如何在 F# 中记录 http 请求

Question

I have a F# console app (.Net 5) sending http requests via FSharp.Data and I haven't found a way to log the raw http requests. I tried using the F#.Net 6 web app template and enabling HttpLogging, but this won't log my http requests executed in the code. Other tools like fiddler or wireshark are not an option because of work policies.

Is there a way to enable such logging, for example in this minimal example console app?

open FSharp.Data

[<EntryPoint>]
let main argv =
    let html = Http.Request("http://tomasp.net")
    printfn "%s" (html.ToString())
    0

Answer 1

You can pass a customization function to Http.Request, I think it would be OK to pass one that has a side effect of logging something about the request. For example:

open System.Net
open FSharp.Data

let requestHeaders =
    [
        "User-Agent", "Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:47.0) Gecko/20100101 Firefox/47.0"
        "Accept", "*/*"
    ]

let requestCustomizeFunc =
    fun (request: HttpWebRequest) -> 
        printfn "Address: %O" request.Address
        printfn "Method: %O" request.Method
        printfn "Headers: %O" request.Headers
        request

[<EntryPoint>]
let main argv =
    let response = Http.Request ("http://tomasp.net", headers = requestHeaders, customizeHttpRequest = requestCustomizeFunc)

    response.StatusCode
    |> printfn "%O"

    0

This is quick and dirty; if you're really serious about logging what's going on at the network level in your .NET app, you probably want to consider taking advantage of the built-in tracing capability. See

https://docs.microsoft.com/en-us/dotnet/framework/network-programming/network-tracing

That will be a bit more work.