Use Eventarc to receive events from Cloud Storage

This tutorial shows you how to deploy a containerized application using an authenticated Cloud Run service that receives events through Eventarc.

By specifying filters for an Eventarc trigger, you can configure the routing of events, including the event source and the event target. In this case, an update to a Cloud Storage bucket triggers the event and a request is sent to your Cloud Run service in the form of an of HTTP request.

Objectives

In this tutorial, you will:

Create a Cloud Storage bucket to be the event source.
Deploy an event receiver service to Cloud Run that requires authenticated invocations.
Create an Eventarc trigger that routes events from the Cloud Storage bucket to the Cloud Run service.
Generate an event by uploading a file to the Cloud Storage bucket and view the event in the Cloud Run logs.

Costs

In this document, you use the following billable components of Google Cloud:

To generate a cost estimate based on your projected usage, use the pricing calculator. New Google Cloud users might be eligible for a free trial.

Before you begin

Security constraints defined by your organization might prevent you from completing the following steps. For troubleshooting information, see Develop applications in a constrained Google Cloud environment.

Sign in to your Google Cloud account. If you're new to Google Cloud, create an account to evaluate how our products perform in real-world scenarios. New customers also get $300 in free credits to run, test, and deploy workloads.

Install the Google Cloud CLI.

To initialize the gcloud CLI, run the following command:

gcloud init

Create or select a Google Cloud project.

Create a Google Cloud project:
```
gcloud projects create PROJECT_ID
```
Replace PROJECT_ID with a name for the Google Cloud project you are creating.
Select the Google Cloud project that you created:
```
gcloud config set project PROJECT_ID
```
Replace PROJECT_ID with your Google Cloud project name.

Make sure that billing is enabled for your Google Cloud project.

Install the Google Cloud CLI.

To initialize the gcloud CLI, run the following command:

gcloud init

Create or select a Google Cloud project.

Create a Google Cloud project:
```
gcloud projects create PROJECT_ID
```
Replace PROJECT_ID with a name for the Google Cloud project you are creating.
Select the Google Cloud project that you created:
```
gcloud config set project PROJECT_ID
```
Replace PROJECT_ID with your Google Cloud project name.

Make sure that billing is enabled for your Google Cloud project.

If you are not using Cloud Shell, update the Google Cloud CLI components and log in using your account:
```
gcloud components update
gcloud auth login
```

Enable the APIs:

gcloud services enable artifactregistry.googleapis.com \
    cloudbuild.googleapis.com \
    eventarc.googleapis.com \
    run.googleapis.com \
    storage.googleapis.com

Set the configuration variables used in this tutorial:

export REGION=us-central1
gcloud config set run/region ${REGION}
gcloud config set run/platform managed
gcloud config set eventarc/location ${REGION}

If you are the project creator, you are granted the basic Owner role (roles/owner). By default, this Identity and Access Management (IAM) role includes the permissions necessary for full access to most Google Cloud resources and you can skip this step.

If you are not the project creator, required permissions must be granted on the project to the appropriate principal. For example, a principal can be a Google Account (for end users) or a service account (for applications and compute workloads). For more information, see the Roles and permissions page for your event destination.

Note that by default, Cloud Build permissions include permissions to upload and download Artifact Registry artifacts.
Required permissions

To get the permissions that you need to complete this tutorial, ask your administrator to grant you the following IAM roles on your project:
- Cloud Build Editor (roles/cloudbuild.builds.editor)
- Cloud Run Admin (roles/run.admin)
- Eventarc Admin (roles/eventarc.admin)
- Logs View Accessor (roles/logging.viewAccessor)
- Project IAM Admin (roles/resourcemanager.projectIamAdmin)
- Service Account Admin (roles/iam.serviceAccountAdmin)
- Service Account User (roles/iam.serviceAccountUser)
- Service Usage Admin (roles/serviceusage.serviceUsageAdmin)
- Storage Admin (roles/storage.admin)
For more information about granting roles, see Manage access to projects, folders, and organizations.

You might also be able to get the required permissions through custom roles or other predefined roles.
Make note of the Compute Engine default service account as you will you attach it to an Eventarc trigger to represent the identity of the trigger for testing purposes. This service account is automatically created after enabling or using a Google Cloud service that uses Compute Engine, and with the following email format:
```
PROJECT_NUMBER-compute@developer.gserviceaccount.com
```
Replace PROJECT_NUMBER with your Google Cloud project number. You can find your project number on the Welcome page of the Google Cloud console or by running the following command:
```
gcloud projects describe PROJECT_ID --format='value(projectNumber)'
```
For production environments, we strongly recommend creating a new service account and granting it one or more IAM roles that contain the minimum permissions required and follow the principle of least privilege.

