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DelegatingHandler

The RA.Utilities.Integrations.DelegatingHandlers namespace contains classes that act as middleware for HttpClient instances. These handlers intercept outgoing HTTP requests to add functionality like authentication, header propagation, and logging before the request is sent.

Here is a breakdown of the purpose of each class in that namespace:

ApiKeyAuthenticationHandler<TSettings>​

  • Purpose: This is a DelegatingHandler designed to automate API key authentication. It retrieves an API key from a configured settings object (any class that implements IApiKeySettings) and automatically adds it to the X-Api-Key header of every outgoing request.
  • Use Case: This is ideal for integrations with external APIs that require a static API key for authentication. By adding this handler to the HttpClient pipeline, you don't need to manually add the key to every request you make.

InternalHeadersForwardHandler​

  • Purpose: This handler is designed for internal, service-to-service communication within a microservices architecture. It accesses the current incoming request's context via IHttpContextAccessor and forwards critical headers to the outgoing request. Specifically, it propagates:
    • The Authorization header, to maintain the user's authentication context across services.
    • The x-request-id header (or the TraceIdentifier as a fallback), to ensure end-to-end traceability of a request as it travels through multiple services.
  • Use Case: When Service A receives a request from a user and needs to call Service B to fulfill it, this handler ensures that Service B receives the original user's credentials and the same tracing ID, making security and logging consistent.

ProxyMessageHandler​

  • Purpose: This is a factory class, not a delegating handler. Its sole responsibility is to create and configure the primary HttpClientHandler with proxy settings. An HttpClient's proxy must be set on its innermost handler, which is why this logic is separated from the chain of delegating handlers.
  • How it Works: It takes an IProxySettings object and, if a proxy address is specified, it constructs an HttpClientHandler with a WebProxy instance, including credentials if they are provided. If no proxy is configured, it returns a default handler.
  • Use Case: This factory is used by the dependency injection extensions when setting up an HttpClient. It allows integrations to transparently route traffic through a corporate or development proxy based on configuration, without the application code needing to be aware of it.