public async Task ExecuteAsync(HttpContext context, HttpConnectionDispatcherOptions options, ConnectionDelegate connectionDelegate)
{
// Create the log scope and attempt to pass the Connection ID to it so as many logs as possible contain
// the Connection ID metadata. If this is the negotiate request then the Connection ID for the scope will
// be set a little later.
var logScope = new ConnectionLogScope(GetConnectionId(context));
using (_logger.BeginScope(logScope))
{
if (HttpMethods.IsPost(context.Request.Method))
{
// POST /{path}
await ProcessSend(context, options);
}
else if (HttpMethods.IsGet(context.Request.Method))
{
// GET /{path}
await ExecuteAsync(context, connectionDelegate, options, logScope);
}
else if (HttpMethods.IsDelete(context.Request.Method))
{
// DELETE /{path}
await ProcessDeleteAsync(context);
}
else
{
context.Response.ContentType = "text/plain";
context.Response.StatusCode = StatusCodes.Status405MethodNotAllowed;
}
}
}
public async Task ExecuteNegotiateAsync(HttpContext context, HttpConnectionDispatcherOptions options)
{
// Create the log scope and the scope connectionId param will be set when the connection is created.
var logScope = new ConnectionLogScope(connectionId: string.Empty);
using (_logger.BeginScope(logScope))
{
if (HttpMethods.IsPost(context.Request.Method))
{
// POST /{path}/negotiate
await ProcessNegotiate(context, options, logScope);
}
else
{
context.Response.ContentType = "text/plain";
context.Response.StatusCode = StatusCodes.Status405MethodNotAllowed;
}
}
}
public async Task ExecuteAsync(HttpContext context, HttpConnectionDispatcherOptions options, ConnectionDelegate connectionDelegate)
{
// Create the log scope and attempt to pass the Connection ID to it so as many logs as possible contain
// the Connection ID metadata. If this is the negotiate request then the Connection ID for the scope will
// be set a little later.
HttpConnectionContext?connectionContext = null;
var connectionToken = GetConnectionToken(context);
if (!StringValues.IsNullOrEmpty(connectionToken))
{
// Use ToString; IsNullOrEmpty doesn't tell the compiler anything about implicit conversion to string.
_manager.TryGetConnection(connectionToken.ToString(), out connectionContext);
}
var logScope = new ConnectionLogScope(connectionContext?.ConnectionId);
using (_logger.BeginScope(logScope))
{
if (HttpMethods.IsPost(context.Request.Method))
{
// POST /{path}
await ProcessSend(context, options);
}
else if (HttpMethods.IsGet(context.Request.Method))
{
// GET /{path}
await ExecuteAsync(context, connectionDelegate, options, logScope);
}
else if (HttpMethods.IsDelete(context.Request.Method))
{
// DELETE /{path}
await ProcessDeleteAsync(context);
}
else
{
context.Response.ContentType = "text/plain";
context.Response.StatusCode = StatusCodes.Status405MethodNotAllowed;
}
}
}
private async Task <bool> EnsureConnectionStateAsync(HttpConnectionContext connection, HttpContext context, HttpTransportType transportType, HttpTransportType supportedTransports, ConnectionLogScope logScope, HttpConnectionDispatcherOptions options)
{
if ((supportedTransports & transportType) == 0)
{
context.Response.ContentType = "text/plain";
context.Response.StatusCode = StatusCodes.Status404NotFound;
Log.TransportNotSupported(_logger, transportType);
await context.Response.WriteAsync($"{transportType} transport not supported by this end point type");
return(false);
}
// Set the IHttpConnectionFeature now that we can access it.
connection.Features.Set(context.Features.Get <IHttpConnectionFeature>());
if (connection.TransportType == HttpTransportType.None)
{
connection.TransportType = transportType;
}
else if (connection.TransportType != transportType)
{
context.Response.ContentType = "text/plain";
context.Response.StatusCode = StatusCodes.Status400BadRequest;
Log.CannotChangeTransport(_logger, connection.TransportType, transportType);
await context.Response.WriteAsync("Cannot change transports mid-connection");
return(false);
}
// Configure transport-specific features.
if (transportType == HttpTransportType.LongPolling)
{
connection.HasInherentKeepAlive = true;
// For long polling, the requests come and go but the connection is still alive.
// To make the IHttpContextFeature work well, we make a copy of the relevant properties
// to a new HttpContext. This means that it's impossible to affect the context
// with subsequent requests.
var existing = connection.HttpContext;
if (existing == null)
{
CloneHttpContext(context, connection);
}
else
{
// Set the request trace identifier to the current http request handling the poll
existing.TraceIdentifier = context.TraceIdentifier;
// Don't copy the identity if it's a windows identity
// We specifically clone the identity on first poll if it's a windows identity
// If we swapped the new User here we'd have to dispose the old identities which could race with the application
// trying to access the identity.
if (!(context.User.Identity is WindowsIdentity))
{
existing.User = context.User;
}
}
}
else
{
connection.HttpContext = context;
}
// Setup the connection state from the http context
connection.User = connection.HttpContext?.User;
// Set the Connection ID on the logging scope so that logs from now on will have the
// Connection ID metadata set.
logScope.ConnectionId = connection.ConnectionId;
return(true);
}
private async Task ProcessNegotiate(HttpContext context, HttpConnectionDispatcherOptions options, ConnectionLogScope logScope)
{
context.Response.ContentType = "application/json";
string?error = null;
int clientProtocolVersion = 0;
if (context.Request.Query.TryGetValue("NegotiateVersion", out var queryStringVersion))
{
// Set the negotiate response to the protocol we use.
var queryStringVersionValue = queryStringVersion.ToString();
if (!int.TryParse(queryStringVersionValue, out clientProtocolVersion))
{
error = $"The client requested an invalid protocol version '{queryStringVersionValue}'";
Log.InvalidNegotiateProtocolVersion(_logger, queryStringVersionValue);
}
else if (clientProtocolVersion < options.MinimumProtocolVersion)
{
error = $"The client requested version '{clientProtocolVersion}', but the server does not support this version.";
Log.NegotiateProtocolVersionMismatch(_logger, clientProtocolVersion);
}
else if (clientProtocolVersion > _protocolVersion)
{
clientProtocolVersion = _protocolVersion;
}
}
else if (options.MinimumProtocolVersion > 0)
{
// NegotiateVersion wasn't parsed meaning the client requests version 0.
error = $"The client requested version '0', but the server does not support this version.";
Log.NegotiateProtocolVersionMismatch(_logger, 0);
}
// Establish the connection
HttpConnectionContext?connection = null;
if (error == null)
{
connection = CreateConnection(options, clientProtocolVersion);
}
// Set the Connection ID on the logging scope so that logs from now on will have the
// Connection ID metadata set.
logScope.ConnectionId = connection?.ConnectionId;
// Don't use thread static instance here because writer is used with async
var writer = new MemoryBufferWriter();
try
{
// Get the bytes for the connection id
WriteNegotiatePayload(writer, connection?.ConnectionId, connection?.ConnectionToken, context, options, clientProtocolVersion, error);
Log.NegotiationRequest(_logger);
// Write it out to the response with the right content length
context.Response.ContentLength = writer.Length;
await writer.CopyToAsync(context.Response.Body);
}
finally
{
writer.Reset();
}
}
private async Task ExecuteAsync(HttpContext context, ConnectionDelegate connectionDelegate, HttpConnectionDispatcherOptions options, ConnectionLogScope logScope)
{
// set a tag to allow Application Performance Management tools to differentiate long running requests for reporting purposes
context.Features.Get <IHttpActivityFeature>()?.Activity.AddTag("http.long_running", "true");
var supportedTransports = options.Transports;
// Server sent events transport
// GET /{path}
// Accept: text/event-stream
var headers = context.Request.GetTypedHeaders();
if (headers.Accept?.Contains(new Net.Http.Headers.MediaTypeHeaderValue("text/event-stream")) == true)
{
// Connection must already exist
var connection = await GetConnectionAsync(context);
if (connection == null)
{
// No such connection, GetConnection already set the response status code
return;
}
if (!await EnsureConnectionStateAsync(connection, context, HttpTransportType.ServerSentEvents, supportedTransports, logScope, options))
{
// Bad connection state. It's already set the response status code.
