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Pub/Sub 推送订阅的载荷解封

构建 Pub/Sub 系统时，载荷解封可以帮助您连接到不遵循标准 Pub/Sub 推送端点实现的所有系统要求的其他系统。

载荷解封的一些潜在用例如下：

您不希望为 HTTP 推送端点编写特定于 Pub/Sub 的消息解析代码。
您更希望将 Pub/Sub 消息元数据作为 HTTP 标头接收，而不是在 HTTP POST 正文中接收元数据。
您希望发送 Pub/Sub 消息并排除 Pub/Sub 元数据，例如在向第三方 API 发送数据时。

载荷解封的工作原理

载荷解封是一项功能，可剥离除消息数据以外的所有其他消息元数据。通过发送原始消息数据，订阅者可以处理消息，而无需遵循 Pub/Sub 的任何系统要求。

通过载荷解封，消息数据将作为 HTTP 正文直接传送。
在未解封载荷的情况下，Pub/Sub 会传送一个包含多个消息元数据字段和一个消息数据字段的 JSON 对象。在这种情况下，必须解析 JSON 以检索消息数据，然后进行 base64 解码。

写入元数据

启用载荷解封后，您可以使用写入元数据选项，将先前移除的消息元数据添加到请求标头中。

已启用写入元数据。将消息元数据重新添加到请求标头中。还会传递已解码的原始消息数据。
已停用写入元数据。仅传送已解码的原始消息数据。

写入元数据通过 Pub/Sub、Google Cloud CLI 参数 --push-no-wrapper-write-metadata 和 API 属性 NoWrapper 公开。默认情况下，此值为 null。

准备工作

了解 Pub/Sub 订阅和推送订阅。载荷解封只能用于推送订阅。
了解如何配置推送订阅。

已封装和未封装的消息示例

以下示例说明了发送已封装和未封装的 HTTP 消息之间的区别。在这些示例中，消息数据包含字符串 {"status": "Hello there"}。

在此示例中，订阅在启用载荷解封功能的情况下创建，并将消息发布到 mytopic。它使用值为 some-key 的排序键，并且媒体类型声明为 application/json。

gcloud pubsub topics publish mytopic
   --message='{"status": "Hello there"}'
   --ordering-key="some-key"
   --attribute "Content-Type=application/json"

以下部分展示了封装消息和解封装消息之间的区别。

已封装的消息

以下示例展示了一条标准 Pub/Sub 封装的消息。在这种情况下，未启用载荷解封。

发布	推送端点接收
data="{"status": "Hello there"}" ordering_key="some-key" attributes= { {"Content-Type", "application/json"} }	Content-Length: 361 Content-Type: application/json User-Agent: CloudPubSub-Google Host: subscription-project.uc.r.appspot.com { "message": { "attributes": { "Content-Type": "application/json" }, "data": "eyJzdGF0dXMiOiAiSGVsbG8gdGhlcmUifQ==", // Base64 - {"status": "Hello there"} "messageId": "2070443601311540", "message_id": "2070443601311540", "publishTime": "2021-02-26T19:13:55.749Z", "publish_time": "2021-02-26T19:13:55.749Z" }, "subscription": "projects/myproject/..." }

发布

推送端点接收

data="{"status": "Hello there"}"
ordering_key="some-key"
attributes=
  {
     {"Content-Type", "application/json"}
  }

Content-Length: 361
Content-Type: application/json
User-Agent: CloudPubSub-Google
Host: subscription-project.uc.r.appspot.com

{
  "message": {
      "attributes": {
          "Content-Type": "application/json"
      },
      "data": "eyJzdGF0dXMiOiAiSGVsbG8gdGhlcmUifQ==", //  Base64 - {"status": "Hello there"}
      "messageId": "2070443601311540",
      "message_id": "2070443601311540",
      "publishTime": "2021-02-26T19:13:55.749Z",
      "publish_time": "2021-02-26T19:13:55.749Z"
  },
  "subscription": "projects/myproject/..."
}

已解除封装的消息，且写入元数据已停用

以下示例展示了停用了“写入元数据”选项的未封装消息。在这种情况下，不包括 x-goog-pubsub-* 标头和邮件属性。

发布	推送端点接收
data="{"status": "Hello there"}" ordering_key="some-key" attributes= { {"Content-Type", "application/json"} }	Content-Length: 25 User-Agent: CloudPubSub-Google Host: subscription-project.uc.r.appspot.com {"status": "Hello there"}

