let db_connection caqti_switch : (unit, Caqti_miou.connection) Vif.Device.device =
let f () =
  let db_uri= Config.Exchangedb_postgres.config in
  match Caqti_miou_unix.connect ~sw:caqti_switch db_uri with
  | Error err ->
      Fmt.failwith "Database connection failure: %a." Caqti_error.pp err
  | Ok conn -> (
      match Pg.preflight conn with
      | Error err ->
          Fmt.failwith "Database preflight failure: %a." Caqti_error.pp err
      | Ok () ->
          Logs.info (fun m -> m "database connection initialized");
          conn)
in
  let finally (module Conn : Caqti_miou.CONNECTION) = Conn.disconnect () in
  Vif.Device.v ~name:"db_connection" ~finally [] f

let keys storage =
let f (module Conn : Pg.CONN) () =
  let (module Fs) = (module (struct let t = storage end)) in
  let keys : (module Keys.S) = (module Keys.Make (Conn) (Fs) ) in
  keys
in
  let finally _key = () in
  Vif.Device.v ~name:"keys" ~finally [ Vif.Device.value db_connection ]
  f