What is a simple build and deploy process using kubectl? - kubernetes

Question

I'm trying to understand what a good practice is for what I would assume is a pretty common scenario of building and deploying a kubernetes deployment using kubectl.
Scenario:
I want to build a project and deploy it to my cluster.
I’ve got a yaml file with my deployment (and related things), and some src code with a Dockerfile.
I want to avoid using :latest in the image tag as per Best Practice recommendation and instead use a unique tag for that image.
I have easy access to a unique identifier, either coming from CI or git sha that is available as an environment variable at time of building.
So that seems pretty simple:
docker build -t my-registry/my-app:${BUILD_NUMBER} .
docker push my-registry/my-app:${BUILD_NUMBER}
kubectl apply -f kube.yaml
Except that there is no native way to tell kubectl what image name to use.
I understand that kubectl does not support environment variable template substitution, but I've never seen just the usecase of image tags being mentioned explicitly.
I can use sed replacement but that seems to go against the spirit of 'no variable template support', and I barely understand what sed does when I write it, so I pitty the next developer who has to read my commands.
I feel like for such a basic scenario "I want to build and deploy to my cluster" there might be a simpler solution that doesn’t feel like it’s fighting kubectl.
Skaffold does a great job of assigning a tag and digest for each built image, but it would be nice to have a simple process to start with before bringing in more high level tooling.
Besides "Use Skaffold" or "Use Helm" what should I do to have a simple build + deploy process?
Is templating yaml files okay, either with sed, mo, or other replacement tools?
Are there any example projects that have a simple build and deploy pipeline using just kubectl and maybe kustomize?
kube.yaml (Note the lack of version on the image name)
apiVersion: apps/v1
kind: Deployment
metadata:
namespace: example
name: my-app
spec:
minReadySeconds: 2
strategy:
rollingUpdate:
maxSurge: 1
maxUnavailable: 0
replicas: 1
selector:
matchLabels:
app: my-app
template:
metadata:
name: my-app
labels:
app: my-app
spec:
containers:
- name: my-app
image: "my-registry/my-app"
ports:
- containerPort: 3000
resources:
limits:
cpu: 300m
memory: 600m
requests:
cpu: 50m
memory: 100m

Answer 1

Is kubectl set image <deployment> <image> an option? It does what you are looking for, but it won't be reflected in your local copy of kube.yaml, so you would need to specify a dummy image for "my-registry/my-app" in kube.yaml to not confuse other developers that they have to change that value each time they want to re-deploy.

Answer 2

for simple cases you can use kubectl run. for example:
kubectl run my-app --image=my-registry/my-app:${BUILD_NUMBER} --port=3000 --replicas=1 --env VAR=value --expose --limits 'cpu=300m,memory=600Mi'
in theory it's a deprecated command, but it's been deprecated for 2 years now and it's still there ;] anyway, if you feel unsafe about it, the message gives a hint how you can waste a day or 2 to make it in a non-deprecated way ;]