Source file lock.ml

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(** Writer lock *)

open Lwt.Syntax

type t =
  { fn : string
  ; fd : Lwt_unix.file_descr
  ; mutable closed : bool
  }

let filename t = t.fn

let lock fn =
  let* fd = Lwt_unix.openfile fn [O_CREAT; O_RDWR] 0o644 in
  let+ () =
    Lwt.catch
      (fun () -> Lwt_unix.lockf fd F_TLOCK 0)
      (fun e -> Log.fatal "Plebeia writer lock failed: %s" fn; Lwt.fail e)
  in
  { fn ; fd ; closed= false }

let release ({ fd ; closed; _ } as t) =
  if closed then Lwt.return_unit
  else
    let+ () = Lwt_unix.close fd in
    t.closed <- true