Manage multi-environment Kubernetes application on GKE? - kubernetes

Question

We are starting a project from scratch that will be managed on Google Cloud Services. I'd like to use Google Kubernetes Engine. Our application will have multiple environments (Dev, Staging, Production). Each environment is setup as a new Project on Google Cloud.
What is unclear to me is how to parameterize our service/manifest files. For instance our deploy file below, anything in {} I'd like to pull from a list of variables per environment. In a previous post someone mentioned using Helm, but I cannot find much documentation supporting the use of helm this way.
apiVersion: apps/v1beta1
kind: Deployment
metadata:
name: webapp
spec:
replicas: 1
strategy:
type: RollingUpdate
rollingUpdate:
maxSurge: {max-surge}
maxUnavailable: 0
selector:
matchLabels:
run: webapp
template:
metadata:
labels:
run: webapp
spec:
containers:
- name: webapp
image: {gcr-image-url}
imagePullPolicy: Always
ports:
- containerPort: 3000
env:
- name: DATABASE_URL
valueFrom:
secretKeyRef:
name: app-secrets
key: DATABASE_URL
- name: SECRET_KEY_BASE
valueFrom:
secretKeyRef:
name: app-secrets
key: SECRET_KEY_BASE
What tools are available to manage my GKE environments? We'll use terraform for our infrastructure management, but again is there a larger wrapper I can use to set parameters per environment?

Answer 1

Helm would work for this, as would kustomize. In the case of helm, you'll have separate values.yaml files (e.g. dev-values.yaml) with e.g.:
max-surge: 2
gcr-image-url: project-23456/test
And then reference them in the yaml via:
{{ .Values.max-surge }}
The when installing you would use helm upgrade --install my-app . --values=dev-values.yaml

Answer 2

https://get-ytt.io could be a solution.
Particularly if you look at this github discussion you will notice that you can configure your environment and then pass in values in the form of flags or environment variables.
In case of your example, given the following config.yml:
## load("#ytt:data", "data")
apiVersion: apps/v1beta1
kind: Deployment
metadata:
name: webapp
annotations:
environment: ## data.values.env
spec:
replicas: 1
strategy:
type: RollingUpdate
rollingUpdate:
maxSurge: ## data.values.max_surge
maxUnavailable: 0
selector:
matchLabels:
run: webapp
template:
metadata:
labels:
run: webapp
spec:
containers:
- name: webapp
image: ## data.values.gcr_image_url
imagePullPolicy: Always
ports:
- containerPort: 3000
env:
- name: DATABASE_URL
valueFrom:
secretKeyRef:
name: app-secrets
key: DATABASE_URL
- name: SECRET_KEY_BASE
valueFrom:
secretKeyRef:
name: app-secrets
key: SECRET_KEY_BASE
and values.yml:
##data/values
---
env: staging
max-surge: 1
gcr-image-url: some/other-image:latest
assuming that everything is in the same directory, you can template config.yml like:
ytt -f .
or customize the values on the fly from env vars and command line arguments:
export CUSTOM_env=production
ytt -f . \
--data-value max_surge=10 \
--data-value gcr_image_url=some/image:1.0 \
--data-values-env CUSTOM