Table of Contents

Request lifecycle

Below is explained the entire life cycle of a request through an example of an HTTP request.

  • Receiving the request: each request creates an HTTP context between the request itself and the response that will be delivered to the client. This context comes from the built-in listener in Sisk, which can be the HttpListener, Kestrel, or Cadente.
    • External request validation: the validation of HttpServerConfiguration.RemoteRequestsAction is validated for the request.
      • If the request is external and the property is Drop, the connection is closed without a response to the client with an HttpServerExecutionStatus = RemoteRequestDropped.
    • Forwarding Resolver configuration: if a ForwardingResolver is configured, it will call the OnResolveRequestHost method on the original host of the request.
    • DNS matching: with the host resolved and with more than one ListeningHost configured, the server will look for the corresponding host for the request.
      • If no ListeningHost matches, a 400 Bad Request response is returned to the client and an HttpServerExecutionStatus = DnsUnknownHost status is returned to the HTTP context.
      • If a ListeningHost matches, but its Router is not yet initialized, a 503 Service Unavailable response is returned to the client and an HttpServerExecutionStatus = ListeningHostNotReady status is returned to the HTTP context.
    • Router binding: the router of the corresponding ListeningHost is associated with the received HTTP server.
      • If the router is already associated with another HTTP server, which is not allowed because the router actively uses the server's configuration resources, an InvalidOperationException is thrown. This only occurs during the initialization of the HTTP server, not during the creation of the HTTP context.
    • Pre-definition of headers:
      • Predefines the X-Request-Id header in the response if it is configured to do so.
      • Predefines the X-Powered-By header in the response if it is configured to do so.
    • Content size validation: validates if the request content is less than HttpServerConfiguration.MaximumContentLength only if it is greater than zero.
      • If the request sends a Content-Length greater than the configured one, a 413 Payload Too Large response is returned to the client and an HttpServerExecutionStatus = ContentTooLarge status is returned to the HTTP context.
    • The OnHttpRequestOpen event is invoked for all configured HTTP server handlers.
  • Routing the action: the server invokes the router for the received request.
    • If the router does not find a route that matches the request:
      • If the Router.NotFoundErrorHandler property is configured, the action is invoked, and the response of the action is forwarded to the HTTP client.
      • If the previous property is null, a default 404 Not Found response is returned to the client.
    • If the router finds a matching route, but the route's method does not match the request's method:
      • If the Router.MethodNotAllowedErrorHandler property is configured, the action is invoked and the response of the action is forwarded to the HTTP client.
      • If the previous property is null, a default 405 Method Not Allowed response is returned to the client.
    • If the request is of the OPTIONS method:
      • The router returns a 200 Ok response to the client only if no route matches the request method (the route's method is not explicitly RouteMethod.Options).
    • If the HttpServerConfiguration.ForceTrailingSlash property is enabled, the matched route is not a regex, the request path does not end with /, and the request method is GET:
      • A 307 Temporary Redirect HTTP response with the Location header with the path and query to the same location with a / at the end is returned to the client.
    • The OnContextBagCreated event is invoked for all configured HTTP server handlers.
    • All global IRequestHandler instances with the BeforeResponse flag are executed.
      • If any handler returns a non-null response, that response is forwarded to the HTTP client and the context is closed.
      • If an error is thrown in this step and HttpServerConfiguration.ThrowExceptions is disabled:
        • If the Router.CallbackErrorHandler property is enabled, it is invoked and the resulting response is returned to the client.
        • If the previous property is not defined, an empty response is returned to the server, which forwards a response according to the type of exception thrown, which is usually 500 Internal Server Error.
    • All IRequestHandler instances defined in the route and with the BeforeResponse flag are executed.
      • If any handler returns a non-null response, that response is forwarded to the HTTP client and the context is closed.
      • If an error is thrown in this step and HttpServerConfiguration.ThrowExceptions is disabled:
        • If the Router.CallbackErrorHandler property is enabled, it is invoked and the resulting response is returned to the client.
        • If the previous property is not defined, an empty response is returned to the server, which forwards a response according to the type of exception thrown, which is usually 500 Internal Server Error.
    • The router's action is invoked and transformed into an HTTP response.
      • If an error is thrown in this step and HttpServerConfiguration.ThrowExceptions is disabled:
        • If the Router.CallbackErrorHandler property is enabled, it is invoked and the resulting response is returned to the client.
        • If the previous property is not defined, an empty response is returned to the server, which forwards a response according to the type of exception thrown, which is usually 500 Internal Server Error.
    • All global IRequestHandler instances with the AfterResponse flag are executed.
      • If any handler returns a non-null response, the handler's response replaces the previous response and is immediately forwarded to the HTTP client.
      • If an error is thrown in this step and HttpServerConfiguration.ThrowExceptions is disabled:
        • If the Router.CallbackErrorHandler property is enabled, it is invoked and the resulting response is returned to the client.
        • If the previous property is not defined, an empty response is returned to the server, which forwards a response according to the type of exception thrown, which is usually 500 Internal Server Error.
    • All IRequestHandler instances defined in the route and with the AfterResponse flag are executed.
      • If any handler returns a non-null response, the handler's response replaces the previous response and is immediately forwarded to the HTTP client.
      • If an error is thrown in this step and HttpServerConfiguration.ThrowExceptions is disabled:
        • If the Router.CallbackErrorHandler property is enabled, it is invoked and the resulting response is returned to the client.
        • If the previous property is not defined, an empty response is returned to the server, which forwards a response according to the type of exception thrown, which is usually 500 Internal Server Error.
  • Processing the response: with the response ready, the server prepares it for sending to the client.
    • The Cross-Origin Resource Sharing Policy (CORS) headers are defined in the response according to what was configured in the current ListeningHost.CrossOriginResourceSharingPolicy.
    • The status code and headers of the response are sent to the client.
    • The response content is sent to the client:
      • If the response content is a descendant of ByteArrayContent, the response bytes are directly copied to the response output stream.
      • If the previous condition is not met, the response is serialized to a stream and copied to the response output stream.
    • The streams are closed and the response content is discarded.
    • If HttpServerConfiguration.DisposeDisposableContextValues is enabled, all objects defined in the request context that inherit from IDisposable are discarded.
    • The OnHttpRequestClose event is invoked for all configured HTTP server handlers.
    • If an exception was thrown on the server, the OnException event is invoked for all configured HTTP server handlers.
    • If the route allows access-logging and HttpServerConfiguration.AccessLogsStream is not null, a log line is written to the log output.
    • If the route allows error-logging, there is an exception, and HttpServerConfiguration.ErrorsLogsStream is not null, a log line is written to the error log output.
    • If the server is waiting for a request through HttpServer.WaitNext, the mutex is released and the context becomes available to the user.
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