logs

Logging infrastructure for OCaml
Library logs_lwt
Module Logs_lwt

Log functions

type 'a log = ( 'a, unit Lwt.t ) Logs.msgf -> unit Lwt.t

The type for Lwt log functions. The returned thread only proceeds once the log operation is over. See Logs.log.

val msg : ?src:Logs.src -> Logs.level -> 'a log
val app : ?src:Logs.src -> 'a log
val err : ?src:Logs.src -> 'a log
val warn : ?src:Logs.src -> 'a log
val info : ?src:Logs.src -> 'a log
val debug : ?src:Logs.src -> 'a log
val kmsg : ( unit -> 'b Lwt.t ) -> ?src:Logs.src -> Logs.level -> ( 'a, 'b Lwt.t ) Logs.msgf -> 'b Lwt.t

Logging value Errors

val on_error : ?src:Logs.src -> ?level:Logs.level -> ?header:string -> ?tags:Logs.Tag.set -> pp:( Format.formatter -> 'b -> unit ) -> use:( 'b -> 'a Lwt.t ) -> ( 'a, 'b ) result Lwt.t -> 'a Lwt.t
val on_error_msg : ?src:Logs.src -> ?level:Logs.level -> ?header:string -> ?tags:Logs.Tag.set -> use:( unit -> 'a Lwt.t ) -> ( 'a, [ `Msg of string ] ) result Lwt.t -> 'a Lwt.t

Source specific log functions

module type LOG = sig ... end
val src_log : Logs.src -> (module LOG)

src_log src is a set of logging functions for src.

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 sync).

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