alt text

Quick Start

Below are instructions to quickly install and configure Downscaler.

Prerequisites

Make sure you have a Kubernetes cluster up and running. For local installation minikube can be used as well.

Install the binary releases of the Helm and Kubectl clients depending on your OS. Please follow Helm client and Kubectl client for detailed instructions.

Installing Downscaler

  1. Make sure connected to right cluster:
kubectl config current-context
  1. Create new namespace 'opendata' if not exist, and set as default for context being used:
kubectl config set-context minikube --namespace=opendata
  1. Install Helm server(Tiller) in Kubernetes cluster:
helm init
  1. Make sure Tiller is up and running:
kubectl get pods --namespace kube-system

NAME                                                 READY     STATUS    RESTARTS   AGE
tiller-deploy-f44659b6c-p48hf                        1/1       Running   0          51m
  1. Clone Sandbox repository:
git clone https://github.com/sakomws/sandbox.git |  cd sandbox
  1. Before deploy make sure to update values.yaml in Downscaler chart depending on your cluster support for RBAC:
rbac:
  create: true

Note: In case RBAC is active new service account will be created for Downscaler with certain privileges, otherwise 'default' one will be used.

  1. Deploy Downscaler:
helm install ./downscaler
  1. Check the deployed release status:
helm list

NAME            	REVISION	UPDATED                 	STATUS  	CHART                	APP VERSION	NAMESPACE
bold-guppy      	1       	Tue Sep 25 02:07:58 2018	DEPLOYED	kube-downscaler-0.5.0	0.5.0      	default
  1. Check downscaler pod is up and running:
kubectl get pods

NAME                                               READY     STATUS    RESTARTS   AGE
fantastic-chimp-kube-downscaler-7f58c6b5b7-rnglz   1/1       Running   0          6m
  1. Check Kubernetes event logs, to make sure of successful deployment of downscaler:
kubectl get events -w -n opendata

Deploy Sample Applications

In this section we will deploy the Flask applications. Please see tutorial in opendata-ops repository under OpenGov organization for more details.

  1. Deploy Flask applications:
kubectl apply -f flaskapp/flask_1.yaml
kubectl apply -f flaskapp/flask_2.yaml
  1. Ensure the following Kubernetes pods are up and running: flask-v1-tutorial-* , flask-v2-tutorial-* :
kubectl get pods

NAME                                 READY     STATUS    RESTARTS   AGE
flask-v1-tutorial-6b59556b55-kd2tv   1/1       Running   0          1m
flask-v2-tutorial-575fd64689-rkf55   1/1       Running   0          1m

Note: Deployments have grace period, which means Downscaler will wait 15min to take any actions after pods get started.

  1. Check downscaler pod logs:
kubectl logs -f kube-downscaler-55b9f8ffd8-5k9q4 -n opendata

2018-09-25 18:13:56,253 INFO: Deployment default/flask-v1-tutorial within grace period (900s), not scaling down (yet)
2018-09-25 18:13:56,253 INFO: Deployment default/flask-v2-tutorial within grace period (900s), not scaling down (yet)
2018-09-25 18:14:01,310 INFO: Scaling down Deployment default/flask-v1-tutorial from 1 to 0 replicas (uptime: Mon-FRI 07:00-19:00 US/Eastern, downtime: never)
2018-09-25 18:14:01,327 INFO: Scaling down Deployment default/flask-v2-tutorial from 1 to 0 replicas (uptime: Thu-Fri 07:00-19:00 US/Pacific, downtime: never)

Uninstalling Sample Applications

  1. To uninstall applications, run:
kubectl delete -f flaskapp/flask_1.yaml
kubectl delete -f flaskapp/flask_2.yaml

Uninstalling Downscaler

  1. Check Downscaler release name:
helm  list

NAME            	REVISION	UPDATED                 	STATUS  	CHART                	APP VERSION	NAMESPACE
bold-guppy      	1       	Tue Sep 25 02:07:58 2018	DEPLOYED	kube-downscaler-0.5.0	0.5.0      	default
  1. Delete Downscaler release from cluster:
helm delete bold-guppy
  1. Delete Tiller deployment:
kubectl delete deployment tiller-deploy --namespace kube-system
  1. Delete namespace 'opendata':
kubectl delete ns opendata

Warning: Make sure, namespace does not have other pods deployed.

Limitations

Still in testing phase, will be updated later.

Authors

Opengov Devops team.

License

This project is licensed under the MIT License - see the LICENSE file for details.

Acknowledgments

Thanks to Kube-downscaler project authored by Henning Jacobs