Memublikasikan pesan dengan setelan kontrol alur

Membuat klien penayang dengan setelan kontrol alur kustom dan menggunakannya untuk memublikasikan beberapa pesan.

Jelajahi lebih lanjut

Untuk dokumentasi mendetail yang menyertakan contoh kode ini, lihat artikel berikut:

• Kontrol alur

Contoh kode

C++

Sebelum mencoba contoh ini, ikuti petunjuk penyiapan C++ di panduan memulai Pub/Sub menggunakan library klien. Untuk informasi selengkapnya, lihat dokumentasi referensi API C++ Pub/Sub.

Untuk melakukan autentikasi ke Pub/Sub, siapkan Kredensial Default Aplikasi. Untuk mengetahui informasi selengkapnya, baca Menyiapkan autentikasi untuk lingkungan pengembangan lokal.

namespace pubsub = ::google::cloud::pubsub;
using ::google::cloud::future;
using ::google::cloud::Options;
using ::google::cloud::StatusOr;
[](std::string project_id, std::string topic_id) {
  auto topic = pubsub::Topic(std::move(project_id), std::move(topic_id));
  // Configure the publisher to block if either (1) 100 or more messages, or
  // (2) messages with 100MiB worth of data have not been acknowledged by the
  // service. By default the publisher never blocks, and its capacity is only
  // limited by the system's memory.
  auto publisher = pubsub::Publisher(pubsub::MakePublisherConnection(
      std::move(topic),
      Options{}
          .set<pubsub::MaxPendingMessagesOption>(100)
          .set<pubsub::MaxPendingBytesOption>(100 * 1024 * 1024L)
          .set<pubsub::FullPublisherActionOption>(
              pubsub::FullPublisherAction::kBlocks)));

  std::vector<future<void>> ids;
  for (char const* data : {"a", "b", "c"}) {
    ids.push_back(
        publisher.Publish(pubsub::MessageBuilder().SetData(data).Build())
            .then([data](future<StatusOr<std::string>> f) {
              auto s = f.get();
              if (!s) return;
              std::cout << "Sent '" << data << "' (" << *s << ")\n";
            }));
  }
  publisher.Flush();
  // Block until they are actually sent.
  for (auto& id : ids) id.get();
}

Go

Sebelum mencoba contoh ini, ikuti petunjuk penyiapan Go di panduan memulai Pub/Sub menggunakan library klien. Untuk informasi selengkapnya, lihat dokumentasi referensi API Go Pub/Sub.

Untuk melakukan autentikasi ke Pub/Sub, siapkan Kredensial Default Aplikasi. Untuk mengetahui informasi selengkapnya, baca Menyiapkan autentikasi untuk lingkungan pengembangan lokal.

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

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

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

	t := client.Topic(topicID)
	t.PublishSettings.FlowControlSettings = pubsub.FlowControlSettings{
		MaxOutstandingMessages: 100,                     // default 1000
		MaxOutstandingBytes:    10 * 1024 * 1024,        // default 0 (unlimited)
		LimitExceededBehavior:  pubsub.FlowControlBlock, // default Ignore, other options: Block and SignalError
	}

	var wg sync.WaitGroup
	var totalErrors uint64

	numMsgs := 1000
	// Rapidly publishing 1000 messages in a loop may be constrained by flow control.
	for i := 0; i < numMsgs; i++ {
		wg.Add(1)
		result := t.Publish(ctx, &pubsub.Message{
			Data: []byte("message #" + strconv.Itoa(i)),
		})
		go func(i int, res *pubsub.PublishResult) {
			fmt.Fprintf(w, "Publishing message %d\n", i)
			defer wg.Done()
			// The Get method blocks until a server-generated ID or
			// an error is returned for the published message.
			_, err := res.Get(ctx)
			if err != nil {
				// Error handling code can be added here.
				fmt.Fprintf(w, "Failed to publish: %v", err)
				atomic.AddUint64(&totalErrors, 1)
				return
			}
		}(i, result)
	}

	wg.Wait()

	if totalErrors > 0 {
		return fmt.Errorf("%d of %d messages did not publish successfully", totalErrors, numMsgs)
	}
	return nil
}

Java

Sebelum mencoba contoh ini, ikuti petunjuk penyiapan Java di panduan memulai Pub/Sub menggunakan library klien. Untuk informasi selengkapnya, lihat dokumentasi referensi API Java Pub/Sub.