发布

推送端点接收

data="{"status": "Hello there"}"
ordering_key="some-key"
attributes=
  {
     {"Content-Type", "application/json"}
  }

Content-Length: 25
User-Agent: CloudPubSub-Google
Host: subscription-project.uc.r.appspot.com

{"status": "Hello there"}

已启用写入元数据的未封装消息

以下示例展示了启用了写入元数据选项的解封装消息。在这种情况下，包含 x-goog-pubsub-* 标头和消息属性。

发布	推送端点接收
data="{"status": "Hello there"}" ordering_key="some-key" attributes= { {"Content-Type", "application/json"} }	x-goog-pubsub-subscription-name: "projects/myproject/..." x-goog-pubsub-message-id: "2070443601311540" x-goog-pubsub-publish-time: "2021-02-26T19:13:55.749Z" x-goog-pubsub-ordering-key: "some-key" Content-Type: application/json Content-Length: 12 User-Agent: CloudPubSub-Google Host: subscription-project.uc.r.appspot.com {"status": "Hello there"}

发布

推送端点接收

data="{"status": "Hello there"}"
ordering_key="some-key"
attributes=
  {
     {"Content-Type", "application/json"}
  }

x-goog-pubsub-subscription-name: "projects/myproject/..."
x-goog-pubsub-message-id: "2070443601311540"
x-goog-pubsub-publish-time: "2021-02-26T19:13:55.749Z"
x-goog-pubsub-ordering-key: "some-key"
Content-Type: application/json
Content-Length: 12
User-Agent: CloudPubSub-Google
Host: subscription-project.uc.r.appspot.com

{"status": "Hello there"}

配置载荷解封

您可以使用 Google Cloud 控制台订阅详情页面、Google Cloud CLI 或客户端库为订阅启用载荷解封推送传送。

控制台

在 Google Cloud 控制台中，进入订阅页面。

打开 Pub/Sub 订阅
点击创建订阅。
在订阅 ID 字段中，输入一个名称。

如需了解如何为订阅命名，请参阅主题或订阅命名准则。
从下拉菜单中选择主题。订阅会从主题接收消息。
对于传送类型，选择推送。
如需启用载荷解封，请选择启用载荷解封。
（可选）如需保留请求标头中的消息元数据，请选择写入元数据。您必须启用此选项才能为消息设置 Content-Type 标头。
指定端点网址。
保留所有其他默认值。
点击创建。

gcloud

如需配置订阅的载荷解封（包含标准 HTTP 标头），请运行以下 gcloud pubsub subscriptions create 命令：

gcloud pubsub subscriptions create SUBSCRIPTION \
  --topic TOPIC \
  --push-endpoint=PUSH_ENDPOINT \
  --push-no-wrapper

替换以下内容：

SUBSCRIPTION：您的拉取订阅的名称或 ID。
TOPIC：主题的 ID。
PUSH_ENDPOINT：要用作此订阅端点的网址。例如 https://myproject.appspot.com/myhandler
--push-no-wrapper：直接传递消息数据作为 HTTP 正文。

如需配置带有载荷解封的订阅并控制 x-goog-pubsub-* 标头的使用，请运行以下命令：

gcloud pubsub subscriptions create SUBSCRIPTION \
  --topic TOPIC \
  --push-endpoint=PUSH_ENDPOINT \
  --push-no-wrapper \
  --push-no-wrapper-write-metadata

--push-no-wrapper-write-metadata：如果为 true，则将 Pub/Sub 消息元数据写入 HTTP 请求的 x-goog-pubsub-<KEY>:<VAL> 标头。将 Pub/Sub 消息属性写入 HTTP 请求的 <KEY>:<VAL> 标头。

Python

在尝试此示例之前，请按照《快速入门：使用客户端库》中的 Python 设置说明进行操作。如需了解详情，请参阅 Pub/Sub Python API 参考文档。

from google.cloud import pubsub_v1

# TODO(developer)
# project_id = "your-project-id"
# topic_id = "your-topic-id"
# subscription_id = "your-subscription-id"
# endpoint = "https://my-test-project.appspot.com/push"

publisher = pubsub_v1.PublisherClient()
subscriber = pubsub_v1.SubscriberClient()
topic_path = publisher.topic_path(project_id, topic_id)
subscription_path = subscriber.subscription_path(project_id, subscription_id)

no_wrapper = pubsub_v1.types.PushConfig.NoWrapper(write_metadata=True)
push_config = pubsub_v1.types.PushConfig(
    push_endpoint=endpoint, no_wrapper=no_wrapper
)

