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Como publicar mensagens em tópicos do Lite

Nesta página, explicamos como publicar mensagens em tópicos do Lite. É possível publicar mensagens com a biblioteca de cliente do Pub/Sub Lite para Java.

Depois de publicar mensagens e criar uma assinatura do Lite em um tópico, é possível receber mensagens da assinatura do Lite.

Formato de mensagem

Uma mensagem consiste em campos com os dados e os metadados da mensagem. Especifique qualquer um dos itens a seguir na mensagem:

A biblioteca de cliente atribui a mensagem automaticamente a uma partição, e o serviço Pub/Sub Lite adiciona os campos a seguir à mensagem:

  • Um ID de mensagem exclusivo na partição
  • Um carimbo de data/hora para quando o serviço Pub/Sub Lite armazena a mensagem na partição

Como publicar mensagens

Para publicar mensagens, solicite uma conexão de streaming para o tópico do Lite e, em seguida, envie mensagens pela conexão de streaming.

O exemplo a seguir mostra como publicar mensagens em um tópico do Lite:

Go

Antes de tentar esse exemplo, siga as instruções de configuração do Go em Guia de início rápido: como usar bibliotecas de cliente. Para mais informações, consulte a documentação de referência da API Pub/Sub Go. 


package main

import (
	"context"
	"flag"
	"fmt"
	"log"
	"sync"

	"cloud.google.com/go/pubsub"
	"cloud.google.com/go/pubsublite/pscompat"
	"golang.org/x/sync/errgroup"
)

func main() {
	// NOTE: Set these flags for an existing Pub/Sub Lite topic when running this
	// sample.
	projectID := flag.String("project_id", "", "Cloud Project ID")
	zone := flag.String("zone", "", "Cloud Zone where the topic resides, e.g. us-central1-a")
	topicID := flag.String("topic_id", "", "Existing Pub/Sub Lite topic")
	messageCount := flag.Int("message_count", 100, "The number of messages to send")
	flag.Parse()

	ctx := context.Background()
	topicPath := fmt.Sprintf("projects/%s/locations/%s/topics/%s", *projectID, *zone, *topicID)

	// Create the publisher client.
	publisher, err := pscompat.NewPublisherClient(ctx, topicPath)
	if err != nil {
		log.Fatalf("pscompat.NewPublisherClient error: %v", err)
	}

	// Ensure the publisher will be shut down.
	defer publisher.Stop()

	// Collect any messages that need to be republished with a new publisher
	// client.
	var toRepublish []*pubsub.Message
	var toRepublishMu sync.Mutex

	// Publish messages. Messages are automatically batched.
	g := new(errgroup.Group)
	for i := 0; i < *messageCount; i++ {
		msg := &pubsub.Message{
			Data: []byte(fmt.Sprintf("message-%d", i)),
		}
		result := publisher.Publish(ctx, msg)

		g.Go(func() error {
			// Get blocks until the result is ready.
			id, err := result.Get(ctx)
			if err != nil {
				// NOTE: A failed PublishResult indicates that the publisher client
				// encountered a fatal error and has permanently terminated. After the
				// fatal error has been resolved, a new publisher client instance must
				// be created to republish failed messages.
				fmt.Printf("Publish error: %v\n", err)
				toRepublishMu.Lock()
				toRepublish = append(toRepublish, msg)
				toRepublishMu.Unlock()
				return err
			}

			// Metadata decoded from the id contains the partition and offset.
			metadata, err := pscompat.ParseMessageMetadata(id)
			if err != nil {
				fmt.Printf("Failed to parse message metadata %q: %v\n", id, err)
				return err
			}
			fmt.Printf("Published: partition=%d, offset=%d\n", metadata.Partition, metadata.Offset)
			return nil
		})
	}
	if err := g.Wait(); err != nil {
		fmt.Printf("Publishing finished with error: %v\n", err)
	}
	fmt.Printf("Published %d messages\n", *messageCount-len(toRepublish))

