在终端窗口中，将示例应用代码库克隆到本地机器：
```
git clone https://github.com/GoogleCloudPlatform/getting-started-dotnet.git
```
或者，您也可以下载该示例的 zip 文件并将其解压缩。
切换到包含后台任务示例代码的目录：
```
cd getting-started-dotnet/BackgroundProcessing
```

了解 `TranslateWorker` 服务

该服务首先导入多个依赖项，例如 Firestore 和 Translation。

BackgroundProcessing/TranslateWorker/Startup.cs

在 GitHub 上查看
```
using Google.Cloud.Firestore;
using Google.Cloud.Translation.V2;
```

系统初始化 Firestore 和 Translation 客户端，以便可以在各处理程序调用之间重复使用它们。这样，您便无需针对每次调用初始化新的客户端（此操作会降低执行速度）。

BackgroundProcessing/TranslateWorker/Startup.cs

在 GitHub 上查看

public void ConfigureServices(IServiceCollection services)
{
    services.AddSingleton<FirestoreDb>(provider =>
        FirestoreDb.Create(GetFirestoreProjectId()));
    services.AddSingleton<TranslationClient>(
        TranslationClient.Create());
    services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
}

Translation API 会将字符串翻译为您选择的语言。

BackgroundProcessing/TranslateWorker/Controllers/TranslateController.cs

在 GitHub 上查看
```
var result = await _translator.TranslateTextAsync(sourceText, "es");
```

控制器的构造函数接收 Firestore 和 Pub/Sub 客户端。

Post 方法解析 Pub/Sub 消息以获取要翻译的文本。它使用消息 ID 作为翻译请求的唯一名称，以确保它不存储任何重复的翻译。

BackgroundProcessing/TranslateWorker/Controllers/TranslateController.cs

在 GitHub 上查看

using Google.Cloud.Firestore;
using Google.Cloud.Translation.V2;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Logging;
using System;
using System.Collections.Generic;
using System.Text;
using System.Threading.Tasks;

namespace TranslateWorker.Controllers
{
    /// <summary>
    /// The message Pubsub posts to our controller.
    /// </summary>
    public class PostMessage
    {
        public PubsubMessage message { get; set; }
        public string subscription { get; set; }
    }

    /// <summary>
    /// Pubsub's inner message.
    /// </summary>
    public class PubsubMessage
    {
        public string data { get; set; }
        public string messageId { get; set; }
        public Dictionary<string, string> attributes { get; set; }
    }

    [Route("api/[controller]")]
    [ApiController]
    public class TranslateController : ControllerBase
    {
        private readonly ILogger<TranslateController> _logger;
        private readonly FirestoreDb _firestore;
        private readonly TranslationClient _translator;
        // The Firestore collection where we store translations.
        private readonly CollectionReference _translations;

        public TranslateController(ILogger<TranslateController> logger,
            FirestoreDb firestore,
            TranslationClient translator)
        {
            _logger = logger ?? throw new ArgumentNullException(nameof(logger));
            _firestore = firestore ?? throw new ArgumentNullException(
                nameof(firestore));
            _translator = translator ?? throw new ArgumentNullException(
                nameof(translator));
            _translations = _firestore.Collection("Translations");
        }

        /// <summary>
        /// Handle a posted message from Pubsub.
        /// </summary>
        /// <param name="request">The message Pubsub posts to this process.</param>
        /// <returns>NoContent on success.</returns>
        [HttpPost]
        public async Task<IActionResult> Post([FromBody] PostMessage request)
        {
            // Unpack the message from Pubsub.
            string sourceText;
            try
            {
                byte[] data = Convert.FromBase64String(request.message.data);
                sourceText = Encoding.UTF8.GetString(data);
            }
            catch (Exception e)
            {
                _logger.LogError(1, e, "Bad request");
                return BadRequest();
            }
            // Translate the source text.
            _logger.LogDebug(2, "Translating {0} to Spanish.", sourceText);
            var result = await _translator.TranslateTextAsync(sourceText, "es");
            // Store the result in Firestore.
            Translation translation = new Translation()
            {
                TimeStamp = DateTime.UtcNow,
                SourceText = sourceText,
                TranslatedText = result.TranslatedText
            };
            _logger.LogDebug(3, "Saving translation {0} to {1}.",
                translation.TranslatedText, _translations.Path);
            await _translations.Document(request.message.messageId)
                .SetAsync(translation);
            // Return a success code.
            return NoContent();
        }

