Pub/Sub triggers (1st gen)

In Cloud Functions, a Pub/Sub trigger enables a function to be called in response to Pub/Sub messages. When you specify a Pub/Sub trigger for a function, you also specify a Pub/Sub topic. Your function will be called whenever a message is published to the specified topic.

For a function to use a Pub/Sub trigger, it must be implemented as an event-driven function:

The Google Events repository contains additional resources for working with event data.

Deployment

You can specify a Pub/Sub trigger when you deploy a function. See Deploy a Cloud Function for general instructions on how to deploy a function, and see this section for additional information specific to configuring Pub/Sub triggers during deployment.

gcloud

If you are deploying using the gcloud CLI, the flags shown here are used to configure Pub/Sub triggers:

gcloud functions deploy YOUR_FUNCTION_NAME \
--trigger-topic=YOUR_PUBSUB_TOPIC \
[--retry] \
...
  • The --trigger-topic flag specifies the Pub/Sub topic that the trigger will monitor. Messages published to this topic trigger calls to your function.
  • The --retry flag controls whether failed function calls are automatically retried. See Retrying event-driven functions for more information.

Legacy Pub/Sub events

Legacy functions in Cloud Functions (1st gen) use a different event type for Pub/Sub triggers:

gcloud functions deploy YOUR_FUNCTION_NAME \
--trigger-event=providers/cloud.pubsub/eventTypes/topic.publish \
--trigger-resource=YOUR_PUBSUB_TOPIC \
...

This event type is supported for legacy functions already consuming these events. However, we recommend using the --trigger-topic flag instead, as the legacy event type might be removed at a future date.

Console

If you are deploying using the Google Cloud console, you can configure a Pub/Sub trigger in the Trigger section:

  1. In the Trigger type field, select Cloud Pub/Sub.
  2. In the Select a Cloud Pub/Sub topic field, select a topic for the trigger to monitor, or select Create a topic to open a window to create a new topic. When a message is published to your function's topic, that triggers a call to your function.
  3. Select or clear the Retry on failure checkbox to control whether failed function calls are automatically retried. See Retrying event-driven functions for more information.

Next steps