If you are creating a new function, see the Console Quickstart on Cloud Run. The content on this page only applies to existing legacy functions created with the Cloud Functions v1 API.
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Pub/Sub triggers (1st gen)
In Cloud Run 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:
If you use a
background function,
the Pub/Sub event data payload is passed directly to your function
in the
PubsubMessage
format.
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 Run 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.
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.
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.
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.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-28 UTC."],[[["\u003cp\u003ePub/Sub triggers in Cloud Run functions (1st gen) allow functions to be invoked in response to Pub/Sub messages published to a specified topic.\u003c/p\u003e\n"],["\u003cp\u003eFunctions using Pub/Sub triggers must be implemented as event-driven functions, either CloudEvent functions or background functions, and handle data in the appropriate format.\u003c/p\u003e\n"],["\u003cp\u003eDeployment of functions with Pub/Sub triggers can be configured using either the gcloud CLI with the \u003ccode\u003e--trigger-topic\u003c/code\u003e flag or the Google Cloud console by selecting the Cloud Pub/Sub trigger type.\u003c/p\u003e\n"],["\u003cp\u003eThe \u003ccode\u003e--retry\u003c/code\u003e flag in the gcloud CLI or the "Retry on failure" checkbox in the console controls whether failed function calls triggered by Pub/Sub events are automatically retried.\u003c/p\u003e\n"],["\u003cp\u003eLegacy functions can use a different event type specified by \u003ccode\u003eproviders/cloud.pubsub/eventTypes/topic.publish\u003c/code\u003e, however it is recommended to use \u003ccode\u003e--trigger-topic\u003c/code\u003e as this method might be removed in the future.\u003c/p\u003e\n"]]],[],null,["# Pub/Sub triggers (1st gen)\n==========================\n\nIn Cloud Run functions, a Pub/Sub trigger enables a function to be called\nin response to [Pub/Sub](/pubsub/docs) messages. When you specify a\nPub/Sub trigger for a function, you also specify a Pub/Sub\ntopic. Your function will be called whenever a message is published to the\nspecified topic.\n\nFor a function to use a Pub/Sub trigger, it must be implemented as an\n[event-driven function](/functions/1stgendocs/writing/write-event-driven-functions):\n\n- If you use a\n [CloudEvent function](/functions/1stgendocs/writing/write-event-driven-functions#cloudevent-functions),\n the Pub/Sub event data is passed to your function in the\n [CloudEvents format](/eventarc/docs/cloudevents) and the CloudEvent data\n payload is of type\n [`MessagePublishedData`](https://github.com/googleapis/google-cloudevents/blob/main/proto/google/events/cloud/pubsub/v1/data.proto).\n\n- If you use a\n [background function](/functions/1stgendocs/writing/write-event-driven-functions#background-functions),\n the Pub/Sub event data payload is passed directly to your function\n in the\n [`PubsubMessage`](https://github.com/googleapis/google-cloudevents/blob/main/proto/google/events/cloud/pubsub/v1/data.proto)\n format.\n\nThe\n[Google Events](https://github.com/googleapis/google-cloudevents)\nrepository contains additional resources for working with event data.\n\nDeployment\n----------\n\nYou can specify a Pub/Sub trigger when you deploy a function. See\n[Deploy a Cloud Run function](/functions/1stgendocs/deploy) for\ngeneral instructions on how to deploy a function, and see this\nsection for additional information specific to configuring Pub/Sub\ntriggers during deployment. \n\n### gcloud\n\nIf you are\n[deploying using the gcloud CLI](/functions/1stgendocs/deploy#gcloud),\nthe flags shown here are used to configure Pub/Sub triggers: \n\n```sh\ngcloud functions deploy YOUR_FUNCTION_NAME \\\n--no-gen2 \\\n--trigger-topic=YOUR_PUBSUB_TOPIC \\\n[--retry] \\\n...\n```\n\n- The [`--trigger-topic`](/sdk/gcloud/reference/functions/deploy#--trigger-topic) flag specifies the Pub/Sub topic that the trigger will monitor. Messages published to this topic trigger calls to your function.\n- The [`--retry`](/sdk/gcloud/reference/functions/deploy#--retry) flag controls whether failed function calls are automatically retried. See [Retrying event-driven functions](/functions/1stgendocs/bestpractices/retries) for more information.\n\n**Legacy Pub/Sub events**\n\nLegacy functions in Cloud Run functions (1st gen) use a different event type\nfor Pub/Sub triggers: \n\n```sh\ngcloud functions deploy YOUR_FUNCTION_NAME \\\n--no-gen2 \\\n--trigger-event=providers/cloud.pubsub/eventTypes/topic.publish \\\n--trigger-resource=YOUR_PUBSUB_TOPIC \\\n...\n```\n\nThis event type is supported for legacy functions already consuming these\nevents. However, we recommend using the `--trigger-topic` flag instead, as\nthe legacy event type might be removed at a future date.\n\n### Console\n\nIf you are\n[deploying using the Google Cloud console](/functions/1stgendocs/deploy#console),\nyou can configure a Pub/Sub trigger in the **Trigger** section:\n\n1. In the **Trigger type** field, select **Cloud Pub/Sub**.\n2. 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.\n3. Select or clear the **Retry on failure** checkbox to control whether failed function calls are automatically retried. See [Retrying event-driven functions](/functions/1stgendocs/bestpractices/retries) for more information.\n\nNext steps\n----------\n\n- Learn how to [write event-driven functions](/functions/1stgendocs/writing/write-event-driven-functions).\n- Learn how to [deploy a Cloud Run function](/functions/1stgendocs/deploy).\n- See the [Pub/Sub tutorial](/functions/1stgendocs/tutorials/pubsub-1st-gen) for an example of writing, deploying, and calling a function with a Pub/Sub trigger."]]
