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Weitere Informationen

Eine ausführliche Dokumentation, die dieses Codebeispiel enthält, finden Sie hier:

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Codebeispiel

C++

Folgen Sie der Einrichtungsanleitung für C++ in der Kurzanleitung zur Verwendung von Clientbibliotheken, bevor Sie dieses Beispiel anwenden. Weitere Informationen finden Sie in der Referenzdokumentation zur Pub/Sub C++ API.

Richten Sie die Standardanmeldedaten für Anwendungen ein, um sich bei Pub/Sub zu authentifizieren. Weitere Informationen finden Sie unter Authentifizierung für eine lokale Entwicklungsumgebung einrichten.

namespace pubsub = ::google::cloud::pubsub;
using ::google::cloud::future;
using ::google::cloud::Options;
using ::google::cloud::StatusOr;
auto sample = [](std::string project_id, std::string subscription_id) {
  // Change the flow control watermarks, by default the client library uses
  // 0 and 1,000 for the message count watermarks, and 0 and 10MiB for the
  // size watermarks. Recall that the library stops requesting messages if
  // any of the high watermarks are reached, and the library resumes
  // requesting messages when *both* low watermarks are reached.
  auto constexpr kMiB = 1024 * 1024L;
  auto subscriber = pubsub::Subscriber(pubsub::MakeSubscriberConnection(
      pubsub::Subscription(std::move(project_id), std::move(subscription_id)),
      Options{}
          .set<pubsub::MaxOutstandingMessagesOption>(1000)
          .set<pubsub::MaxOutstandingBytesOption>(8 * kMiB)));

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

C#

Folgen Sie der Einrichtungsanleitung für C# in der Kurzanleitung zur Verwendung von Clientbibliotheken, bevor Sie dieses Beispiel anwenden. Weitere Informationen finden Sie in der Referenzdokumentation zur Pub/Sub C# API.


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

public class PullMessagesWithFlowControlAsyncSample
{
    public async Task<int> PullMessagesWithFlowControlAsync(string projectId, string subscriptionId, bool acknowledge)
    {
        SubscriptionName subscriptionName = SubscriptionName.FromProjectSubscription(projectId, subscriptionId);
        int messageCount = 0;
        SubscriberClient subscriber = await new SubscriberClientBuilder
        {
            SubscriptionName = subscriptionName,
            Settings = new SubscriberClient.Settings
            {
                AckExtensionWindow = TimeSpan.FromSeconds(4),
                AckDeadline = TimeSpan.FromSeconds(10),
                FlowControlSettings = new FlowControlSettings(maxOutstandingElementCount: 100, maxOutstandingByteCount: 10240)
            }
        }.BuildAsync();
        // SubscriberClient runs your message handle function on multiple
        // threads to maximize throughput.
        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

Folgen Sie der Einrichtungsanleitung für Go in der Kurzanleitung zur Verwendung von Clientbibliotheken, bevor Sie dieses Beispiel anwenden. Weitere Informationen finden Sie in der Referenzdokumentation zur Pub/Sub Go API.

import (
	"context"
	"fmt"
	"io"

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

func pullMsgsFlowControlSettings(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()

	sub := client.Subscription(subID)
	// MaxOutstandingMessages is the maximum number of unprocessed messages the
	// subscriber client will pull from the server before pausing. This also configures
	// the maximum number of concurrent handlers for received messages.
	//
	// For more information, see https://cloud.google.com/pubsub/docs/pull#streamingpull_dealing_with_large_backlogs_of_small_messages.
	sub.ReceiveSettings.MaxOutstandingMessages = 100
	// MaxOutstandingBytes is the maximum size of unprocessed messages,
	// that the subscriber client will pull from the server before pausing.
	sub.ReceiveSettings.MaxOutstandingBytes = 1e8
	err = sub.Receive(ctx, func(ctx context.Context, msg *pubsub.Message) {
		fmt.Fprintf(w, "Got message: %q\n", string(msg.Data))
		msg.Ack()
	})
	if err != nil {
		return fmt.Errorf("sub.Receive: %w", err)
	}
	return nil
}

Java

Folgen Sie der Einrichtungsanleitung für Java in der Kurzanleitung zur Verwendung von Clientbibliotheken, bevor Sie dieses Beispiel anwenden. Weitere Informationen finden Sie in der Referenzdokumentation zur Pub/Sub Java API.


