Cloud Pub/Sub 教學課程 (第 1 代)

準備應用程式

1. 將應用程式存放區範例複製到本機電腦中：

   Node.js

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

   您也可以 下載 zip 格式的範例，然後解壓縮該檔案。

   Python

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

   您也可以 下載 zip 格式的範例，然後解壓縮該檔案。

   Go

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

   您也可以 下載 zip 格式的範例，然後解壓縮該檔案。

   Java

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

   您也可以 下載 zip 格式的範例，然後解壓縮該檔案。

   Ruby

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

   您也可以 下載 zip 格式的範例，然後解壓縮該檔案。

2. 變更為包含 Cloud Run 函式範例程式碼的目錄，以存取 Pub/Sub：

   Node.js

   cd nodejs-docs-samples/functions/helloworld/

   Python

   cd python-docs-samples/functions/helloworld/

   Go

   cd golang-samples/functions/helloworld/

   Java

   cd java-docs-samples/functions/helloworld/hello-pubsub/

   Ruby

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

3. 查看程式碼範例：

   Node.js

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

   Python

   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 `@type` field maps to
                            `type.googleapis.com/google.pubsub.v1.PubsubMessage`.
                           The `data` field maps to the PubsubMessage data
                           in a base64-encoded string. The `attributes` field maps
                           to the PubsubMessage attributes if any is present.
            context (google.cloud.functions.Context): Metadata of triggering event
                           including `event_id` which maps to the PubsubMessage
                           messageId, `timestamp` which maps to the PubsubMessage
                           publishTime, `event_type` which maps to
                           `google.pubsub.topic.publish`, and `resource` which is
                           a dictionary that describes the service API endpoint
                           pubsub.googleapis.com, the triggering topic's name, and
                           the triggering event type
                           `type.googleapis.com/google.pubsub.v1.PubsubMessage`.
       Returns:
           None. The output is written to Cloud Logging.
       """
       import base64
   
       print(
           """This Function was triggered by messageId {} published at {} to {}
       """.format(
               context.event_id, context.timestamp, context.resource["name"]
           )
       )
   
       if "data" in event:
           name = base64.b64decode(event["data"]).decode("utf-8")
       else:
           name = "World"
       print(f"Hello {name}!")
   
   

   Go

   
   // Package helloworld provides a set of Cloud Functions samples.
   package helloworld
   
   import (
   	"context"
   	"log"
   )
   
   // PubSubMessage is the payload of a Pub/Sub event.
   // See the documentation for more details:
   // https://cloud.google.com/pubsub/docs/reference/rest/v1/PubsubMessage
   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) // Automatically decoded from base64.
   	if name == "" {
   		name = "World"
   	}
   	log.Printf("Hello, %s!", name)
   	return nil
   }
   

   Java

   
   import com.google.cloud.functions.BackgroundFunction;
   import com.google.cloud.functions.Context;
   import functions.eventpojos.PubsubMessage;
   import java.nio.charset.StandardCharsets;
   import java.util.Base64;
   import java.util.logging.Level;
   import java.util.logging.Logger;
   
   public class HelloPubSub implements BackgroundFunction<PubsubMessage> {
     private static final Logger logger = Logger.getLogger(HelloPubSub.class.getName());
   
     @Override
     public void accept(PubsubMessage message, Context context) {
       String name = "world";
       if (message != null && message.getData() != null) {
         name = new String(
             Base64.getDecoder().decode(message.getData().getBytes(StandardCharsets.UTF_8)),
             StandardCharsets.UTF_8);
       }
       logger.info(String.format("Hello %s!", name));
       return;
     }
   }

   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.html
     name = Base64.decode64 event.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

部署函式

如要使用 Pub/Sub 觸發條件部署函式，請在包含範例程式碼的目錄中執行下列指令 (如果是 Java，則在 pom.xml 檔案中執行)：

gcloud functions deploy helloPubSub \
--runtime nodejs20 \
--trigger-topic YOUR_TOPIC_NAME

gcloud functions deploy hello_pubsub \
--runtime python312 \
--trigger-topic YOUR_TOPIC_NAME

gcloud functions deploy HelloPubSub \
--runtime go121 \
--trigger-topic YOUR_TOPIC_NAME

gcloud functions deploy java-pubsub-function \
--entry-point functions.HelloPubSub \
--runtime java17 \
--memory 512MB \
--trigger-topic YOUR_TOPIC_NAME

gcloud functions deploy hello_pubsub --runtime ruby33 \
--trigger-topic YOUR_TOPIC_NAME

其中 YOUR_TOPIC_NAME 是函式要訂閱的 Pub/Sub 主題名稱。

如果 YOUR_TOPIC_NAME 不存在，這項指令會為您建立。您也可以在執行 deploy 指令前，使用Google Cloud 主控台或下列 gcloud 指令建立主題：

gcloud pubsub topics create YOUR_TOPIC_NAME

觸發函式

1. 將訊息發布至 Pub/Sub 主題。在本例中，訊息是函式會在問候語中加入的名稱：

   gcloud pubsub topics publish YOUR_TOPIC_NAME --message YOUR_NAME

   將 YOUR_TOPIC_NAME 替換為 Pub/Sub 主題名稱，並將 YOUR_NAME 替換為任意字串。

2. 檢查記錄以確定執行已經完成：

   gcloud functions logs read --limit 50

您也可以從函式內部將訊息發布至 Pub/Sub 主題。