	// Print the error that caused the publisher client to terminate (if any),
	// which may contain more context than PublishResults.
	if err := publisher.Error(); err != nil {
		fmt.Printf("Publisher client terminated due to error: %v\n", publisher.Error())
	}
}

Java

Antes de executar este exemplo, siga as instruções de configuração do Java nas bibliotecas de cliente do Pub/Sub Lite. 

import com.google.api.core.ApiFuture;
import com.google.api.core.ApiFutures;
import com.google.api.gax.rpc.ApiException;
import com.google.cloud.pubsublite.CloudRegion;
import com.google.cloud.pubsublite.CloudZone;
import com.google.cloud.pubsublite.MessageMetadata;
import com.google.cloud.pubsublite.ProjectNumber;
import com.google.cloud.pubsublite.TopicName;
import com.google.cloud.pubsublite.TopicPath;
import com.google.cloud.pubsublite.cloudpubsub.Publisher;
import com.google.cloud.pubsublite.cloudpubsub.PublisherSettings;
import com.google.protobuf.ByteString;
import com.google.pubsub.v1.PubsubMessage;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ExecutionException;

public class PublisherExample {

  public static void main(String... args) throws Exception {
    // TODO(developer): Replace these variables before running the sample.
    String cloudRegion = "your-cloud-region";
    char zoneId = 'b';
    // Choose an existing topic for the publish example to work.
    String topicId = "your-topic-id";
    long projectNumber = Long.parseLong("123456789");
    int messageCount = 100;

    publisherExample(cloudRegion, zoneId, projectNumber, topicId, messageCount);
  }

  // Publish messages to a topic.
  public static void publisherExample(
      String cloudRegion, char zoneId, long projectNumber, String topicId, int messageCount)
      throws ApiException, ExecutionException, InterruptedException {

    TopicPath topicPath =
        TopicPath.newBuilder()
            .setProject(ProjectNumber.of(projectNumber))
            .setLocation(CloudZone.of(CloudRegion.of(cloudRegion), zoneId))
            .setName(TopicName.of(topicId))
            .build();
    Publisher publisher = null;
    List<ApiFuture<String>> futures = new ArrayList<>();

    try {
      PublisherSettings publisherSettings =
          PublisherSettings.newBuilder().setTopicPath(topicPath).build();

      publisher = Publisher.create(publisherSettings);

      // Start the publisher. Upon successful starting, its state will become RUNNING.
      publisher.startAsync().awaitRunning();

      for (int i = 0; i < messageCount; i++) {
        String message = "message-" + i;

        // Convert the message to a byte string.
        ByteString data = ByteString.copyFromUtf8(message);
        PubsubMessage pubsubMessage = PubsubMessage.newBuilder().setData(data).build();

        // Publish a message. Messages are automatically batched.
        ApiFuture<String> future = publisher.publish(pubsubMessage);
        futures.add(future);
      }
    } finally {
      ArrayList<MessageMetadata> metadata = new ArrayList<>();
      List<String> ackIds = ApiFutures.allAsList(futures).get();
      for (String id : ackIds) {
        // Decoded metadata contains partition and offset.
        metadata.add(MessageMetadata.decode(id));
      }
      System.out.println(metadata + "\nPublished " + ackIds.size() + " messages.");

      if (publisher != null) {
        // Shut down the publisher.
        publisher.stopAsync().awaitTerminated();
        System.out.println("Publisher is shut down.");
      }
    }
  }
}

Python

Antes de executar este exemplo, siga as instruções de configuração do Java nas bibliotecas de cliente do Pub/Sub Lite. 

from google.cloud.pubsublite.cloudpubsub import PublisherClient
from google.cloud.pubsublite.types import (
    CloudRegion,
    CloudZone,
    MessageMetadata,
    TopicPath,
)

# TODO(developer):
# project_number = 1122334455
# cloud_region = "us-central1"
# zone_id = "a"
# topic_id = "your-topic-id"

location = CloudZone(CloudRegion(cloud_region), zone_id)
topic_path = TopicPath(project_number, location, topic_id)

