ASP.NET Core设计初衷是开源跨平台、高性能Web服务器,其中跨平台特性较早期ASP.NET是一个显著的飞跃,.NET现可以理直气壮与JAVA同台竞技,而ASP.NET Core的高性能特性更是成为致胜法宝。
ASP.NET Core 2.1+为IIS托管新增In-Process模型并作为默认选项(使用IISHttpServer替代了Kestrel,dotnet程序由IIS网站进程w3wp.exe内部托管)。
为展示ASP.NET Core跨平台特性,本文重点着墨经典的Out-Process托管模型。
宏观设计
为解耦平台web服务器差异,程序内置Http服务组件Kestrel,由web服务器转发请求到Kestrel。
老牌web服务器定位成反向代理服务器,转发请求到ASP.NET Core程序(分别由IIS ASP.NET Core Module和Nginx负责)
常规代理服务器,只用于代理内部主机对外网的连接需求,一般不支持外部对内部网络的访问请求; 当一个代理服务器能够代理外部网络的主机,访问内部网络,这种代理服务器被称为反向代理服务器 。
平台web代理服务器、ASP.NET Core程序(dotnet.exe) 均为独立进程,平台自行决定互动细节,只需确保平台web服务器与Kestrel形成Http通信。
Kestrel
与老牌web服务器解耦,实现跨平台部署。
Kestrel使ASP.NET Core具备了基本web服务器的能力,在内网部署和开发环境完全可使用dotnet.exe自宿模式运行。
Kestrel定位是Http服务组件,实力还比不上老牌web服务器,在timeout机制、web缓存、响应压缩等不占优势,在安全性等方面还有缺陷。
因此在生产环境中必须使用老牌web服务器反向代理请求。
跨平台管控程序,转发请求
要实现企业级稳定部署:
*nix平台
将ASP.NET Core程序以dotnet.exe自宿模式运行,并配置为系统守护进程(管控应用),再由Nginx转发请求。
以下使用systemd创建进程服务文件 /etc/systemd/system/kestrel-eqidproxyserver.service
[Unit]
Description=EqidProxyServer deploy on centos[Service]
WorkingDirectory=/var/www/eqidproxyserver/eqidproxyServer
ExecStart=/usr/bin/dotnet /var/www/eqidproxyserver/eqidproxyServer/EqidProxyServer.dll
Restart=always
# Restart service after 10 seconds if the dotnet service crashes:
RestartSec=10
TimeoutStopSec=90
KillSignal=SIGINT
SyslogIdentifier=dotnet-example
User=root
Environment=ASPNETCORE_ENVIRONMENT=Production
Environment=DOTNET_PRINT_TELEMETRY_MESSAGE=false[Install]
WantedBy=multi-user.target
// 启用服务,在localhost:5000端口侦听请求
sudo systemctl enable kestrel-eqidproxyserver.service
安装Nginx,并配置Nginx转发请求到localhost:5000:
server {listen 80;server_name default_website;root /usr/share/nginx/html;# Load configuration files for the default server block.include /etc/nginx/default.d/*.conf;location / {proxy_pass http://localhost:5000;proxy_http_version 1.1;proxy_set_header Upgrade $http_upgrade;proxy_set_header Connection keep-alive;proxy_set_header Host $host;proxy_cache_bypass $http_upgrade;proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;proxy_set_header X-Forwarded-Proto $scheme;}}
Windows平台
[ 管控应用、转发请求] 由ASP.NET Core Module(插入在IIS Pipeline中的原生组件,下面简称ACM)一手操办,w3wp.exe、dotnet.exe的互动关系是通过父子进程维系。
下图脚本力证dotnet.exe进程是w3wp.exe创建出来的子进程:
得益此关系,ACM在创建dotnet.exe子进程时能指定环境变量,约定donet.exe接收(IIS转发的请求)的侦听端口。
实际源码看ACM为子进程设定三个重要的环境变量:
ASPNETCORE_PORT 约定 Kestrel将会在此端口上监听
ASPNETCORE_APPL_PATH
ASPNETCORE_TOKEN 约定 携带该Token的请求为合法的转发请求
与ACM夫唱妇随的是UseIISIntegration()扩展方法,完成如下工作:
① 启动Kestrel服务在http://localhost:{ASPNETCORE_PORT}上监听
② 根据 {ASPNETCORE_TOKEN} 检查请求是否来自ACM转发
ACM转发的请求,会携带名为MS-ASPNETCORE-TOKEN:******的Request Header,以便dotnet.exe对比研判。
③ 利用ForwardedHeaderMiddleware中间件保存原始请求信息
linux平台部署需要手动启用ForwardedHeader middleware https://docs.microsoft.com/en-us/aspnet/core/host-and-deploy/proxy-load-balancer?view=aspnetcore-3.1
源码快速验证:
namespace Microsoft.AspNetCore.Hosting
