How can I log rejected requests? i.e. transport.MultipartForm

[jetaggart]

I have a configuration like this:

gql.AddTransport(transport.MultipartForm{
    MaxUploadSize: 1 * 1024 * 1024,
})

which will reject large file sizes just fine. I want to hook into the rejection and log it and add telemetry. I can't seem to figure out how to hook into this rejection. I see it bail here: https://github.com/99designs/gqlgen/blob/master/graphql/handler/transport/http_form_multipart.go#L65

but that seems to short circuit all my handlers error presenters, around operations, etc. It sort of just bails and returns a simple response with a 200. Any ideas on how to log these failures?

[SrOscuroBlck]

You might want to create a logging middleware, something like this:

func LoggingMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        // Create a response writer wrapper to capture the status code
        rw := &responseWriter{ResponseWriter: w, statusCode: http.StatusOK}

        // Call the next handler, which includes gqlgen's handler
        next.ServeHTTP(rw, r)

        // After the handler, check if the response contains file upload size errors
        if rw.statusCode == http.StatusOK {
            // This is a simplistic check, you might need to look at the response body or specific headers
            if strings.Contains(rw.responseBody, "file size exceeds") { // Adjust the string condition based on actual response content
                log.Printf("File size exceeds limit: %v", rw.responseBody)
                // Add telemetry or further logging here
            }
        }
    })
}

type responseWriter struct {
    http.ResponseWriter
    statusCode   int
    responseBody string
}

func (rw *responseWriter) WriteHeader(statusCode int) {
    rw.statusCode = statusCode
    rw.ResponseWriter.WriteHeader(statusCode)
}

func (rw *responseWriter) Write(b []byte) (int, error) {
    rw.responseBody = string(b) // You may want to capture only part of the response or use a different method
    return rw.ResponseWriter.Write(b)
}

This might work to you if you want to log.

[jetaggart]

I tried that, but it returns a 200 so I have no idea if it failed cause it was too large.