Pub/Sub vs Cloud Tasks in GCP - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a Pub/Sub topic named 'my-topic'.

GCP

gcloud pubsub topics create [1]

Drag options to blanks, or click blank then click option'

Amy-queue

Bmy-subscription

Cmy-topic

Dmy-task

Attempts:

3 left

💡 Hint

Common Mistakes

Using a subscription name instead of a topic name.

Confusing Cloud Tasks queue names with Pub/Sub topics.

The command gcloud pubsub topics create my-topic creates a Pub/Sub topic named 'my-topic'.

2fill in blank

medium

Complete the code to create a Cloud Tasks queue named 'my-queue'.

GCP

gcloud tasks queues create [1]

Drag options to blanks, or click blank then click option'

Amy-topic

Bmy-queue

Cmy-subscription

Dmy-topic-queue

Attempts:

3 left

💡 Hint

Common Mistakes

Using a Pub/Sub topic name instead of a queue name.

Using a subscription name in place of a queue.

The command gcloud tasks queues create my-queue creates a Cloud Tasks queue named 'my-queue'.

3fill in blank

hard

Fix the error in the code to publish a message to a Pub/Sub topic.

GCP

gcloud pubsub topics publish my-topic --message=[1]

Drag options to blanks, or click blank then click option'

A'Hello World'

BHello World

CHello_World

D"Hello World"

Attempts:

3 left

💡 Hint

Common Mistakes

Not using quotes causes the message to be split or misinterpreted.

Using single quotes may not work in some shells.

The message must be enclosed in double quotes to be correctly parsed by the command line.

4fill in blank

hard

Fill both blanks to define a Cloud Tasks task with an HTTP request and schedule time.

GCP

gcloud tasks create-http-task --queue=[1] --url=[2] --schedule-time=2024-06-01T12:00:00Z

Drag options to blanks, or click blank then click option'

Amy-queue

Bmy-topic

Chttps://example.com/taskhandler

Dhttps://example.com/publish

Attempts:

3 left

💡 Hint

Common Mistakes

Using a Pub/Sub topic name instead of a queue name.

Using the wrong URL for the task handler.

The task is created in the queue 'my-queue' and sends an HTTP request to the URL 'https://example.com/taskhandler'.

5fill in blank

hard

Fill all three blanks to create a Pub/Sub subscription with a push endpoint and ack deadline.

GCP

gcloud pubsub subscriptions create [1] --topic=[2] --push-endpoint=[3] --ack-deadline=20

Drag options to blanks, or click blank then click option'

Amy-subscription

Bmy-topic

Chttps://example.com/pushhandler

Dmy-queue

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing queue names with subscription names.

Using the wrong URL for the push endpoint.

This command creates a subscription named 'my-subscription' to the topic 'my-topic' with a push endpoint URL and an acknowledgment deadline of 20 seconds.

Practice

1. Which Google Cloud service is best suited for sending messages to multiple subscribers quickly and asynchronously?

easy

A. Cloud Functions

B. Cloud Tasks

C. Pub/Sub

D. Cloud Run

Solution

1. Step 1: Understand Pub/Sub's purpose

   Pub/Sub is designed to send messages to many subscribers quickly and asynchronously, enabling event-driven architectures.

2. Step 2: Compare with Cloud Tasks

   Cloud Tasks manages individual work items with control over retries and timing, not broad message delivery.

3. Final Answer:

   Pub/Sub -> Option C

4. Quick Check:

   Event broadcasting = Pub/Sub [OK]

Hint: Pub/Sub = many subscribers fast; Cloud Tasks = controlled retries [OK]

Common Mistakes:

• Confusing Cloud Tasks as a message broadcaster
• Thinking Pub/Sub controls task retries
• Mixing Cloud Functions with messaging services

2. Which of the following is the correct way to create a Cloud Task with a scheduled delay in Google Cloud?

easy

A. Use Pub/Sub with a delay attribute

B. Use Cloud Tasks client and set scheduleTime to future timestamp

C. Send a message to Pub/Sub and rely on subscriber delay

D. Create a Cloud Function with a timer trigger instead

Solution

1. Step 1: Identify scheduling method in Cloud Tasks

   Cloud Tasks allows setting a scheduleTime property to delay task execution until a future timestamp.