{public static class WebHostBuilderIISExtensions{// These are defined as ASPNETCORE_ environment variables by IIS's AspNetCoreModule.private static readonly string ServerPort = "PORT";private static readonly string ServerPath = "APPL_PATH";private static readonly string PairingToken = "TOKEN";private static readonly string IISAuth = "IIS_HTTPAUTH";private static readonly string IISWebSockets = "IIS_WEBSOCKETS_SUPPORTED";/// <summary>/// Configures the port and base path the server should listen on when running behind AspNetCoreModule./// The app will also be configured to capture startup errors.public static IWebHostBuilder UseIISIntegration(this IWebHostBuilder hostBuilder){var port = hostBuilder.GetSetting(ServerPort) ?? Environment.GetEnvironmentVariable($"ASPNETCORE_{ServerPort}");var path = hostBuilder.GetSetting(ServerPath) ?? Environment.GetEnvironmentVariable($"ASPNETCORE_{ServerPath}");var pairingToken = hostBuilder.GetSetting(PairingToken) ?? Environment.GetEnvironmentVariable($"ASPNETCORE_{PairingToken}");var iisAuth = hostBuilder.GetSetting(IISAuth) ?? Environment.GetEnvironmentVariable($"ASPNETCORE_{IISAuth}");var websocketsSupported = hostBuilder.GetSetting(IISWebSockets) ?? Environment.GetEnvironmentVariable($"ASPNETCORE_{IISWebSockets}");bool isWebSocketsSupported;if (!bool.TryParse(websocketsSupported, out isWebSocketsSupported)){// If the websocket support variable is not set, we will always fallback to assuming websockets are enabled.isWebSocketsSupported = (Environment.OSVersion.Version >= new Version(6, 2));}if (!string.IsNullOrEmpty(port) && !string.IsNullOrEmpty(path) && !string.IsNullOrEmpty(pairingToken)){// Set flag to prevent double service configurationhostBuilder.UseSetting(nameof(UseIISIntegration), true.ToString());var enableAuth = false;if (string.IsNullOrEmpty(iisAuth)){// back compat with older ANCM versionsenableAuth = true;}else{// Lightup a new ANCM variable that tells us if auth is enabled.foreach (var authType in iisAuth.Split(new[] { ';' }, StringSplitOptions.RemoveEmptyEntries)){if (!string.Equals(authType, "anonymous", StringComparison.OrdinalIgnoreCase)){enableAuth = true;break;}}}var address = "http://127.0.0.1:" + port;hostBuilder.CaptureStartupErrors(true);hostBuilder.ConfigureServices(services =>{// Delay register the url so users don't accidentally overwrite it.hostBuilder.UseSetting(WebHostDefaults.ServerUrlsKey, address);hostBuilder.PreferHostingUrls(true);services.AddSingleton<IServerIntegratedAuth>(_ => new ServerIntegratedAuth(){IsEnabled = enableAuth,AuthenticationScheme = IISDefaults.AuthenticationScheme});services.AddSingleton<IStartupFilter>(new IISSetupFilter(pairingToken, new PathString(path), isWebSocketsSupported));services.Configure<ForwardedHeadersOptions>(options =>{options.ForwardedHeaders = ForwardedHeaders.XForwardedFor | ForwardedHeaders.XForwardedProto;});services.Configure<IISOptions>(options =>{options.ForwardWindowsAuthentication = enableAuth;});services.AddAuthenticationCore();});}return hostBuilder;}}
}
总结
ASP.NET Core跨平台的核心在于 程序内置Kestrel HTTP通信组件,解耦web服务器差异;依平台特性约定Http通信细节。
本文从框架设计初衷、进程模型、组件交互验证我对ASP.NET Core跨平台特性的理解。
+ CentOS上部署ASP.NET Core完整版请参考:https://www.cnblogs.com/JulianHuang/p/10455644.html
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