andreypopp / ocaml-tf

OCaml bindings to terraform

ocaml-tf

WARNING: EXPERIMENTAL, DO NOT USE

how it works

The output of terraform providers schema -json is parsed and then used to generate OCaml code that provides a type-safe interface to define tf resources and datasources programmatically.

Each provider is represented by a library, each resource or datasource is represented by a module.

For example for a resource named digitalocean_droplet there's a module generated with the following signature.

First there are constructors for the resource block and for nested blocks:

type timeouts

val timeouts : ... -> unit -> timeouts

type digitalocean_droplet

val digitalocean_droplet : image:string prop -> ... -> unit -> digitalocean_droplet

Followed by the function to serialize the resource to JSON:

val yojson_of_digitalocean_droplet : digitalocean_droplet -> json

Then a type t is defined which represents the resource's exported attributes.

One can use values of such types to construct further resources which reference the current resource:

type t = private {
  id : string prop;
  ...
}

To obtain a value of t one can use the register function.

The function automatically registers the resource with the global registry which is then used to generate .tf.json file:

val register : ... string -> t

In case one wants to handle the registration manually, and have full control over .tf.json generation, there's a more low level api:

val make : string -> t Tf_core.resource

The 'attrs Tf_core.resource type is a type contains attributes of the resource and the JSON payload to be written to the .tf.json file.

example

dune:

(executable
 (name main)
 (modules main)
 (libraries tf tf_digitalocean))

main.ml

open Tf_core.Prop
open Tf_digitalocean

let public_key =
  In_channel.(
    with_open_bin "/Users/andreypopp/.ssh/id_rsa.pub" input_all)

let region = string "fra1"

let () =
  let ssh_key =
    Digitalocean_ssh_key.register "id_rsa" ~name:(string "id_rsa")
      ~public_key:(string public_key)
  in
  let wg0_ip = Digitalocean_reserved_ip.register "wg0_ip" ~region in
  let wg0 =
    Digitalocean_droplet.register "wg0" ~name:(string "wg0") ~region
      ~image:(string "debian-12-x64")
      ~size:(string "s-1vcpu-1gb") ~ssh_keys:[ ssh_key.id ]
  in
  let _ =
    Digitalocean_reserved_ip_assignment.register "wg0_ip_assignment"
      ~droplet_id:(magic wg0.id) ~ip_address:wg0_ip.id
  in
  ()

let () = Tf_run.run ()

then:

dune exec ./main.exe apply