#suave.io

let build_proxy_resolver (fwd_to_host : String) fwd_to_port = let heserver = System.Net.Dns.GetHostEntry(fwd_to_host) let ipaddr = heserver.AddressList.[0] fun (request : HttpRequest) -> Some (ipaddr, fwd_to_port) let build_headers ctx = //add and remove headers from the ctx, return the header list ctx.request.headers let proxy_app (ctx:HttpContext) = let new_headers = build_headers ctx let fwd_ctx = {ctx with request={ctx.request with headers=new_headers}} let pxy = proxy (build_proxy_resolver "PROXY_TO.com" 80us) fwd_ctx {ctx with response = { ctx.response with status=Suave.Types.Codes.HTTP_200; content=SocketTask pxy }} |> Some

To use in an actual application, proxy_app can be inserted directly into the routing chain >>=

build_headers should be extended to add authorization headers or rewrite the host header as necessary. Also, build_proxy_resolver should only be called once so the IP lookup can be cached.

let vdir (s : String) choose_list (ctx : HttpContext) = if ctx.request.url.StartsWith(s) then let us = if ctx.user_state.ContainsKey("original_url") then ctx.user_state else ctx.user_state.Add("original_url", ctx.request.url) let new_req = { ctx with request={ctx.request with url=ctx.request.url.Substring(s.Length)} ; user_state = us } in choose choose_list new_req else None let subapp = vdir "/sub" [ url "/abc" >>= OK "subapp abc route" warbler(fun {request=req ; user_state=us} -> OK ( sprintf "subapp - url %s - original url %A" req.url us)) ]

Now when subapp is loaded inside an application's choose chain, if /sub/xyz is visited, the browser will print: subapp - url /xyz - original url map [("original_url", "/sub/xyz")]

Is this an abuse of the user_state list maintained by Suave?

As an alternative, we can define the vdir function to take a WebPart: