#asp.net core#先让我们看一下最小API的代码,通过以下几行代码就可以搭建一个简单的asp.net core web服务器,是不是十分简洁?
var builder = WebApplication.CreateBuilder(args);var app = builder.Build();app.MapGet("/", () => "Hello World!");app.Run();访问localhost:5001浏览器即可响应helloworld,那源码到底是如何实现http请求监听的呢?可以通过IIS,Kestrel实现,我们来看下Kestrel的实现,下图是实现的总体流程
整体运行图
让我们通过源码整体看一下执行过程,源码以.NET 7为例
1.WebApplication执行Run()方法
/// <summary>/// Runs an application and block the calling thread until host shutdown./// </summary>/// <param name="url">The URL to listen to if the server hasn't been configured directly.</param>public void Run(string? url = null){ Listen(url); HostingAbstractionsHostExtensions.Run(this);}2.HostingAbstractionsHostExtensions执行RunAsync()方法
/// <summary> /// Runs an application and returns a <see cref="Task"/> that only completes when the token is triggered or shutdown is triggered. /// The <paramref name="host"/> instance is disposed of after running. /// </summary> /// <param name="host">The <see cref="IHost"/> to run.</param> /// <param name="token">The token to trigger shutdown.</param> /// <returns>The <see cref="Task"/> that represents the asynchronous operation.</returns> public static async Task RunAsync(this IHost host, CancellationToken token = default) { try { await host.StartAsync(token).ConfigureAwait(false); await host.WaitForShutdownAsync(token).ConfigureAwait(false); } finally { if (host is IAsyncDisposable asyncDisposable) { await asyncDisposable.DisposeAsync().ConfigureAwait(false); } else { host.Dispose(); } } }3 KestrelServer执行StartAsync()方法
public Task StartAsync<TContext>(IHttpApplication<TContext> application, CancellationToken cancellationToken) where TContext : notnull{ return _innerKestrelServer.StartAsync(application, cancellationToken);}4.我们来看下Start方法,重点看_transportManager.BindAsync方法
public async Task StartAsync<TContext>(IHttpApplication<TContext> application, CancellationToken cancellationToken) where TContext : notnull { try { ValidateOptions(); if (_hasStarted) { // The server has already started and/or has not been cleaned up yet throw new InvalidOperationException(CoreStrings.ServerAlreadyStarted); } _hasStarted = true; ServiceContext.Heartbeat?.Start(); async Task OnBind(ListenOptions options, CancellationToken onBindCancellationToken) { var hasHttp1 = options.Protocols.HasFlag(HttpProtocols.Http1); var hasHttp2 = options.Protocols.HasFlag(HttpProtocols.Http2); var hasHttp3 = options.Protocols.HasFlag(HttpProtocols.Http3); var hasTls = options.IsTls; // Filter out invalid combinations. if (!hasTls) { // Http/1 without TLS, no-op HTTP/2 and 3. if (hasHttp1) { hasHttp2 = false; hasHttp3 = false; } // Http/3 requires TLS. Note we only let it fall back to HTTP/1, not HTTP/2 else if (hasHttp3) { throw new InvalidOperationException("HTTP/3 requires HTTPS."); } } // Quic isn't registered if it's not supported, throw if we can't fall back to 1 or 2 if (hasHttp3 && _multiplexedTransportFactory is null && !(hasHttp1 || hasHttp2)) { throw new InvalidOperationException("This platform doesn't support QUIC or HTTP/3."); } // Disable adding alt-svc header if endpoint has configured not to or there is no // multiplexed transport factory, which happens if QUIC isn't supported. var addAltSvcHeader = !options.DisableAltSvcHeader && _multiplexedTransportFactory != null; var configuredEndpoint = options.EndPoint; // Add the HTTP middleware as the terminal connection middleware if (hasHttp1 || hasHttp2 || options.Protocols == HttpProtocols.None) // TODO a test fails because it doesn't throw an exception in the right place // when there is no HttpProtocols in KestrelServer, can we remove/change the test? { if (_transportFactory is null) { throw new InvalidOperationException($"Cannot start HTTP/1.x or HTTP/2 server if no {nameof(IConnectionListenerFactory)} is