# PublisherClient() must be used in a `with` block or have __enter__() called before use.
with PublisherClient() as publisher_client:
    data = "Hello world!"
    api_future = publisher_client.publish(topic_path, data.encode("utf-8"))
    # result() blocks. To resolve API futures asynchronously, use add_done_callback().
    message_id = api_future.result()
    message_metadata = MessageMetadata.decode(message_id)
    print(
        f"Published a message to partition {message_metadata.partition.value} and offset {message_metadata.cursor.offset}."
    )

A biblioteca de cliente envia mensagens de forma assíncrona e lida com erros. Se ocorrer um erro, a biblioteca de cliente enviará a mensagem novamente.

  1. O serviço do Pub/Sub Lite fecha o stream.
  2. A biblioteca de cliente armazena em buffer as mensagens e restabelece uma conexão com o tópico do Lite.
  3. A biblioteca cliente envia as mensagens em ordem.

Depois de publicar uma mensagem, o serviço Pub/Sub Lite armazena a mensagem em uma partição e retorna os ID da mensagem para o editor.

Como usar chaves de ordenação

Se as mensagens tiverem a mesma chave de ordenação, a biblioteca de cliente atribuirá as mensagens à mesma partição. A chave de ordenação precisa ser uma string de, no máximo, 1.024 bytes.

A chave de ordenação está no campo key de uma mensagem. É possível definir chaves de ordenação com a biblioteca de cliente.

Go

Antes de tentar esse exemplo, siga as instruções de configuração do Go em Guia de início rápido: como usar bibliotecas de cliente. Para mais informações, consulte a documentação de referência da API Pub/Sub Go. 

import (
	"context"
	"fmt"
	"io"

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

func publishWithOrderingKey(w io.Writer, projectID, zone, topicID string, messageCount int) error {
	// projectID := "my-project-id"
	// zone := "us-central1-a"
	// topicID := "my-topic"
	// messageCount := 10
	ctx := context.Background()
	topicPath := fmt.Sprintf("projects/%s/locations/%s/topics/%s", projectID, zone, topicID)

	// Create the publisher client.
	publisher, err := pscompat.NewPublisherClient(ctx, topicPath)
	if err != nil {
		return fmt.Errorf("pscompat.NewPublisherClient error: %v", err)
	}

	// Ensure the publisher will be shut down.
	defer publisher.Stop()

	// Messages of the same ordering key will always get published to the same
	// partition. When OrderingKey is unset, messages can get published to
	// different partitions if more than one partition exists for the topic.
	var results []*pubsub.PublishResult
	for i := 0; i < messageCount; i++ {
		r := publisher.Publish(ctx, &pubsub.Message{
			OrderingKey: "test_ordering_key",
			Data:        []byte(fmt.Sprintf("message-%d", i)),
		})
		results = append(results, r)
	}

	// Print publish results.
	var publishedCount int
	for _, r := range results {
		// Get blocks until the result is ready.
		id, err := r.Get(ctx)
		if err != nil {
			// NOTE: A failed PublishResult indicates that the publisher client
			// encountered a fatal error and has permanently terminated. After the
			// fatal error has been resolved, a new publisher client instance must be
			// created to republish failed messages.
			fmt.Fprintf(w, "Publish error: %v\n", err)
			continue
		}

		// Metadata decoded from the id contains the partition and offset.
		metadata, err := pscompat.ParseMessageMetadata(id)
		if err != nil {
			return fmt.Errorf("failed to parse message metadata %q: %v", id, err)
		}
		fmt.Fprintf(w, "Published: partition=%d, offset=%d\n", metadata.Partition, metadata.Offset)
		publishedCount++
	}

	fmt.Fprintf(w, "Published %d messages with ordering key\n", publishedCount)
	return publisher.Error()
}

Java

Antes de executar este exemplo, siga as instruções de configuração do Java nas bibliotecas de cliente do Pub/Sub Lite. 

