How to log http requests in F#

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

Jim Foye · Accepted Answer · 2022-01-16 18:02:25Z

2

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.

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

edited Jan 16, 2022 at 18:02

answered Jan 16, 2022 at 3:45

Jim Foye

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1 Comment

Constantin Fischer Over a year ago

I think that should be enough for my case. I even used the customizeHttpRequest already in my code but did not think of using it this way. Thanks for pointing this out and giving some source in case I need to dig deeper.

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