public static class WebHostBuilderIISExtensions
{
    public static IWebHostBuilder UseIIS(this IWebHostBuilder hostBuilder);
}

三、Out-of-Process部署模式

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <location path="." inheritInChildApplications="false">
    <system.webServer>
      <handlers>
        <add name="aspNetCore" path="*" verb="*" modules="AspNetCoreModuleV2"resourceType="Unspecified" />
      </handlers>
      <aspNetCore processPath="dotnet" arguments=".\App.dll" stdoutLogEnabled="false" stdoutLogFile=".\logs\stdout" hostingModel="outofprocess" />
    </system.webServer>
  </location>
</configuration>

我們?cè)谏厦嫜菔玖薎n-Process的部署方式，現(xiàn)在我們直接修改配置文件web.config，按照上面的方式將<aspNetCore>配置節(jié)的hostingModel屬性設(shè)置為“outofprocess”，部署的應(yīng)用就自動(dòng)切換到Out-of-Process。此時(shí)再次以相同的方式訪問(wèn)部署的應(yīng)用，我們會(huì)發(fā)現(xiàn)瀏覽器上顯示的進(jìn)程名稱變成了“dotnet”。

<Project Sdk="Microsoft.NET.Sdk.Web">
    <PropertyGroup>
        <TargetFramework>net6.0</TargetFramework>
        <Nullable>enable</Nullable>
        <ImplicitUsings>enable</ImplicitUsings>
        <NoDefaultLaunchSettingsFile>true</NoDefaultLaunchSettingsFile>
        <AspNetCoreHostingModel>OutOfProcess</AspNetCoreHostingModel>
   </PropertyGroup>
</Project>

為了進(jìn)一步驗(yàn)證上述的這一系列環(huán)境變量是否存在，如下所示的演示程序會(huì)將以“ASPNETCORE_”為前綴的環(huán)境變量作為響應(yīng)內(nèi)容輸出來(lái)。除此之外，作為響應(yīng)輸出的還有進(jìn)程名稱、請(qǐng)求的PathBase和“MS-ASPNETCORE-TOKEN”報(bào)頭。

using System.Diagnostics;
using System.Text;

var app = WebApplication.Create(args);
app.Run(HandleAsync);
app.Run();

Task HandleAsync(HttpContext httpContext)
{
    var request = httpContext.Request;
    var configuration = httpContext.RequestServices.GetRequiredService<IConfiguration>();
    var builder = new StringBuilder();
    builder.AppendLine($"Process: {Process.GetCurrentProcess().ProcessName}");
    builder.AppendLine($"MS-ASPNETCORE-TOKEN: {request.Headers["MS-ASPNETCORE-TOKEN"]}");
    builder.AppendLine($"PathBase: {request.PathBase}");
    builder.AppendLine("Environment Variables");
    foreach (string key in Environment.GetEnvironmentVariables().Keys)
    {
        if (key.StartsWith("ASPNETCORE_"))
        {
            builder.AppendLine($"\t{key}={Environment.GetEnvironmentVariable(key)}");
        }
    }
    return httpContext.Response.WriteAsync(builder.ToString());
}

應(yīng)用重新發(fā)布之后，再次利用瀏覽器訪問(wèn)后回得到如圖5所示的結(jié)果。我們可以從這里找到上述的環(huán)境變量，請(qǐng)求攜帶的“MS-ASPNETCORE-TOKEN”報(bào)頭正好與對(duì)應(yīng)環(huán)境變量的值一致，應(yīng)用在IIS中的虛擬目錄作為了應(yīng)用路徑被寫(xiě)入環(huán)境變量并成為請(qǐng)求的PathBase。如果站點(diǎn)提供了HTTPS終結(jié)點(diǎn)，其端口還會(huì)寫(xiě)入“ASPNETCORE_ANCM_HTTPS_PORT”這個(gè)環(huán)境變量，這是為了實(shí)現(xiàn)針對(duì)HTTPS終結(jié)點(diǎn)的重定向而設(shè)計(jì)的。

public class IISMiddleware
{
    public IISMiddleware(RequestDelegate next, ILoggerFactory loggerFactory, IOptions<IISOptions> options, string pairingToken, IAuthenticationSchemeProvider authentication, IHostApplicationLifetime applicationLifetime);
    public IISMiddleware(RequestDelegate next, ILoggerFactory loggerFactory, IOptions<IISOptions> options, string pairingToken, bool isWebsocketsSupported, IAuthenticationSchemeProvider authentication, IHostApplicationLifetime applicationLifetime);
    public Task Invoke(HttpContext httpContext);
    public Task Invoke(HttpContext httpContext)
}
public class IISOptions
{
    public bool AutomaticAuthentication { get; set; }
    public string? AuthenticationDisplayName { get; set; }
    public bool ForwardClientCertificate { get; set; }
}

