Configuring SMTP 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 SMTP 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

Configuring email notifications

To send email notifications, you will need a running SMTP server and access to an account on that server, including the account's username and password that will be used to send notifications. Please ensure that your SMTP server's delivery quotas can handle the volume of email you expect to generate.

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

To configure email notifications:

  1. Store the sender's email account password 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 the sender's email account password.

    5. To save your secret, click Create secret.

  2. While your Cloud Run service account may have the Editor role for your project, the Editor role is not sufficient to access your secret in Secret Manager. You will need to 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 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 sender's email account password.

    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.

  3. 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.

  4. Write a notifier configuration file to configure your SMTP 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: SMTPNotifier
    metadata:
      name: example-smtp-notifier
    spec:
      notification:
        filter: build.status == Build.Status.SUCCESS
        delivery:
          server: server-host-name
          port: "port"
          sender: sender-email
          from: from-email
          recipients:
            - recipient-email
            # optional: more emails here
          password:
            secretRef: smtp-password
      secrets:
      - name: smtp-password
        value: projects/project-id/secrets/secret-name/versions/latest
    

    Where:

    • server-host-name is the address of your SMTP server.
    • port is the port that will handle SMTP requests. This value should be specified as a string.
    • sender-email is the email address of the sender account that is seen by the specified server-host-name.
    • from-email is the email address that is seen by recipients.
    • recipient-email is a list of one or more email addresses to receive messages from the sender.
    • smtp-password is the configuration variable used in this example to reference the sender's email account password 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 the password to the sender's email account.

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

    For additional fields you can filter by, see the Build resource. For additional filtering examples, see the Using CEL to filter build events.

  5. 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.
  6. Deploy your notifier to Cloud Run:

     gcloud run deploy service-name \
       --image=us-east1-docker.pkg.dev/gcb-release/cloud-build-notifiers/smtp:latest \
       --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 SMTP 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.

  7. 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.
  8. 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.

  9. 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.
  10. Create the cloud-builds topic to receive build update messages for your notifier:

    gcloud pubsub topics create cloud-builds
    
  11. 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, specified recipients will receive an email with a notification if the build matches the filter you've configured.

Using CEL to filter build events

Cloud Build uses CEL with the variable, build, on fields listed in the Build resource to access fields associated with your build event such as your trigger ID, image list, or substitution values. You can use the filter string to filter build events in your build config file using any field listed in the Build resource. To find the exact syntax associated with your field, see the cloudbuild.proto file.

Filtering by trigger ID

To filter by trigger ID, specify the value of your trigger ID in the filter field using build.build_trigger_id, where trigger-id is your trigger ID as a string:

filter: build.build_trigger_id == trigger-id

Filtering by status

To filter by status, specify the build status you want to filter on in the filter field using build.status.

The following example shows how to filter build events with a SUCCESS status using the filter field:

filter: build.status == Build.Status.SUCCESS

You can also filter builds with varying statuses. The following example shows how to filter build events that have a SUCCESS, FAILURE, or TIMEOUT status using the filter field:

filter: build.status in [Build.Status.SUCCESS, Build.Status.FAILURE, Build.Status.TIMEOUT]

To see additional status values you can filter by, see Status under the Build resource reference.

Filtering by tag

To filter by tag, specify the value of your tag in the filter field using build.tags, where tag-name is the name of your tag:

filter: tag-name in build.tags

You can filter based on the number of tags specified in your build event using size. In the following example, the filter field filters build events that have exactly two tags specified with one tag specified as v1:

filter: size(build.tags) == 2 && "v1" in build.tags

Filtering by images

To filter by images, specify the value of your image in the filter field using build.images, where image-name is the full name of your image as listed in Container Registry such as gcr.io/example/image-one:

filter: image-name in build.images

In the following example, the filter filters on build events that have either gcr.io/example/image-one or gcr.io/example/image-two specified as image names:

filter: "gcr.io/example/image-one" in build.images || "gcr.io/example/image-two" in build.images

Filtering by time

You can filter build events based on a build's create time, start time, or finish time by specifying one of the following options in your filter field: build.create_time, build.start_time, or build.finish_time.

In the following example, the filter field uses timestamp to filter build events with a request time to create the build at July 20, 2020 at 6:00 AM:

filter: build.create_time == timestamp("2020-07-20:T06:00:00Z")

You can also filter on build events by time comparisons. In the following example, the filter field uses timestamp to filter build events with a start time between July 20, 2020 at 6:00 AM and July 30, 2020 at 6:00 AM.

filter: timestamp("2020-07-20:T06:00:00Z") >= build.start_time && build.start_time <= timestamp("2020-07-30:T06:00:00Z")

To learn more about how timezones are expressed in CEL, see the language definition for timezones.

To filter by duration of a build, you can use duration to compare timestamps. In the following example, the filter field uses duration to filter build events with a builds that run for at least five minutes:

filter: build.finish_time - build.start_time >= duration("5m")

Filtering by substitution

You can filter by substitution by specifying the substitution variable in the filter field using build.substitutions. In the following example, the filter field lists builds that contain the substitution variable substitution-variable and checks if the substitution-variable matches the specified substitution-value:

filter: build.substitutions[substitution-variable] == substitution-value

Where:

  • substitution-variable is the name of your substitution variable.
  • substitution-value is the name of your substitution value.

You can also filter by default substitution variable values. In the following example, the filter field lists builds that have the branch name master and builds that have the repository name github.com/user/my-example-repo. The default substitution variables BRANCH_NAME and REPO_NAME are passed in as keys to the build.substitutions:

filter: build.substitutions["BRANCH_NAME"] == "master" && build.substitutions["REPO_NAME"] == "github.com/user/my-example-repo"

If you want to filter on strings using regular expressions, you can use the built-in matches function. In the example below, the filter field filters for builds with a status of FAILURE or TIMEOUT and that also have a build substitution variable TAG_NAME with a value that matches the regular expression v{DIGIT}.{DIGIT}.{3 DIGITS}).

filter: build.status in [Build.Status.FAILURE, Build.Status.TIMEOUT] && build.substitutions["TAG_NAME"].matches("^v\\d{1}\\.\\d{1}\\.\\d{3}$")`

To see a list of default substitution values, see Using default substitutions.

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