使用用戶端程式庫在 Pub/Sub 中發布及接收訊息

透過 Pub/Sub 服務，應用程式就能以可靠、快速、非同步的方式交換訊息。事件順序如下：

  1. 資料生產者將訊息發布至 Pub/Sub 主題。
  2. 訂閱端用戶端會建立對該主題的訂閱，並提取來自訂閱項目的訊息。

您可以透過下列任一方法設定 Pub/Sub 環境： Trusted Cloud 控制台、Cloud Shell、用戶端程式庫或 REST API。本頁面說明如何開始使用用戶端程式庫，以 Pub/Sub 發布訊息。

Pub/Sub 提供高階和低階的自動產生用戶端程式庫。根據預設，如本快速入門導覽課程所示，我們建議使用高階用戶端程式庫。

事前準備

  1. Install the Google Cloud CLI.

  2. 設定 gcloud CLI 以使用您的聯合身分。

    詳情請參閱「 使用聯合身分登入 gcloud CLI」。

  3. 如要初始化 gcloud CLI，請執行下列指令： 

    gcloud init

  4. Create or select a Trusted Cloud project.

    • Create a Trusted Cloud project:

      gcloud projects create PROJECT_ID

      Replace PROJECT_ID with a name for the Trusted Cloud project you are creating.

    • Select the Trusted Cloud project that you created:

      gcloud config set project PROJECT_ID

      Replace PROJECT_ID with your Trusted Cloud project name.

  5. Verify that billing is enabled for your Trusted Cloud project.

  6. Enable the Pub/Sub API: 

    gcloud services enable pubsub.googleapis.com

  7. Create local authentication credentials for your user account: 

    gcloud auth application-default login

    If an authentication error is returned, and you are using an external identity provider (IdP), confirm that you have signed in to the gcloud CLI with your federated identity.

  8. Grant roles to your user account. Run the following command once for each of the following IAM roles: roles/pubsub.admin 

    gcloud projects add-iam-policy-binding PROJECT_ID --member="user:USER_IDENTIFIER" --role=ROLE

    Replace the following:

    9. 安裝用戶端程式庫

    下列範例說明如何安裝用戶端程式庫：

    Python

    如要進一步瞭解如何設定 Python 開發環境，請參閱 Python 開發環境設定指南。 

    # ensure that you are using virtualenv
    # as described in the python dev setup guide

    pip install --upgrade google-cloud-pubsub

    C++

    如要進一步瞭解如何安裝 C++ 程式庫，請參閱 GitHub README。

    C#

    Install-Package Google.Cloud.PubSub.V1 -Pre

    Go

    go get cloud.google.com/go/pubsub

    Java

    If you are using Maven, add the following to your pom.xml file. For more information about BOMs, see The Google Cloud Platform Libraries BOM.

    <dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>com.google.cloud</groupId>
      <artifactId>libraries-bom</artifactId>
      <version>26.65.0</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
  </dependencies>
</dependencyManagement>

<dependencies>
  <dependency>
    <groupId>com.google.cloud</groupId>
    <artifactId>google-cloud-pubsub</artifactId>
  </dependency>

</dependencies>

    If you are using Gradle, add the following to your dependencies:

    implementation platform('com.google.cloud:libraries-bom:26.65.0')

implementation 'com.google.cloud:google-cloud-pubsub'

    If you are using sbt, add the following to your dependencies:

    libraryDependencies += "com.google.cloud" % "google-cloud-pubsub" % "1.141.2"

    If you're using Visual Studio Code, IntelliJ, or Eclipse, you can add client libraries to your project using the following IDE plugins:

    The plugins provide additional functionality, such as key management for service accounts. Refer to each plugin's documentation for details.