Untuk melakukan autentikasi ke Pub/Sub, siapkan Kredensial Default Aplikasi. Untuk mengetahui informasi selengkapnya, baca Menyiapkan autentikasi untuk lingkungan pengembangan lokal.

import com.google.api.core.ApiFuture;
import com.google.api.core.ApiFutures;
import com.google.api.gax.batching.BatchingSettings;
import com.google.api.gax.batching.FlowControlSettings;
import com.google.api.gax.batching.FlowController.LimitExceededBehavior;
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.ArrayList;
import java.util.List;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;

public class PublishWithFlowControlExample {
  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";

    publishWithFlowControlExample(projectId, topicId);
  }

  public static void publishWithFlowControlExample(String projectId, String topicId)
      throws IOException, ExecutionException, InterruptedException {
    TopicName topicName = TopicName.of(projectId, topicId);
    Publisher publisher = null;
    List<ApiFuture<String>> messageIdFutures = new ArrayList<>();

    try {
      // Configure how many messages the publisher client can hold in memory
      // and what to do when messages exceed the limit.
      FlowControlSettings flowControlSettings =
          FlowControlSettings.newBuilder()
              // Block more messages from being published when the limit is reached. The other
              // options are Ignore (or continue publishing) and ThrowException (or error out).
              .setLimitExceededBehavior(LimitExceededBehavior.Block)
              .setMaxOutstandingRequestBytes(10 * 1024 * 1024L) // 10 MiB
              .setMaxOutstandingElementCount(100L) // 100 messages
              .build();

      // By default, messages are not batched.
      BatchingSettings batchingSettings =
          BatchingSettings.newBuilder().setFlowControlSettings(flowControlSettings).build();

      publisher = Publisher.newBuilder(topicName).setBatchingSettings(batchingSettings).build();

      // Publish 1000 messages in quick succession may be constrained by publisher flow control.
      for (int i = 0; i < 1000; i++) {
        String message = "message " + i;
        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);
        messageIdFutures.add(messageIdFuture);
      }
    } finally {
      // Wait on any pending publish requests.
      List<String> messageIds = ApiFutures.allAsList(messageIdFutures).get();

      System.out.println(
          "Published " + messageIds.size() + " messages with flow control settings.");

      if (publisher != null) {
        // When finished with the publisher, shut down to free up resources.
        publisher.shutdown();
        publisher.awaitTermination(1, TimeUnit.MINUTES);
      }
    }
  }
}

Node.js

/**
 * TODO(developer): Uncomment this variable before running the sample.
 */
// const topicNameOrId = 'YOUR_TOPIC_NAME_OR_ID';

// 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 publishWithFlowControl(topicNameOrId) {
  // Create publisher options
  const options = {
    flowControlOptions: {
      maxOutstandingMessages: 50,
      maxOutstandingBytes: 10 * 1024 * 1024, // 10 MB
    },
  };

  // Get a publisher.
  const topic = pubSubClient.topic(topicNameOrId, options);

  // For flow controlled publishing, we'll use a publisher flow controller
  // instead of `topic.publish()`.
  const flow = topic.flowControlled();

  // Publish messages in a fast loop.
  const testMessage = {data: Buffer.from('test!')};
  for (let i = 0; i < 1000; i++) {
    // You can also just `await` on `publish()` unconditionally, but if
    // you want to avoid pausing to the event loop on each iteration,
    // you can manually check the return value before doing so.
    const wait = flow.publish(testMessage);
    if (wait) {
      await wait;
    }
  }

  // Wait on any pending publish requests. Note that you can call `all()`
  // earlier if you like, and it will return a Promise for all messages
  // that have been sent to `flowController.publish()` so far.
  const messageIds = await flow.all();
  console.log(`Published ${messageIds.length} with flow control settings.`);
}

Node.js

/**
 * TODO(developer): Uncomment this variable before running the sample.
 */
// const topicNameOrId = 'YOUR_TOPIC_NAME_OR_ID';

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

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

async function publishWithFlowControl(topicNameOrId: string) {
  // Create publisher options
  const options: PublishOptions = {
    flowControlOptions: {
      maxOutstandingMessages: 50,
      maxOutstandingBytes: 10 * 1024 * 1024, // 10 MB
    },
  };

