Update subscription SMTs

This document explains how to update a Single Message Transform (SMT) for a Pub/Sub subscription. Changes to SMTs take effect within a few minutes. For subscription SMTs, the changes take effect for new messages delivered to the subscription after the UDF is updated.

To update subscription SMTs, you can use the Google Cloud console, the Google Cloud CLI, the client library, or the Pub/Sub API.

Required roles and permissions

To get the permissions that you need to update subscription SMTs, ask your administrator to grant you the Pub/Sub Editor (roles/pubsub.editor) IAM role on your project. For more information about granting roles, see Manage access to projects, folders, and organizations.

This predefined role contains the permissions required to update subscription SMTs. To see the exact permissions that are required, expand the Required permissions section:

Required permissions

The following permissions are required to update subscription SMTs:

  • Grant the update a subscription permission on the subscription: projects.subscriptions.patch
  • Grant the view a subscription permission on the project. This permission is only required if you are using the Google Cloud console: pubsub.subscriptions.view

You might also be able to get these permissions with custom roles or other predefined roles.

You can configure access control at the project level and at the individual resource level.

Update subscription SMTs

To update subscription SMTs, follow these steps:

Console

  1. In the Google Cloud console, go to the Pub/Sub Subscriptions page.

    Go to Subscriptions

  2. Click the subscription for which you want to edit SMTs.

  3. In the subscription details page, click Edit.

    The Transforms tab lists all the SMTs that are attached to the subscription.

  4. In the Edit subscription page, you can do the following tasks:

    1. Add a new SMT. Click Add a transform.

    2. Edit an existing SMT. Expand any SMT to edit the SMT.

    3. Rearrange the SMTs. Use the up and down arrows.

    4. Delete an SMT. Click the delete button.

  5. Click Update.

gcloud

  1. In the Google Cloud console, activate Cloud Shell.

    Activate Cloud Shell

    At the bottom of the Google Cloud console, a Cloud Shell session starts and displays a command-line prompt. Cloud Shell is a shell environment with the Google Cloud CLI already installed and with values already set for your current project. It can take a few seconds for the session to initialize.

  2. Run the gcloud pubsub subscriptions updatecommand:

    gcloud pubsub subscriptions update SUBSCRIPTION_ID \
    --message-transforms-file=TRANSFORMS_FILE

    Replace the following:

    • SUBSCRIPTION_ID: The ID or name of the subscription you want to update.

    • TRANSFORMS_FILE: The path to the YAML or JSON file containing the updated SMTs.

      The following is an example of a YAML transforms file:

      - javascriptUdf:
    code: >
        function redactSSN(message, metadata) {
          const data = JSON.parse(message.data);
          delete data['ssn'];
          message.data = JSON.stringify(data);
          return message;
        }
    functionName: redactSSN
- javascriptUdf:
    code: >
        function filterHighAmount(message, metadata) {
          const data = JSON.parse(message.data);
          if (data['amount'] > 100 ) { return null; }
          return message;
        }
    functionName: filterHighAmount

    To clear all the SMTs from the subscription, use the following command:

    gcloud pubsub subscriptions update SUBSCRIPTION_ID --clear-message-transforms

    Replace SUBSCRIPTION_ID with the ID or name of the subscription you want to update.

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