    Node.js

    npm install @google-cloud/pubsub

    PHP

    composer require google/cloud-pubsub

    Ruby

    gem install google-cloud-pubsub

    建立主題與訂閱項目

    您建立主題後，就可訂閱或發布至該主題。

    請使用下列 gcloud pubsub topics create 指令，建立名為 my-topic 的主題。請勿變更主題名稱，因為本教學課程的其餘部分會參考這個名稱。

    gcloud pubsub topics create my-topic

    請使用 gcloud pubsub subscriptions create 指令以建立訂閱。只有在訂閱後發佈至主題的訊息才能在訂閱者應用程式中找到。

    gcloud pubsub subscriptions create my-sub --topic my-topic

    如要進一步瞭解為主題及訂閱命名的資訊，請參閱資源名稱。

    發布訊息

    執行下列範例前，請務必取消註解並填入程式碼中標示的所有必要值。這是將範例連結至專案和先前建立的 Pub/Sub 資源的必要步驟。

    請使用 my-topic 做為主題 ID。

    Python

    from google.cloud import pubsub_v1

# TODO(developer)
# project_id = "your-project-id"
# topic_id = "your-topic-id"

publisher = pubsub_v1.PublisherClient()
# The `topic_path` method creates a fully qualified identifier
# in the form `projects/{project_id}/topics/{topic_id}`
topic_path = publisher.topic_path(project_id, topic_id)

for n in range(1, 10):
    data_str = f"Message number {n}"
    # Data must be a bytestring
    data = data_str.encode("utf-8")
    # When you publish a message, the client returns a future.
    future = publisher.publish(topic_path, data)
    print(future.result())

print(f"Published messages to {topic_path}.")

    C++

    #include "google/cloud/pubsub/publisher.h"
#include <iostream>

int main(int argc, char* argv[]) try {
  if (argc != 3) {
    std::cerr << "Usage: " << argv[0] << " <project-id> <topic-id>\n";
    return 1;
  }

  std::string const project_id = argv[1];
  std::string const topic_id = argv[2];

  // Create a namespace alias to make the code easier to read.
  namespace pubsub = ::google::cloud::pubsub;

  auto publisher = pubsub::Publisher(
      pubsub::MakePublisherConnection(pubsub::Topic(project_id, topic_id)));
  auto id =
      publisher
          .Publish(pubsub::MessageBuilder{}.SetData("Hello World!").Build())
          .get();
  if (!id) throw std::move(id).status();
  std::cout << "Hello World published with id=" << *id << "\n";

  return 0;
} catch (google::cloud::Status const& status) {
  std::cerr << "google::cloud::Status thrown: " << status << "\n";
  return 1;
}

    C#

    
using Google.Cloud.PubSub.V1;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

public class PublishMessagesAsyncSample
{
    public async Task<int> PublishMessagesAsync(string projectId, string topicId, IEnumerable<string> messageTexts)
    {
        TopicName topicName = TopicName.FromProjectTopic(projectId, topicId);
        PublisherClient publisher = await PublisherClient.CreateAsync(topicName);

        int publishedMessageCount = 0;
        var publishTasks = messageTexts.Select(async text =>
        {
            try
            {
                string message = await publisher.PublishAsync(text);
                Console.WriteLine($"Published message {message}");
                Interlocked.Increment(ref publishedMessageCount);
            }
            catch (Exception exception)
            {
                Console.WriteLine($"An error occurred when publishing message {text}: {exception.Message}");
            }
        });
        await Task.WhenAll(publishTasks);
        return publishedMessageCount;
    }
}

    Go

    import (
	"context"
	"fmt"
	"io"

	"cloud.google.com/go/pubsub/v2"
)

func publish(w io.Writer, projectID, topicID, msg string) error {
	// projectID := "my-project-id"
	// topicID := "my-topic"
	// msg := "Hello World"
	ctx := context.Background()
	client, err := pubsub.NewClient(ctx, projectID)
	if err != nil {
		return fmt.Errorf("pubsub: NewClient: %w", err)
	}
	defer client.Close()

