How to Create Subscription in Google Cloud Pub/Sub

To create a subscription in Google Cloud Pub/Sub, use the gcloud pubsub subscriptions create command or the client library method createSubscription. You must specify the subscription name and the topic it subscribes to.

Syntax

The basic syntax to create a subscription using the gcloud command-line tool is:

• gcloud pubsub subscriptions create SUBSCRIPTION_NAME --topic=TOPIC_NAME

Here, SUBSCRIPTION_NAME is the name you want for your subscription, and TOPIC_NAME is the existing topic you want to subscribe to.

In client libraries, the method usually looks like createSubscription(subscriptionName) called on a topic object, where you provide the subscription name.

bash

gcloud pubsub subscriptions create SUBSCRIPTION_NAME --topic=TOPIC_NAME

Example

This example shows how to create a subscription named my-subscription to the topic my-topic using the gcloud CLI and Node.js client library.

bash and javascript

gcloud pubsub subscriptions create my-subscription --topic=my-topic

// Node.js example
const {PubSub} = require('@google-cloud/pubsub');
const pubSubClient = new PubSub();

async function createSubscription() {
  const topicName = 'my-topic';
  const subscriptionName = 'my-subscription';
  await pubSubClient.topic(topicName).createSubscription(subscriptionName);
  console.log(`Subscription ${subscriptionName} created.`);
}

createSubscription().catch(console.error);

Output

Subscription my-subscription created.

Common Pitfalls

Common mistakes when creating subscriptions include:

• Trying to create a subscription for a topic that does not exist.
• Using invalid characters or names for subscriptions or topics.
• Not having the right permissions to create subscriptions.
• Confusing subscription names with topic names.

Always verify the topic exists before creating a subscription and ensure your account has pubsub.subscriptions.create permission.

bash

gcloud pubsub subscriptions create my-subscription --topic=nonexistent-topic
# Error: NOT_FOUND: Topic does not exist

# Correct way:
gcloud pubsub topics create my-topic

gcloud pubsub subscriptions create my-subscription --topic=my-topic

Quick Reference

Command or Parameter	Description
gcloud pubsub subscriptions create SUBSCRIPTION_NAME --topic=TOPIC_NAME	Create a new subscription to a topic
SUBSCRIPTION_NAME	Name of the subscription to create
TOPIC_NAME	Name of the existing topic to subscribe to
--ack-deadline	Optional: Set acknowledgment deadline in seconds
--push-endpoint	Optional: Set push endpoint URL for push subscriptions

Key Takeaways

Use the gcloud command or client libraries to create Pub/Sub subscriptions by specifying subscription and topic names.

Ensure the topic exists before creating a subscription to avoid errors.

Check you have the necessary permissions to create subscriptions in your Google Cloud project.

Subscription names must be unique within the project and follow naming rules.

Use optional flags like acknowledgment deadline or push endpoint to customize subscription behavior.