import com.google.api.core.ApiFuture;
import com.google.api.gax.rpc.ApiException;
import com.google.cloud.pubsublite.CloudRegion;
import com.google.cloud.pubsublite.CloudZone;
import com.google.cloud.pubsublite.MessageMetadata;
import com.google.cloud.pubsublite.ProjectNumber;
import com.google.cloud.pubsublite.TopicName;
import com.google.cloud.pubsublite.TopicPath;
import com.google.cloud.pubsublite.cloudpubsub.Publisher;
import com.google.cloud.pubsublite.cloudpubsub.PublisherSettings;
import com.google.protobuf.ByteString;
import com.google.pubsub.v1.PubsubMessage;
import java.util.concurrent.ExecutionException;

public class PublishWithOrderingKeyExample {
  public static void main(String... args) throws Exception {
    // TODO(developer): Replace these variables before running the sample.
    String cloudRegion = "your-cloud-region";
    char zoneId = 'b';
    // Choose an existing topic for the publish example to work.
    String topicId = "your-topic-id";
    long projectNumber = Long.parseLong("123456789");

    publishWithOrderingKeyExample(cloudRegion, zoneId, projectNumber, topicId);
  }

  // Publish a message to a topic with an ordering key.
  public static void publishWithOrderingKeyExample(
      String cloudRegion, char zoneId, long projectNumber, String topicId)
      throws ApiException, ExecutionException, InterruptedException {

    TopicPath topicPath =
        TopicPath.newBuilder()
            .setProject(ProjectNumber.of(projectNumber))
            .setLocation(CloudZone.of(CloudRegion.of(cloudRegion), zoneId))
            .setName(TopicName.of(topicId))
            .build();

    PublisherSettings publisherSettings =
        PublisherSettings.newBuilder().setTopicPath(topicPath).build();

    Publisher publisher = Publisher.create(publisherSettings);

    // Start the publisher. Upon successful starting, its state will become RUNNING.
    publisher.startAsync().awaitRunning();

    String message = "message-with-ordering-key";

    // Convert the message to a byte string.
    ByteString data = ByteString.copyFromUtf8(message);
    PubsubMessage pubsubMessage =
        PubsubMessage.newBuilder()
            .setData(data)
            // Messages of the same ordering key will always get published to the
            // same partition. When OrderingKey is unset, messages can get published
            // to different partitions if more than one partition exists for the topic.
            .setOrderingKey("testing")
            .build();

    // Publish a message.
    ApiFuture<String> future = publisher.publish(pubsubMessage);

    // Shut down the publisher.
    publisher.stopAsync().awaitTerminated();

    String ackId = future.get();
    MessageMetadata metadata = MessageMetadata.decode(ackId);
    System.out.println("Published a message with ordering key:\n" + metadata);
  }
}

Python

Antes de executar este exemplo, siga as instruções de configuração do Java nas bibliotecas de cliente do Pub/Sub Lite. 

from google.cloud.pubsublite.cloudpubsub import PublisherClient
from google.cloud.pubsublite.types import (
    CloudRegion,
    CloudZone,
    MessageMetadata,
    TopicPath,
)

# TODO(developer):
# project_number = 1122334455
# cloud_region = "us-central1"
# zone_id = "a"
# topic_id = "your-topic-id"
# num_messages = 100

location = CloudZone(CloudRegion(cloud_region), zone_id)
topic_path = TopicPath(project_number, location, topic_id)

# PublisherClient() must be used in a `with` block or have __enter__() called before use.
with PublisherClient() as publisher_client:
    for message in range(num_messages):
        data = f"{message}"
        # Messages of the same ordering key will always get published to the same partition.
        # When ordering_key is unset, messsages can get published ot different partitions if
        # more than one partition exists for the topic.
        api_future = publisher_client.publish(
            topic_path, data.encode("utf-8"), ordering_key="testing"
        )
        # result() blocks. To resolve api futures asynchronously, use add_done_callback().
        message_id = api_future.result()
        message_metadata = MessageMetadata.decode(message_id)
        print(
            f"Published {data} to partition {message_metadata.partition.value} and offset {message_metadata.cursor.offset}."
        )

print(
    f"Finished publishing {num_messages} messages with an ordering key to {str(topic_path)}."
)

É possível enviar várias mensagens para a mesma partição usando as chaves de ordem. Assim, os assinantes recebem as mensagens na ordem. A biblioteca de cliente pode atribuir várias chaves de ordenação à mesma partição.

