Desarrollar receptores de eventos

En esta página, se muestra cómo crear e implementar un servicio de receptor de eventos. El servicio de destino recibe solicitudes HTTP que contienen el evento en el formato de CloudEvents.

Los proveedores de eventos (fuentes) pueden proporcionar los siguientes tipos de eventos:

• Directamente desde una fuente de Google Cloud
• Usar registros de auditoría de Cloud
• Usa fuentes de terceros

Respuesta del receptor de eventos

El servicio del receptor debe enviar una respuesta HTTP 2xx para indicarle al router que el evento se entregó de forma correcta. El router trata todas las demás respuestas HTTP como errores en la entrega y reenvía el evento.

Repositorio de código abierto

La estructura del cuerpo HTTP para todos los eventos está disponible en el repositorio de GitHub de CloudEvents.

El repositorio contiene lo siguiente para ayudarte a comprender y usar los datos de CloudEvents en tu lenguaje de programación:

• Búferes de protocolo de Google para cargas útiles de datos de CloudEvents
• Esquemas JSON generados
• Un catálogo de esquemas JSON público

También se incluyen vínculos a bibliotecas cliente.

Usa una biblioteca del SDK de CloudEvents

Puedes desarrollar servicios de receptor de eventos mediante la biblioteca del SDK de CloudEvents, que está disponible para los siguientes lenguajes:

• C#
• Go
• Java
• JavaScript
• Python
• Ruby

Estas bibliotecas son de código abierto y facilitan la transformación de la solicitud HTTP en un objeto de CloudEvent de lenguaje idiomático.

Ejemplo de código fuente del receptor

Registros de auditoría de Cloud

El código de muestra indica cómo leer los eventos de Cloud Storage con Registros de auditoría de Cloud en un servicio implementado en Cloud Run.

Python

@app.route("/", methods=["POST"])
def index():
    # Create a CloudEvent object from the incoming request
    event = from_http(request.headers, request.data)
    # Gets the GCS bucket name from the CloudEvent
    # Example: "storage.googleapis.com/projects/_/buckets/my-bucket"
    bucket = event.get("subject")

    print(f"Detected change in Cloud Storage bucket: {bucket}")
    return (f"Detected change in Cloud Storage bucket: {bucket}", 200)

Java

import io.cloudevents.CloudEvent;
import io.cloudevents.rw.CloudEventRWException;
import io.cloudevents.spring.http.CloudEventHttpUtils;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestHeader;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class EventController {

  @RequestMapping(value = "/", method = RequestMethod.POST, consumes = "application/json")
  public ResponseEntity<String> receiveMessage(
      @RequestBody String body, @RequestHeader HttpHeaders headers) {
    CloudEvent event;
    try {
      event =
          CloudEventHttpUtils.fromHttp(headers)
              .withData(headers.getContentType().toString(), body.getBytes())
              .build();
    } catch (CloudEventRWException e) {
      return new ResponseEntity<>(e.getMessage(), HttpStatus.BAD_REQUEST);
    }

    String ceSubject = event.getSubject();
    String msg = "Detected change in Cloud Storage bucket: " + ceSubject;
    System.out.println(msg);
    return new ResponseEntity<>(msg, HttpStatus.OK);
  }
}

Node.js

const express = require('express');
const app = express();

app.use(express.json());
app.post('/', (req, res) => {
  if (!req.header('ce-subject')) {
    return res
      .status(400)
      .send('Bad Request: missing required header: ce-subject');
  }

  console.log(
    `Detected change in Cloud Storage bucket: ${req.header('ce-subject')}`
  );
  return res
    .status(200)
    .send(
      `Detected change in Cloud Storage bucket: ${req.header('ce-subject')}`
    );
});

module.exports = app;

Go

// Processes CloudEvents containing Cloud Audit Logs for Cloud Storage
package main

import (
	"fmt"
	"log"
	"net/http"
	"os"

	cloudevent "github.com/cloudevents/sdk-go/v2"
)

