Vif, a simple webserver in OCaml

Vif is a small program that allows you to initiate a web server (http/1.1 & h2) from an OCaml script:

$ opam install vif
$ cat >main.ml <<EOF
#require "vif" ;;
open Vif ;;

let default req _server () =
  let str = "Hello World!\n" in
  let* () = Response.with_string req str in
  Response.respond `OK
;;

let routes =
  let open Vif.Uri in
  let open Vif.Route in
  [ get (rel /?? nil) --> default ]
;;

let () = Miou_unix.run @@ fun () ->
  Vif.run routes ()
;;
EOF
$ vif main.ml --pid vif.pid &
[1] 1337
$ curl http://localhost:8080/
Hello World!
$ kill -SIGINT $(cat vif.pid)

The aim is to have a small web server for cheap and to be able to iterate on it quickly without necessarily having a workflow that involves compiling and executing an OCaml project. The OCaml script is executed by vif just as it could be executed by ocaml and it describes what your webserver should do.

In this short tutorial, we will see how to use Vif to implement more or less complex web services.

Vif as a library

Of course, vif is also a library. You don't need to write an OCaml script to get a web server. You can also develop your own application and compile it with Vif to get an executable that will be your web server.

However, in terms of iterations, the loop ocaml script → web server test is faster than ocaml program → compilation → web server test.

How to install Vif

Vif is available on opam. You can install it using the command:

$ opam install vif

You can also obtain the development version of Vif via:

$ opam pin add https://git.robur.coop/robur/vif.git

The Vif project is hosted on our server git.robur.coop. You can also access a mirror on GitHub. Issues and pull requests can be proposed on both repositories (pull requests will be merged into our cooperative's repository).