	// client.Publisher can be passed a topic ID (e.g. "my-topic") or
	// a fully qualified name (e.g. "projects/my-project/topics/my-topic").
	// If a topic ID is provided, the project ID from the client is used.
	// Reuse this publisher for all publish calls to send messages in batches.
	publisher := client.Publisher(topicID)
	result := publisher.Publish(ctx, &pubsub.Message{
		Data: []byte(msg),
	})
	// Block until the result is returned and a server-generated
	// ID is returned for the published message.
	id, err := result.Get(ctx)
	if err != nil {
		return fmt.Errorf("pubsub: result.Get: %w", err)
	}
	fmt.Fprintf(w, "Published a message; msg ID: %v\n", id)
	return nil
}

    Java

    
import com.google.api.core.ApiFuture;
import com.google.cloud.pubsub.v1.Publisher;
import com.google.protobuf.ByteString;
import com.google.pubsub.v1.PubsubMessage;
import com.google.pubsub.v1.TopicName;
import java.io.IOException;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;

public class PublisherExample {
  public static void main(String... args) throws Exception {
    // TODO(developer): Replace these variables before running the sample.
    String projectId = "your-project-id";
    String topicId = "your-topic-id";

    publisherExample(projectId, topicId);
  }

  public static void publisherExample(String projectId, String topicId)
      throws IOException, ExecutionException, InterruptedException {
    TopicName topicName = TopicName.of(projectId, topicId);

    Publisher publisher = null;
    try {
      // Create a publisher instance with default settings bound to the topic
      publisher = Publisher.newBuilder(topicName).build();

      String message = "Hello World!";
      ByteString data = ByteString.copyFromUtf8(message);
      PubsubMessage pubsubMessage = PubsubMessage.newBuilder().setData(data).build();

      // Once published, returns a server-assigned message id (unique within the topic)
      ApiFuture<String> messageIdFuture = publisher.publish(pubsubMessage);
      String messageId = messageIdFuture.get();
      System.out.println("Published message ID: " + messageId);
    } finally {
      if (publisher != null) {
        // When finished with the publisher, shutdown to free up resources.
        publisher.shutdown();
        publisher.awaitTermination(1, TimeUnit.MINUTES);
      }
    }
  }
}

    Node.js

    /**
 * TODO(developer): Uncomment these variables before running the sample.
 */
// const topicNameOrId = 'YOUR_TOPIC_NAME_OR_ID';
// const data = JSON.stringify({foo: 'bar'});

// Imports the Google Cloud client library
const {PubSub} = require('@google-cloud/pubsub');

// Creates a client; cache this for further use
const pubSubClient = new PubSub();

async function publishMessage(topicNameOrId, data) {
  // Publishes the message as a string, e.g. "Hello, world!" or JSON.stringify(someObject)
  const dataBuffer = Buffer.from(data);

  // Cache topic objects (publishers) and reuse them.
  const topic = pubSubClient.topic(topicNameOrId);

  try {
    const messageId = await topic.publishMessage({data: dataBuffer});
    console.log(`Message ${messageId} published.`);
  } catch (error) {
    console.error(`Received error while publishing: ${error.message}`);
    process.exitCode = 1;
  }
}

    Node.js

    /**
 * TODO(developer): Uncomment these variables before running the sample.
 */
// const topicNameOrId = 'YOUR_TOPIC_NAME_OR_ID';
// const data = JSON.stringify({foo: 'bar'});

// Imports the Google Cloud client library
import {PubSub} from '@google-cloud/pubsub';

// Creates a client; cache this for further use
const pubSubClient = new PubSub();

async function publishMessage(topicNameOrId: string, data: string) {
  // Publishes the message as a string, e.g. "Hello, world!" or JSON.stringify(someObject)
  const dataBuffer = Buffer.from(data);