        /// <summary>
        /// Serve a root page so Cloud Run knows this process is healthy.
        /// </summary>
        [Route("/")]
        public IActionResult Index()
        {
            return Content("Serving translate requests...");
        }
    }
}

部署 `TranslateWorker` 服务

在 BackgroundProcessing 目录中，运行 PowerShell 脚本以构建服务并将其部署到 Cloud Run：
```
PublishTo-CloudRun.ps1
```

了解 `PublishTo-CloudRun.ps1` 脚本

PublishTo-CloudRun.ps1 脚本将服务发布到 Cloud Run，并保护 TranslateWorker 服务不被滥用。如果该服务允许所有传入连接，则任何人都可以将翻译请求发布到控制器，从而产生成本。因此，您将服务设置为仅接受来自 Pub/Sub 的 POST 请求。

该脚本将执行以下操作：

使用 dotnet publish 在本地构建应用。
使用 Cloud Build 构建运行应用的容器。
将应用部署到 Cloud Run。
让项目能够创建 Pub/Sub 身份验证令牌。
创建一个服务帐号来表示 Pub/Sub 订阅身份。
授予服务帐号调用 TranslateWorker 服务的权限。

创建 Pub/Sub 主题和订阅。

BackgroundProcessing/PublishTo-CloudRun.ps1

在 GitHub 上查看

# 1. Build the application locally.
dotnet publish -c Release

# Collect some details about the project that we'll need later.
$projectId = gcloud config get-value project
$projectNumber = gcloud projects describe $projectId --format="get(projectNumber)"
$region = "us-central1"

# 2. Use Google Cloud Build to build the worker's container and publish to Google
# Container Registry.
gcloud builds submit --tag gcr.io/$projectId/translate-worker `
    TranslateWorker/bin/Release/netcoreapp2.1/publish

# 3. Run the container with Google Cloud Run.
gcloud beta run deploy translate-worker --region $region --platform managed `
    --image gcr.io/$projectId/translate-worker --no-allow-unauthenticated
$url = gcloud beta run services describe translate-worker --platform managed `
    --region $region --format="get(status.address.hostname)"

# 4. Enable the project to create pubsub authentication tokens.
gcloud projects add-iam-policy-binding $projectId `
     --member=serviceAccount:service-$projectNumber@gcp-sa-pubsub.iam.gserviceaccount.com `
     --role=roles/iam.serviceAccountTokenCreator

# 5. Create a service account to represent the Cloud Pub/Sub subscription identity.
$serviceAccountExists = gcloud iam service-accounts describe `
    cloud-run-pubsub-invoker@$projectId.iam.gserviceaccount.com 2> $null
if (-not $serviceAccountExists) {
    gcloud iam service-accounts create cloud-run-pubsub-invoker `
        --display-name "Cloud Run Pub/Sub Invoker"
}

# 6. For Cloud Run, give this service account permission to invoke
# translate-worker service.
gcloud beta run services add-iam-policy-binding translate-worker `
     --member=serviceAccount:cloud-run-pubsub-invoker@$projectId.iam.gserviceaccount.com `
     --role=roles/run.invoker --region=$region