Como usar atributos

Atributos da mensagem são pares de chave-valor com metadados sobre a mensagem. Os atributos podem ser strings de texto ou de byte.

Os atributos estão no campo attributes de uma mensagem. Você pode definir atributos com a biblioteca de cliente.

Go

Antes de tentar esse exemplo, siga as instruções de configuração do Go em Guia de início rápido: como usar bibliotecas de cliente. Para mais informações, consulte a documentação de referência da API Pub/Sub Go. 

import (
	"context"
	"fmt"
	"io"

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

func publishWithCustomAttributes(w io.Writer, projectID, zone, topicID string) error {
	// projectID := "my-project-id"
	// zone := "us-central1-a"
	// topicID := "my-topic"
	ctx := context.Background()
	topicPath := fmt.Sprintf("projects/%s/locations/%s/topics/%s", projectID, zone, topicID)

	// Create the publisher client.
	publisher, err := pscompat.NewPublisherClient(ctx, topicPath)
	if err != nil {
		return fmt.Errorf("pscompat.NewPublisherClient error: %v", err)
	}

	// Ensure the publisher will be shut down.
	defer publisher.Stop()

	// Publish a message with custom attributes.
	result := publisher.Publish(ctx, &pubsub.Message{
		Data: []byte("message-with-custom-attributes"),
		Attributes: map[string]string{
			"year":   "2020",
			"author": "unknown",
		},
	})

	// Get blocks until the result is ready.
	id, err := result.Get(ctx)
	if err != nil {
		return fmt.Errorf("publish error: %v", err)
	}

	fmt.Fprintf(w, "Published a message with custom attributes: %v\n", id)
	return publisher.Error()
}

Java

Antes de executar este exemplo, siga as instruções de configuração do Java nas bibliotecas de cliente do Pub/Sub Lite. 

import com.google.api.core.ApiFuture;
import com.google.api.gax.rpc.ApiException;
import com.google.cloud.pubsublite.CloudRegion;
import com.google.cloud.pubsublite.CloudZone;
import com.google.cloud.pubsublite.MessageMetadata;
import com.google.cloud.pubsublite.ProjectNumber;
import com.google.cloud.pubsublite.TopicName;
import com.google.cloud.pubsublite.TopicPath;
import com.google.cloud.pubsublite.cloudpubsub.Publisher;
import com.google.cloud.pubsublite.cloudpubsub.PublisherSettings;
import com.google.common.collect.ImmutableMap;
import com.google.protobuf.ByteString;
import com.google.pubsub.v1.PubsubMessage;
import java.util.concurrent.ExecutionException;

public class PublishWithCustomAttributesExample {
  public static void main(String... args) throws Exception {
    // TODO(developer): Replace these variables before running the sample.
    String cloudRegion = "your-cloud-region";
    char zoneId = 'b';
    // Choose an existing topic for the publish example to work.
    String topicId = "your-topic-id";
    long projectNumber = Long.parseLong("123456789");

    publishWithCustomAttributesExample(cloudRegion, zoneId, projectNumber, topicId);
  }

  // Publish messages to a topic with custom attributes.
  public static void publishWithCustomAttributesExample(
      String cloudRegion, char zoneId, long projectNumber, String topicId)
      throws ApiException, ExecutionException, InterruptedException {

    TopicPath topicPath =
        TopicPath.newBuilder()
            .setProject(ProjectNumber.of(projectNumber))
            .setLocation(CloudZone.of(CloudRegion.of(cloudRegion), zoneId))
            .setName(TopicName.of(topicId))
            .build();