  // Cache topic objects (publishers) and reuse them.
  const topic = pubSubClient.topic(topicNameOrId);

  try {
    const messageId = await topic.publishMessage({data: dataBuffer});
    console.log(`Message ${messageId} published.`);
  } catch (error) {
    console.error(
      `Received error while publishing: ${(error as Error).message}`,
    );
    process.exitCode = 1;
  }
}

    PHP

    use Google\Cloud\PubSub\MessageBuilder;
use Google\Cloud\PubSub\PubSubClient;

/**
 * Publishes a message for a Pub/Sub topic.
 *
 * @param string $projectId  The Google project ID.
 * @param string $topicName  The Pub/Sub topic name.
 * @param string $message  The message to publish.
 */
function publish_message($projectId, $topicName, $message)
{
    $pubsub = new PubSubClient([
        'projectId' => $projectId,
    ]);

    $topic = $pubsub->topic($topicName);
    $topic->publish((new MessageBuilder)->setData($message)->build());

    print('Message published' . PHP_EOL);
}

    Ruby

    # topic_id = "your-topic-id"

pubsub = Google::Cloud::PubSub.new
publisher = pubsub.publisher topic_id

publisher.publish "This is a test message."

puts "Message published."

    接收郵件

    設定訂閱者，提取您剛才發布的訊息。每個訂閱者都必須確認可設定時間範圍內的每個訊息。未確認的訊息會重新傳送。請注意，Pub/Sub 偶爾會重複傳送訊息，確保所有訊息至少會傳送給訂閱者一次。

    執行下列範例前，請務必取消註解並填入程式碼中標示的所有必要值。這是將範例連結至專案和先前建立的 Pub/Sub 資源的必要步驟

    使用 my-sub 做為訂閱 ID。

    如需更多擷取訊息的範例，請參閱用戶端程式庫程式碼範例。

    Python

    from concurrent.futures import TimeoutError
from google.cloud import pubsub_v1

# TODO(developer)
# project_id = "your-project-id"
# subscription_id = "your-subscription-id"
# Number of seconds the subscriber should listen for messages
# timeout = 5.0

subscriber = pubsub_v1.SubscriberClient()
# The `subscription_path` method creates a fully qualified identifier
# in the form `projects/{project_id}/subscriptions/{subscription_id}`
subscription_path = subscriber.subscription_path(project_id, subscription_id)

def callback(message: pubsub_v1.subscriber.message.Message) -> None:
    print(f"Received {message}.")
    message.ack()

streaming_pull_future = subscriber.subscribe(subscription_path, callback=callback)
print(f"Listening for messages on {subscription_path}..\n")

# Wrap subscriber in a 'with' block to automatically call close() when done.
with subscriber:
    try:
        # When `timeout` is not set, result() will block indefinitely,
        # unless an exception is encountered first.
        streaming_pull_future.result(timeout=timeout)
    except TimeoutError:
        streaming_pull_future.cancel()  # Trigger the shutdown.
        streaming_pull_future.result()  # Block until the shutdown is complete.

    C++

    #include "google/cloud/pubsub/message.h"
#include "google/cloud/pubsub/subscriber.h"
#include <iostream>

int main(int argc, char* argv[]) try {
  if (argc != 3) {
    std::cerr << "Usage: " << argv[0] << " <project-id> <subscription-id>\n";
    return 1;
  }

  std::string const project_id = argv[1];
  std::string const subscription_id = argv[2];

  auto constexpr kWaitTimeout = std::chrono::seconds(30);

  // Create a namespace alias to make the code easier to read.
  namespace pubsub = ::google::cloud::pubsub;

  auto subscriber = pubsub::Subscriber(pubsub::MakeSubscriberConnection(
      pubsub::Subscription(project_id, subscription_id)));

  auto session =
      subscriber.Subscribe([&](pubsub::Message const& m, pubsub::AckHandler h) {
        std::cout << "Received message " << m << "\n";
        std::move(h).ack();
      });

  std::cout << "Waiting for messages on " + subscription_id + "...\n";

