Kubernetes test app

The following instructions assume a Ubuntu 24.04LTS host system.

Preliminaries

For convenience, we have created a git root alias:

git config --global alias.root 'rev-parse --show-toplevel'

Ensure that you are in the project root before continuing below.

Database mounts

Create a mount point for each database server in our app; currently, this is just the postgres0 database. From the project root:

mkdir -p mnt/postgres0

Software packages

Ensure that docker, kubectl, kind, helm, and screen are installed. For docker, follow the apt install instructions. For the other packages:

sudo snap install kubectl --classic
sudo snap install go --classic
sudo snap install helm --classic
go install sigs.k8s.io/kind@v0.23.0
sudo apt install screen

Scripts

A set of shell scripts and aliases are provided in scripts/ and load_scripts.sh. A utility script prepend_path is required; copy this to a directory on your $PATH, e.g. $HOME/.local/bin.

cp copy_this_to_local_bin/prepend_path $HOME/.local/bin/prepend_path

Finally, enable and load our utility scripts:

chmod +x ./scripts/*.sh
. load_scripts.sh

We can read the documentation for each script using the bashdoc script, which displays the block comment at the top of the specified .sh file.

./scripts/bashdoc init.sh

Secrets

This repo contains a number of example secret files. Locate them using:

find . -path './mnt/*' -prune -o -name '*.example*' -print

Copy these files, removing ".example" from the filenames, and edit as desired.

Running the cluster

All Kubernetes resources are associated with the myapp namespace.

Initialisation

Use kind to start a cluster. The file kind.yaml is used to set up our file mounts (e.g. for databases).

kind create cluster --config kind.yaml

Next, initialise all our resources (secrets, services, persistent volumes etc.):

. init.sh

Ensure that everything is running:

kubectl get pod -n myapp

Example output:

NAME                                   READY   STATUS    RESTARTS   AGE
myapp-frontend-main-77548d65d7-dmmkc   1/1     Running   0          11m
myapp-test-api-76b9486764-5rgp7        1/1     Running   0          12m
myapp-test-frontend-5b6b74f48d-whldq   1/1     Running   0          11m
postgres0-0                            1/1     Running   0          12m
traefik-5f9ddf59c-krgvf                1/1     Running   0          12m

Tear-down

. destroy.sh

Port forwarding (Kubernetes)

To expose a Kubernetes service, we can run kubectl port-forward. Utility functions for doing so are included in load_scripts.sh, i.e. xxx_expose(). The init.sh script forwards the necessary ports automatically, using screen to provide persistence.

Port forwarding (Docker)

For development, we may deploy containers on Docker without inserting them into the Kubernetes cluster. The Docker Compose file defines host.docker.internal so that Docker containers can communicate with the host machine and access any Kubernetes services that have been set up with kubectl port-forward.

yinchi / k8s-demo