    PublisherSettings publisherSettings =
        PublisherSettings.newBuilder().setTopicPath(topicPath).build();

    Publisher publisher = Publisher.create(publisherSettings);

    // Start the publisher. Upon successful starting, its state will become RUNNING.
    publisher.startAsync().awaitRunning();

    String message = "message-with-custom-attributes";

    // Convert the message to a byte string.
    ByteString data = ByteString.copyFromUtf8(message);
    PubsubMessage pubsubMessage =
        PubsubMessage.newBuilder()
            .setData(data)
            // Add two sets of custom attributes to the message.
            .putAllAttributes(ImmutableMap.of("year", "2020", "author", "unknown"))
            .build();

    // Publish a message.
    ApiFuture<String> future = publisher.publish(pubsubMessage);

    // Shut down the publisher.
    publisher.stopAsync().awaitTerminated();

    String ackId = future.get();
    MessageMetadata metadata = MessageMetadata.decode(ackId);
    System.out.println("Published a message with custom attributes:\n" + metadata);
  }
}

Python

Antes de executar este exemplo, siga as instruções de configuração do Java nas bibliotecas de cliente do Pub/Sub Lite. 

from google.cloud.pubsublite.cloudpubsub import PublisherClient
from google.cloud.pubsublite.types import (
    CloudRegion,
    CloudZone,
    MessageMetadata,
    TopicPath,
)

# TODO(developer):
# project_number = 1122334455
# cloud_region = "us-central1"
# zone_id = "a"
# topic_id = "your-topic-id"

location = CloudZone(CloudRegion(cloud_region), zone_id)
topic_path = TopicPath(project_number, location, topic_id)

# PublisherClient() must be used in a `with` block or have __enter__() called before use.
with PublisherClient() as publisher_client:
    data = "Hello world!"
    api_future = publisher_client.publish(
        topic_path, data.encode("utf-8"), year="2020", author="unknown",
    )
    # result() blocks. To resolve api futures asynchronously, use add_done_callback().
    message_id = api_future.result()
    message_metadata = MessageMetadata.decode(message_id)
    print(
        f"Published {data} to partition {message_metadata.partition.value} and offset {message_metadata.cursor.offset}."
    )

print(f"Finished publishing a message with custom attributes to {str(topic_path)}.")

Os atributos podem indicar como processar uma mensagem. Os assinantes podem analisar o campo attributes de uma mensagem e processar a mensagem de acordo com os atributos dela.

Mensagens em lote

A biblioteca de cliente publica mensagens em lotes. Os lotes maiores usam menos recursos de computação, mas aumentam a latência. É possível alterar o tamanho do lote com configurações de lote.

A tabela a seguir lista as configurações de lote que podem ser definidas:

Configuração Descrição Padrão
Tamanho da solicitação O tamanho máximo, em bytes, do lote. 3.5 MiB
número de mensagens O número máximo de mensagens em um lote. 1.000 mensagens
Atraso na publicação O tempo, em milissegundos, entre adicionar a mensagem a um lote e enviá-lo ao tópico do Lite. 50 milissegundos

É possível definir configurações em lote com a biblioteca de cliente.

Go

Antes de tentar esse exemplo, siga as instruções de configuração do Go em Guia de início rápido: como usar bibliotecas de cliente. Para mais informações, consulte a documentação de referência da API Pub/Sub Go. 

import (
	"context"
	"fmt"
	"io"
	"time"

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

func publishWithBatchSettings(w io.Writer, projectID, zone, topicID string, messageCount int) error {
	// projectID := "my-project-id"
	// zone := "us-central1-a"
	// topicID := "my-topic"
	// messageCount := 10
	ctx := context.Background()
	topicPath := fmt.Sprintf("projects/%s/locations/%s/topics/%s", projectID, zone, topicID)

