Logging middleware¶

LoggingMiddleware writes a structured log line for every incoming request and the corresponding response. It includes the request method, path, protocol version, response status code, elapsed time, and client IP.

Enabling it¶

The header is pulled in via the umbrella <Baldr/Baldr.hpp>. Add the middleware to your application:

src/main.cpp

#include <Baldr/Baldr.hpp>

int main()
{
    auto builder = skr::ApplicationBuilder().WithExtension<BaldrExtension>();
    auto app = builder.Build<WebApplication>();

    app->Use<LoggingMiddleware>();

    app->MapGet("/", [] { return Payload { .message = "ok" }; });

    app->Run();
}

LoggingMiddleware is defined in src/Baldr/Middleware/Logging.hpp. It depends on a skr::Logger<LoggingMiddleware>, which is provided automatically by Skirnir — no service registration is required.

What gets logged¶

For a request like GET /weather HTTP/1.1 from 192.0.2.1, the middleware emits:

Request  - 'HTTP/1.1' 'GET' '/weather'
Response - '200' 'GET' '/weather' - 312us - '192.0.2.1'

The first line is emitted before the request is dispatched; the second line is emitted after the response is produced and includes the elapsed microseconds.

Where to put it¶

Register LoggingMiddleware first, so it wraps every other middleware and route handler:

src/main.cpp

app.Use<RequestIdMiddleware>()
   .Use<ExceptionHandlerMiddleware>()
   .Use<LoggingMiddleware>()
   .Use<RateLimitMiddleware>();

This ensures every response — including those short-circuited by the rate limiter — is logged with accurate timing, and the request id is in scope for the log line.

Implementation note¶

LoggingMiddleware uses C++26 reflection (std::meta::info via Skirnir's refl::enum_to_string) to format the request method. Consumers do not need to opt in to reflection themselves — the dependency is compiled inside the baldr target.