Trigger Workflows with direct events from Cloud Storage (gcloud CLI)

This quickstart shows you how to execute a workflow using an Eventarc trigger that receives events from Cloud Storage.

The trigger executes the workflow by listening for an object creation event in a Cloud Storage bucket and passes the event as a runtime argument to a destination workflow.

In this quickstart, you:

  1. Create a Cloud Storage bucket as an event source.

  2. Use Workflows to create and deploy a workflow that extracts and returns the name of the storage bucket and the name of an uploaded file.

  3. Create an Eventarc trigger that connects the Cloud Storage bucket to the Workflows event receiver.

  4. Generate an event by uploading a text file to the Cloud Storage bucket. This event is passed as a runtime argument to the destination workflow.

  5. View the name of the bucket and the name of the text file as a result of the workflow execution.


For step-by-step guidance on this task directly in Google Cloud console, click Guide me:

Guide me


The following sections take you through the same steps as clicking Guide me.

Before you begin

Some of the steps in this document might not work correctly if your organization applies constraints to your Google Cloud environment. In that case, you might not be able to complete tasks like creating public IP addresses or service account keys. If you make a request that returns an error about constraints, see how to Develop applications in a constrained Google Cloud environment.

  1. 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.
  2. In the Google Cloud console, on the project selector page, select or create a Google Cloud project.

    Go to project selector

  3. Make sure that billing is enabled for your Cloud project. Learn how to check if billing is enabled on a project.

  4. Install and initialize the Google Cloud CLI.
  5. In the Google Cloud console, on the project selector page, select or create a Google Cloud project.

    Go to project selector

  6. Make sure that billing is enabled for your Cloud project. Learn how to check if billing is enabled on a project.

  7. Install and initialize the Google Cloud CLI.
  8. Enable the Eventarc, Pub/Sub, and Workflows APIs.

    gcloud services enable eventarc.googleapis.com pubsub.googleapis.com workflows.googleapis.com workflowexecutions.googleapis.com
  9. Update gcloud components:
    gcloud components update
  10. Log in using your account:
    gcloud auth login

Set your environment variables

Set the environment variables used in this quickstart.

export PROJECT_ID=PROJECT_ID
export WORKFLOW_LOCATION=us-central1
export TRIGGER_LOCATION=us-central1
gcloud config set project ${PROJECT_ID}
gcloud config set workflows/location ${WORKFLOW_LOCATION}
gcloud config set eventarc/location ${TRIGGER_LOCATION}

Replace PROJECT_ID with your Google Cloud project ID.

You can find your project ID on the Dashboard page of the Google Cloud console.

Set up your service accounts

Grant the required permissions to the service accounts used in this quickstart.

  1. Grant the pubsub.publisher role to the Cloud Storage service account:

    SERVICE_ACCOUNT="$(gsutil kms serviceaccount -p ${PROJECT_ID})"
    
    gcloud projects add-iam-policy-binding ${PROJECT_ID} \
        --member="serviceAccount:${SERVICE_ACCOUNT}" \
        --role='roles/pubsub.publisher'
    
  2. If you enabled the Pub/Sub service account on or before April 8, 2021, grant the iam.serviceAccountTokenCreator role to the Pub/Sub service account:

    gcloud projects add-iam-policy-binding ${PROJECT_ID} \
        --member="serviceAccount:service-PROJECT_NUMBER@gcp-sa-pubsub.iam.gserviceaccount.com" \
        --role='roles/iam.serviceAccountTokenCreator'
    

    Replace PROJECT_NUMBER with your Google Cloud project number.

    You can find your project number on the Dashboard page of the Google Cloud console.

  3. Create a service account and give it a name; for example, my-service-account:

    export MY_SERVICE_ACCOUNT=my-service-account
    gcloud iam service-accounts create ${MY_SERVICE_ACCOUNT}
    
  4. Grant the roles/workflows.invoker role to the service account:

    gcloud projects add-iam-policy-binding ${PROJECT_ID} \
        --member="serviceAccount:${MY_SERVICE_ACCOUNT}@${PROJECT_ID}.iam.gserviceaccount.com" \
        --role='roles/workflows.invoker'
    

Create a Cloud Storage bucket

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

  gsutil mb -l us-central1 gs://${PROJECT_ID}-bucket/

Create and deploy a workflow

Create and deploy a workflow that is executed when an object created in the Cloud Storage bucket triggers a workflow with an HTTP request.

  1. In your home directory, create a new file called myEventWorkflow.yaml or myEventWorkflow.json.

  2. Copy and paste the following into the new file and save it:

    YAML

      main:
        params: [event]
        steps:
            - log_event:
                call: sys.log
                args:
                    text: ${event}
                    severity: INFO
            - extract_bucket_object:
                assign:
                - bucket: ${event.data.bucket}
                - object: ${event.data.name}
            - return_bucket_object:
                    return:
                        bucket: ${bucket}
                        object: ${object}
      

    JSON

    {
    "main": {
    "params": [
      "event"
    ],
    "steps": [
      {
        "log_event": {
          "call": "sys.log",
          "args": {
            "text": "${event}",
            "severity": "INFO"
          }
        }
      },
      {
        "extract_bucket_object": {
          "assign": [
            {
              "bucket": "${event.data.bucket}"
            },
            {
              "object": "${event.data.name}"
            }
          ]
        }
      },
      {
        "return_bucket_object": {
          "return": {
            "bucket": "${bucket}",
            "object": "${object}"
          }
        }
      }
    ]
    }
    }
  3. Deploy the workflow:

    export MY_WORKFLOW=myEventWorkflow
    gcloud workflows deploy ${MY_WORKFLOW} --source=myEventWorkflow.yaml
    

    Replace .yaml with .json if you copied the JSON version of the example workflow.

