How can you get hands-on experience with Cloud Pub/Sub?

/ / Published in Cloud Computing, EITC/CL/GCP Google Cloud Platform, GCP labs, Event driven processing with Cloud Pub/Sub, Examination review

To gain hands-on experience with Cloud Pub/Sub, one can follow a step-by-step approach that involves setting up the necessary infrastructure, creating a Cloud Pub/Sub topic and subscription, and then using the Cloud Pub/Sub API to publish and consume messages. This process allows users to understand the fundamental concepts and functionalities of Cloud Pub/Sub while actively engaging with the platform.

To begin, it is essential to have a Google Cloud Platform (GCP) account and a project created within it. Once the project is set up, the next step is to enable the Cloud Pub/Sub API. This can be done by navigating to the GCP Console, selecting the project, and then enabling the API from the API Library. Enabling the API ensures that the necessary resources and services are available for utilization.

After enabling the Cloud Pub/Sub API, the next step is to create a Cloud Pub/Sub topic. A topic acts as a channel or a feed to which messages can be published. To create a topic, one can use the Cloud SDK command-line tool called "gcloud" or the Cloud Pub/Sub API directly. For example, using the gcloud command, the following syntax can be used:

gcloud pubsub topics create [TOPIC_NAME]

This command creates a topic with the specified name. Topics are identified by their unique names within a project.

Once the topic is created, the next step is to create a subscription. A subscription represents a connection point that allows the consumption of messages from a topic. Subscriptions can be created using the same tools as topics, such as the gcloud command or the Cloud Pub/Sub API. For example, using the gcloud command:

gcloud pubsub subscriptions create [SUBSCRIPTION_NAME] --topic=[TOPIC_NAME]

This command creates a subscription with the specified name and associates it with the previously created topic. Subscriptions can be configured with various parameters, such as acknowledgment deadlines and push endpoints, to suit specific requirements.

With the topic and subscription in place, one can now start publishing and consuming messages. The Cloud Pub/Sub API provides client libraries in multiple programming languages, such as Java, Python, and Go, which can be used to interact with the platform. These libraries abstract away the underlying complexity and provide a straightforward interface for message publishing and consumption.

To publish messages, one can use the client library to create a publisher and then call the appropriate methods to publish messages to the topic. For example, in Python:

python
from google.cloud import pubsub_v1

publisher = pubsub_v1.PublisherClient()
topic_path = publisher.topic_path('[PROJECT_ID]', '[TOPIC_NAME]')

data = 'Hello, Cloud Pub/Sub!'
message_future = publisher.publish(topic_path, data.encode('utf-8'))
message_future.result()  # Wait for the publish operation to complete

In this example, the Python client library is used to create a publisher, specify the topic path, and publish a message to the topic. The message is encoded as bytes before being published.

To consume messages, one can similarly use the client library to create a subscriber and then call the appropriate methods to receive and process messages from the subscription. For example, in Java:

java
import com.google.cloud.pubsub.v1.MessageReceiver;
import com.google.cloud.pubsub.v1.Subscriber;
import com.google.pubsub.v1.ProjectSubscriptionName;
import com.google.pubsub.v1.PubsubMessage;

class MessageReceiverImpl implements MessageReceiver {
  @Override
  public void receiveMessage(PubsubMessage message, AckReplyConsumer consumer) {
    // Process the received message
    System.out.println("Received message: " + message.getData().toStringUtf8());

    // Acknowledge the message
    consumer.ack();
  }
}

public class PubSubSubscriber {
  public static void main(String[] args) throws Exception {
    String projectId = "[PROJECT_ID]";
    String subscriptionId = "[SUBSCRIPTION_NAME]";
    ProjectSubscriptionName subscriptionName =
        ProjectSubscriptionName.of(projectId, subscriptionId);

    MessageReceiver receiver = new MessageReceiverImpl();
    Subscriber subscriber = Subscriber.newBuilder(subscriptionName, receiver).build();
    subscriber.startAsync().awaitRunning();

    // Keep the main thread alive to continue receiving messages
    Thread.sleep(Long.MAX_VALUE);
  }
}

In this Java example, a custom implementation of the `MessageReceiver` interface is provided to process received messages. The `receiveMessage` method is called for each message received, allowing the user to define custom logic to handle the message. After processing, the message is acknowledged using the `AckReplyConsumer`.

By following these steps and utilizing the Cloud Pub/Sub API and client libraries, individuals can gain hands-on experience with Cloud Pub/Sub. This approach allows users to understand the core concepts of topics and subscriptions, as well as the process of publishing and consuming messages in an event-driven architecture.

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