Cloud Storage triggers (2nd gen)

In Cloud Functions, a Cloud Storage trigger enables a function to be called in response to changes in Cloud Storage . When you specify a Cloud Storage trigger for a function, you choose an event type and specify a Cloud Storage bucket. Your function will be called whenever a change occurs on an object (file) within the specified bucket.

The following Cloud Storage event types are supported:

Event Event type Description
Object finalized
  • google.cloud.storage.object.v1.finalized (through Eventarc)
Occurs when a new object is created, or an existing object is overwritten and a new generation of that object is created.
Object deleted
  • google.cloud.storage.object.v1.deleted (through Eventarc)
Occurs when an object is permanently deleted.
Object archived
  • google.cloud.storage.object.v1.archived (through Eventarc)
Occurs when a live version of an object becomes a noncurrent version. See Object versioning for more information.
Object metadata updated
  • google.cloud.storage.object.v1.metadataUpdated (through Eventarc)
Occurs when the metadata of an existing object changes.

A Cloud Storage trigger is implemented as a CloudEvent function , in which the Cloud Storage event data is passed to your function in the CloudEvents format , and the CloudEvent data payload is of type StorageObjectData .

The Google Events repository contains additional resources for working with event data.

Permissions

In order to use Cloud Storage triggers in Cloud Functions, the Cloud Storage service agent must have the Pub/Sub Publisher ( roles/pubsub.publisher ) IAM role on your project.

Deployment

You can specify a Cloud Storage trigger when you deploy a function. See Deploy a Cloud Function for general instructions on how to deploy a function, and see the following for additional information specific to configuring Cloud Storage triggers during deployment.

gcloud

If you are deploying using the gcloud CLI , you can use the Cloud Storage Object finalized event type with the following flags: 

gcloud functions deploy 
YOUR_FUNCTION_NAME
 \
--trigger-bucket=
YOUR_STORAGE_BUCKET
 \
[--retry] \
...
  • The --trigger-bucket flag specifies the Cloud Storage bucket that the trigger will monitor. Object finalized events within this bucket will trigger calls to your function.
  • The --retry flag controls whether failed function calls are automatically retried. See Retrying event-driven functions for more information.

To use event types other than Object finalized , use the following flags: 

  gcloud functions deploy 
YOUR_FUNCTION_NAME
 

  --gen2 


  --trigger-event-filters="type=
EVENT_TYPE
" 


  --trigger-event-filters="bucket=
YOUR_STORAGE_BUCKET
" 


  ...

When deploying functions, specify the bucket name alone without the leading gs:// ; for example, --trigger-event-filters="bucket=my-bucket" .

Console

If you are deploying using the Google Cloud console , you can configure a Cloud Storage trigger in the Trigger section:

  1. In the Trigger type field, choose Cloud Storage .

  2. In the Event type field, choose a triggering event. The default is google.cloud.storage.object.v1.finalized .

    For a Cloud Storage event that uses Cloud Audit Logs, refer to the trigger configuration instructions for an Eventarc trigger .

  3. In the Bucket field, click Browse to select a Cloud Storage bucket for the trigger to monitor. Changes to objects within this bucket will trigger calls to your function.

  4. Select or deselect the Retry on failure checkbox to control whether Cloud Functions automatically retries a failed function invocation. See Retrying event-driven functions for more information.

  5. Click More options to perform additional configuration on your trigger:

    • In the Trigger type field, specify one of Google sources , Custom , or Third-party :

      • Google sources lets you specify triggers for Pub/Sub, Cloud Storage, Firestore, and other Google event providers.In the Eventarc trigger pane, use the Event provider field to select the product that provides the type of event you want to trigger your function. Then in the Event field, select the event you want to use as a trigger.

      • The Custom option lets you produce and consume events from your application code. Follow the prompts in the Eventarc trigger pane to create a channel . A channel is a resource that is used as a pipeline to deliver custom events from producers to consumers. Custom events are published to a channel and an Eventarc trigger subscribes to those events.

      • The Third-party option let you integrate with non-Google providers that offer an Eventarc source. See third-party events in Eventarc for details.

    • In the Event field, select a triggering event. The default is google.cloud.storage.object.v1.finalized .

    • Optionally, in the Service account field, select a service account to be used as the identity of the Eventarc trigger. See Trigger identity for more information.

  6. Click Save trigger .

Event delivery

Cloud Storage triggers are implemented with Pub/Sub notifications for Cloud Storage . Events are subject to Pub/Sub notification delivery guarantees .

A Cloud Storage bucket can have up to 10 notification configurations set to trigger for a specific event. Exceeding the bucket's notifications limits will cause further function deployments to fail with an error like the following: 

Cloud Storage bucket ...: Pub/Sub notification limit reached

See Cloud Storage Quotas and limits to learn more.

Next steps