Module Logs_lwtSource

Lwt logging.

The log functions of this module return Lwt threads that proceed only when the log operation is over, as defined by the current Logs.reporter.

See a cooperative reporter example.

Log functions

Logging result value Errors

Source specific log functions

Cooperative reporter example

The following reporter will play nice with Lwt's runtime, it will behave synchronously for the log functions of this module and asynchronously for those of the Logs module (see Note on synchronous logging).

It reuses Reporter and will produce colorful output if the standard formatters are setup to do so. For example it can be used instead of Reporter in the full setup example.

let lwt_reporter () =
  let buf_fmt ~like =
    let b = Buffer.create 512 in
    Fmt.with_buffer ~like b,
    fun () -> let m = Buffer.contents b in Buffer.reset b; m
  in
  let app, app_flush = buf_fmt ~like:Fmt.stdout in
  let dst, dst_flush = buf_fmt ~like:Fmt.stderr in
  let reporter = Logs_fmt.reporter ~app ~dst () in
  let report src level ~over k msgf =
    let k () =
      let write () = match level with
      | Logs.App -> Lwt_io.write Lwt_io.stdout (app_flush ())
      | _ -> Lwt_io.write Lwt_io.stderr (dst_flush ())
      in
      let unblock () = over (); Lwt.return_unit in
      Lwt.finalize write unblock |> Lwt.ignore_result;
      k ()
    in
    reporter.Logs.report src level ~over:(fun () -> ()) k msgf;
  in
  { Logs.report = report }