  // Blocks until the timeout is reached.
  auto result = session.wait_for(kWaitTimeout);
  if (result == std::future_status::timeout) {
    std::cout << "timeout reached, ending session\n";
    session.cancel();
  }

  return 0;
} catch (google::cloud::Status const& status) {
  std::cerr << "google::cloud::Status thrown: " << status << "\n";
  return 1;
}

    C#

    
using Google.Cloud.PubSub.V1;
using System;
using System.Threading;
using System.Threading.Tasks;

public class PullMessagesAsyncSample
{
    public async Task<int> PullMessagesAsync(string projectId, string subscriptionId, bool acknowledge)
    {
        SubscriptionName subscriptionName = SubscriptionName.FromProjectSubscription(projectId, subscriptionId);
        SubscriberClient subscriber = await SubscriberClient.CreateAsync(subscriptionName);
        // SubscriberClient runs your message handle function on multiple
        // threads to maximize throughput.
        int messageCount = 0;
        Task startTask = subscriber.StartAsync((PubsubMessage message, CancellationToken cancel) =>
        {
            string text = message.Data.ToStringUtf8();
            Console.WriteLine($"Message {message.MessageId}: {text}");
            Interlocked.Increment(ref messageCount);
            return Task.FromResult(acknowledge ? SubscriberClient.Reply.Ack : SubscriberClient.Reply.Nack);
        });
        // Run for 5 seconds.
        await Task.Delay(5000);
        await subscriber.StopAsync(CancellationToken.None);
        // Lets make sure that the start task finished successfully after the call to stop.
        await startTask;
        return messageCount;
    }
}

    Go

    import (
	"context"
	"fmt"
	"io"
	"sync/atomic"
	"time"

	"cloud.google.com/go/pubsub/v2"
)

func pullMsgs(w io.Writer, projectID, subID string) error {
	// projectID := "my-project-id"
	// subID := "my-sub"
	ctx := context.Background()
	client, err := pubsub.NewClient(ctx, projectID)
	if err != nil {
		return fmt.Errorf("pubsub.NewClient: %w", err)
	}
	defer client.Close()

	// client.Subscriber can be passed a subscription ID (e.g. "my-sub") or
	// a fully qualified name (e.g. "projects/my-project/subscriptions/my-sub").
	// If a subscription ID is provided, the project ID from the client is used.
	sub := client.Subscriber(subID)

	// Receive messages for 10 seconds, which simplifies testing.
	// Comment this out in production, since `Receive` should
	// be used as a long running operation.
	ctx, cancel := context.WithTimeout(ctx, 10*time.Second)
	defer cancel()

	var received int32
	err = sub.Receive(ctx, func(_ context.Context, msg *pubsub.Message) {
		fmt.Fprintf(w, "Got message: %q\n", string(msg.Data))
		atomic.AddInt32(&received, 1)
		msg.Ack()
	})
	if err != nil {
		return fmt.Errorf("sub.Receive: %w", err)
	}
	fmt.Fprintf(w, "Received %d messages\n", received)

	return nil
}

    Java

    
import com.google.cloud.pubsub.v1.AckReplyConsumer;
import com.google.cloud.pubsub.v1.MessageReceiver;
import com.google.cloud.pubsub.v1.Subscriber;
import com.google.pubsub.v1.ProjectSubscriptionName;
import com.google.pubsub.v1.PubsubMessage;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

public class SubscribeAsyncExample {
  public static void main(String... args) throws Exception {
    // TODO(developer): Replace these variables before running the sample.
    String projectId = "your-project-id";
    String subscriptionId = "your-subscription-id";

    subscribeAsyncExample(projectId, subscriptionId);
  }

  public static void subscribeAsyncExample(String projectId, String subscriptionId) {
    ProjectSubscriptionName subscriptionName =
        ProjectSubscriptionName.of(projectId, subscriptionId);