registered."); } options.UseHttpServer(ServiceContext, application, options.Protocols, addAltSvcHeader); var connectionDelegate = options.Build(); // Add the connection limit middleware connectionDelegate = EnforceConnectionLimit(connectionDelegate, Options.Limits.MaxConcurrentConnections, Trace); options.EndPoint = await _transportManager.BindAsync(configuredEndpoint, connectionDelegate, options.EndpointConfig, onBindCancellationToken).ConfigureAwait(false); } if (hasHttp3 && _multiplexedTransportFactory is not null) { // Check if a previous transport has changed the endpoint. If it has then the endpoint is dynamic and we can't guarantee it will work for other transports. // For more details, see https://github.com/dotnet/aspnetcore/issues/42982 if (!configuredEndpoint.Equals(options.EndPoint)) { Trace.LogError(CoreStrings.DynamicPortOnMultipleTransportsNotSupported); } else { // 增加 ConnectionContext 中间件,后面处理Http请求会用到 options.UseHttp3Server(ServiceContext, application, options.Protocols, addAltSvcHeader); var multiplexedConnectionDelegate = ((IMultiplexedConnectionBuilder)options).Build(); // Add the connection limit middleware multiplexedConnectionDelegate = EnforceConnectionLimit(multiplexedConnectionDelegate, Options.Limits.MaxConcurrentConnections, Trace); // 绑定 options.EndPoint = await _transportManager.BindAsync(configuredEndpoint, multiplexedConnectionDelegate, options, onBindCancellationToken).ConfigureAwait(false); } } } AddressBindContext = new AddressBindContext(_serverAddresses, Options, Trace, OnBind); await BindAsync(cancellationToken).ConfigureAwait(false); } catch { // Don't log the error https://github.com/dotnet/aspnetcore/issues/29801 Dispose(); throw; } // Register the options with the event source so it can be logged (if necessary) KestrelEventSource.Log.AddServerOptions(Options); }5 开始绑定socket端口
public async Task<EndPoint> BindAsync(EndPoint endPoint, ConnectionDelegate connectionDelegate, EndpointConfig? endpointConfig, CancellationToken cancellationToken){ if (_transportFactory is null) { throw new InvalidOperationException($"Cannot bind with {nameof(ConnectionDelegate)} no {nameof(IConnectionListenerFactory)} is registered."); } var transport = await _transportFactory.BindAsync(endPoint, cancellationToken).ConfigureAwait(false); StartAcceptLoop(new GenericConnectionListener(transport), c => connectionDelegate(c), endpointConfig); return transport.EndPoint;}6.注意下这种线程的写法
ThreadPool.UnsafeQueueUserWorkItem(StartAcceptingConnectionsCore, listener, preferLocal: false);7 通过 while循环不断监听socket连接请求
private void StartAcceptingConnectionsCore(IConnectionListener<T> listener){ // REVIEW: Multiple accept loops in parallel? _ = AcceptConnectionsAsync(); async Task AcceptConnectionsAsync() { try { while (true) { var connection = await listener.AcceptAsync(); if (connection == null) { // We're done listening break; } // Add the connection to the connection manager before we queue it for execution var id = _transportConnectionManager.GetNewConnectionId(); var kestrelConnection = new KestrelConnection<T>( id, _serviceContext, _transportConnectionManager, _connectionDelegate, connection, Log); _transportConnectionManager.AddConnection(id, kestrelConnection); Log.ConnectionAccepted(connection.ConnectionId); KestrelEventSource.Log.ConnectionQueuedStart(connection); ThreadPool.UnsafeQueueUserWorkItem(kestrelConnection, preferLocal: false); } } catch (Exception ex) { // REVIEW: If the accept loop ends should this trigger a server shutdown? It will manifest as a hang Log.LogCritical(0, ex, "The connection listener failed to accept any new connections."); } finally { _acceptLoopTcs.TrySetResult(); } }}8 使用Socket AcceptAsync的方法
