Pub/Sub topic properties are the characteristics of a topic. You can set topic properties when you create or update a topic.
This document describes the different topic properties you can set for a topic.
Before you begin
Common topic properties
When you create a topic, you must specify a number of options to set up the topic. Some of these properties are common to all types of topics and are discussed in the next sections.
Add a default subscription
Adds a default subscription to the Pub/Sub topic. You can create another subscription for the topic after the topic is created. The default subscription has the following properties:
- Subscription ID of
- Pull delivery type
- Message retention duration of seven days
- Expiration after 31 days of inactivity
- Acknowledgment deadline of 10 seconds
- Immediate retry policy
A schema is a format that the message data field must follow. A schema is a contract between the publisher and subscriber that Pub/Sub enforces.
Topic schemas help standardize message types and permissions to allow them to be consumed by different teams in your organization. Pub/Sub creates a central authority for message types and permissions. To create a topic with schema, see Create and manage schemas.
Message retention duration
Specifies how long the Pub/Sub topic retains messages after publication. After the message retention duration is over, Pub/Sub might discard the message regardless of its acknowledgment state. Message storage fees are charged for storing all messages published to the topic.
- Default = Not enabled
- Minimum value = 10 minutes
- Maximum value = 31 days
Use a customer-managed encryption key (CMEK)
Specifies if the topic is encrypted with a CMEK. Pub/Sub encrypts messages with Google-managed keys by default. If you specify this option, Pub/Sub uses the envelope encryption pattern with CMEK. In this approach, Cloud KMS does not encrypt the messages. Instead, Cloud KMS encrypts the Data Encryption Keys (DEKs) that Pub/Sub creates for each topic.
Pub/Sub encrypts the messages using the newest DEK that was generated for the topic. Pub/Sub decrypts the messages shortly before they are delivered to subscribers.
For more information about creating a key, see Configure message encryption.
- Create a pull subscription.
- Create a push subscription.
- Create a BigQuery subscription.
- Create a Cloud Storage subscription.