Note:
The iam.automaticIamGrantsForDefaultServiceAccounts organization policy constraint prevents the Editor role from being automatically granted to default service accounts. If you created your organization after May 3, 2024, this constraint is enforced by default.

We strongly recommend that you enforce this constraint to disable the automatic role grant. If you disable the automatic role grant, you must decide which roles to grant to the default service accounts, and then grant these roles yourself.

If the default service account already has the Editor role, we recommend that you replace the Editor role with less permissive roles. To safely modify the service account's roles, use Policy Simulator to see the impact of the change, and then grant and revoke the appropriate roles.
By default, Cloud Run services are only callable by Project Owners, Project Editors, and Cloud Run Admins and Invokers. You can control access on a per-service basis; however, for testing purposes, grant the Cloud Run Invoker role (run.invoker) on the Google Cloud project to the Compute Engine service account. This grants the role on all Cloud Run services and jobs in a project.
```
gcloud projects add-iam-policy-binding PROJECT_ID \
    --member=serviceAccount:PROJECT_NUMBER-compute@developer.gserviceaccount.com \
    --role=roles/run.invoker
```
Note that if you create a trigger for an authenticated Cloud Run service without granting the Cloud Run Invoker role, the trigger is created successfully and is active. However, the trigger will not work as expected and a message similar to the following appears in the logs:
The request was not authenticated. Either allow unauthenticated invocations or set the proper Authorization header.
Grant the Eventarc Event Receiver role (roles/eventarc.eventReceiver) on the project to the Compute Engine default service account so that the Eventarc trigger can receive events from event providers.
```
gcloud projects add-iam-policy-binding PROJECT_ID \
    --member=serviceAccount:PROJECT_NUMBER-compute@developer.gserviceaccount.com \
    --role=roles/eventarc.eventReceiver
```
If you enabled the Cloud Pub/Sub service agent on or before April 8, 2021, to support authenticated Pub/Sub push requests, grant the Service Account Token Creator role (roles/iam.serviceAccountTokenCreator) to the service agent. Otherwise, this role is granted by default:
```
gcloud projects add-iam-policy-binding PROJECT_ID \
    --member=serviceAccount:service-PROJECT_NUMBER@gcp-sa-pubsub.iam.gserviceaccount.com \
    --role=roles/iam.serviceAccountTokenCreator
```

Create an Artifact Registry standard repository

Create an Artifact Registry standard repository to store your container image:

gcloud artifacts repositories create REPOSITORY \
    --repository-format=docker \
    --location=$REGION

Replace REPOSITORY with a unique name for the repository.

Create a Cloud Storage bucket

Create a Cloud Storage bucket to use as the event source:

gcloud storage buckets create gs://PROJECT_ID-bucket/ --location=us-central1

After the event source is created, you can deploy the event receiver service on Cloud Run.

Deploy an event receiver to Cloud Run

Deploy a Cloud Run service that receives and logs events.

Clone the GitHub repository:
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.
Python
```
git clone https://github.com/GoogleCloudPlatform/python-docs-samples.git
```
Alternatively, you can download the sample as a zip file and extract it.
Go
```
git clone https://github.com/GoogleCloudPlatform/golang-samples.git
```
Alternatively, you can download the sample as a zip file and extract it.
Java
```
git clone https://github.com/GoogleCloudPlatform/java-docs-samples.git
```
Alternatively, you can download the sample as a zip file and extract it.
C#
```
git clone https://github.com/GoogleCloudPlatform/dotnet-docs-samples.git
```
Alternatively, you can download the sample as a zip file and extract it.

Change to the directory that contains the Cloud Run sample code:

Node.js

cd nodejs-docs-samples/eventarc/audit-storage/

Python

cd python-docs-samples/eventarc/audit-storage/

Go

cd golang-samples/eventarc/audit_storage/

Java

cd java-docs-samples/eventarc/audit-storage/

C#

cd dotnet-docs-samples/eventarc/audit-storage/

Build the container for the Cloud Run service:

export PROJECT_ID=$(gcloud config get-value project)
export SERVICE_NAME=helloworld-events
gcloud builds submit --tag $REGION-docker.pkg.dev/${PROJECT_ID}/REPOSITORY/${SERVICE_NAME}:v1

Deploy the container image to Cloud Run:

gcloud run deploy ${SERVICE_NAME} \
    --image $REGION-docker.pkg.dev/${PROJECT_ID}/REPOSITORY/${SERVICE_NAME}:v1

At the Allow unauthenticated invocations to helloworld-events (y/N)? prompt, respond n for "No".