Create an Eventarc trigger

The Eventarc trigger sends events from the Cloud Storage bucket to the Workflows destination.

  1. Create a trigger that filters Cloud Storage events:

    gcloud eventarc triggers create storage-events-trigger \
       --destination-workflow=${MY_WORKFLOW} \
       --destination-workflow-location=${WORKFLOW_LOCATION} \
       --event-filters="type=google.cloud.storage.object.v1.finalized" \
       --event-filters="bucket=${PROJECT_ID}-bucket" \
       --service-account="${MY_SERVICE_ACCOUNT}@${PROJECT_ID}.iam.gserviceaccount.com"
    

    This creates a trigger called storage-events-trigger.

  2. To confirm storage-events-trigger was successfully created, run:

    gcloud eventarc triggers describe storage-events-trigger --location=${TRIGGER_LOCATION}
    

Generate and view an event

  1. To generate an event, upload a text file to Cloud Storage:

    echo "Hello World" > random.txt
    gsutil cp random.txt gs://${PROJECT_ID}-bucket/random.txt
    

    The upload generates an event that is passed as a runtime argument to the workflow which returns the names of the storage bucket and uploaded file.

  2. To verify that a workflows execution was triggered, list the last five executions:

    gcloud workflows executions list ${MY_WORKFLOW} --limit=5
    

    The output should be similar to the following, listing a NAME and STATE equal to SUCCEEDED for each workflow execution:

    NAME: projects/606789101455/locations/us-central1/workflows/myFirstWorkflow/executions/8c02b8f1-8836-4a6d-99d9-fc321eb9668f
    STATE: SUCCEEDED
    START_TIME: 2021-10-13T03:38:03.019148617Z
    END_TIME: 2021-10-13T03:38:03.249705805Z
    NAME: projects/606789101455/locations/us-central1/workflows/myFirstWorkflow/executions/a6319d9d-36a6-4117-904e-3d1118bdc90a
    STATE: SUCCEEDED
    START_TIME: 2021-10-13T17:28:51.492864252Z
    END_TIME: 2021-10-13T17:28:52.227212414Z
    

    Note that in the NAME field in the preceding example, a6319d9d-36a6-4117-904e-3d1118bdc90a is the ID of the workflow execution. Copy your execution ID as it is used in the next step.

  3. To view the event message:

    1. View the execution status:

      gcloud workflows executions describe WORKFLOW_EXECUTION_ID --workflow=${MY_WORKFLOW}
      

      Replace WORKFLOW_EXECUTION_ID with the ID of the workflow execution that corresponds to the time at which the file was uploaded to the bucket.

      The output is similar to the following:

      argument: '{"bucket":"PROJECT_ID-bucket","data":{"bucket":"PROJECT_ID-bucket","[...]","timeCreated":"2021-10-13T03:38:01.735Z","
      [...]","subject":"objects/random.txt","time":"2021-10-13T03:38:01.735384Z","type":"google.cloud.storage.object.v1.finalized"}'
      endTime: '2021-10-13T03:38:03.249705805Z'
      name: projects/218898424763/locations/us-central1/workflows/myFirstWorkflow/executions/86d2567b-0f1e-49b3-8b10-cdac5d0f6239
      result: '{"bucket":"PROJECT_ID-bucket","object":"random.txt"}'
      startTime: '2021-10-13T03:38:03.019148617Z'
      state: SUCCEEDED
      workflowVersionId: '1'
      

      Verify that the time,"timeCreated": "2021-10-13T03:38" at which the Cloud Storage bucket was updated and the startTime of the workflow execution correspond to each other.

    2. Look for an event message similar to the following:

      result: '{"bucket":"PROJECT_ID-bucket","object":"random.txt"}'
      

Congratulations, you have successfully generated a Cloud Storage event that has triggered a Workflows event receiver using Eventarc.

Clean up

To avoid incurring charges to your Google Cloud account for the resources used on this page, follow these steps.

  1. Delete the workflow you created:

    gcloud workflows delete ${MY_WORKFLOW}
    

    When asked if you want to continue, enter y.

  2. Delete your storage bucket:

    gsutil rm -r gs://${PROJECT_ID}-bucket/
    
  3. Delete the trigger created in this tutorial:

    gcloud eventarc triggers delete storage-events-trigger
    

Alternatively, you can delete your Google Cloud project to avoid stop billing for all the resources used within that project.

To delete your project:

gcloud projects delete PROJECT_ID_OR_NUMBER

Replace PROJECT_ID_OR_NUMBER with your Google Cloud project ID or number.

What's next