Fazer streaming de mensagens do Pub/Sub usando o Dataflow

O Dataflow é um serviço totalmente gerenciado para transformar e enriquecer dados em modos de stream (em tempo real) e em lote com a mesma confiabilidade e expressividade. Ele fornece um ambiente simplificado de desenvolvimento de pipeline usando o SDK do Apache Beam, que tem um conjunto avançado de primitivos de análise de sessões e janelas, além de um ecossistema de conectores de origem e de coletor. Este guia de início rápido mostra como usar o Dataflow para:

  • ler mensagens publicadas em um tópico do Pub/Sub;
  • organizar em janelas (ou agrupar) as mensagens por carimbo de data/hora;
  • gravar as mensagens no Cloud Storage.

Este guia de início rápido apresenta o uso do Dataflow em Java e Python. O SQL também é compatível. Este guia de início rápido também é oferecido como um tutorial do Google Cloud Ensina, que oferece credenciais temporárias para você começar.

Comece usando os modelos do Dataflow baseados na IU se não pretende fazer o processamento de dados personalizado.

Antes de começar

  1. Sign in to your Google Cloud account. If you're new to Google Cloud, create an account to evaluate how our products perform in real-world scenarios. New customers also get $300 in free credits to run, test, and deploy workloads.
  2. Install the Google Cloud CLI.

  3. To initialize the gcloud CLI, run the following command: 

    gcloud init

  4. Create or select a Google Cloud project.

    • Create a Google Cloud project:

      gcloud projects create PROJECT_ID

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

    • Select the Google Cloud project that you created:

      gcloud config set project PROJECT_ID

      Replace PROJECT_ID with your Google Cloud project name.

  5. Make sure that billing is enabled for your Google Cloud project.

  6. Enable the Dataflow, Compute Engine, Cloud Logging, Cloud Storage, Google Cloud Storage JSON API, Pub/Sub, Resource Manager, and Cloud Scheduler APIs: 

    gcloud services enable dataflow.googleapis.com  compute.googleapis.com  logging.googleapis.com  storage-component.googleapis.com  storage-api.googleapis.com  pubsub.googleapis.com  cloudresourcemanager.googleapis.com  cloudscheduler.googleapis.com

  7. Set up authentication:

    1. Create the service account: 

      gcloud iam service-accounts create SERVICE_ACCOUNT_NAME

      Replace SERVICE_ACCOUNT_NAME with a name for the service account.

    2. Grant roles to the service account. Run the following command once for each of the following IAM roles: roles/dataflow.worker, roles/storage.objectAdmin, roles/pubsub.admin: 

      gcloud projects add-iam-policy-binding PROJECT_ID --member="serviceAccount:SERVICE_ACCOUNT_NAME@PROJECT_ID.iam.gserviceaccount.com" --role=ROLE

      Replace the following:

      • SERVICE_ACCOUNT_NAME: the name of the service account
      • PROJECT_ID: the project ID where you created the service account
      • ROLE: the role to grant

    3. Grant the required role to the principal that will attach the service account to other resources. 

      gcloud iam service-accounts add-iam-policy-binding SERVICE_ACCOUNT_NAME@PROJECT_ID.iam.gserviceaccount.com --member="user:USER_EMAIL" --role=roles/iam.serviceAccountUser

      Replace the following:

      • SERVICE_ACCOUNT_NAME: the name of the service account
      • PROJECT_ID: the project ID where you created the service account
      • USER_EMAIL: the email address for a Google Account
    8.
  8. Install the Google Cloud CLI.

  9. To initialize the gcloud CLI, run the following command: 

    gcloud init

  10. Create or select a Google Cloud project.

    • Create a Google Cloud project:

      gcloud projects create PROJECT_ID

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

    • Select the Google Cloud project that you created:

      gcloud config set project PROJECT_ID

      Replace PROJECT_ID with your Google Cloud project name.

  11. Make sure that billing is enabled for your Google Cloud project.

  12. Enable the Dataflow, Compute Engine, Cloud Logging, Cloud Storage, Google Cloud Storage JSON API, Pub/Sub, Resource Manager, and Cloud Scheduler APIs: 

    gcloud services enable dataflow.googleapis.com  compute.googleapis.com  logging.googleapis.com  storage-component.googleapis.com  storage-api.googleapis.com  pubsub.googleapis.com  cloudresourcemanager.googleapis.com  cloudscheduler.googleapis.com

  13. Set up authentication:

    1. Create the service account: 

      gcloud iam service-accounts create SERVICE_ACCOUNT_NAME

      Replace SERVICE_ACCOUNT_NAME with a name for the service account.

