Event triggered functions in GCP - Commands & Configuration

Introduction

Event triggered functions run automatically when something happens, like a file upload or a message arrival. They help you react quickly without checking all the time.

When you want to process images right after they are uploaded to cloud storage.

When you need to update a database after a new message arrives in a queue.

When you want to send notifications automatically after a user signs up.

When you want to clean up resources after a file is deleted.

When you want to trigger workflows based on changes in cloud services.

Config File - function.yaml

function.yaml

name: projects/example-project/locations/us-central1/functions/my-function
runtime: python39
entryPoint: hello_world
eventTrigger:
  eventType: google.storage.object.finalize
  resource: projects/_/buckets/my-bucket
failurePolicy:
  retry: {}

name: The full path to your function in your project and region.

runtime: The language and version your function uses.

entryPoint: The function name in your code that runs when triggered.

eventTrigger: Defines what event starts the function. Here, it triggers when a file is added to the bucket 'my-bucket'.

failurePolicy: Tells the system to retry if the function fails.

Commands

Deploys the function named 'my-function' to Google Cloud. It sets the runtime to Python 3.9, triggers on new files in 'my-bucket', and uses 'hello_world' as the function to run.

Terminal

gcloud functions deploy my-function --runtime python39 --trigger-resource my-bucket --trigger-event google.storage.object.finalize --entry-point hello_world --region us-central1 --project example-project

Expected Output

Deploying function (may take a while)...

Deploying function (my-function)...done.



availableMemoryMb: 256

entryPoint: hello_world

httpsTrigger: {}

name: projects/example-project/locations/us-central1/functions/my-function

runtime: python39

status: ACTIVE

trigger:

  eventType: google.storage.object.finalize

  resource: projects/_/buckets/my-bucket

updateTime: '2024-06-01T12:00:00Z'

versionId: '1'

→

--runtime - Specifies the language and version for the function.

→

--trigger-resource - Sets the cloud resource that triggers the function.

→

--trigger-event - Defines the event type that triggers the function.

Shows details about the deployed function to confirm it is set up correctly and active.

Terminal

gcloud functions describe my-function --region us-central1 --project example-project

Expected Output

name: projects/example-project/locations/us-central1/functions/my-function

status: ACTIVE

entryPoint: hello_world

runtime: python39

trigger:

  eventType: google.storage.object.finalize

  resource: projects/_/buckets/my-bucket

updateTime: '2024-06-01T12:00:00Z'

versionId: '1'

Uploads a file named 'sample-image.png' to the bucket 'my-bucket' to trigger the function.

Terminal

gsutil cp sample-image.png gs://my-bucket/

Expected Output

Copying file://sample-image.png [Content-Type=image/png]...

/ [1 files][  123 KiB/  123 KiB] 100% Done

Operation completed over 1 objects/123 KiB.

Reads the last 5 log entries from the function to see if it ran after the file upload.

Terminal

gcloud functions logs read my-function --region us-central1 --project example-project --limit 5

Expected Output

2024-06-01 12:01:00 my-function: Function execution started

2024-06-01 12:01:01 my-function: Processing file sample-image.png

2024-06-01 12:01:02 my-function: Function execution finished successfully

→

--limit - Limits the number of log entries shown.

Key Concept

If you remember nothing else from this pattern, remember: event triggered functions run automatically when specific cloud events happen, so you don't have to check manually.

Common Mistakes

Using the wrong event type or resource name when deploying the function.

The function will not trigger because it listens to the wrong event or resource.

Double-check the event type and resource name match exactly what you want to trigger on.

Not specifying the correct entry point function name in the deployment.

The cloud platform won't find the function to run, causing errors.

Ensure the entry point matches the function name in your code exactly.

Uploading files to the wrong bucket or region.

The function won't trigger because the event never happens on the expected resource.

Verify the bucket name and region match the trigger settings.

Summary

Deploy the function with the correct runtime, trigger event, and entry point.

Verify the function is active and correctly configured using describe command.

Trigger the function by performing the event, like uploading a file to the bucket.

Check function logs to confirm it ran and processed the event.