# Wrap the subscriber in a 'with' block to automatically call close() to
# close the underlying gRPC channel when done.
with subscriber:
    subscription = subscriber.create_subscription(
        request={
            "name": subscription_path,
            "topic": topic_path,
            "push_config": push_config,
        }
    )

print(f"Push no wrapper subscription created: {subscription}.")
print(f"Endpoint for subscription is: {endpoint}")
print(f"No wrapper configuration for subscription is: {no_wrapper}")

Java

在尝试此示例之前，请按照《快速入门：使用客户端库》中的 Java 设置说明进行操作。如需了解详情，请参阅 Pub/Sub Java API 参考文档。

/*
 * Copyright 2016 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package pubsub;


import com.google.cloud.pubsub.v1.SubscriptionAdminClient;
import com.google.pubsub.v1.PushConfig;
import com.google.pubsub.v1.PushConfig.NoWrapper;
import com.google.pubsub.v1.Subscription;
import com.google.pubsub.v1.SubscriptionName;
import com.google.pubsub.v1.TopicName;
import java.io.IOException;

public class CreateUnwrappedPushSubscriptionExample {
  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";
    String topicId = "your-topic-id";
    String pushEndpoint = "https://my-test-project.appspot.com/push";

    createPushSubscriptionExample(projectId, subscriptionId, topicId, pushEndpoint);
  }

  public static void createPushSubscriptionExample(
      String projectId, String subscriptionId, String topicId, String pushEndpoint)
      throws IOException {
    try (SubscriptionAdminClient subscriptionAdminClient = SubscriptionAdminClient.create()) {
      TopicName topicName = TopicName.of(projectId, topicId);
      SubscriptionName subscriptionName = SubscriptionName.of(projectId, subscriptionId);
      NoWrapper noWrapper =
          NoWrapper.newBuilder()
              // Determines if message metadata is added to the HTTP headers of
              // the delivered message.
              .setWriteMetadata(true)
              .build();
      PushConfig pushConfig =
          PushConfig.newBuilder().setPushEndpoint(pushEndpoint).setNoWrapper(noWrapper).build();

      // Create a push subscription with default acknowledgement deadline of 10 seconds.
      // Messages not successfully acknowledged within 10 seconds will get resent by the server.
      Subscription subscription =
          subscriptionAdminClient.createSubscription(subscriptionName, topicName, pushConfig, 10);
      System.out.println("Created push subscription: " + subscription.getName());
    }
  }
}

C++

在尝试此示例之前，请按照《快速入门：使用客户端库》中的 C++ 设置说明进行操作。如需了解详情，请参阅 Pub/Sub C++ API 参考文档。

namespace pubsub = ::google::cloud::pubsub;
namespace pubsub_admin = ::google::cloud::pubsub_admin;
[](pubsub_admin::SubscriptionAdminClient client,
   std::string const& project_id, std::string const& topic_id,
   std::string const& subscription_id, std::string const& endpoint) {
  google::pubsub::v1::Subscription request;
  request.set_name(
      pubsub::Subscription(project_id, subscription_id).FullName());
  request.set_topic(pubsub::Topic(project_id, topic_id).FullName());
  request.mutable_push_config()->set_push_endpoint(endpoint);
  request.mutable_push_config()->mutable_no_wrapper()->set_write_metadata(
      true);
  auto sub = client.CreateSubscription(request);
  if (sub.status().code() == google::cloud::StatusCode::kAlreadyExists) {
    std::cout << "The subscription already exists\n";
    return;
  }
  if (!sub) throw std::move(sub).status();

  std::cout << "The subscription was successfully created: "
            << sub->DebugString() << "\n";
}

