Event triggered functions in GCP - Mini Project: Build & Apply

Deploying a Google Cloud Function Triggered by Cloud Storage Events

📖 Scenario: You work for a company that stores images in Google Cloud Storage. You want to automatically process images whenever a new file is uploaded to a storage bucket.To do this, you will create a Google Cloud Function that triggers when a new file is added to a specific Cloud Storage bucket.

🎯 Goal: Build a Google Cloud Function that triggers on new file uploads to a Cloud Storage bucket named image-uploads. The function will log the file name and bucket name.

📋 What You'll Learn

Create a Cloud Storage bucket named image-uploads.

Create a Cloud Function named log_new_file triggered by new file creation in the image-uploads bucket.

The function should log the file name and bucket name from the event data.

Deploy the function with the correct trigger and runtime.

💡 Why This Matters

🌍 Real World

Automating tasks like image processing or data ingestion when files are uploaded to cloud storage is common in many businesses.

💼 Career

Cloud engineers and developers often create event-driven functions to build scalable, reactive cloud applications.

1

Create the Cloud Storage bucket

Write the gsutil command to create a Cloud Storage bucket named image-uploads in the us-central1 region.

GCP

# Your command here

Hint

Use gsutil mb -l REGION gs://BUCKET_NAME/ to create a bucket.

2

Write the Cloud Function code

Create a Python function named log_new_file that accepts event and context parameters. Inside the function, assign file_name to event['name'] and bucket_name to event['bucket']. Then, write a log statement using print that outputs: New file {file_name} uploaded to {bucket_name}.

GCP

def log_new_file(event, context):
    # Your code here

Hint

Use event['name'] and event['bucket'] to get file and bucket names.

3

Configure the Cloud Function trigger

Write the gcloud command to deploy the Cloud Function named log_new_file using Python 3.9 runtime. Set the trigger to activate on new object creation events in the image-uploads bucket.

GCP

def log_new_file(event, context):
    file_name = event['name']
    bucket_name = event['bucket']
    print(f"New file {file_name} uploaded to {bucket_name}")

# Your deployment command here

Hint

Use --trigger-event google.storage.object.finalize for new file uploads.

4

Verify the Cloud Function trigger configuration

Write the gcloud command to describe the Cloud Function log_new_file and confirm it is triggered by the image-uploads bucket on new object creation events.

GCP

def log_new_file(event, context):
    file_name = event['name']
    bucket_name = event['bucket']
    print(f"New file {file_name} uploaded to {bucket_name}")

gcloud functions deploy log_new_file --runtime python39 --trigger-resource image-uploads --trigger-event google.storage.object.finalize

# Your verification command here

Hint

Use gcloud functions describe FUNCTION_NAME to check configuration.

Practice

1. What is the main purpose of an event triggered function in Google Cloud Functions?

easy

A. To store data permanently in the cloud

B. To manually start a function from the console

C. To schedule functions to run at fixed times

D. To automatically run code when a specific event occurs

Solution

1. Step 1: Understand event triggered functions

   Event triggered functions run automatically when a specific event happens, like a file upload or database change.

2. Step 2: Compare options with the definition

   Only To automatically run code when a specific event occurs describes automatic running on events. Options B and C describe manual or scheduled runs, and D is unrelated.

3. Final Answer:

   To automatically run code when a specific event occurs -> Option D

4. Quick Check:

   Event triggered function = automatic run on event [OK]

Hint: Event triggered means automatic run on event [OK]

Common Mistakes:

• Confusing event triggered with scheduled functions
• Thinking manual start is event triggered
• Mixing storage with function triggers

2. Which of the following is the correct way to specify a Cloud Function triggered by a Cloud Storage event in deployment?

easy

A. gcloud functions deploy myFunc --trigger-resource my-bucket --trigger-event google.storage.object.finalize

B. gcloud functions deploy myFunc --trigger-topic myTopic

C. gcloud functions deploy myFunc --trigger-http

D. gcloud functions deploy myFunc --trigger-schedule "every 5 minutes"

Solution

1. Step 1: Identify Cloud Storage event trigger syntax

   Cloud Storage events use --trigger-resource for the bucket and --trigger-event for the event type like object finalize.