	// Batch settings control how the publisher batches messages. These settings
	// apply per partition.
	// See https://pkg.go.dev/cloud.google.com/go/pubsublite/pscompat#pkg-variables
	// for DefaultPublishSettings.
	settings := pscompat.PublishSettings{
		ByteThreshold:  5 * 1024, // 5 KiB
		CountThreshold: 1000,     // 1,000 messages
		DelayThreshold: 100 * time.Millisecond,
	}

	// Create the publisher client.
	publisher, err := pscompat.NewPublisherClientWithSettings(ctx, topicPath, settings)
	if err != nil {
		return fmt.Errorf("pscompat.NewPublisherClientWithSettings error: %v", err)
	}

	// Ensure the publisher will be shut down.
	defer publisher.Stop()

	// Publish requests are sent to the server based on request size, message
	// count and time since last publish, whichever condition is met first.
	var results []*pubsub.PublishResult
	for i := 0; i < messageCount; i++ {
		r := publisher.Publish(ctx, &pubsub.Message{
			Data: []byte(fmt.Sprintf("message-%d", i)),
		})
		results = append(results, r)
	}

	// Print publish results.
	var publishedCount int
	for _, r := range results {
		// Get blocks until the result is ready.
		id, err := r.Get(ctx)
		if err != nil {
			// NOTE: A failed PublishResult indicates that the publisher client
			// encountered a fatal error and has permanently terminated. After the
			// fatal error has been resolved, a new publisher client instance must be
			// created to republish failed messages.
			fmt.Fprintf(w, "Publish error: %v\n", err)
			continue
		}
		fmt.Fprintf(w, "Published: %v\n", id)
		publishedCount++
	}

	fmt.Fprintf(w, "Published %d messages with batch settings\n", publishedCount)
	return publisher.Error()
}

Java

Antes de executar este exemplo, siga as instruções de configuração do Java nas bibliotecas de cliente do Pub/Sub Lite. 

import com.google.api.core.ApiFuture;
import com.google.api.core.ApiFutures;
import com.google.api.gax.batching.BatchingSettings;
import com.google.api.gax.rpc.ApiException;
import com.google.cloud.pubsublite.CloudRegion;
import com.google.cloud.pubsublite.CloudZone;
import com.google.cloud.pubsublite.MessageMetadata;
import com.google.cloud.pubsublite.ProjectNumber;
import com.google.cloud.pubsublite.TopicName;
import com.google.cloud.pubsublite.TopicPath;
import com.google.cloud.pubsublite.cloudpubsub.Publisher;
import com.google.cloud.pubsublite.cloudpubsub.PublisherSettings;
import com.google.protobuf.ByteString;
import com.google.pubsub.v1.PubsubMessage;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ExecutionException;
import org.threeten.bp.Duration;

public class PublishWithBatchSettingsExample {
  public static void main(String... args) throws Exception {
    // TODO(developer): Replace these variables before running the sample.
    String cloudRegion = "your-cloud-region";
    char zoneId = 'b';
    // Choose an existing topic for the publish example to work.
    String topicId = "your-topic-id";
    long projectNumber = Long.parseLong("123456789");
    int messageCount = 100;

    publishWithBatchSettingsExample(cloudRegion, zoneId, projectNumber, topicId, messageCount);
  }

  // Publish messages to a topic with batch settings.
  public static void publishWithBatchSettingsExample(
      String cloudRegion, char zoneId, long projectNumber, String topicId, int messageCount)
      throws ApiException, ExecutionException, InterruptedException {

    TopicPath topicPath =
        TopicPath.newBuilder()
            .setProject(ProjectNumber.of(projectNumber))
            .setLocation(CloudZone.of(CloudRegion.of(cloudRegion), zoneId))
            .setName(TopicName.of(topicId))
            .build();
    Publisher publisher = null;
    List<ApiFuture<String>> futures = new ArrayList<>();

    try {
      // Batch settings control how the publisher batches messages
      long requestBytesThreshold = 5000L; // default : 3_500_000 bytes
      long messageCountBatchSize = 100L; // default : 1000L message
      Duration publishDelayThreshold = Duration.ofMillis(100); // default : 50 ms