Go

在尝试此示例之前，请按照《快速入门：使用客户端库》中的 Go 设置说明进行操作。如需了解详情，请参阅 Pub/Sub Go API 参考文档。

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

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

// createPushNoWrapperSubscription creates a push subscription where messages are delivered in the HTTP body.
func createPushNoWrapperSubscription(w io.Writer, projectID, subID string, topic *pubsub.Topic, endpoint string) error {
	// projectID := "my-project-id"
	// subID := "my-sub"
	// topic of type https://godoc.org/cloud.google.com/go/pubsub#Topic
	// endpoint := "https://my-test-project.appspot.com/push"
	ctx := context.Background()
	client, err := pubsub.NewClient(ctx, projectID)
	if err != nil {
		return fmt.Errorf("pubsub.NewClient: %w", err)
	}
	defer client.Close()

	sub, err := client.CreateSubscription(ctx, subID, pubsub.SubscriptionConfig{
		Topic:       topic,
		AckDeadline: 10 * time.Second,
		PushConfig: pubsub.PushConfig{
			Endpoint: endpoint,
			Wrapper: &pubsub.NoWrapper{
				// Determines if message metadata is added to the HTTP headers of
				// the delivered message.
				WriteMetadata: true,
			},
		},
	})
	if err != nil {
		return fmt.Errorf("CreateSubscription: %w", err)
	}
	fmt.Fprintf(w, "Created push no wrapper subscription: %v\n", sub)
	return nil
}

Node.js

在尝试此示例之前，请按照《快速入门：使用客户端库》中的 Node.js 设置说明进行操作。如需了解详情，请参阅 Pub/Sub Node.js API 参考文档。

/**
 * TODO(developer): Uncomment these variables before running the sample.
 */
// const pushEndpoint = 'YOUR_ENDPOINT_URL';
// const topicNameOrId = 'YOUR_TOPIC_NAME_OR_ID';
// const subscriptionNameOrId = 'YOUR_SUBSCRIPTION_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 createPushSubscriptionNoWrapper(
  pushEndpoint,
  topicNameOrId,
  subscriptionNameOrId
) {
  const options = {
    pushConfig: {
      // Set to an HTTPS endpoint of your choice. If necessary, register
      // (authorize) the domain on which the server is hosted.
      pushEndpoint,
      // When true, writes the Pub/Sub message metadata to
      // `x-goog-pubsub-<KEY>:<VAL>` headers of the HTTP request. Writes the
      // Pub/Sub message attributes to `<KEY>:<VAL>` headers of the HTTP request.
      noWrapper: {
        writeMetadata: true,
      },
    },
  };

  await pubSubClient
    .topic(topicNameOrId)
    .createSubscription(subscriptionNameOrId, options);
  console.log(`Subscription ${subscriptionNameOrId} created.`);
}

Node.js

在尝试此示例之前，请按照《快速入门：使用客户端库》中的 Node.js 设置说明进行操作。如需了解详情，请参阅 Pub/Sub Node.js API 参考文档。

/**
 * TODO(developer): Uncomment these variables before running the sample.
 */
// const pushEndpoint = 'YOUR_ENDPOINT_URL';
// const topicNameOrId = 'YOUR_TOPIC_NAME_OR_ID';
// const subscriptionNameOrId = 'YOUR_SUBSCRIPTION_NAME_OR_ID';

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

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

async function createPushSubscriptionNoWrapper(
  pushEndpoint: string,
  topicNameOrId: string,
  subscriptionNameOrId: string
) {
  const options: CreateSubscriptionOptions = {
    pushConfig: {
      // Set to an HTTPS endpoint of your choice. If necessary, register
      // (authorize) the domain on which the server is hosted.
      pushEndpoint,
      // When true, writes the Pub/Sub message metadata to
      // `x-goog-pubsub-<KEY>:<VAL>` headers of the HTTP request. Writes the
      // Pub/Sub message attributes to `<KEY>:<VAL>` headers of the HTTP request.
      noWrapper: {
        writeMetadata: true,
      },
    },
  };

  await pubSubClient
    .topic(topicNameOrId)
    .createSubscription(subscriptionNameOrId, options);
  console.log(`Subscription ${subscriptionNameOrId} created.`);
}

在邮件中设置内容类型标头

启用载荷解封后，Pub/Sub 不会在您的请求中自动设置媒体类型标头字段。如果您未明确设置 Content-Type 标头字段，则处理请求的 Web 服务器可能会设置默认值 application/octet-stream 或以非预期方式解释该请求。

如果您需要使用 Content-Type 标头，请务必在发布时对每条发布的消息进行明确声明。为此，您必须先启用写入元数据。提供的示例显示了启用写入元数据的这一结果。

后续步骤

如果您在载荷解封时遇到问题，请参阅对载荷解封进行问题排查。