Configuring Slack notifications

Cloud Build can notify you of build updates by sending you notifications to desired channels, such as Slack or your SMTP server. This page explains how to configure notifications using the Slack notifier.

Before you begin

  • Enable the Cloud Build, Compute Engine, Cloud Run, Pub/Sub, and Secret Manager APIs.

    Enable the APIs

Cloud Build notifiers

Cloud Build sends all build event updates, along with build metadata, to Pub/Sub on the cloud-builds topic. Cloud Build notifiers can be configured to listen to that topic, filter the messages it receives, and send messages to your service.

Cloud Build notifiers are Docker images that can be run as containers on Cloud Run. When polled by a subscriber application, Cloud Build notifiers use push subscriptions to deliver messages to the configured service. All notifiers use a common YAML spec for configuration, stored in Cloud Storage.

Cloud Build provides and maintains deployable notifier images in the cloud-build-notifiers repository. The following table lists available notifiers:

Notifier Description
bigquery writes build data to a BigQuery table
http sends a JSON payload to another HTTP endpoint
slack uses a Slack webhook to post messages to a Slack channel
smtp sends emails via an SMTP server
bigquery pushes build data to a BigQuery instance

Configuring Slack notifications

The following section explains how you can manually configure Slack notifications using the Slack notifier. If you would like to automate the configuration instead, see Automating configuration for notifications.

To configure Slack notifications:

  1. Create a Slack app for your desired Slack workspace.

  2. Activate incoming webhooks to post messages from Cloud Build to Slack.

  3. Navigate to your Slack app to locate the URL for the incoming webhook. Your URL will look similar to the following:

    http://hooks.slack.com/services/...
    
  4. Store your incoming webhook URL in Secret Manager:

    1. Open the Secret Manager page in the Google Cloud Console:

      Open the Secret Manager page

    2. Click Create secret.

    3. Enter a name for your secret.

    4. Under Secret value, add your incoming webhook URL for your Slack app.

    5. To save your secret, click Create secret.

  5. Give your Cloud Run service account access to your secret:

    1. Go to the IAM page in the Google Cloud Console:

      Open the IAM page

    2. Locate the Compute Engine default service account associated with with your project:

      Your Compute Engine default service account will look similar to the following:

      project-number-compute@developer.gserviceaccount.com
      

      Take note of your Compute Engine default service account.

    3. Open the Secret Manager page in the Google Cloud Console:

      Open the Secret Manager page

    4. Click on your secret name that contains the secret for your Slack app.

    5. In the Permissions tab, click Add member.

    6. Add the Compute Engine default service account associated with your project as a member.

    7. Select Secret Manager Secret Accessor permission as the role.

    8. Click Save.

  6. Give your Cloud Run service account permission to read and write to Cloud Storage buckets:

    1. Go to the IAM page in the Google Cloud Console:

      Open the IAM page

    2. Locate the Compute Engine default service account associated with with your project:

      Your Compute Engine default service account will look similar to the following:

      project-number-compute@developer.gserviceaccount.com
      
    3. Click on the pencil icon in the row containing your Compute Engine default service account. You will see the Edit permissions tab.

    4. Click Add another role.

    5. Add the following role:

      • Storage Object Viewer
    6. Click Save.

  7. Write a notifier configuration file to configure your Slack notifier and filter on build events:

    In the following example notifier configuration file, the filter field uses Common Expression Language with the available variable, build, to filter build events with a SUCCESS status:

    apiVersion: cloud-build-notifiers/v1
    kind: SlackNotifier
    metadata:
      name: example-slack-notifier
    spec:
      notification:
        filter: build.status == Build.Status.SUCCESS
        delivery:
          webhookUrl:
            secretRef: webhook-url
      secrets:
      - name: webhook-url
        value: projects/project-id/secrets/secret-name/versions/latest
    

    Where:

    • webhook-url is the configuration variable used in this example to reference the Slack webhook URL path stored in Secret Manager. The variable name you specify here should match the name field under secrets.
    • project-id is the ID of your Cloud project.
    • secret-name is the name of your secret that contains your Slack webhook URL.

    To view the example, see the notifier configuration file for the Slack notifier.

    For additional fields you can filter by, see the Build resource. For additional filtering examples, see the Filtering builds in notifications.

  8. Upload your notifier configuration file to a Cloud Storage bucket:

    1. If you do not have a Cloud Storage bucket, run the following command to create a bucket, where bucket-name is the name you want to give your bucket, subject to naming requirements.

      gsutil mb gs://bucket-name/
      
    2. Upload the notifier configuration file to your bucket:

      gsutil cp config-file-name gs://bucket-name/config-file-name
      

      Where:

      • bucket-name is the name of your bucket.
      • config-file-name is the name of your configuration file.
  9. Deploy your notifier to Cloud Run:

     gcloud run deploy service-name \
       --image=us-east1-docker.pkg.dev/gcb-release/cloud-build-notifiers/slack:latest \
       --no-allow-unauthenticated \
       --update-env-vars=CONFIG_PATH=config-path,PROJECT_ID=project-id
    

    Where:

    • service-name is the name of the Cloud Run service to which you're deploying the image.
    • config-path is the path to the notifier config file for your Slack notifier, gs://bucket-name/config-file-name.
    • project-id is the ID of your Cloud project.

    The gcloud run deploy command pulls the latest version of the hosted image from the Cloud Build-owned Artifact Registry. Cloud Build supports notifier images for nine months. After nine months, Cloud Build deletes the image version. If you would like to use a prior image version, you will need to specify the full semantic version of the image tag in the image attribute of your gcloud run deploy command. Previous image versions and tags can be found in Artifact Registry.

  10. Grant Pub/Sub permissions to create authentication tokens in your project:

     gcloud projects add-iam-policy-binding project-id \
       --member=serviceAccount:service-project-number@gcp-sa-pubsub.iam.gserviceaccount.com \
       --role=roles/iam.serviceAccountTokenCreator
    

    Where:

    • project-id is the ID of your Cloud project.
    • project-number is your Cloud project number.
  11. Create a service account to represent your Pub/Sub subscription identity:

    gcloud iam service-accounts create cloud-run-pubsub-invoker \
      --display-name "Cloud Run Pub/Sub Invoker"
    

    You can use cloud-run-pubsub-invoker or use a name unique within your Google Cloud project.

  12. Give the cloud-run-pubsub-invoker service account the Cloud Run Invoker permission:

    gcloud run services add-iam-policy-binding service-name \
       --member=serviceAccount:cloud-run-pubsub-invoker@project-id.iam.gserviceaccount.com \
       --role=roles/run.invoker
    

    Where:

    • service-name is the name of the Cloud Run service to which you're deploying the image.
    • project-id is the ID of your Cloud project.
  13. Create the cloud-builds topic to receive build update messages for your notifier:

    gcloud pubsub topics create cloud-builds
    
  14. Create a Pub/Sub push subscriber for your notifier:

     gcloud pubsub subscriptions create subscriber-id \
       --topic=cloud-builds \
       --push-endpoint=service-url \
       --push-auth-service-account=cloud-run-pubsub-invoker@project-id.iam.gserviceaccount.com
    

    Where:

    • subscriber-id is the name you want to give your subscription.
    • service-url is the Cloud Run-generated URL for your new service.
    • project-id is the ID of your Cloud project.

Notifications for your Cloud Build project are now set up. The next time you invoke a build, you will receive a notification in Slack if the build matches the filter you've configured.

What's next