    2. Grant roles to the service account. Run the following command once for each of the following IAM roles: roles/dataflow.worker, roles/storage.objectAdmin, roles/pubsub.admin: 

      gcloud projects add-iam-policy-binding PROJECT_ID --member="serviceAccount:SERVICE_ACCOUNT_NAME@PROJECT_ID.iam.gserviceaccount.com" --role=ROLE

      Replace the following:

      • SERVICE_ACCOUNT_NAME: the name of the service account
      • PROJECT_ID: the project ID where you created the service account
      • ROLE: the role to grant

    3. Grant the required role to the principal that will attach the service account to other resources. 

      gcloud iam service-accounts add-iam-policy-binding SERVICE_ACCOUNT_NAME@PROJECT_ID.iam.gserviceaccount.com --member="user:USER_EMAIL" --role=roles/iam.serviceAccountUser

      Replace the following:

      • SERVICE_ACCOUNT_NAME: the name of the service account
      • PROJECT_ID: the project ID where you created the service account
      • USER_EMAIL: the email address for a Google Account
    14.

  14. Create local authentication credentials for your user account: 

    gcloud auth application-default login

Configurar seu projeto do Pub/Sub

  1. Crie variáveis para o bucket, o projeto e a região. Os nomes dos intervalos do Cloud Storage precisam ser globalmente exclusivos. Selecione uma região do Dataflow perto de onde você executa os comandos neste guia de início rápido. O valor da variável REGION precisa ser um nome de região válido. Para mais informações sobre regiões e locais, consulte Locais do Dataflow. 

    BUCKET_NAME=BUCKET_NAME
PROJECT_ID=$(gcloud config get-value project)
TOPIC_ID=TOPIC_ID
REGION=DATAFLOW_REGION
SERVICE_ACCOUNT=SERVICE_ACCOUNT_NAME@PROJECT_ID.iam.gserviceaccount.com

  2. Crie um bucket do Cloud Storage que pertença a este projeto: 

    gcloud storage buckets create gs://$BUCKET_NAME

  3. Crie um tópico do Pub/Sub neste projeto: 

    gcloud pubsub topics create $TOPIC_ID

  4. Crie um job do Cloud Scheduler neste projeto. O job publica uma mensagem em um tópico do Pub/Sub em intervalos de um minuto.

    Esta etapa criará um aplicativo do App Engine para o projeto, se já não houver um. 

    gcloud scheduler jobs create pubsub publisher-job --schedule="* * * * *" \
    --topic=$TOPIC_ID --message-body="Hello!" --location=$REGION

    Inicie o job. 

    gcloud scheduler jobs run publisher-job --location=$REGION

  5. Use os seguintes comandos para clonar o repositório do guia de início rápido e navegar até o diretório do código de amostra:

    Java

    git clone https://github.com/GoogleCloudPlatform/java-docs-samples.git
cd java-docs-samples/pubsub/streaming-analytics

    Python

    git clone https://github.com/GoogleCloudPlatform/python-docs-samples.git
cd python-docs-samples/pubsub/streaming-analytics
pip install -r requirements.txt  # Install Apache Beam dependencies

Fazer streaming de mensagens do Pub/Sub para o Cloud Storage

Exemplo de código

Este exemplo de código usa o Dataflow para:

  • Leia as mensagens do Pub/Sub.
  • Janela (ou grupo) de mensagens em intervalos de tamanho fixo por carimbos de data/hora de publicação.

  • Grave as mensagens em cada janela nos arquivos no Cloud Storage.

Java


import java.io.IOException;
import org.apache.beam.examples.common.WriteOneFilePerWindow;
import org.apache.beam.sdk.Pipeline;
import org.apache.beam.sdk.io.gcp.pubsub.PubsubIO;
import org.apache.beam.sdk.options.Default;
import org.apache.beam.sdk.options.Description;
import org.apache.beam.sdk.options.PipelineOptionsFactory;
import org.apache.beam.sdk.options.StreamingOptions;
import org.apache.beam.sdk.options.Validation.Required;
import org.apache.beam.sdk.transforms.windowing.FixedWindows;
import org.apache.beam.sdk.transforms.windowing.Window;
import org.joda.time.Duration;

public class PubSubToGcs {
  /*
   * Define your own configuration options. Add your own arguments to be processed
   * by the command-line parser, and specify default values for them.
   */
  public interface PubSubToGcsOptions extends StreamingOptions {
    @Description("The Cloud Pub/Sub topic to read from.")
    @Required
    String getInputTopic();

    void setInputTopic(String value);

    @Description("Output file's window size in number of minutes.")
    @Default.Integer(1)
    Integer getWindowSize();

    void setWindowSize(Integer value);