import com.google.api.gax.batching.FlowControlSettings;
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 SubscribeWithFlowControlSettingsExample {
  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";

    subscribeWithFlowControlSettingsExample(projectId, subscriptionId);
  }

  public static void subscribeWithFlowControlSettingsExample(
      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;

    // The subscriber will pause the message stream and stop receiving more messsages from the
    // server if any one of the conditions is met.
    FlowControlSettings flowControlSettings =
        FlowControlSettings.newBuilder()
            // 1,000 outstanding messages. Must be >0. It controls the maximum number of messages
            // the subscriber receives before pausing the message stream.
            .setMaxOutstandingElementCount(1000L)
            // 100 MiB. Must be >0. It controls the maximum size of messages the subscriber
            // receives before pausing the message stream.
            .setMaxOutstandingRequestBytes(100L * 1024L * 1024L)
            .build();

    try {
      subscriber =
          Subscriber.newBuilder(subscriptionName, receiver)
              .setFlowControlSettings(flowControlSettings)
              .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 maxInProgress = 5;
// const timeout = 10;

// 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 subscribeWithFlowControlSettings(
  subscriptionNameOrId,
  maxInProgress,
  timeout
) {
  const subscriberOptions = {
    flowControl: {
      maxMessages: maxInProgress,
    },
  };

  // References an existing subscription.
  // Note that flow control settings are not persistent across subscribers.
  const subscription = pubSubClient.subscription(
    subscriptionNameOrId,
    subscriberOptions
  );

  console.log(
    `Subscriber to subscription ${subscription.name} is ready to receive messages at a controlled volume of ${maxInProgress} messages.`
  );

  const messageHandler = message => {
    console.log(`Received message: ${message.id}`);
    console.log(`\tData: ${message.data}`);
    console.log(`\tAttributes: ${message.attributes}`);

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

  subscription.on('message', messageHandler);

  // Wait a while for the subscription to run. (Part of the sample only.)
  setTimeout(() => {
    subscription.close();
  }, timeout * 1000);
}

Node.js

/**
 * TODO(developer): Uncomment these variables before running the sample.
 */
// const subscriptionNameOrId = 'YOUR_SUBSCRIPTION_NAME_OR_ID';
// const maxInProgress = 5;
// const timeout = 10;

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

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

async function subscribeWithFlowControlSettings(
  subscriptionNameOrId: string,
  maxInProgress: number,
  timeout: number
) {
  const subscriberOptions: SubscriberOptions = {
    flowControl: {
      maxMessages: maxInProgress,
    },
  };

  // References an existing subscription.
  // Note that flow control settings are not persistent across subscribers.
  const subscription = pubSubClient.subscription(
    subscriptionNameOrId,
    subscriberOptions
  );

  console.log(
    `Subscriber to subscription ${subscription.name} is ready to receive messages at a controlled volume of ${maxInProgress} messages.`
  );

  const messageHandler = (message: Message) => {
    console.log(`Received message: ${message.id}`);
    console.log(`\tData: ${message.data}`);
    console.log(`\tAttributes: ${message.attributes}`);

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

  subscription.on('message', messageHandler);

  // Wait a while for the subscription to run. (Part of the sample only.)
  setTimeout(() => {
    subscription.close();
  }, timeout * 1000);
}

Python

Folgen Sie der Einrichtungsanleitung für Python in der Kurzanleitung zur Verwendung von Clientbibliotheken, bevor Sie dieses Beispiel anwenden. Weitere Informationen finden Sie in der Referenzdokumentation zur Pub/Sub Python API.

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()
subscription_path = subscriber.subscription_path(project_id, subscription_id)

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

# Limit the subscriber to only have ten outstanding messages at a time.
flow_control = pubsub_v1.types.FlowControl(max_messages=10)

streaming_pull_future = subscriber.subscribe(
    subscription_path, callback=callback, flow_control=flow_control
)
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.

Ruby

Folgen Sie der Einrichtungsanleitung für Ruby in der Kurzanleitung zur Verwendung von Clientbibliotheken, bevor Sie dieses Beispiel anwenden. Weitere Informationen finden Sie in der Referenzdokumentation zur Pub/Sub Ruby API.

# subscription_id = "your-subscription-id"

pubsub = Google::Cloud::Pubsub.new

subscription = pubsub.subscription subscription_id
subscriber   = subscription.listen inventory: 10 do |received_message|
  puts "Received message: #{received_message.data}"
  received_message.acknowledge!
end

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

Nächste Schritte

Informationen zum Suchen und Filtern von Codebeispielen für andere Google Cloud -Produkte finden Sie im Google Cloud Beispielbrowser.