// HelloEventsStorage receives and processes a Cloud Audit Log event with Cloud Storage data.
func HelloEventsStorage(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "Expected HTTP POST request with CloudEvent payload", http.StatusMethodNotAllowed)
		return
	}

	event, err := cloudevent.NewEventFromHTTPRequest(r)
	if err != nil {
		log.Printf("cloudevent.NewEventFromHTTPRequest: %v", err)
		http.Error(w, "Failed to create CloudEvent from request.", http.StatusBadRequest)
		return
	}
	s := fmt.Sprintf("Detected change in Cloud Storage bucket: %s", event.Subject())
	fmt.Fprintln(w, s)
}

C#

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env, ILogger<Startup> logger)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        logger.LogInformation("Service is starting...");

        app.UseRouting();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapPost("/", async context =>
            {
                logger.LogInformation("Handling HTTP POST");

                var ceSubject = context.Request.Headers["ce-subject"];
                logger.LogInformation($"ce-subject: {ceSubject}");

                if (string.IsNullOrEmpty(ceSubject))
                {
                    context.Response.StatusCode = 400;
                    await context.Response.WriteAsync("Bad Request: expected header Ce-Subject");
                    return;
                }

                await context.Response.WriteAsync($"GCS CloudEvent type: {ceSubject}");
            });
        });
    }
}

Pub/Sub

El código de muestra indica cómo leer eventos de Pub/Sub en un servicio implementado en Cloud Run.

Python

@app.route("/", methods=["POST"])
def index():
    data = request.get_json()
    if not data:
        msg = "no Pub/Sub message received"
        print(f"error: {msg}")
        return f"Bad Request: {msg}", 400

    if not isinstance(data, dict) or "message" not in data:
        msg = "invalid Pub/Sub message format"
        print(f"error: {msg}")
        return f"Bad Request: {msg}", 400

    pubsub_message = data["message"]

    name = "World"
    if isinstance(pubsub_message, dict) and "data" in pubsub_message:
        name = base64.b64decode(pubsub_message["data"]).decode("utf-8").strip()

    resp = f"Hello, {name}! ID: {request.headers.get('ce-id')}"
    print(resp)

    return (resp, 200)

Java

import com.example.cloudrun.eventpojos.PubSubBody;
import java.util.Base64;
import java.util.Map;
import org.apache.commons.lang3.StringUtils;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestHeader;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class EventController {
  @RequestMapping(value = "/", method = RequestMethod.POST)
  public ResponseEntity<String> receiveMessage(
      @RequestBody PubSubBody body, @RequestHeader Map<String, String> headers) {
    // Get PubSub message from request body.
    PubSubBody.PubSubMessage message = body.getMessage();
    if (message == null) {
      String msg = "No Pub/Sub message received.";
      System.out.println(msg);
      return new ResponseEntity<>(msg, HttpStatus.BAD_REQUEST);
    }

    String data = message.getData();
    if (data == null || data.isEmpty()) {
      String msg = "Invalid Pub/Sub message format.";
      System.out.println(msg);
      return new ResponseEntity<>(msg, HttpStatus.BAD_REQUEST);
    }

    String name =
        !StringUtils.isEmpty(data) ? new String(Base64.getDecoder().decode(data)) : "World";
    String ceId = headers.getOrDefault("ce-id", "");
    String msg = String.format("Hello, %s! ID: %s", name, ceId);
    System.out.println(msg);
    return new ResponseEntity<>(msg, HttpStatus.OK);
  }
}