    @Description("Path of the output file including its filename prefix.")
    @Required
    String getOutput();

    void setOutput(String value);
  }

  public static void main(String[] args) throws IOException {
    // The maximum number of shards when writing output.
    int numShards = 1;

    PubSubToGcsOptions options =
        PipelineOptionsFactory.fromArgs(args).withValidation().as(PubSubToGcsOptions.class);

    options.setStreaming(true);

    Pipeline pipeline = Pipeline.create(options);

    pipeline
        // 1) Read string messages from a Pub/Sub topic.
        .apply("Read PubSub Messages", PubsubIO.readStrings().fromTopic(options.getInputTopic()))
        // 2) Group the messages into fixed-sized minute intervals.
        .apply(Window.into(FixedWindows.of(Duration.standardMinutes(options.getWindowSize()))))
        // 3) Write one file to GCS for every window of messages.
        .apply("Write Files to GCS", new WriteOneFilePerWindow(options.getOutput(), numShards));

    // Execute the pipeline and wait until it finishes running.
    pipeline.run().waitUntilFinish();
  }
}

Python

import argparse
from datetime import datetime
import logging
import random

from apache_beam import (
    DoFn,
    GroupByKey,
    io,
    ParDo,
    Pipeline,
    PTransform,
    WindowInto,
    WithKeys,
)
from apache_beam.options.pipeline_options import PipelineOptions
from apache_beam.transforms.window import FixedWindows


class GroupMessagesByFixedWindows(PTransform):
    """A composite transform that groups Pub/Sub messages based on publish time
    and outputs a list of tuples, each containing a message and its publish time.
    """

    def __init__(self, window_size, num_shards=5):
        # Set window size to 60 seconds.
        self.window_size = int(window_size * 60)
        self.num_shards = num_shards

    def expand(self, pcoll):
        return (
            pcoll
            # Bind window info to each element using element timestamp (or publish time).
            | "Window into fixed intervals"
            >> WindowInto(FixedWindows(self.window_size))
            | "Add timestamp to windowed elements" >> ParDo(AddTimestamp())
            # Assign a random key to each windowed element based on the number of shards.
            | "Add key" >> WithKeys(lambda _: random.randint(0, self.num_shards - 1))
            # Group windowed elements by key. All the elements in the same window must fit
            # memory for this. If not, you need to use `beam.util.BatchElements`.
            | "Group by key" >> GroupByKey()
        )


class AddTimestamp(DoFn):
    def process(self, element, publish_time=DoFn.TimestampParam):
        """Processes each windowed element by extracting the message body and its
        publish time into a tuple.
        """
        yield (
            element.decode("utf-8"),
            datetime.utcfromtimestamp(float(publish_time)).strftime(
                "%Y-%m-%d %H:%M:%S.%f"
            ),
        )


class WriteToGCS(DoFn):
    def __init__(self, output_path):
        self.output_path = output_path

    def process(self, key_value, window=DoFn.WindowParam):
        """Write messages in a batch to Google Cloud Storage."""

        ts_format = "%H:%M"
        window_start = window.start.to_utc_datetime().strftime(ts_format)
        window_end = window.end.to_utc_datetime().strftime(ts_format)
        shard_id, batch = key_value
        filename = "-".join([self.output_path, window_start, window_end, str(shard_id)])

        with io.gcsio.GcsIO().open(filename=filename, mode="w") as f:
            for message_body, publish_time in batch:
                f.write(f"{message_body},{publish_time}\n".encode())


def run(input_topic, output_path, window_size=1.0, num_shards=5, pipeline_args=None):
    # Set `save_main_session` to True so DoFns can access globally imported modules.
    pipeline_options = PipelineOptions(
        pipeline_args, streaming=True, save_main_session=True
    )

    with Pipeline(options=pipeline_options) as pipeline:
        (
            pipeline
            # Because `timestamp_attribute` is unspecified in `ReadFromPubSub`, Beam
            # binds the publish time returned by the Pub/Sub server for each message
            # to the element's timestamp parameter, accessible via `DoFn.TimestampParam`.
            # https://beam.apache.org/releases/pydoc/current/apache_beam.io.gcp.pubsub.html#apache_beam.io.gcp.pubsub.ReadFromPubSub
            | "Read from Pub/Sub" >> io.ReadFromPubSub(topic=input_topic)
            | "Window into" >> GroupMessagesByFixedWindows(window_size, num_shards)
            | "Write to GCS" >> ParDo(WriteToGCS(output_path))
        )


if __name__ == "__main__":
    logging.getLogger().setLevel(logging.INFO)

