Required roles

You or your administrator must grant the deployer account, the trigger identity,and optionally, the Pub/Sub service agent and the Cloud Storageservice agent the following IAM roles.

Create a Pub/Sub topic

In Cloud Run, Pub/Sub topics are not automatically createdwhen you deploy a function. Before deploying your function, publish a message tothis Pub/Sub topic to trigger the function:

gcloudpubsubtopicscreateYOUR_TOPIC_NAME

Prepare the application

1. Clone the sample app repository to your local machine:

   Node.js

   git clone https://github.com/GoogleCloudPlatform/nodejs-docs-samples.git

   Python

   git clone https://github.com/GoogleCloudPlatform/python-docs-samples.git

   Go

   git clone https://github.com/GoogleCloudPlatform/golang-samples.git

   Java

   git clone https://github.com/GoogleCloudPlatform/java-docs-samples.git

   .NET

   git clone https://github.com/GoogleCloudPlatform/dotnet-docs-samples.git

   Ruby

   git clone https://github.com/GoogleCloudPlatform/ruby-docs-samples.git

   PHP

   git clone https://github.com/GoogleCloudPlatform/php-docs-samples.git

2. Change to the directory that contains the sample code for accessing Pub/Sub:

   Node.js

   cd nodejs-docs-samples/functions/v2/helloPubSub/

   Python

   cd python-docs-samples/functions/v2/pubsub/

   Go

   cd golang-samples/functions/functionsv2/hellopubsub/

   Java

   cd java-docs-samples/functions/v2/pubsub/

   .NET

   cd dotnet-docs-samples/functions/helloworld/HelloPubSub/

   Ruby

   cd ruby-docs-samples/functions/helloworld/pubsub/

   PHP

   cd php-docs-samples/functions/helloworld_pubsub/

3. Take a look at the sample code:

   Node.js

   constfunctions=require('@google-cloud/functions-framework');// Register a CloudEvent callback with the Functions Framework that will// be executed when the Pub/Sub trigger topic receives a message.functions.cloudEvent('helloPubSub',cloudEvent=>{// The Pub/Sub message is passed as the CloudEvent's data payload.constbase64name=cloudEvent.data.message.data;constname=base64name?Buffer.from(base64name,'base64').toString():'World';console.log(`Hello,${name}!`);});

   Python

   importbase64fromcloudevents.httpimportCloudEventimportfunctions_framework# Triggered from a message on a Cloud Pub/Sub topic.@functions_framework.cloud_eventdefsubscribe(cloud_event:CloudEvent)->None:# Print out the data from Pub/Sub, to prove that it workedprint("Hello, "+base64.b64decode(cloud_event.data["message"]["data"]).decode()+"!")

   Go

   // Package helloworld provides a set of Cloud Functions samples.packagehelloworldimport("context""fmt""log""github.com/GoogleCloudPlatform/functions-framework-go/functions""github.com/cloudevents/sdk-go/v2/event")funcinit(){functions.CloudEvent("HelloPubSub",helloPubSub)}// MessagePublishedData contains the full Pub/Sub message// See the documentation for more details:// https://cloud.google.com/eventarc/docs/cloudevents#pubsubtypeMessagePublishedDatastruct{MessagePubSubMessage}// PubSubMessage is the payload of a Pub/Sub event.// See the documentation for more details:// https://cloud.google.com/pubsub/docs/reference/rest/v1/PubsubMessagetypePubSubMessagestruct{Data[]byte`json:"data"`}// helloPubSub consumes a CloudEvent message and extracts the Pub/Sub message.funchelloPubSub(ctxcontext.Context,eevent.Event)error{varmsgMessagePublishedDataiferr:=e.DataAs(&msg);err!=nil{returnfmt.Errorf("event.DataAs: %w",err)}name:=string(msg.Message.Data)// Automatically decoded from base64.ifname==""{name="World"}log.Printf("Hello, %s!",name)returnnil}

   Java

   importcom.google.cloud.functions.CloudEventsFunction;importcom.google.gson.Gson;importfunctions.eventpojos.PubSubBody;importio.cloudevents.CloudEvent;importjava.nio.charset.StandardCharsets;importjava.util.Base64;importjava.util.logging.Logger;publicclassSubscribeToTopicimplementsCloudEventsFunction{privatestaticfinalLoggerlogger=Logger.getLogger(SubscribeToTopic.class.getName());@Overridepublicvoidaccept(CloudEventevent){// The Pub/Sub message is passed as the CloudEvent's data payload.if(event.getData()!=null){// Extract Cloud Event data and convert to PubSubBodyStringcloudEventData=newString(event.getData().toBytes(),StandardCharsets.UTF_8);Gsongson=newGson();PubSubBodybody=gson.fromJson(cloudEventData,PubSubBody.class);// Retrieve and decode PubSub message dataStringencodedData=body.getMessage().getData();StringdecodedData=newString(Base64.getDecoder().decode(encodedData),StandardCharsets.UTF_8);logger.info("Hello, "+decodedData+"!");}}}

