Cloud Pub/Sub Tutorial

This simple tutorial demonstrates writing, deploying, and triggering a Background Cloud Function with a Cloud Pub/Sub trigger. To learn more about Cloud Pub/Sub, see the Cloud Pub/Sub documentation.

Note: You can also use HTTP-triggered functions to listen to Pub/Sub push subscriptions. This allows a single Cloud Function to subscribe to multiple topics.

Objectives

• Write and deploy a Background Cloud Function.
• Trigger the function by publishing a message to a Cloud Pub/Sub topic.

Costs

This tutorial uses billable components of Cloud Platform, including:

• Google Cloud Functions
• Google Cloud Pub/Sub

Use the Pricing Calculator to generate a cost estimate based on your projected usage.

New Cloud Platform users might be eligible for a free trial.

Before you begin

1. Connectez-vous à votre compte Google.

   Si vous n'en possédez pas déjà un, vous devez en créer un.

2. Sélectionnez ou créez un projet Google Cloud Platform.

   Remarque : Si vous ne prévoyez pas de conserver les ressources créées au cours de cette procédure, créez un projet au lieu de sélectionner un projet existant. Après avoir suivi ces étapes, vous pouvez supprimer le projet en supprimant toutes les ressources qui lui sont associées.

   Accéder à la page "Gérer les ressources"

3. Assurez-vous que la facturation est activée pour votre projet Google Cloud Platform.

   Découvrir comment activer la facturation

4. Activez Cloud Functions and Cloud Pub/Subles API requises.

   Activer les API.

5. Install and initialize the Cloud SDK.
6. Update gcloud components:

   gcloud components update

7. Prepare your development environment.

   Node.js

   Go to the Node.js setup guide

   Python

   Go to the Python setup guide

   Go

   Go to the Go setup guide

Preparing the application

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

   Node.js

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

   Alternatively, you can download the sample as a zip file and extract it.

   Python

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

   Alternatively, you can download the sample as a zip file and extract it.

   Go

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

   Alternatively, you can download the sample as a zip file and extract it.

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

   Node.js

   cd nodejs-docs-samples/functions/helloworld/

   Python

   cd python-docs-samples/functions/helloworld/

   Go

   cd golang-samples/functions/helloworld/

3. Take a look at the sample code:

   Node.js

   Note: The following sample function uses the Node.js 8+ background function signature and is not compatible with the Node.js 6 runtime.

   functions/helloworld/index.js

   View on GitHub Feedback

   /**
    * Background Cloud Function to be triggered by Pub/Sub.
    * This function is exported by index.js, and executed when
    * the trigger topic receives a message.
    *
    * @param {object} data The event payload.
    * @param {object} context The event metadata.
    */
   exports.helloPubSub = (data, context) => {
     const pubSubMessage = data;
     const name = pubSubMessage.data
       ? Buffer.from(pubSubMessage.data, 'base64').toString()
       : 'World';
   
     console.log(`Hello, ${name}!`);
   };

   Python

   functions/helloworld/main.py

   View on GitHub Feedback

   def hello_pubsub(event, context):
       """Background Cloud Function to be triggered by Pub/Sub.
       Args:
            event (dict):  The dictionary with data specific to this type of
            event. The `data` field contains the PubsubMessage message. The
            `attributes` field will contain custom attributes if there are any.
            context (google.cloud.functions.Context): The Cloud Functions event
            metadata. The `event_id` field contains the Pub/Sub message ID. The
            `timestamp` field contains the publish time.
       """
       import base64
   
       print("""This Function was triggered by messageId {} published at {}
       """.format(context.event_id, context.timestamp))
   
       if 'data' in event:
           name = base64.b64decode(event['data']).decode('utf-8')
       else:
           name = 'World'
       print('Hello {}!'.format(name))

   Go

   functions/helloworld/hello_pubsub.go

   View on GitHub Feedback

   
   // Package helloworld provides a set of Cloud Functions samples.
   package helloworld
   
   import (
   	"context"
   	"log"
   )
   
