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. 登入您的 Google 帳戶。

   如果您沒有帳戶，請申請新帳戶。

2. 選取或建立 Google Cloud Platform 專案。

   附註：如果您不打算保留您在這項程序中建立的資源，請建立新專案，而不要選取現有專案，這樣在完成這些步驟之後，您就可以刪除專案，並移除與該專案相關聯的所有資源。

   前往「Manage resources」(管理資源) 頁面

3. 請確認您已啟用 Google Cloud Platform 專案的計費功能。

   瞭解如何啟用計費功能

4. 啟用Cloud Functions and Cloud Pub/Sub API。

   啟用 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 8/10

   cd nodejs-docs-samples/functions/node8/

   Node.js 6 (Deprecated)

   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 8/10

   functions/node8/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} pubSubEvent The event payload.
    * @param {object} context The event metadata.
    */
   exports.helloPubSub = (pubSubEvent, context) => {
     const name = pubSubEvent.data
       ? Buffer.from(pubSubEvent.data, 'base64').toString()
       : 'World';
   
     console.log(`Hello, ${name}!`);
   };

   Node.js 6 (Deprecated)

   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 8

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

Node.js 10 (Beta)

gcloud functions deploy helloPubSub --runtime nodejs10 --trigger-topic YOUR_TOPIC_NAME

Node.js 6 (Deprecated)

gcloud functions deploy helloPubSub --runtime nodejs6 --trigger-topic YOUR_TOPIC_NAME

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.

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:

警告：刪除專案會出現以下結果：

• 刪除專案中的所有內容。 若學習本教學課程時使用現有專案，當您刪除專案時，會一併刪除您在專案中完成的任何其他工作。
• 自訂專案 ID 不復存在。當您建立此專案時，可能會建立一個日後想要使用的自訂專案 ID。若要保留使用該專案 ID 的網址，例如 appspot.com 網址，請刪除在專案中選定的資源，不要刪除整個專案。

若打算瀏覽多個教學課程及快速入門導覽課程，重複使用專案有助於避免超出專案配額限制。

1. 前往 GCP 主控台的「Projects」(專案) 頁面。

   前往專案頁面

2. 在專案清單中選取要刪除的專案，然後按一下 [Delete] (刪除)。
3. 在對話方塊中輸入專案 ID，按一下 [Shut down] (關閉) 即可刪除專案。

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 Platform Console.