IIS利用WAS根據(jù)請(qǐng)求激活工作進(jìn)程w3wp.exe。如果站點(diǎn)長(zhǎng)時(shí)間未曾訪問(wèn)，它還會(huì)自動(dòng)關(guān)閉工作進(jìn)程。如果工作進(jìn)程都關(guān)閉了，承載ASP.NET CORE應(yīng)用的dotnet.exe進(jìn)程自然也應(yīng)該關(guān)閉。為了關(guān)閉應(yīng)用承載進(jìn)程，ASP.NET CORE Core Module會(huì)發(fā)送一個(gè)特殊的請(qǐng)求，該請(qǐng)求攜帶一個(gè)值為“shutdown”的“MS-ASPNETCORE-EVENT”報(bào)頭，IISMiddleware中間件在接收到該請(qǐng)求時(shí)會(huì)利用注入的IHostApplicationLifetime對(duì)象關(guān)閉當(dāng)前應(yīng)用。如果不支持WebSocket，該中間件還會(huì)將代表“可升級(jí)到雙向通信”的IHttpUpgradeFeature特性刪除。將應(yīng)用路徑設(shè)置為請(qǐng)求的PathBase也是由這個(gè)中間件完成的。由于IISMiddleware中間件所作的實(shí)際上是對(duì)HttpContext上下文進(jìn)行初始化的工作，所以它必須優(yōu)先執(zhí)行才有意義，為了將此中間件置于管道的前端，如下這個(gè)IISSetupFilter被定義出來(lái)完成對(duì)該中間件的注冊(cè)。

internal class IISSetupFilter : IStartupFilter
{
    internal IISSetupFilter(string pairingToken, PathString pathBase, bool isWebsocketsSupported);
    public Action<IApplicationBuilder> Configure(Action<IApplicationBuilder> next);
}

IISSetupFilter最終是通過(guò)IWebHostBuilder接口如下這個(gè)UseIISIntegration擴(kuò)展方法進(jìn)行注冊(cè)的。這個(gè)方法還負(fù)責(zé)從當(dāng)前配置和環(huán)境變量提取端口號(hào)，并完成監(jiān)聽(tīng)地址的注冊(cè)。由于KestrelServer默認(rèn)會(huì)選擇注冊(cè)到服務(wù)器上的終結(jié)點(diǎn)，所以該方法會(huì)利用配置將IServerAddressesFeature特性的PreferHostingUrls屬性設(shè)置為True，這里設(shè)置的監(jiān)聽(tīng)地址才會(huì)生效。這個(gè)方法還會(huì)根據(jù)當(dāng)前IIS站點(diǎn)的設(shè)置對(duì)IISOptions作相應(yīng)設(shè)置。由于IHostBuider接口ConfigureWebHostDefaults擴(kuò)展方法內(nèi)部也會(huì)調(diào)用這個(gè)方法，我們并不需要為此做額外的工作。

public static class WebHostBuilderIISExtensions
{
    public static IWebHostBuilder UseIISIntegration(this IWebHostBuilder hostBuilder);
}

四、<aspnetcore>配置

<aspNetCore
    processPath 		= "dotnet"
    arguments 			= ".\App.dll"
    stdoutLogEnabled 		= "false"
    stdoutLogFile 		= ".\logs\stdout"
    hostingModel		= "outofprocess"
    forwardWindowsAuthToken	= "true"
    processesPerApplication	= "10"
    rapidFailsPerMinute	= "5"
    requestTimeout		= "00:02:00"
    shutdownTimeLimit		= "60"
    startupRetryCount		= "3"
    startupTimeLimit		= "60">
    <environmentVariables>
        <environmentVariable name = "ASPNETCORE_ENVIRONMENT" value = "Development"/>
    </environmentVariables>
    <handlerSettings>
        <handlerSetting name = "stackSize" value = "2097152" />
        <handlerSetting name = "debugFile" value = ".\logs\aspnetcore-debug.log" />
        <handlerSetting name = "debugLevel" value = "FILE,TRACE" />
    </handlerSettings>
</aspNetCore>

上面這段XML片段包含了完整的<aspNetCore>配置屬性，下表對(duì)這些配置進(jìn)行了簡(jiǎn)單的說(shuō)明。設(shè)置的文件可以采用絕對(duì)路徑和相對(duì)于部署目錄（通過(guò) “.”表示）的相對(duì)路徑。