    parser = argparse.ArgumentParser()
    parser.add_argument(
        "--input_topic",
        help="The Cloud Pub/Sub topic to read from."
        '"projects/<PROJECT_ID>/topics/<TOPIC_ID>".',
    )
    parser.add_argument(
        "--window_size",
        type=float,
        default=1.0,
        help="Output file's window size in minutes.",
    )
    parser.add_argument(
        "--output_path",
        help="Path of the output GCS file including the prefix.",
    )
    parser.add_argument(
        "--num_shards",
        type=int,
        default=5,
        help="Number of shards to use when writing windowed elements to GCS.",
    )
    known_args, pipeline_args = parser.parse_known_args()

    run(
        known_args.input_topic,
        known_args.output_path,
        known_args.window_size,
        known_args.num_shards,
        pipeline_args,
    )

Iniciar o pipeline

Para iniciar o pipeline, execute o seguinte comando:

Java

mvn compile exec:java \
  -Dexec.mainClass=com.examples.pubsub.streaming.PubSubToGcs \
  -Dexec.cleanupDaemonThreads=false \
  -Dexec.args=" \
    --project=$PROJECT_ID \
    --region=$REGION \
    --inputTopic=projects/$PROJECT_ID/topics/$TOPIC_ID \
    --output=gs://$BUCKET_NAME/samples/output \
    --gcpTempLocation=gs://$BUCKET_NAME/temp \
    --runner=DataflowRunner \
    --windowSize=2 \
    --serviceAccount=$SERVICE_ACCOUNT"

Python

python PubSubToGCS.py \
  --project=$PROJECT_ID \
  --region=$REGION \
  --input_topic=projects/$PROJECT_ID/topics/$TOPIC_ID \
  --output_path=gs://$BUCKET_NAME/samples/output \
  --runner=DataflowRunner \
  --window_size=2 \
  --num_shards=2 \
  --temp_location=gs://$BUCKET_NAME/temp \
  --service_account_email=$SERVICE_ACCOUNT

O comando anterior é executado localmente e inicia um job do Dataflow executado na nuvem. Quando o comando retornar JOB_MESSAGE_DETAILED: Workers have started successfully, saia do programa local usando Ctrl+C.

Observar o andamento do job e do pipeline

Observe o progresso do job no console do Dataflow.

Acessar o console do Dataflow

Observar o progresso do job

Abra a visualização de detalhes do job para ver:

  • a estrutura do job;
  • os registros da tarefa;
  • as métricas do cenário.

Observar o progresso do job

Talvez seja necessário aguardar alguns minutos para ver os arquivos de saída no Cloud Storage.

Observar o progresso do job

Como alternativa, use a linha de comando abaixo para verificar quais arquivos foram gravados.

gcloud storage ls gs://${BUCKET_NAME}/samples/

A saída será semelhante a esta:

Java

gs://{$BUCKET_NAME}/samples/output-22:30-22:32-0-of-1
gs://{$BUCKET_NAME}/samples/output-22:32-22:34-0-of-1
gs://{$BUCKET_NAME}/samples/output-22:34-22:36-0-of-1
gs://{$BUCKET_NAME}/samples/output-22:36-22:38-0-of-1

Python

gs://{$BUCKET_NAME}/samples/output-22:30-22:32-0
gs://{$BUCKET_NAME}/samples/output-22:30-22:32-1
gs://{$BUCKET_NAME}/samples/output-22:32-22:34-0
gs://{$BUCKET_NAME}/samples/output-22:32-22:34-1

Limpar

Para evitar cobranças na sua conta do Google Cloud pelos recursos usados nesta página, exclua o projeto do Google Cloud com esses recursos.

  1. Exclua o job do Cloud Scheduler.

    gcloud scheduler jobs delete publisher-job --location=$REGION

  2. No console do Dataflow, interrompa o job. Cancele o pipeline sem esvaziá-lo.

  3. Exclua o tópico.

    gcloud pubsub topics delete $TOPIC_ID

  4. Exclua os arquivos criados pelo pipeline.

    gcloud storage rm "gs://${BUCKET_NAME}/samples/output*" --recursive --continue-on-error
gcloud storage rm "gs://${BUCKET_NAME}/temp/*" --recursive --continue-on-error

  5. Remova o bucket do Cloud Storage.

    gcloud storage rm gs://${BUCKET_NAME} --recursive

  6. Exclua a conta de serviço: 
    gcloud iam service-accounts delete SERVICE_ACCOUNT_EMAIL

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

    gcloud auth application-default revoke

  8. Optional: Revoke credentials from the gcloud CLI. 

    gcloud auth revoke

A seguir