2. Step 2: Match options with correct syntax

   gcloud functions deploy myFunc --trigger-resource my-bucket --trigger-event google.storage.object.finalize correctly uses --trigger-resource and --trigger-event for Cloud Storage. Others are for HTTP, Pub/Sub, or scheduled triggers.

3. Final Answer:

   gcloud functions deploy myFunc --trigger-resource my-bucket --trigger-event google.storage.object.finalize -> Option A

4. Quick Check:

   Cloud Storage trigger = resource + event flags [OK]

Hint: Storage triggers need resource and event flags [OK]

Common Mistakes:

• Using --trigger-http for storage events
• Confusing Pub/Sub topic triggers with storage
• Using schedule flags for event triggers

3. Consider this Cloud Function triggered by a Pub/Sub topic named 'updates'. What will happen when a message is published to 'updates'?

exports.processUpdate = (event, context) => {
  const message = Buffer.from(event.data, 'base64').toString();
  console.log(`Received message: ${message}`);
};

medium

A. The function ignores the message and does nothing

B. The function throws an error due to missing parameters

C. The function logs the decoded message content

D. The function logs the raw base64 message without decoding

Solution

1. Step 1: Understand event data decoding

   The function decodes the base64 event.data to a string and logs it.

2. Step 2: Check function behavior on message publish

   When a message is published, the function runs and logs the decoded message content.

3. Final Answer:

   The function logs the decoded message content -> Option C

4. Quick Check:

   Pub/Sub event data decoded and logged [OK]

Hint: Pub/Sub data is base64 decoded before use [OK]

Common Mistakes:

• Forgetting to decode base64 data
• Assuming function errors without checking code
• Thinking function ignores messages

4. You deployed a Cloud Function triggered by Firestore document creation, but it never runs. Which of these is the most likely cause?

medium

A. The function is missing the correct Firestore trigger path

B. The function code has a syntax error preventing deployment

C. The Cloud Function is set to trigger on HTTP instead of Firestore

D. The Firestore database is empty

Solution

1. Step 1: Check trigger configuration

   If the trigger path is incorrect, the function won't run on document creation events.

2. Step 2: Eliminate other causes

   Syntax errors prevent deployment (not silent failure). HTTP trigger won't respond to Firestore events. Firestore being empty doesn't stop triggers on new documents.

3. Final Answer:

   The function is missing the correct Firestore trigger path -> Option A

4. Quick Check:

   Wrong trigger path = no function run [OK]

Hint: Check trigger path matches Firestore event exactly [OK]

Common Mistakes:

• Assuming empty Firestore blocks triggers
• Confusing HTTP triggers with event triggers
• Ignoring trigger path correctness

5. You want to create a Cloud Function that triggers when a new file is uploaded to any folder inside a Cloud Storage bucket named 'photos'. Which trigger configuration is correct?

hard

A. Use --trigger-resource photos and --trigger-event google.storage.object.metadataUpdate

B. Use --trigger-resource photos and --trigger-event google.storage.object.finalize

C. Use --trigger-resource photos and --trigger-event google.storage.object.archive

D. Use --trigger-resource photos/* and --trigger-event google.storage.object.delete

Solution

1. Step 1: Identify correct event for new file upload

   The event google.storage.object.finalize triggers when a new object is created or overwritten.

2. Step 2: Confirm resource and event usage

   The resource is the bucket name 'photos'. Wildcards like 'photos/*' are not valid for --trigger-resource.

3. Final Answer:

   Use --trigger-resource photos and --trigger-event google.storage.object.finalize -> Option B

4. Quick Check:

   New file upload = finalize event on bucket resource [OK]

Hint: Use bucket name and finalize event for new uploads [OK]

Common Mistakes:

• Using delete or archive events instead of finalize
• Trying to use wildcards in trigger-resource
• Using metadataUpdate event which triggers on metadata changes