GCP Cloud Build Slack Notifier

Purpose

Via a Cloud Function, send a Slack webhook notification when a GCP Cloud Build successfully completes or fails via build-in Cloud Build Pub/Sub notifications.

Overview

Given a Pub/Sub topic called cloud-builds, Cloud Build will automatically send build status notifications to the topic. The Cloud Function deployed here watches the topic and sends slack notifications to Slack on successes and failtures.

Requirements if webhook URL is in the code

• Existing Slack webhook URL and Cloud Build APIs and Cloud Functions enabled
• cloud-builds Pub/Sub topic that Cloud Build is sending Pub/Sub messages to (to create topic: gcloud pubsub topics create cloud-builds)

Optional if webhook URL is in Secret Manager

• Service account with roles/secretmanager.secretAccessor
• Secret Manager secret with the webhook URL in it

Configuration

• Replace your project ID in source/main.py in place of "{PROJECT_ID}"
• (optional) Replace your secret manager secret ID in source/main.py in place of "{SECRET_ID}"
• (optional) Insert your slack webhook url into source/main.py for the SLACK_WEBHOOK variable

Deploy Cloud Function via bash script

• With webhook in code: deploy_function.sh {PROJECT_ID}
• With webhook in Secret Manager: deploy_function.sh {PROJECT_ID} {SERVICE_ACCOUNT}

Deploy Cloud Function via Cloud Build trigger

1. Modify the cloudbuild.yaml, putting your project ID in place of {PROJECT_ID} and service account in place of {SERVICE_ACCOUNT} (or delete that line if not using secret manager)

• Documentation on the below steps: https://cloud.google.com/cloud-build/docs/automating-builds/create-manage-triggers

2. Add the code to a repo that you control and connect it to Cloud Build
3. Create a cloud build trigger for the repo
4. Run the trigger to deploy the cloud function

Example Slack Notifications

Notes

• There are a lot of other details that you can pull out of the Pub/Sub message. This is a basic example. If you look at the Cloud Function logs, you'll see the full Pub/Sub json message.

Troubleshooting

• If the cloud-builds topic is not receiving Pub/Sub messages, disable and re-enable the Cloud Builds API after creating the topic.
• If you see Pub/Sub messages going in but no notifications, check the Cloud Function logs. Depending on where you get the bulid from, the fields may be different, e.g. lines 29-53 might need to be updated to point to the JSON location of the repo or SHA values.