Introduction to Google Cloud Pub/Sub - Messaging Service

Google Cloud Pub/Sub is a fully managed messaging service that enables you to build event-driven systems and decouple applications for better scalability and reliability. In this guide, we'll explore the fundamentals of Google Cloud Pub/Sub and provide a sample Python code snippet for publishing and subscribing to Pub/Sub topics.

Key Concepts

Before we dive into the code, let's cover some key concepts related to Google Cloud Pub/Sub:

• Topics and Subscriptions: Messages are sent to topics, and subscribers receive messages from subscriptions to those topics.
• Publisher: A publisher sends messages to a topic. A publisher can be any application or service.
• Subscriber: A subscriber receives messages from a subscription. Subscribers can process messages, perform actions, or forward messages to other services.

Sample Code: Publishing and Subscribing to Pub/Sub

Here's a sample Python code snippet for publishing and subscribing to Google Cloud Pub/Sub topics:

Publishing to a Topic

from google.cloud import pubsub_v1
# Initialize the Publisher client
publisher = pubsub_v1.PublisherClient()
# Set your project ID and topic name
project_id = 'your-project-id'
topic_name = 'your-topic-name'
# Create a topic path
topic_path = publisher.topic_path(project_id, topic_name)
# Define a message
message_data = 'Hello, Pub/Sub!'
message_data = message_data.encode('utf-8')
# Publish the message
future = publisher.publish(topic_path, data=message_data)
print(f"Published message: {message_data}")
    

Subscribing to a Topic

from google.cloud import pubsub_v1
# Initialize the Subscriber client
subscriber = pubsub_v1.SubscriberClient()
# Set your project ID, subscription name, and topic name
project_id = 'your-project-id'
subscription_name = 'your-subscription-name'
topic_name = 'your-topic-name'
# Create a subscription path
subscription_path = subscriber.subscription_path(project_id, subscription_name)
topic_path = subscriber.topic_path(project_id, topic_name)
# Define a callback function to handle received messages
def callback(message):
    print(f"Received message: {message.data}")
    message.ack()
# Subscribe to the topic and start receiving messages
subscriber.subscribe(subscription_path, callback=callback)
print(f"Subscribed to {subscription_name} for topic {topic_name}")
# Keep the script running to continue receiving messages
import time
while True:
    time.sleep(5)
    

Make sure to replace

your-project-id

your-topic-name

Conclusion

Google Cloud Pub/Sub is a robust messaging service that allows you to build scalable and decoupled applications. By leveraging Pub/Sub, you can create event-driven systems and efficiently process messages within your cloud-based applications.