return;
}
Log.EstablishedConnection(_logger);
// ServerSentEvents is a text protocol only
connection.SupportedFormats = TransferFormat.Text;
// We only need to provide the Input channel since writing to the application is handled through /send.
var sse = new ServerSentEventsServerTransport(connection.Application.Input, connection.ConnectionId, connection, _loggerFactory);
await DoPersistentConnection(connectionDelegate, sse, context, connection);
}
else if (context.WebSockets.IsWebSocketRequest)
{
// Connection can be established lazily
var connection = await GetOrCreateConnectionAsync(context, options);
if (connection == null)
{
// No such connection, GetOrCreateConnection already set the response status code
return;
}
if (!await EnsureConnectionStateAsync(connection, context, HttpTransportType.WebSockets, supportedTransports, logScope, options))
{
// Bad connection state. It's already set the response status code.
return;
}
Log.EstablishedConnection(_logger);
// Allow the reads to be canceled
connection.Cancellation = new CancellationTokenSource();
var ws = new WebSocketsServerTransport(options.WebSockets, connection.Application, connection, _loggerFactory);
await DoPersistentConnection(connectionDelegate, ws, context, connection);
}
else
{
// GET /{path} maps to long polling
// Connection must already exist
var connection = await GetConnectionAsync(context);
if (connection == null)
{
// No such connection, GetConnection already set the response status code
return;
}
if (!await EnsureConnectionStateAsync(connection, context, HttpTransportType.LongPolling, supportedTransports, logScope, options))
{
// Bad connection state. It's already set the response status code.
return;
}
if (!await connection.CancelPreviousPoll(context))
{
// Connection closed. It's already set the response status code.
return;
}
// Create a new Tcs every poll to keep track of the poll finishing, so we can properly wait on previous polls
var currentRequestTcs = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
if (!connection.TryActivateLongPollingConnection(
connectionDelegate, context, options.LongPolling.PollTimeout,
currentRequestTcs.Task, _loggerFactory, _logger))
{
return;
}
var resultTask = await Task.WhenAny(connection.ApplicationTask !, connection.TransportTask !);
try
{
// If the application ended before the transport task then we potentially need to end the connection
if (resultTask == connection.ApplicationTask)
{
// Complete the transport (notifying it of the application error if there is one)
connection.Transport.Output.Complete(connection.ApplicationTask.Exception);
// Wait for the transport to run
// Ignore exceptions, it has been logged if there is one and the application has finished
// So there is no one to give the exception to
await connection.TransportTask !.NoThrow();
// If the status code is a 204 it means the connection is done
if (context.Response.StatusCode == StatusCodes.Status204NoContent)
{
// Cancel current request to release any waiting poll and let dispose acquire the lock
currentRequestTcs.TrySetCanceled();
// We should be able to safely dispose because there's no more data being written
// We don't need to wait for close here since we've already waited for both sides
await _manager.DisposeAndRemoveAsync(connection, closeGracefully : false);
}
else
{
// Only allow repoll if we aren't removing the connection.
connection.MarkInactive();
}
}
else if (resultTask.IsFaulted || resultTask.IsCanceled)
{
// Cancel current request to release any waiting poll and let dispose acquire the lock
currentRequestTcs.TrySetCanceled();
// We should be able to safely dispose because there's no more data being written
// We don't need to wait for close here since we've already waited for both sides
await _manager.DisposeAndRemoveAsync(connection, closeGracefully : false);
}
else
{
// Only allow repoll if we aren't removing the connection.
