Cloud Storage Tutorial

This simple tutorial demonstrates writing, deploying, and triggering a Background Cloud Function with a Cloud Storage trigger.

Objectives

Costs

This tutorial uses billable components of Cloud Platform, including:

  • Google Cloud Functions
  • Google Cloud Storage

Use the Pricing Calculator to generate a cost estimate based on your projected usage.

New Cloud Platform users might be eligible for a free trial.

Before you begin

  1. Sign in to your Google Account.

    If you don't already have one, sign up for a new account.

  2. Select or create a GCP project.

    Go to the Manage resources page

  3. Make sure that billing is enabled for your project.

    Learn how to enable billing

  4. Enable the Cloud Functions and Cloud Storage APIs.

    Enable the APIs

  5. Install and initialize the Cloud SDK.
  6. Update and install gcloud components:
    gcloud components update &&
    gcloud components install beta
  7. Prepare your development environment.

Preparing the application

  1. Create a Cloud Storage bucket to upload a test file, where YOUR_TRIGGER_BUCKET_NAME is a globally unique bucket name:

    gsutil mb gs://YOUR_TRIGGER_BUCKET_NAME
    

  2. Clone the sample app repository to your local machine:

    Node.js

    git clone https://github.com/GoogleCloudPlatform/nodejs-docs-samples.git

    Alternatively, you can download the sample as a zip file and extract it.

  3. Change to the directory that contains the Cloud Functions sample code:

    Node.js

    cd nodejs-docs-samples/functions/helloworld/

Deploying and triggering the function

Currently, Cloud Storage functions are based on Pub/Sub notifications from Cloud Storage and support similar event types:

The following sections describe how to deploy and trigger a function for each of these event types.

Object Finalize

Object finalize events trigger when a "write" of a Cloud Storage Object is successfully finalized. In particular, this means that creating a new object or overwriting an existing object triggers this event. Archive and metadata update operations are ignored by this trigger.

Object Finalize: deploying the function

Take a look at the sample function, which handles Cloud Storage events:

Node.js

/**
 * Generic background Cloud Function to be triggered by Cloud Storage.
 *
 * @param {object} event The Cloud Functions event.
 * @param {function} callback The callback function.
 */
exports.helloGCSGeneric = (event, callback) => {
  const file = event.data;

  console.log(`  Event ${event.eventId}`);
  console.log(`  Event Type: ${event.eventType}`);
  console.log(`  Bucket: ${file.bucket}`);
  console.log(`  File: ${file.name}`);
  console.log(`  Metageneration: ${file.metageneration}`);
  console.log(`  Created: ${file.timeCreated}`);
  console.log(`  Updated: ${file.updated}`);

  callback();
};

By default, Cloud Functions looks for your code in a file named index.js.

To deploy the function, run the following command in the helloworld directory:

Node.js

gcloud beta functions deploy helloGCSGeneric --trigger-resource YOUR_TRIGGER_BUCKET_NAME --trigger-event google.storage.object.finalize

where YOUR_TRIGGER_BUCKET_NAME is the name of the Cloud Storage bucket that triggers the function.

Object Finalize: triggering the function

To trigger the function:

  1. Create an empty gcf-test.txt file in the helloworld directory.

  2. Upload the file to Cloud Storage in order to trigger the function:

    gsutil cp gcf-test.txt gs://YOUR_TRIGGER_BUCKET_NAME
    

    where YOUR_TRIGGER_BUCKET_NAME is the name of your Cloud Storage bucket where you will upload a test file.

  3. Check the logs to make sure the executions have completed:

    gcloud beta functions logs read --limit 50
    

Object Delete

Object delete events are most useful for non-versioning buckets. They are triggered when an old version of an object is deleted. In addition, they are triggered when an object is overwritten. Object delete triggers can also be used with versioning buckets, triggering when a version of an object is permanently deleted.

Object Delete: deploying the function

Using the same sample code as in the finalize example, deploy the function with object delete as the trigger event. Run the following command in the helloworld directory:

Node.js

gcloud beta functions deploy helloGCSGeneric --trigger-resource YOUR_TRIGGER_BUCKET_NAME --trigger-event google.storage.object.delete

where YOUR_TRIGGER_BUCKET_NAME is the name of the Cloud Storage bucket that triggers the function.