public async ValueTask<ConnectionContext?> AcceptAsync(CancellationToken cancellationToken = default){ while (true) { try { Debug.Assert(_listenSocket != null, "Bind must be called first."); var acceptSocket = await _listenSocket.AcceptAsync(cancellationToken); // Only apply no delay to Tcp based endpoints if (acceptSocket.LocalEndPoint is IPEndPoint) { acceptSocket.NoDelay = _options.NoDelay; } return _factory.Create(acceptSocket); } catch (ObjectDisposedException) { // A call was made to UnbindAsync/DisposeAsync just return null which signals we're done return null; } catch (SocketException e) when (e.SocketErrorCode == SocketError.OperationAborted) { // A call was made to UnbindAsync/DisposeAsync just return null which signals we're done return null; } catch (SocketException) { // The connection got reset while it was in the backlog, so we try again. SocketsLog.ConnectionReset(_logger, connectionId: "(null)"); } }}9 当有连接过来后执行 KestrelConnection的Execute方法
internal async Task ExecuteAsync(){ var connectionContext = _transportConnection; try { KestrelEventSource.Log.ConnectionQueuedStop(connectionContext); Logger.ConnectionStart(connectionContext.ConnectionId); KestrelEventSource.Log.ConnectionStart(connectionContext); using (BeginConnectionScope(connectionContext)) { try { await _connectionDelegate(connectionContext); } catch (Exception ex) { Logger.LogError(0, ex, "Unhandled exception while processing {ConnectionId}.", connectionContext.ConnectionId); } } } finally { await FireOnCompletedAsync(); Logger.ConnectionStop(connectionContext.ConnectionId); KestrelEventSource.Log.ConnectionStop(connectionContext); // Dispose the transport connection, this needs to happen before removing it from the // connection manager so that we only signal completion of this connection after the transport // is properly torn down. await connectionContext.DisposeAsync(); _transportConnectionManager.RemoveConnection(_id); }}10 监听到socket连接后,开始执行连接的委托,就是我们第4步注释提到的提前注入的一个中间件
public Task OnConnectionAsync(ConnectionContext connectionContext){ var memoryPoolFeature = connectionContext.Features.Get<IMemoryPoolFeature>(); var protocols = connectionContext.Features.Get<HttpProtocolsFeature>()?.HttpProtocols ?? _endpointDefaultProtocols; var localEndPoint = connectionContext.LocalEndPoint as IPEndPoint; var altSvcHeader = _addAltSvcHeader && localEndPoint != null ? HttpUtilities.GetEndpointAltSvc(localEndPoint, protocols) : null; var httpConnectionContext = new HttpConnectionContext( connectionContext.ConnectionId, protocols, altSvcHeader, connectionContext, _serviceContext, connectionContext.Features, memoryPoolFeature?.MemoryPool ?? System.Buffers.MemoryPool<byte>.Shared, localEndPoint, connectionContext.RemoteEndPoint as IPEndPoint); httpConnectionContext.Transport = connectionContext.Transport; var connection = new HttpConnection(httpConnectionContext); return connection.ProcessRequestsAsync(_application);}11 通过while循环监听Http请求,如果连接是keepAlive则不需要重复连接socket,一直在监听即可（如果是keeplive http连接不会断开）
private async Task ProcessRequests<TContext>(IHttpApplication<TContext> application) where TContext : notnull { while (_keepAlive) { if (_context.InitialExecutionContext is null) { // If this is a first request on a non-Http2Connection, capture a clean ExecutionContext. _context.InitialExecutionContext = ExecutionContext.Capture(); } else { // Clear any AsyncLocals set during the request; back to a clean state ready for next request // And/or reset to Http2Connection's ExecutionContext giving access to the connection logging scope // and any other AsyncLocals set by connection middleware. ExecutionContext.Restore(_context.InitialExecutionContext); } BeginRequestProcessing(); var result = default(ReadResult); bool endConnection; do { if (BeginRead(out var awaitable)) { result = await awaitable; } } while (!TryParseRequest(result, out endConnection)); if (endConnection) { // Connection finished, stop processing requests return; } var messageBody = CreateMessageBody(); if (!messageBody.RequestKeepAlive) { _keepAlive = false; } IsUpgradableRequest = messageBody.RequestUpgrade; InitializeBodyControl(messageBody); var context = application.CreateContext(this); try { KestrelEventSource.Log.RequestStart(this); // Run the application code for this request await application.ProcessRequestAsync(context); // Trigger OnStarting if it hasn't been called yet and the app hasn't // already failed. If an OnStarting callback throws we can go through // our normal error handling in ProduceEnd. // https://github.com/aspnet/KestrelHttpServer/issues/43 if (!HasResponseStarted && _applicationException == null && _onStarting?.Count > 0) { await FireOnStarting(); } if (!_connectionAborted && !VerifyResponseContentLength(out var lengthException)) { ReportApplicationError(lengthException); } } catch (BadHttpRequestException ex) { // Capture BadHttpRequestException for further processing // This has to be caught here so StatusCode is set properly before disposing the HttpContext // (DisposeContext logs StatusCode). SetBadRequestState(ex); ReportApplicationError(ex); } catch (Exception ex) { ReportApplicationError(ex); } KestrelEventSource.Log.RequestStop(this); // At this point all user code that needs use to the request or response streams has completed. // Using these streams in the OnCompleted callback is not allowed. try { Debug.Assert(_bodyControl != null); await _bodyControl.StopAsync(); } catch (Exception ex) { // BodyControl.StopAsync() can throw if the PipeWriter was completed prior to the application writing // enough bytes to satisfy the specified Content-Length. This risks double-logging the exception, // but this scenario generally indicates an app bug, so I don't want to risk not logging it. ReportApplicationError(ex); } // 4XX responses are written by TryProduceInvalidRequestResponse during connection tear down. if (_requestRejectedException == null) { if (!_connectionAborted) { // Call ProduceEnd() before consuming the rest of the request body to prevent // delaying clients waiting for the chunk terminator: // // https://github.com/dotnet/corefx/issues/17330#issuecomment-288248663 // // This also prevents the 100 Continue response from being sent if the app // never tried to read the body. // https://github.com/aspnet/KestrelHttpServer/issues/2102 // // ProduceEnd() must be called before _application.DisposeContext(), to ensure // HttpContext.Response.StatusCode is correctly set when // IHttpContextFactory.Dispose(HttpContext) is called. await ProduceEnd(); } else if (!HasResponseStarted) { // If the request was aborted and no response was sent, there's no // meaningful status code to log. StatusCode = 0; } } if (_onCompleted?.Count > 0) { await FireOnCompleted(); } application.DisposeContext(context, _applicationException); // Even for non-keep-alive requests, try to consume the entire body to avoid RSTs. if (!_connectionAborted && _requestRejectedException == null && !messageBody.IsEmpty) { await messageBody.ConsumeAsync(); } if (HasStartedConsumingRequestBody) { await messageBody.StopAsync(); } } }11 处理Http请求中间再执行我们在Http管道里的委托方法,用来进行HTTP的构造和HTTP Response,管道这里就不展开介绍了,可以看下官网的介绍
12 最后通过Http1OutputProducer最终响应结果
public ValueTask<FlushResult> WriteStreamSuffixAsync(){ ValueTask<FlushResult> result = default; lock (_contextLock) { if (!_writeStreamSuffixCalled) { if (_autoChunk) { var writer = new BufferWriter<PipeWriter>(_pipeWriter); result = WriteAsyncInternal(ref writer, EndChunkedResponseBytes); } else if (_unflushedBytes > 0) { result = FlushAsync(); } _writeStreamSuffixCalled = true; } } return result;}版权声明：内容来源于互联网和用户投稿 如有侵权请联系删除