connection.MarkInactive();
}
}
finally
{
// Artificial task queue
// This will cause incoming polls to wait until the previous poll has finished updating internal state info
currentRequestTcs.TrySetResult();
}
}
}
private async Task ProcessNegotiate(HttpContext context, HttpConnectionDispatcherOptions options, ConnectionLogScope logScope)
{
context.Response.ContentType = "application/json";
// Establish the connection
var connection = CreateConnection(options);
// Set the Connection ID on the logging scope so that logs from now on will have the
// Connection ID metadata set.
logScope.ConnectionId = connection.ConnectionId;
// Don't use thread static instance here because writer is used with async
var writer = new MemoryBufferWriter();
try
{
// Get the bytes for the connection id
WriteNegotiatePayload(writer, connection.ConnectionId, context, options);
Log.NegotiationRequest(_logger);
// Write it out to the response with the right content length
context.Response.ContentLength = writer.Length;
await writer.CopyToAsync(context.Response.Body);
}
finally
{
writer.Reset();
}
}
private async Task ExecuteAsync(HttpContext context, ConnectionDelegate connectionDelegate, HttpConnectionDispatcherOptions options, ConnectionLogScope logScope)
{
var supportedTransports = options.Transports;
// Server sent events transport
// GET /{path}
// Accept: text/event-stream
var headers = context.Request.GetTypedHeaders();
if (headers.Accept?.Contains(new Net.Http.Headers.MediaTypeHeaderValue("text/event-stream")) == true)
{
// Connection must already exist
var connection = await GetConnectionAsync(context);
if (connection == null)
{
// No such connection, GetConnection already set the response status code
return;
}
if (!await EnsureConnectionStateAsync(connection, context, HttpTransportType.ServerSentEvents, supportedTransports, logScope, options))
{
// Bad connection state. It's already set the response status code.
return;
}
Log.EstablishedConnection(_logger);
// ServerSentEvents is a text protocol only
connection.SupportedFormats = TransferFormat.Text;
// We only need to provide the Input channel since writing to the application is handled through /send.
var sse = new ServerSentEventsTransport(connection.Application.Input, connection.ConnectionId, _loggerFactory);
await DoPersistentConnection(connectionDelegate, sse, context, connection);
}
else if (context.WebSockets.IsWebSocketRequest)
{
// Connection can be established lazily
var connection = await GetOrCreateConnectionAsync(context, options);
if (connection == null)
{
// No such connection, GetOrCreateConnection already set the response status code
return;
}
if (!await EnsureConnectionStateAsync(connection, context, HttpTransportType.WebSockets, supportedTransports, logScope, options))
{
// Bad connection state. It's already set the response status code.
return;
}
Log.EstablishedConnection(_logger);
// Allow the reads to be cancelled
connection.Cancellation = new CancellationTokenSource();
var ws = new WebSocketsTransport(options.WebSockets, connection.Application, connection, _loggerFactory);
await DoPersistentConnection(connectionDelegate, ws, context, connection);
}
else
{
// GET /{path} maps to long polling
// Connection must already exist
var connection = await GetConnectionAsync(context);
if (connection == null)
{
// No such connection, GetConnection already set the response status code
return;
}
if (!await EnsureConnectionStateAsync(connection, context, HttpTransportType.LongPolling, supportedTransports, logScope, options))
{
// Bad connection state. It's already set the response status code.
