Google Cloud Builder setup to auto-deploy to a kuberneter engine cluster

cloudbuild.yaml

# We can use this cloudbuild.yaml setup with a trigger type tag
# on Google Cloud Build using default variable substitution.
#
# Use environment substitution in the trigger to add the additional parameters:
#
# _CLUSTER    = kubernetes engine cluster. Ex. my-test-cluster
# _DEPLOYMENT = deployment name Ex. my-project
# _CONTAINER  = container name within deployment. Ex. my-project-api
# _GCS_ZONE   = compute engine zone. Ex. europe-west-1c
#
# Reference docs:
# https://cloud.google.com/cloud-build/docs/configuring-builds/build-test-deploy-artifacts
# https://cloud.google.com/cloud-build/docs/configuring-builds/substitute-variable-values
#
steps:
# Build the docker image using git tag as a version
- name: 'gcr.io/cloud-builders/docker'
  args: ["build", "-t", "gcr.io/$PROJECT_ID/$REPO_NAME:$TAG_NAME", "."]
# Publish the docker image to google repository
- name: 'gcr.io/cloud-builders/docker'
  args: ["push", "gcr.io/$PROJECT_ID/$REPO_NAME:$TAG_NAME"]
# Update test cluster deployment to this new image
- name: 'gcr.io/cloud-builders/kubectl'
  args:
  - set
  - image
  - deployment
  - $_DEPLOYMENT
  - $_CONTAINER=gcr.io/$PROJECT_ID/$REPO_NAME:$TAG_NAME
  env:
  - 'CLOUDSDK_COMPUTE_ZONE=$_GCS_ZONE'
  - 'CLOUDSDK_CONTAINER_CLUSTER=$_CLUSTER'
images: ['gcr.io/$PROJECT_ID/$REPO_NAME:$TAG_NAME']

This does require the first deployment to be done by hand. It only updates the image of an existing deployment. This was an intended safety feature for us to not redeploy disabled software on build.

Also ensure your cloudbuilder service agent has the kubernetes engine admin role as per the docs