Pub/Sub Subscribe to a Topic

Demonstrates how to subscribe to a topic and parse the received event with Pub/Sub from Cloud Functions.

Code sample

Java

To authenticate to Cloud Run functions, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

import com.google.cloud.functions.BackgroundFunction;
import com.google.cloud.functions.Context;
import functions.eventpojos.PubsubMessage;
import java.nio.charset.StandardCharsets;
import java.util.Base64;
import java.util.logging.Logger;

public class SubscribeToTopic implements BackgroundFunction<PubsubMessage> {
  private static final Logger logger = Logger.getLogger(SubscribeToTopic.class.getName());

  @Override
  public void accept(PubsubMessage message, Context context) {
    if (message.getData() == null) {
      logger.info("No message provided");
      return;
    }

    String messageString = new String(
        Base64.getDecoder().decode(message.getData().getBytes(StandardCharsets.UTF_8)),
        StandardCharsets.UTF_8);
    logger.info(messageString);
  }
}

Node.js

To authenticate to Cloud Run functions, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

/**
 * Triggered from a message on a Cloud Pub/Sub topic.
 *
 * @param {object} pubsubMessage The Cloud Pub/Sub Message object.
 * @param {string} pubsubMessage.data The "data" property of the Cloud Pub/Sub Message.
 */
exports.subscribe = pubsubMessage => {
  // Print out the data from Pub/Sub, to prove that it worked
  console.log(Buffer.from(pubsubMessage.data, 'base64').toString());
};

Python

To authenticate to Cloud Run functions, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

# Triggered from a message on a Cloud Pub/Sub topic.
def subscribe(event, context):
    # Print out the data from Pub/Sub, to prove that it worked
    print(base64.b64decode(event["data"]))

What's next

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