When you see the Cloud Run service URL, the deployment is complete.

Create an Eventarc trigger

The Eventarc trigger sends events from the Cloud Storage bucket to the helloworld-events Cloud Run service. The service requires authentication, and the event should be triggered by a caller that has a service account with the required IAM roles and permissions to use the resource.

Create a trigger that filters Cloud Storage events:

gcloud eventarc triggers create ${SERVICE_NAME} \
    --destination-run-service=${SERVICE_NAME} \
    --destination-run-region=${REGION} \
    --location=${REGION} \
    --event-filters="type=google.cloud.storage.object.v1.finalized" \
    --event-filters="bucket=PROJECT_ID-bucket" \
    --service-account=PROJECT_NUMBER-compute@developer.gserviceaccount.com

This creates a trigger called helloworld-events.

Note that when creating an Eventarc trigger for the first time in a Google Cloud project, there might be a delay in provisioning the Eventarc service agent. This issue can usually be resolved by attempting to create the trigger again. For more information, see Permission denied errors.

Confirm that the trigger was successfully created. Note that although your trigger is created immediately, it can take up to two minutes for a trigger to be fully functional.
```
gcloud eventarc triggers list --location=${REGION}
```
The output should be similar to the following:
```
NAME: helloworld-events
TYPE: google.cloud.storage.object.v1.finalized
DESTINATION: Cloud Run service: helloworld-events
ACTIVE: Yes
```

Generate and view an event

Upload a text file to the Cloud Storage bucket to generate an event which is routed to the Cloud Run service. The Cloud Run service logs the event in the service logs.

To generate an event:

Upload a text file to Cloud Storage:
```
 echo "Hello World" > random.txt
 gcloud storage cp random.txt gs://PROJECT_ID-bucket/random.txt
```
The upload generates an event and the Cloud Run service logs the event's message.
To view the log entry:
1. Filter the log entries and return the output in JSON format:
```
gcloud logging read "resource.labels.service_name=helloworld-events AND textPayload:random.txt" --format=json
```
2. Look for a log entry similar to:
```
"textPayload": "Detected change in Cloud Storage bucket: objects/random.txt"
```
  Note: If you do not see a log entry, wait a few minutes and retry the gcloud logging read command. The trigger can take up to two minutes after being created to start filtering events.

Logs might take a few moments to appear. If you don't see them immediately, check again after a minute.

You have successfully deployed an event receiver service to Cloud Run, created an Eventarc trigger, generated an event from Cloud Storage, and viewed it in the Cloud Run logs.

Clean up

If you created a new project for this tutorial, delete the project. If you used an existing project and want to keep it without the changes added in this tutorial, delete the resources created for the tutorial.

Delete the project

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

To delete the project:

In the Google Cloud console, go to the Manage resources page.
Go to Manage resources
In the project list, select the project that you want to delete, and then click Delete.
In the dialog, type the project ID, and then click Shut down to delete the project.

Delete tutorial resources

Delete the Cloud Run service you deployed in this tutorial:
```
gcloud run services delete SERVICE_NAME
```
Where SERVICE_NAME is your chosen service name.

You can also delete Cloud Run services from the Google Cloud console.
Remove any gcloud CLI default configurations you added during the tutorial setup.

For example:

gcloud config unset run/region

or

gcloud config unset project
Delete other Google Cloud resources created in this tutorial:
- Delete the Eventarc trigger:
```
gcloud eventarc triggers delete TRIGGER_NAME
```
  Replace TRIGGER_NAME with the name of your trigger.
- Delete your container image

Use Eventarc to receive events from Cloud Storage

Objectives

Costs

Before you begin

Required permissions

Create an Artifact Registry standard repository

Create a Cloud Storage bucket

Deploy an event receiver to Cloud Run

Node.js

Python

Go

Java

C#

Node.js

Python

Go

Java

C#

Create an Eventarc trigger

Generate and view an event

Clean up

Delete the project

Delete tutorial resources

What's next