  // Get a publisher.
  const topic = pubSubClient.topic(topicNameOrId, options);

  // For flow controlled publishing, we'll use a publisher flow controller
  // instead of `topic.publish()`.
  const flow = topic.flowControlled();

  // Publish messages in a fast loop.
  const testMessage = {data: Buffer.from('test!')};
  for (let i = 0; i < 1000; i++) {
    // You can also just `await` on `publish()` unconditionally, but if
    // you want to avoid pausing to the event loop on each iteration,
    // you can manually check the return value before doing so.
    const wait = flow.publish(testMessage);
    if (wait) {
      await wait;
    }
  }

  // Wait on any pending publish requests. Note that you can call `all()`
  // earlier if you like, and it will return a Promise for all messages
  // that have been sent to `flowController.publish()` so far.
  const messageIds = await flow.all();
  console.log(`Published ${messageIds.length} with flow control settings.`);
}

Python

Sebelum mencoba contoh ini, ikuti petunjuk penyiapan Python di panduan memulai Pub/Sub menggunakan library klien. Untuk informasi selengkapnya, lihat dokumentasi referensi API Python Pub/Sub.

Untuk melakukan autentikasi ke Pub/Sub, siapkan Kredensial Default Aplikasi. Untuk mengetahui informasi selengkapnya, baca Menyiapkan autentikasi untuk lingkungan pengembangan lokal.

from concurrent import futures
from google.cloud import pubsub_v1
from google.cloud.pubsub_v1.types import (
    LimitExceededBehavior,
    PublisherOptions,
    PublishFlowControl,
)

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

# Configure how many messages the publisher client can hold in memory
# and what to do when messages exceed the limit.
flow_control_settings = PublishFlowControl(
    message_limit=100,  # 100 messages
    byte_limit=10 * 1024 * 1024,  # 10 MiB
    limit_exceeded_behavior=LimitExceededBehavior.BLOCK,
)
publisher = pubsub_v1.PublisherClient(
    publisher_options=PublisherOptions(flow_control=flow_control_settings)
)
topic_path = publisher.topic_path(project_id, topic_id)
publish_futures = []

# Resolve the publish future in a separate thread.
def callback(publish_future: pubsub_v1.publisher.futures.Future) -> None:
    message_id = publish_future.result()
    print(message_id)

# Publish 1000 messages in quick succession may be constrained by
# publisher flow control.
for n in range(1, 1000):
    data_str = f"Message number {n}"
    # Data must be a bytestring
    data = data_str.encode("utf-8")
    publish_future = publisher.publish(topic_path, data)
    # Non-blocking. Allow the publisher client to batch messages.
    publish_future.add_done_callback(callback)
    publish_futures.append(publish_future)

futures.wait(publish_futures, return_when=futures.ALL_COMPLETED)

print(f"Published messages with flow control settings to {topic_path}.")

Ruby

Sebelum mencoba contoh ini, ikuti petunjuk penyiapan Ruby di panduan memulai Pub/Sub menggunakan library klien. Untuk informasi selengkapnya, lihat dokumentasi referensi API Ruby Pub/Sub.

Untuk melakukan autentikasi ke Pub/Sub, siapkan Kredensial Default Aplikasi. Untuk mengetahui informasi selengkapnya, baca Menyiapkan autentikasi untuk lingkungan pengembangan lokal.

# topic_id = "your-topic-id"

pubsub = Google::Cloud::Pubsub.new

topic = pubsub.topic topic_id, async: {
  # Configure how many messages the publisher client can hold in memory
  # and what to do when messages exceed the limit.
  flow_control: {
    message_limit: 100,
    byte_limit: 10 * 1024 * 1024, # 10 MiB
    # Block more messages from being published when the limit is reached. The
    # other options are :ignore and :error.
    limit_exceeded_behavior: :block
  }
}
# Rapidly publishing 1000 messages in a loop may be constrained by flow control.
1000.times do |i|
  topic.publish_async "message #{i}" do |result|
    raise "Failed to publish the message." unless result.succeeded?
  end
end

# Stop the async_publisher to send all queued messages immediately.
topic.async_publisher.stop.wait!
puts "Published messages with flow control settings to #{topic_id}."

Langkah selanjutnya

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