Node.js

const express = require('express');
const {
  toMessagePublishedData,
} = require('@google/events/cloud/pubsub/v1/MessagePublishedData');
const app = express();

app.use(express.json());
app.post('/', (req, res) => {
  if (!req.body) {
    const errorMessage = 'no Pub/Sub message received';
    res.status(400).send(`Bad Request: ${errorMessage}`);
    console.log(`Bad Request: ${errorMessage}`);
    return;
  }
  if (!req.body.message) {
    const errorMessage = 'invalid Pub/Sub message format';
    res.status(400).send(`Bad Request: ${errorMessage}`);
    console.log(`Bad Request: ${errorMessage}`);
    return;
  }
  // Cast to MessagePublishedEvent for IDE autocompletion
  const pubSubMessage = toMessagePublishedData(req.body);
  const name =
    pubSubMessage.message && pubSubMessage.message.data
      ? Buffer.from(pubSubMessage.message.data, 'base64').toString().trim()
      : 'World';

  const result = `Hello, ${name}! ID: ${req.get('ce-id') || ''}`;
  console.log(result);
  res.send(result);
});

module.exports = app;

Go

// Sample pubsub is a Cloud Run service which handles Pub/Sub messages.
package main

import (
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"os"
)

// PubSubMessage is the payload of a Pub/Sub event.
// See the documentation for more details:
// https://cloud.google.com/pubsub/docs/reference/rest/v1/PubsubMessage
type PubSubMessage struct {
	Message struct {
		Data []byte `json:"data,omitempty"`
		ID   string `json:"id"`
	} `json:"message"`
	Subscription string `json:"subscription"`
}

// HelloEventsPubSub receives and processes a Pub/Sub push message.
func HelloEventsPubSub(w http.ResponseWriter, r *http.Request) {
	var e PubSubMessage
	if err := json.NewDecoder(r.Body).Decode(&e); err != nil {
		http.Error(w, "Bad HTTP Request", http.StatusBadRequest)
		log.Printf("Bad HTTP Request: %v", http.StatusBadRequest)
		return
	}
	name := string(e.Message.Data)
	if name == "" {
		name = "World"
	}
	s := fmt.Sprintf("Hello, %s! ID: %s", name, string(r.Header.Get("Ce-Id")))
	log.Printf(s)
	fmt.Fprintln(w, s)
}

C#

using CloudNative.CloudEvents;
using CloudNative.CloudEvents.AspNetCore;
using Google.Events.Protobuf.Cloud.PubSub.V1;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env, ILogger<Startup> logger)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        logger.LogInformation("Service is starting...");

        app.UseRouting();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapPost("/", async context =>
            {
                var formatter = CloudEventFormatterAttribute.CreateFormatter(typeof(MessagePublishedData));
                var cloudEvent = await context.Request.ToCloudEventAsync(formatter);
                logger.LogInformation("Received CloudEvent\n" + GetEventLog(cloudEvent));

                var messagePublishedData = (MessagePublishedData) cloudEvent.Data;
                var pubSubMessage = messagePublishedData.Message;
                if (pubSubMessage == null)
                {
                    context.Response.StatusCode = 400;
                    await context.Response.WriteAsync("Bad request: Invalid Pub/Sub message format");
                    return;
                }

                var data = pubSubMessage.Data;
                logger.LogInformation($"Data: {data.ToBase64()}");

                var name = data.ToStringUtf8();
                logger.LogInformation($"Extracted name: {name}");

                var id = context.Request.Headers["ce-id"];
                await context.Response.WriteAsync($"Hello {name}! ID: {id}");
            });
        });
    }

    private string GetEventLog(CloudEvent cloudEvent)
    {
        return $"ID: {cloudEvent.Id}\n"
            + $"Source: {cloudEvent.Source}\n"
            + $"Type: {cloudEvent.Type}\n"
            + $"Subject: {cloudEvent.Subject}\n"
            + $"DataSchema: {cloudEvent.DataSchema}\n"
            + $"DataContentType: {cloudEvent.DataContentType}\n"
            + $"Time: {cloudEvent.Time?.UtcDateTime:yyyy-MM-dd'T'HH:mm:ss.fff'Z'}\n"
            + $"SpecVersion: {cloudEvent.SpecVersion}\n"
            + $"Data: {cloudEvent.Data}";
    }
}

¿Qué sigue?

• Proveedores y destinos de eventos
• Rutas de eventos