return;
}
// Create a new Tcs every poll to keep track of the poll finishing, so we can properly wait on previous polls
var currentRequestTcs = new TaskCompletionSource <object>(TaskCreationOptions.RunContinuationsAsynchronously);
await connection.StateLock.WaitAsync();
try
{
if (connection.Status == HttpConnectionStatus.Disposed)
{
Log.ConnectionDisposed(_logger, connection.ConnectionId);
// The connection was disposed
context.Response.StatusCode = StatusCodes.Status404NotFound;
context.Response.ContentType = "text/plain";
return;
}
if (connection.Status == HttpConnectionStatus.Active)
{
var existing = connection.GetHttpContext();
Log.ConnectionAlreadyActive(_logger, connection.ConnectionId, existing.TraceIdentifier);
}
using (connection.Cancellation)
{
// Cancel the previous request
connection.Cancellation?.Cancel();
try
{
// Wait for the previous request to drain
await connection.PreviousPollTask;
}
catch (OperationCanceledException)
{
// Previous poll canceled due to connection closing, close this poll too
context.Response.ContentType = "text/plain";
context.Response.StatusCode = StatusCodes.Status204NoContent;
return;
}
connection.PreviousPollTask = currentRequestTcs.Task;
}
// Mark the connection as active
connection.Status = HttpConnectionStatus.Active;
// Raise OnConnected for new connections only since polls happen all the time
if (connection.ApplicationTask == null)
{
Log.EstablishedConnection(_logger);
connection.ApplicationTask = ExecuteApplication(connectionDelegate, connection);
context.Response.ContentType = "application/octet-stream";
// This request has no content
context.Response.ContentLength = 0;
// On the first poll, we flush the response immediately to mark the poll as "initialized" so future
// requests can be made safely
connection.TransportTask = context.Response.Body.FlushAsync();
}
else
{
Log.ResumingConnection(_logger);
// REVIEW: Performance of this isn't great as this does a bunch of per request allocations
connection.Cancellation = new CancellationTokenSource();
var timeoutSource = new CancellationTokenSource();
var tokenSource = CancellationTokenSource.CreateLinkedTokenSource(connection.Cancellation.Token, context.RequestAborted, timeoutSource.Token);
// Dispose these tokens when the request is over
context.Response.RegisterForDispose(timeoutSource);
context.Response.RegisterForDispose(tokenSource);
var longPolling = new LongPollingTransport(timeoutSource.Token, connection.Application.Input, _loggerFactory);
// Start the transport
connection.TransportTask = longPolling.ProcessRequestAsync(context, tokenSource.Token);
// Start the timeout after we return from creating the transport task
timeoutSource.CancelAfter(options.LongPolling.PollTimeout);
}
}
finally
{
connection.StateLock.Release();
}
var resultTask = await Task.WhenAny(connection.ApplicationTask, connection.TransportTask);
try
{
var pollAgain = true;
// If the application ended before the transport task then we potentially need to end the connection
if (resultTask == connection.ApplicationTask)
{
// Complete the transport (notifying it of the application error if there is one)
connection.Transport.Output.Complete(connection.ApplicationTask.Exception);
// Wait for the transport to run
await connection.TransportTask;
// If the status code is a 204 it means the connection is done
if (context.Response.StatusCode == StatusCodes.Status204NoContent)
{
// Cancel current request to release any waiting poll and let dispose acquire the lock
currentRequestTcs.TrySetCanceled();
// We should be able to safely dispose because there's no more data being written
// We don't need to wait for close here since we've already waited for both sides
await _manager.DisposeAndRemoveAsync(connection, closeGracefully : false);
// Don't poll again if we've removed the connection completely
pollAgain = false;
}
}
else if (resultTask.IsFaulted)
{
// Cancel current request to release any waiting poll and let dispose acquire the lock
currentRequestTcs.TrySetCanceled();
// transport task was faulted, we should remove the connection
await _manager.DisposeAndRemoveAsync(connection, closeGracefully : false);
pollAgain = false;
}
else if (context.Response.StatusCode == StatusCodes.Status204NoContent)
{
// Don't poll if the transport task was canceled
pollAgain = false;
}
if (pollAgain)
{
// Mark the connection as inactive
connection.LastSeenUtc = DateTime.UtcNow;
connection.Status = HttpConnectionStatus.Inactive;
}
}
finally
{
// Artificial task queue
// This will cause incoming polls to wait until the previous poll has finished updating internal state info
currentRequestTcs.TrySetResult(null);
}
}
}
