k8s_example

This repo demonstrates deploying a Kubernetes cluster running a Flask app on Linux virtual machines.

Dependencies

make

Make allows us to run tasks that automate setup and other processes. To install:

sudo apt update
sudo apt install build-essential

multipass

Multipass is a tool to generate cloud-style Ubuntu VMs quickly on Linux, macOS, and Windows. To install:

snap install multipass

Docker Registry

The Docker Registry allows for distribution of private Docker Images. We need a registry so that the Kubernetes cluster can pull images from a single, private source. On the host machine, install Docker then create the registry:

# Install Docker
# See https://docs.docker.com/engine/install/ubuntu/#install-using-the-repository
sudo apt-get update
sudo apt-get install ca-certificates curl
sudo install -m 0755 -d /etc/apt/keyrings
sudo curl -fsSL https://download.docker.com/linux/ubuntu/gpg -o /etc/apt/keyrings/docker.asc
sudo chmod a+r /etc/apt/keyrings/docker.asc

echo \
  "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.asc] https://download.docker.com/linux/ubuntu \
  $(. /etc/os-release && echo "$VERSION_CODENAME") stable" | \
  sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
sudo apt-get update

sudo apt-get install -y docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin
docker run -d -p 5000:5000 --name registry registry:2.7

Build

Flask App

Build the Flask app image and push it to the Docker Registry:

make flask

Kubernetes Cluster

To build the Kubernetes cluster:

make k8s/build NUM_WORKERS=3 CPUS=2 MEMORY=2G DISK=5G

To build the Kubernetes master node with different parameters than the worker nodes:

make k8s/build/master CPUS=2 MEMORY=2G DISK=10G

To build the Kubernetes worker nodes with different parameters than the master node:

make k8s/build/workers NUM_WORKERS=3 CPUS=2 MEMORY=2G DISK=10G

Testing

To test the Kubernetes cluster:

make flask/ping N_THREADS=8

This command sends multiple GET HTTP request in parallel to the Flask app /hello endpoint. This endpoint returns a string indicating the IP of the node that is responding to the request.

Greetings from 10.244.2.3!
Greetings from 10.244.2.6!
Greetings from 10.244.2.4!
Greetings from 10.244.2.3!
Greetings from 10.244.2.4!
Greetings from 10.244.2.3!
Greetings from 10.244.2.6!
Greetings from 10.244.2.3!