Object Delete: triggering the function

To trigger the function:

  1. Create an empty gcf-test.txt file in the helloworld directory.

  2. Make sure that your bucket is non-versioning:

    gsutil versioning set off gs://YOUR_TRIGGER_BUCKET_NAME
    

  3. Upload the file to Cloud Storage:

    gsutil cp gcf-test.txt gs://YOUR_TRIGGER_BUCKET_NAME
    

    where YOUR_TRIGGER_BUCKET_NAME is the name of your Cloud Storage bucket where you will upload a test file. At this point the function should not execute yet.

  4. Delete the file to trigger the function:

    gsutil rm gs://YOUR_TRIGGER_BUCKET_NAME/gcf-test.txt
    

  5. Check the logs to make sure the executions have completed:

    gcloud beta functions logs read --limit 50
    

Note that the function may take some time to finish executing.

Object Archive

Object archive events can be used only with versioning buckets. They are triggered when an old version of an object is archived. In particular, this means that when an object is overwritten or deleted, an archive event is triggered.

Object Archive: deploying the function

Using the same sample code as in the finalize example, deploy the function with object archive as the trigger event. Run the following command in the helloworld directory:

Node.js

gcloud beta functions deploy helloGCSGeneric --trigger-resource YOUR_TRIGGER_BUCKET_NAME --trigger-event google.storage.object.archive

where YOUR_TRIGGER_BUCKET_NAME is the name of the Cloud Storage bucket that triggers the function.

Object Archive: triggering the function

To trigger the function:

  1. Create an empty gcf-test.txt file in the helloworld directory.

  2. Make sure that your bucket has versioning enabled:

    gsutil versioning set on gs://YOUR_TRIGGER_BUCKET_NAME
    

  3. Upload the file to Cloud Storage:

    gsutil cp gcf-test.txt gs://YOUR_TRIGGER_BUCKET_NAME
    

    where YOUR_TRIGGER_BUCKET_NAME is the name of your Cloud Storage bucket where you will upload a test file. At this point the function should not execute yet.

  4. Archive the file to trigger the function:

    gsutil rm gs://YOUR_TRIGGER_BUCKET_NAME/gcf-test.txt
    

  5. Watch the logs to make sure the executions have completed:

    gcloud beta functions logs read --limit 50
    

Object Metadata Update

Metadata update events are triggered when the metadata of existing object is updated.

Object Metadata Update: deploying the function

Using the same sample code as in the finalize example, deploy the function with metadata update as the trigger event. Run the following command in the helloworld directory:

Node.js

gcloud beta functions deploy helloGCSGeneric --trigger-resource YOUR_TRIGGER_BUCKET_NAME --trigger-event google.storage.object.metadataUpdate

where YOUR_TRIGGER_BUCKET_NAME is the name of the Cloud Storage bucket that triggers the function.

Object Metadata Update: triggering the function

To trigger the function:

  1. Create an empty gcf-test.txt file in the helloworld directory.

  2. Make sure that your bucket is non-versioning:

    gsutil versioning set off gs://YOUR_TRIGGER_BUCKET_NAME
    

  3. Upload the file to Cloud Storage:

    gsutil cp gcf-test.txt gs://YOUR_TRIGGER_BUCKET_NAME
    

    where YOUR_TRIGGER_BUCKET_NAME is the name of your Cloud Storage bucket where you will upload a test file. At this point the function should not execute yet.

  4. Update the metadata of the file:

    gsutil -m setmeta -h "Content-Type:text/plain" gs://YOUR_TRIGGER_BUCKET_NAME/gcf-test.txt
    

  5. Watch the logs to make sure the executions have completed:

    gcloud beta functions logs read --limit 50
    

Cleaning up

To avoid incurring charges to your Google Cloud Platform account for the resources used in this tutorial:

Deleting the project

The easiest way to eliminate billing is to delete the project you created for the tutorial.

To delete the project:

  1. In the GCP Console, go to the Projects page.

    Go to the Projects page

  2. In the project list, select the project you want to delete and click Delete project. After selecting the checkbox next to the project name, click
      Delete project
  3. In the dialog, type the project ID, and then click Shut down to delete the project.

Deleting the Cloud Function

Deleting Cloud Functions does not remove any resources stored in Cloud Storage.

To delete the Cloud Function you created in this tutorial, run the following command:

Node.js

gcloud beta functions delete helloGCSGeneric 

You can also delete Cloud Functions from the Google Cloud Platform Console.

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Cloud Functions Documentation