Lwt_lock_file (octez-libs.Tezos_stdlib_unix.Lwt_lock

val lock : 
  when_locked:[ `Block | `Fail of Tezos_error_monad.Error_monad.error ] ->
  filename:string ->
  Lwt_unix.file_descr Tezos_error_monad.Error_monad.tzresult Lwt.t

lock ~when_locked ~filename acquires a lock on the file path and returns the opened file descriptor (for unlocking). If there is already a lock on path, this function call is blocking until the previous lock is released. If there is already a lock on filename, the call will block if when_locked is `Block, and will fail if when_locke = `Fail e.

val unlock : Lwt_unix.file_descr -> unit Lwt.t

unlock fd releases the lock on the opened file descriptor fd. If there is no lock or if it is already released, this function does nothing.

val with_lock : 
  when_locked:[ `Block | `Fail of Tezos_error_monad.Error_monad.error ] ->
  filename:string ->
  (unit -> 'a Tezos_error_monad.Error_monad.tzresult Lwt.t) ->
  'a Tezos_error_monad.Error_monad.tzresult Lwt.t

with_lock ~when_locked ~filename f tries to take a lock on file filename and calls f if the lock was successfully taken. If there is already a lock on filename, the call to f is blocked until the previous lock is released if when_lock is `Block, and will fail with e if when_lock = `Fail e instead. This function may fail with an I/O exception wrapped in the error monad if something unexpected happened.