   .NET

   usingCloudNative.CloudEvents;usingGoogle.Cloud.Functions.Framework;usingGoogle.Events.Protobuf.Cloud.PubSub.V1;usingMicrosoft.Extensions.Logging;usingSystem.Threading;usingSystem.Threading.Tasks;namespaceHelloPubSub;publicclassFunction:ICloudEventFunction<MessagePublishedData>{privatereadonlyILogger_logger;publicFunction(ILogger<Function>logger)=>_logger=logger;publicTaskHandleAsync(CloudEventcloudEvent,MessagePublishedDatadata,CancellationTokencancellationToken){stringnameFromMessage=data.Message?.TextData;stringname=string.IsNullOrEmpty(nameFromMessage)?"world":nameFromMessage;_logger.LogInformation("Hello {name}",name);returnTask.CompletedTask;}}

   Ruby

   require"functions_framework"require"base64"FunctionsFramework.cloud_event"hello_pubsub"do|event|# The event parameter is a CloudEvents::Event::V1 object.# See https://cloudevents.github.io/sdk-ruby/latest/CloudEvents/Event/V1.htmlname=Base64.decode64event.data["message"]["data"]rescue"World"# A cloud_event function does not return a response, but you can log messages# or cause side effects such as sending additional events.logger.info"Hello,#{name}!"end

   PHP

   use CloudEvents\V1\CloudEventInterface;use Google\CloudFunctions\FunctionsFramework;// Register the function with Functions Framework.// This enables omitting the `FUNCTIONS_SIGNATURE_TYPE=cloudevent` environment// variable when deploying. The `FUNCTION_TARGET` environment variable should// match the first parameter.FunctionsFramework::cloudEvent('helloworldPubsub', 'helloworldPubsub');function helloworldPubsub(CloudEventInterface $event): void{    $log = fopen(getenv('LOGGER_OUTPUT') ?: 'php://stderr', 'wb');    $cloudEventData = $event->getData();    $pubSubData = base64_decode($cloudEventData['message']['data']);    $name = $pubSubData ? htmlspecialchars($pubSubData) : 'World';    fwrite($log, "Hello, $name!" . PHP_EOL);}

Deploy an event-driven function

To deploy the function, run the following command in the directory that containsthe sample code:

  gcloud run deployFUNCTION \        --source . \        --function helloPubSub \        --base-imageBASE_IMAGE \

  gcloud run deployFUNCTION \        --source . \        --function subscribe \        --base-imageBASE_IMAGE \

  gcloud run deployFUNCTION \        --source . \        --function HelloPubSub \        --base-imageBASE_IMAGE \

  gcloud run deployFUNCTION \        --source . \        --function functions.SubscribeToTopic \        --base-imageBASE_IMAGE \

  gcloud run deployFUNCTION \        --source . \        --function HelloPubSub.Function \        --base-imageBASE_IMAGE \

  gcloud run deployFUNCTION \        --source . \        --function hello_pubsub \        --base-imageBASE_IMAGE \

  gcloud run deployFUNCTION \        --source . \        --function helloworldPubsub \        --base-imageBASE_IMAGE \

If you are prompted to create a repository in the specified region, respond bypressingy.When the deployment is complete, the Google Cloud CLI displays a URL wherethe service is running.

Create an Eventarc trigger

To deploy the function with a Pub/Sub trigger, run the following commandin the directory that contains the sample code:

1. Create an Eventarc Pub/Sub trigger:

   gcloudeventarctriggerscreateTRIGGER_NAME\--location=${REGION}\--destination-run-service=FUNCTION\--destination-run-region=${REGION}\--event-filters="type=google.cloud.pubsub.topic.v1.messagePublished"\--service-account=PROJECT_NUMBER-compute@developer.gserviceaccount.com

   Replace:

   • TRIGGER_NAME with the name for your trigger.
   • FUNCTION with the name of your function.
   • PROJECT_NUMBER with your Google Cloud project number.

   Note that when creating an Eventarc trigger for the firsttime in a Google Cloud project, there might be a delay in provisioningthe Eventarc service agent. This issue can usually be resolvedby attempting to create the trigger again. For more information, seePermission denied errors.

2. Confirm that the trigger was successfully created. Note that although yourtrigger is created immediately, it can take up to two minutes for a triggerto be fully functional.

   gcloudeventarctriggerslist--location=${REGION}

   The output should be similar to the following:

   NAME: helloworld-eventsTYPE: google.cloud.pubsub.topic.v1.messagePublishedDESTINATION: Cloud Run service: helloworld-eventsACTIVE: YesLOCATION: us-central1

Trigger the function

To test the Pub/Sub function:

1. Assign the topic to a variable:

   TOPIC_ID=$(gcloud eventarc triggers describeTRIGGER_NAME --location $REGION --format='value(transport.pubsub.topic)')

2. Publish a message to the topic:

   gcloud pubsub topics publish $TOPIC_ID --message="Hello World"

The Cloud Run service logs the body of the incoming message. You canview this in the Logs section of your Cloud Run instance:

1. Navigate to theGoogle Cloud console.
2. Click the function.

3. Select theLogs tab.

   Logs might take a few moments to appear. If you don't see them immediately, check again after a few moments.

4. Look for the "Hello World!" message.