# 7. Create a pubsub topic and subscription, if they don't already exist.
$topicExists = gcloud pubsub topics describe translate-requests 2> $null
if (-not $topicExists) {
    gcloud pubsub topics create translate-requests
}
$subscriptionExists = gcloud pubsub subscriptions describe translate-requests 2> $null
if ($subscriptionExists) {
    gcloud beta pubsub subscriptions modify-push-config translate-requests `
        --push-endpoint $url/api/translate `
        --push-auth-service-account cloud-run-pubsub-invoker@$projectId.iam.gserviceaccount.com
} else {
    gcloud beta pubsub subscriptions create translate-requests `
        --topic translate-requests --push-endpoint $url/api/translate `
        --push-auth-service-account cloud-run-pubsub-invoker@$projectId.iam.gserviceaccount.com
}

了解 `TranslateUI` 服务

TranslateUI 服务将呈现一个显示最近翻译的网页，并接受新翻译请求。

StartUp 类将配置 ASP.NET 应用并创建 Pub/Sub 和 Firestore 客户端。

BackgroundProcessing/TranslateUI/Startup.cs

在 GitHub 上查看

using Google.Apis.Auth.OAuth2;
using Google.Cloud.Firestore;
using Google.Cloud.PubSub.V1;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using System;
using System.Net.Http;

namespace TranslateUI
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddSingleton<FirestoreDb>(
                provider => FirestoreDb.Create(GetFirestoreProjectId()));
            services.AddSingleton<PublisherClient>(
                provider => PublisherClient.CreateAsync(new TopicName(
                    GetProjectId(), GetTopicName())).Result);
            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Home/Error");
                // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
                app.UseHsts();
            }

            app.UseHttpsRedirection();
            app.UseStaticFiles();
            app.UseCookiePolicy();

            app.UseMvc(routes =>
            {
                routes.MapRoute(
                    name: "default",
                    template: "{controller=Home}/{action=Index}/{id?}");
            });
        }

    }
}

索引处理程序 Index 从 Firestore 获取所有现有翻译，并用以下列表填充 ViewModel：

BackgroundProcessing/TranslateUI/Controllers/HomeController.cs

在 GitHub 上查看

using Google.Cloud.Firestore;
using Google.Cloud.PubSub.V1;
using Google.Protobuf;
using Microsoft.AspNetCore.Mvc;
using System.Diagnostics;
using System.Linq;
using System.Threading.Tasks;
using TranslateUI.Models;

namespace TranslateUI.Controllers
{
    public class HomeController : Controller
    {
        private readonly FirestoreDb _firestore;
        private readonly PublisherClient _publisher;
        private CollectionReference _translations;

        public HomeController(FirestoreDb firestore, PublisherClient publisher)
        {
            _firestore = firestore;
            _publisher = publisher;
            _translations = _firestore.Collection("Translations");
        }

        [HttpPost]
        [HttpGet]
        public async Task<IActionResult> Index(string SourceText)
        {
            // Look up the most recent 20 translations.
            var query = _translations.OrderByDescending("TimeStamp")
                .Limit(20);
            var snapshotTask = query.GetSnapshotAsync();

            if (!string.IsNullOrWhiteSpace(SourceText))
            {
                // Submit a new translation request.
                await _publisher.PublishAsync(new PubsubMessage()
                {
                    Data = ByteString.CopyFromUtf8(SourceText)
                });
            }

            // Render the page.
            var model = new HomeViewModel()
            {
                Translations = (await snapshotTask).Documents.Select(
                    doc => doc.ConvertTo<Translation>()).ToList(),
                SourceText = SourceText
            };
            return View(model);
        }

        [ResponseCache(Duration = 0, Location = ResponseCacheLocation.None, NoStore = true)]
        public IActionResult Error()
        {
            return View(new ErrorViewModel { RequestId = Activity.Current?.Id ?? HttpContext.TraceIdentifier });
        }
    }
}

通过提交 HTML 表单来请求新的翻译。请求翻译处理程序将验证请求，并将消息发布到 Pub/Sub：

BackgroundProcessing/TranslateUI/Controllers/HomeController.cs

在 GitHub 上查看
```
// Submit a new translation request.
await _publisher.PublishAsync(new PubsubMessage()
{
    Data = ByteString.CopyFromUtf8(SourceText)
});
```

