Module Lwt_main

module Lwt_main : sig..end

Main loop and event queue

This module controls the ``main-loop'' of Lwt.

val run : 'a Lwt.t -> 'a

run t calls the Lwt scheduler repeatedly until t terminates, then returns the value returned by the thread. If t fails with an exception, this exception is raised.

Note that you should avoid using run inside threads

  • The calling threads will not resume before run returns.
  • Successive invocations of run are serialized: an invocation of run will not terminate before all subsequent invocations are terminated.

Note also that it is not safe to call run in a function registered with Pervasives.at_exit, use the Lwt_main.‚Äčat_exit function of this module instead.

val yield : unit -> unit Lwt.t

yield () is a threads which suspends itself and then resumes as soon as possible and terminates.

val enter_iter_hooks : (unit -> unit) Lwt_sequence.t

Functions that are called before the main iteration.

val leave_iter_hooks : (unit -> unit) Lwt_sequence.t

Functions that are called after the main iteration.

val exit_hooks : (unit -> unit Lwt.t) Lwt_sequence.t

Sets of functions executed just before the program exit.


  • each hook is called exactly one time
  • exceptions raised by hooks are ignored
val at_exit : (unit -> unit Lwt.t) -> unit

at_exit hook adds hook at the left of exit_hooks