Embed a badge in your repository's README that reflects the status of the latest build in Cloud Build:

Deploy a Google Cloud Function to auto-update your repository's badge. The function subscribes to events published by Cloud Build. The events contain information on the status of the progress and completion of a build. The function copies a badge reflecting that status to a known URL, which can be hard-coded in a repository README.

It's assumed you've already integrated your repository with Cloud Build. If not, the instructions for doing so are here.

The function supports the following integrations:

• Cloud Build Github App
• Github (mirrored)
• Bitbucket Cloud (mirrored)
• Cloud Source Repositories

You'll need a Cloud Storage bucket in which to store the badges (it's a good idea to prefix the name of the bucket with your Cloud project name, to ensure it's unique):

gsutil mb gs://${GOOGLE_CLOUD_PROJECT}-badges/

Next enable anyone on the internet to be able to read the badges (necessary if you're going to embed them in your README).

gsutil defacl ch -u AllUsers:R gs://${GOOGLE_CLOUD_PROJECT}-badges/

Then upload the pre-generated badges in ./badges to the bucket. Ensure they go into a directory on the bucket named badges/. Disable caching to ensure the latest updates to a badge are visible to end-users.

gsutil -m -h "Cache-Control:no-cache,max-age=0" \
  cp ./badges/*.svg gs://${GOOGLE_CLOUD_PROJECT}-badges/badges/

Note: the -m flag uploads the badges in parallel, speeding it up.

Create a new service account for use by the Cloud Function:

gcloud iam service-accounts create cloud-build-badge

Grant permissions to read and write to the bucket:

gsutil iam ch serviceAccount:cloud-build-badge@${GOOGLE_CLOUD_PROJECT}.iam.gserviceaccount.com:legacyObjectReader,legacyBucketWriter gs://${GOOGLE_CLOUD_PROJECT}-badges/

You can customise the path in the bucket at which the badge gets published, using a template string. The default is:

builds/${repo}/branches/${branch}.svg

Where ${repo} and ${branch} refer to the name of the repository and branch that triggered the build. Only these two variables are available.

Set the environment variable TEMPLATE_PATH accordingly when deploying the function in the next step.

Deploy the function:

gcloud functions deploy cloud-build-badge \
    --source . \
    --runtime python37 \
    --entry-point build_badge \
    --service-account cloud-build-badge@${GOOGLE_CLOUD_PROJECT}.iam.gserviceaccount.com \
    --trigger-topic=cloud-builds \
    --set-env-vars BADGES_BUCKET=${GOOGLE_CLOUD_PROJECT}-badges,TEMPLATE_PATH='builds/${repo}/branches/${branch}.svg'

Embed the badge in your README, replacing ${repo} and ${branch} with the name of your repository and the branch you want to show the latest status for:

![Cloud Build](https://storage.googleapis.com/${GOOGLE_CLOUD_PROJECT}-badges/builds/${repo}/branches/${branch}.svg)

If you've customised the path using TEMPLATE_PATH, ensure it is reflected in the URL above.

Now trigger a build in Cloud Build (e.g. by pushing a commit, or directly via the Google Cloud console). You should see the badge update to reflect the build status.

There is a make task for running integration tests against the deployed function:

make integration

Ensure the following environment variables are set first:

• BADGES_BUCKET: the name of the bucket containing the badges

You'll also need to install jq and xq.