2. Step 2: Eliminate incorrect options

   Pub/Sub does not support scheduling messages; Cloud Functions timer triggers are separate services.

3. Final Answer:

   Use Cloud Tasks client and set scheduleTime to future timestamp -> Option B

4. Quick Check:

   Scheduled tasks = Cloud Tasks scheduleTime [OK]

Hint: Schedule tasks with Cloud Tasks scheduleTime, not Pub/Sub [OK]

Common Mistakes:

• Trying to delay Pub/Sub messages directly
• Confusing Cloud Functions timers with Cloud Tasks scheduling
• Assuming subscribers can delay message processing

3. Given the following scenario: A Cloud Task is created with maxAttempts set to 3 and a retry delay of 10 seconds. If the task fails twice, what happens next?

medium

A. The task is retried after 10 seconds delay for the third attempt

B. The task is retried immediately without delay

C. The task is discarded after the second failure

D. Pub/Sub resends the message automatically

Solution

1. Step 1: Understand Cloud Tasks retry policy

   Cloud Tasks retries failed tasks up to maxAttempts, applying the configured retry delay between attempts.

2. Step 2: Apply to given scenario

   After two failures, the third attempt will be retried after the 10 seconds delay before final failure or success.

3. Final Answer:

   The task is retried after 10 seconds delay for the third attempt -> Option A

4. Quick Check:

   Retries respect delay and maxAttempts in Cloud Tasks [OK]

Hint: Cloud Tasks retries wait delay before next try, up to maxAttempts [OK]

Common Mistakes:

• Assuming immediate retry without delay
• Thinking task is discarded too early
• Confusing Pub/Sub automatic retries with Cloud Tasks

4. You have a Cloud Task that never executes and keeps retrying indefinitely. What is the most likely cause?

medium

A. The Cloud Task queue is paused

B. Pub/Sub subscription is missing

C. The task's maxAttempts is set to 0 or unlimited

D. The task's scheduleTime is in the past

Solution

1. Step 1: Analyze retry behavior

   If a task retries indefinitely, it means it keeps failing but is still being retried.

2. Step 2: Check queue state

   If the Cloud Task queue is paused, tasks will not execute but may keep retrying or remain pending.

3. Step 3: Eliminate other options

   Pub/Sub subscription missing is unrelated to Cloud Tasks; maxAttempts 0 means no retries; scheduleTime in past triggers immediate execution.

4. Final Answer:

   The Cloud Task queue is paused -> Option A

5. Quick Check:

   Paused queue blocks task execution causing retries [OK]

Hint: Paused queue stops tasks but retries may appear stuck [OK]

Common Mistakes:

• Confusing Pub/Sub with Cloud Tasks
• Assuming maxAttempts 0 means infinite retries
• Thinking scheduleTime in past delays execution

5. You need to design a system that processes user signup events by notifying multiple services quickly, but also schedules follow-up tasks with guaranteed retries and delays. Which combination of services should you use?

hard

A. Use only Cloud Tasks for both notifications and follow-ups

B. Use only Pub/Sub with delayed message delivery

C. Use Cloud Functions triggered by HTTP for all processing

D. Use Pub/Sub for notifications and Cloud Tasks for follow-up tasks

Solution

1. Step 1: Identify service for quick multi-subscriber notifications

   Pub/Sub is ideal for sending events quickly to multiple subscribers asynchronously.

2. Step 2: Identify service for scheduled, reliable task execution

   Cloud Tasks provides control over retries, delays, and guaranteed execution for follow-up work.

3. Step 3: Combine services for best fit

   Use Pub/Sub to notify many services fast, and Cloud Tasks to manage follow-up tasks with retries and delays.

4. Final Answer:

   Use Pub/Sub for notifications and Cloud Tasks for follow-up tasks -> Option D

5. Quick Check:

   Pub/Sub for events + Cloud Tasks for reliable tasks [OK]

Hint: Combine Pub/Sub for events and Cloud Tasks for retries/delays [OK]

Common Mistakes:

• Trying to use Pub/Sub for delayed retries
• Using Cloud Tasks for broad event broadcasting
• Ignoring retry guarantees needed for follow-ups