      // Publish request get triggered based on request size, messages count & time since last
      // publish, whichever condition is met first.
      BatchingSettings batchingSettings =
          BatchingSettings.newBuilder()
              .setRequestByteThreshold(requestBytesThreshold)
              .setElementCountThreshold(messageCountBatchSize)
              .setDelayThreshold(publishDelayThreshold)
              .build();

      PublisherSettings publisherSettings =
          PublisherSettings.newBuilder()
              .setTopicPath(topicPath)
              .setBatchingSettings(batchingSettings)
              .build();

      publisher = Publisher.create(publisherSettings);

      // Start the publisher. Upon successful starting, its state will become RUNNING.
      publisher.startAsync().awaitRunning();

      for (int i = 0; i < messageCount; i++) {
        String message = "message-" + i;

        // Convert the message to a byte string.
        ByteString data = ByteString.copyFromUtf8(message);
        PubsubMessage pubsubMessage = PubsubMessage.newBuilder().setData(data).build();

        // Publish a message.
        ApiFuture<String> future = publisher.publish(pubsubMessage);
        futures.add(future);
      }
    } finally {
      ArrayList<MessageMetadata> metadata = new ArrayList<>();
      List<String> ackIds = ApiFutures.allAsList(futures).get();
      System.out.println("Published " + ackIds.size() + " messages with batch settings.");

      if (publisher != null) {
        // Shut down the publisher.
        publisher.stopAsync().awaitTerminated();
      }
    }
  }
}

Python

Antes de executar este exemplo, siga as instruções de configuração do Java nas bibliotecas de cliente do Pub/Sub Lite. 

from google.cloud.pubsub_v1.types import BatchSettings
from google.cloud.pubsublite.cloudpubsub import PublisherClient
from google.cloud.pubsublite.types import (
    CloudRegion,
    CloudZone,
    MessageMetadata,
    TopicPath,
)

# TODO(developer):
# project_number = 1122334455
# cloud_region = "us-central1"
# zone_id = "a"
# topic_id = "your-topic-id"
# num_messages = 100

location = CloudZone(CloudRegion(cloud_region), zone_id)
topic_path = TopicPath(project_number, location, topic_id)
batch_setttings = BatchSettings(
    # 2 MiB. Default to 3 MiB. Must be less than 4 MiB gRPC's per-message limit.
    max_bytes=2 * 1024 * 1024,
    # 100 ms. Default to 50 ms.
    max_latency=0.1,
    # Default to 1000.
    max_messages=100,
)

# PublisherClient() must be used in a `with` block or have __enter__() called before use.
with PublisherClient(
    per_partition_batching_settings=batch_setttings
) as publisher_client:
    for message in range(num_messages):
        data = f"{message}"
        api_future = publisher_client.publish(topic_path, data.encode("utf-8"))
        # result() blocks. To resolve API futures asynchronously, use add_done_callback().
        message_id = api_future.result()
        message_metadata = MessageMetadata.decode(message_id)
        print(
            f"Published {data} to partition {message_metadata.partition.value} and offset {message_metadata.cursor.offset}."
        )

print(
    f"Finished publishing {num_messages} messages with batch settings to {str(topic_path)}."
)

Quando um aplicativo do editor é iniciado, a biblioteca de cliente cria um lote para cada partição em um tópico do Lite. Por exemplo, se um tópico do Lite tem duas partições, os editores criam dois lotes e enviam cada lote para uma partição.

Depois de publicar uma mensagem, a biblioteca cliente a armazena em buffer até que o lote exceda o tamanho máximo da solicitação, o número máximo de mensagens ou o atraso de publicação.

Como ordenar mensagens

Os tópicos do Lite classificam as mensagens em cada partição ao publicar as mensagens. Para atribuir mensagens à mesma partição, use uma chave de ordenação.

O Pub/Sub Lite entrega as mensagens de uma partição em ordem, e os assinantes podem processá-las na ordem. Para mais detalhes, consulte Como receber mensagens.