部署 `TranslateUI` 服务

在 BackgroundProcessing 目录中，运行 PowerShell 脚本以构建服务并将其部署到 Cloud Run：
```
./PublishTo-CloudRun.ps1
```

了解 `PublishTo-CloudRun.ps1` 脚本

PublishTo-CloudRun.ps1 脚本将应用发布到 Cloud Run。

该脚本将执行以下操作：

使用 dotnet publish 在本地构建应用。
使用 Cloud Build 构建运行应用的容器。

将应用部署到 Cloud Run。

BackgroundProcessing/PublishTo-CloudRun.ps1

在 GitHub 上查看

# 1. Build the application locally.
dotnet publish -c Release
# 2. Use Google Cloud Build to build the UI's container and publish to Google
# Container Registry.
gcloud builds submit --tag gcr.io/$projectId/translate-ui `
    TranslateUI/bin/Release/netcoreapp2.1/publish

# 3. Run the container with Google Cloud Run.
gcloud beta run deploy translate-ui --region $region --platform managed `
    --image gcr.io/$projectId/translate-ui --allow-unauthenticated

测试应用

成功运行 PublishTo-CloudRun.ps1 脚本后，尝试请求翻译。

PublishTo-CloudRun.ps1 脚本中的最终命令告诉您 UI 服务的网址。在您的终端窗口中，找到 TranslateUI 服务的网址：
```
gcloud beta run services describe translate-ui --region $region --format="get(status.address.hostname)"
```
在浏览器中，转到上一步获得的网址。

您将看到一个页面，其中包含一个空翻译列表和一个用于请求新翻译的表单。
在要翻译的文本 (Text to translate) 字段中，输入一些要翻译的文本，例如 Hello, World.
点击提交。
如需刷新页面，请点击刷新。翻译列表中有一个新行。如果您未看到翻译，请再等待几秒钟，然后重试。如果您仍未看到翻译，请参阅下一部分，了解如何调试应用。

调试应用

如果您无法连接到 Cloud Run 服务或看不到新的翻译，请检查以下内容：

检查 PublishTo-CloudRun.ps1 脚本是否已成功完成，并且未输出任何错误。如果有错误（如 message=Build failed），请修正这些错误，然后重试运行。
查看日志以了解错误：
1. 在 Google Cloud 控制台中，转到 Cloud Run 页面。
  
  转到 Cloud Run 页面
2. 点击服务名称 translate-ui。
3. 点击日志。

清理

为避免因本教程中使用的资源导致您的 Google Cloud 帐号产生费用，请删除包含这些资源的项目，或者保留项目但删除各个资源。

删除 Google Cloud 项目

在 Google Cloud 控制台中，进入管理资源页面。
转到“管理资源”
在项目列表中，选择要删除的项目，然后点击删除。
在对话框中输入项目 ID，然后点击关闭以删除项目。

删除 Cloud Run 服务。

删除您在本教程中创建的 Cloud Run 服务：

gcloud beta run services delete --region=$region translate-ui

gcloud beta run services delete --region=$region translate-worker

后续步骤

详细了解 Cloud Run。

使用 .NET 进行后台处理

目标

费用

准备工作

准备应用

了解 TranslateWorker 服务

部署 TranslateWorker 服务

了解 PublishTo-CloudRun.ps1 脚本

了解 TranslateUI 服务

部署 TranslateUI 服务

了解 PublishTo-CloudRun.ps1 脚本

测试应用

调试应用

清理

删除 Google Cloud 项目

删除 Cloud Run 服务。

后续步骤

了解 `TranslateWorker` 服务

部署 `TranslateWorker` 服务

了解 `PublishTo-CloudRun.ps1` 脚本

了解 `TranslateUI` 服务

部署 `TranslateUI` 服务

了解 `PublishTo-CloudRun.ps1` 脚本