   // PubSubMessage is the payload of a Pub/Sub event.
   type PubSubMessage struct {
   	Data []byte `json:"data"`
   }
   
   // HelloPubSub consumes a Pub/Sub message.
   func HelloPubSub(ctx context.Context, m PubSubMessage) error {
   	name := string(m.Data)
   	if name == "" {
   		name = "World"
   	}
   	log.Printf("Hello, %s!", name)
   	return nil
   }
   

   Note: The Pub/Sub message's data is stored as a base64-encoded string in the data property of the PubsubMessage object. To extract this data, you may need to decode it as shown in the examples above.

Deploying the function

To deploy the function with a Cloud Pub/Sub trigger, run the following command in the directory where the sample code is located:

Node.js

gcloud functions deploy helloPubSub --runtime nodejs8 --trigger-topic YOUR_TOPIC_NAME

You can use the following values for the --runtime flag to use different Node.js versions:

• nodejs6 (deprecated)
• nodejs8
• nodejs10 (beta)

Python

gcloud functions deploy hello_pubsub --runtime python37 --trigger-topic YOUR_TOPIC_NAME

Go

gcloud functions deploy HelloPubSub --runtime go111 --trigger-topic YOUR_TOPIC_NAME

where YOUR_TOPIC_NAME is the name of the Cloud Pub/Sub topic to which the function will be subscribed.

Note: The function deployment creates the specified Cloud Pub/Sub topic for you. You can also specify an existing topic in your project to subscribe to.

Triggering the function

1. Publish a message to your Cloud Pub/Sub topic. In this example, the message is a name that the function will include in a greeting:

   gcloud pubsub topics publish YOUR_TOPIC_NAME --message YOUR_NAME

   Replace YOUR_TOPIC_NAME with the name of your Cloud Pub/Sub topic, and YOUR_NAME with an arbitrary string.

2. Check the logs to be sure the executions have completed:

   gcloud functions logs read --limit 50
   

   Note: Logs might take a few moments to appear. If you don't see them immediately, check again in a minute or two.

You can also publish a message to a Pub/Sub topic from within a function.

Cleaning up

To avoid incurring charges to your Google Cloud Platform account for the resources used in this tutorial:

Deleting the project

The easiest way to eliminate billing is to delete the project that you created for the tutorial.

To delete the project:

Attention : La suppression d'un projet aura les effets suivants :

• Tout le contenu du projet est supprimé. Si vous avez utilisé un projet existant pour ce tutoriel et que vous le supprimez, vous supprimerez également tout autre travail effectué dans le projet.
• Les ID de projets personnalisés sont perdus. Lorsque vous avez créé ce projet, vous avez peut-être créé un ID de projet personnalisé que vous souhaitez utiliser à l'avenir. Pour conserver les URL qui utilisent l'ID de projet, telle qu'une URL appspot.com, supprimez les ressources sélectionnées dans le projet au lieu de supprimer l'ensemble du projet.

Si vous envisagez d'explorer plusieurs tutoriels et guides de démarrage rapide, vous pouvez constater que réutiliser des projets peut vous aider à éviter de dépasser les limites de quotas des projets.

1. Dans la console GCP, accédez à la page "Projets".

   Accéder à la page Projets

2. Dans la liste des projets, sélectionnez celui que vous souhaitez supprimer, puis cliquez sur Supprimer.
3. Dans la boîte de dialogue, saisissez l'ID du projet, puis cliquez sur Arrêter pour supprimer le projet.

Deleting the Cloud Function

Deleting Cloud Functions does not remove any resources stored in Cloud Storage.

To delete the Cloud Function you created in this tutorial, run the following command:

Node.js

gcloud functions delete helloPubSub 

Python

gcloud functions delete hello_pubsub 

Go

gcloud functions delete HelloPubSub 

You can also delete Cloud Functions from the Google Cloud Console.