    // Instantiate an asynchronous message receiver.
    MessageReceiver receiver =
        (PubsubMessage message, AckReplyConsumer consumer) -> {
          // Handle incoming message, then ack the received message.
          System.out.println("Id: " + message.getMessageId());
          System.out.println("Data: " + message.getData().toStringUtf8());
          consumer.ack();
        };

    Subscriber subscriber = null;
    try {
      subscriber = Subscriber.newBuilder(subscriptionName, receiver).build();
      // Start the subscriber.
      subscriber.startAsync().awaitRunning();
      System.out.printf("Listening for messages on %s:\n", subscriptionName.toString());
      // Allow the subscriber to run for 30s unless an unrecoverable error occurs.
      subscriber.awaitTerminated(30, TimeUnit.SECONDS);
    } catch (TimeoutException timeoutException) {
      // Shut down the subscriber after 30s. Stop receiving messages.
      subscriber.stopAsync();
    }
  }
}

    Node.js

    /**
 * TODO(developer): Uncomment these variables before running the sample.
 */
// const subscriptionNameOrId = 'YOUR_SUBSCRIPTION_NAME_OR_ID';
// const timeout = 60;

// Imports the Google Cloud client library
const {PubSub} = require('@google-cloud/pubsub');

// Creates a client; cache this for further use
const pubSubClient = new PubSub();

function listenForMessages(subscriptionNameOrId, timeout) {
  // References an existing subscription; if you are unsure if the
  // subscription will exist, try the optimisticSubscribe sample.
  const subscription = pubSubClient.subscription(subscriptionNameOrId);

  // Create an event handler to handle messages
  let messageCount = 0;
  const messageHandler = message => {
    console.log(`Received message ${message.id}:`);
    console.log(`\tData: ${message.data}`);
    console.log(`\tAttributes: ${message.attributes}`);
    messageCount += 1;

    // "Ack" (acknowledge receipt of) the message
    message.ack();
  };

  // Listen for new messages until timeout is hit
  subscription.on('message', messageHandler);

  // Wait a while for the subscription to run. (Part of the sample only.)
  setTimeout(() => {
    subscription.removeListener('message', messageHandler);
    console.log(`${messageCount} message(s) received.`);
  }, timeout * 1000);
}

    PHP

    use Google\Cloud\PubSub\PubSubClient;

/**
 * Pulls all Pub/Sub messages for a subscription.
 *
 * @param string $projectId  The Google project ID.
 * @param string $subscriptionName  The Pub/Sub subscription name.
 */
function pull_messages($projectId, $subscriptionName)
{
    $pubsub = new PubSubClient([
        'projectId' => $projectId,
    ]);
    $subscription = $pubsub->subscription($subscriptionName);
    foreach ($subscription->pull() as $message) {
        printf('Message: %s' . PHP_EOL, $message->data());
        // Acknowledge the Pub/Sub message has been received, so it will not be pulled multiple times.
        $subscription->acknowledge($message);
    }
}

    Ruby

    # subscription_id = "your-subscription-id"

pubsub = Google::Cloud::PubSub.new
subscriber = pubsub.subscriber subscription_id

listener = subscriber.listen do |received_message|
  puts "Received message: #{received_message.data}"
  received_message.acknowledge!
end

listener.start
# Let the main thread sleep for 60 seconds so the thread for listening
# messages does not quit
sleep 60
listener.stop.wait!

    還順利嗎？

    清除 (選用)

    1. 如要避免系統向您的 Trusted Cloud by S3NS 帳戶收取本指南所用資源的費用，請使用指令列刪除主題和訂閱項目。
        gcloud pubsub subscriptions delete my-sub
  gcloud pubsub topics delete my-topic

    2. Optional: Revoke the authentication credentials that you created, and delete the local credential file. 

      gcloud auth application-default revoke

    3. Optional: Revoke credentials from the gcloud CLI. 

      gcloud auth revoke

    後續步驟