Publishing messages in GCP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a Pub/Sub client in Python.

GCP

from google.cloud import pubsub_v1

publisher = pubsub_v1.PublisherClient()

topic_path = publisher.topic_path('my-project', [1])

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

Aproject-id

Bmy-topic

Ctopic-name

Dsubscription

Attempts:

3 left

💡 Hint

Common Mistakes

Using project ID instead of topic name.

Using subscription name instead of topic name.

The topic_path method requires the project ID and the topic name. Here, 'my-topic' is the topic name.

2fill in blank

medium

Complete the code to publish a message to the topic.

GCP

data = 'Hello, Cloud!'.encode('utf-8')
publisher.publish(topic_path, [1]=data)

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

Amessage

Bcontent

Cdata

Dpayload

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'message' or 'payload' instead of 'data'.

Passing a string instead of bytes.

The publish method expects the message data as the data parameter.

3fill in blank

hard

Fix the error in the code to correctly publish a message with attributes.

GCP

attributes = {'origin': 'python-sample'}
publisher.publish(topic_path, data=data, [1]=attributes)

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

Aattributes

Battrs

Cmeta

Dprops

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect parameter names like 'attrs' or 'meta'.

Passing attributes as a list instead of a dictionary.

The publish method uses the attributes parameter to send message attributes as a dictionary.

4fill in blank

hard

Fill both blanks to create a topic path and publish a message with attributes.

GCP

topic_path = publisher.[1]('my-project', 'my-topic')
data = 'Test message'.encode('utf-8')
publisher.publish(topic_path, data=data, [2]={'source': 'test'})

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

Atopic_path

Battributes

Ctopic

Dattrs

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'topic' instead of 'topic_path'.

Using 'attrs' instead of 'attributes'.

The method to create a topic path is topic_path, and the message attributes parameter is attributes.

5fill in blank

hard

Fill all three blanks to create a publisher client, build a topic path, and publish a message with attributes.

GCP

from google.cloud import pubsub_v1

publisher = pubsub_v1.[1]()
topic_path = publisher.[2]('project-123', 'events')
data = 'Event data'.encode('utf-8')
publisher.publish(topic_path, data=data, [3]={'env': 'prod'})

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

APublisherClient

Btopic_path

Cattributes

DSubscriberClient

Attempts:

3 left

💡 Hint

Common Mistakes

Using SubscriberClient instead of PublisherClient.

Using wrong method names or parameter names.

The client class is PublisherClient, the method to build the topic path is topic_path, and the attributes parameter is attributes.

Practice

1. What is the main purpose of publishing messages in Google Cloud Pub/Sub?

easy

A. To send data to a topic so other services can receive it

B. To store data permanently in a database

C. To create virtual machines automatically

D. To monitor network traffic in real-time

Solution

1. Step 1: Understand the role of publishing in Pub/Sub

   Publishing messages means sending data to a topic so subscribers can get it.

2. Step 2: Compare with other options

   Storing data, creating VMs, or monitoring traffic are unrelated to publishing messages.

3. Final Answer:

   To send data to a topic so other services can receive it -> Option A

4. Quick Check:

   Publishing = sending data to topic [OK]

Hint: Publishing means sending messages to topics for others [OK]

Common Mistakes:

• Confusing publishing with storing data
• Thinking publishing creates resources like VMs
• Mixing publishing with monitoring tasks

2. Which of the following is the correct way to publish a message using the Google Cloud Pub/Sub Python client?

easy

A. publisher.send_message(topic_path, data="Hello World")

B. publisher.publish(topic_path, data=b"Hello World")

C. publisher.publish(topic_path, message="Hello World")

D. publisher.send(topic_path, "Hello World")

Solution

1. Step 1: Recall the correct method and parameters

   The correct method is publish(), and the message data must be bytes, so data=b"Hello World".

2. Step 2: Check other options for errors

   send() and send_message() are not valid methods; also, data must be bytes, not string.

3. Final Answer:

   publisher.publish(topic_path, data=b"Hello World") -> Option B

4. Quick Check:

   Use publish() with bytes data [OK]

Hint: Use publish() method with bytes data to send messages [OK]

Common Mistakes:

• Passing string instead of bytes as data
• Using incorrect method names like send()
• Using wrong parameter names like message=

3. Given the following Python code snippet, what will be printed?

from google.cloud import pubsub_v1
publisher = pubsub_v1.PublisherClient()
topic_path = publisher.topic_path('my-project', 'my-topic')
future = publisher.publish(topic_path, b'Message 1')
print(future.result())

medium

A. The content of the message 'Message 1'

B. The topic path string

C. An error because publish() returns None

D. The message ID of the published message

Solution

1. Step 1: Understand what publish() returns

   publish() returns a future that resolves to the message ID after publishing.

2. Step 2: Understand future.result() behavior

   Calling future.result() waits for publishing to complete and returns the message ID string.

3. Final Answer:

   The message ID of the published message -> Option D

4. Quick Check:

   future.result() = message ID [OK]

Hint: future.result() returns message ID after publish completes [OK]

Common Mistakes:

• Expecting future.result() to return message content
• Thinking publish() returns None
• Confusing topic path with message ID

4. You wrote this code to publish a message but get a TypeError: 'str' object cannot be interpreted as bytes. What is the mistake?

publisher.publish(topic_path, 'Hello World')

medium

A. The message data must be bytes, not a string

B. The topic_path variable is not defined

C. publish() method does not exist

D. You must call future.result() after publish()

Solution

1. Step 1: Identify the error cause

   The error says a string was given where bytes are expected.

2. Step 2: Fix the data type for message

   Message data must be bytes, so prefix string with b like b'Hello World'.

3. Final Answer:

   The message data must be bytes, not a string -> Option A

4. Quick Check:

   Message data = bytes, not string [OK]

Hint: Always prefix message with b to make bytes [OK]

Common Mistakes:

• Passing string instead of bytes as message data
• Ignoring error message details
• Assuming publish() method is missing

5. You want to publish multiple messages to a topic and ensure all are delivered before your program exits. Which approach is best?

hard

A. Publish messages using a loop but do not wait for any future results

B. Publish all messages and ignore the futures, then exit immediately

C. Publish each message and call future.result() immediately to wait for delivery

D. Publish messages and call future.cancel() to stop waiting

Solution

1. Step 1: Understand message delivery confirmation

   Calling future.result() waits for the message to be confirmed as delivered.

2. Step 2: Ensure program waits for all messages

   Waiting on each future ensures no message is lost before program exits.

3. Step 3: Evaluate other options

   Ignoring futures or cancelling them risks losing messages; not waiting is unsafe.

4. Final Answer:

   Publish each message and call future.result() immediately to wait for delivery -> Option C

5. Quick Check:

   Wait on future.result() to confirm delivery [OK]

Hint: Wait on future.result() for each message to confirm delivery [OK]

Common Mistakes:

• Ignoring futures and exiting too soon
• Cancelling futures instead of waiting
• Assuming publish() is synchronous