nloge 0.0.2 (latest) · OCaml Package

Nloge is a asynchronous logger with Eio.

By default nloge logs with JSON format:

let () =
  Eio_main.run @@ fun env ->
  Eio.Switch.run @@ fun sw ->
  Nloge.run ~clock:env#clock ~sw ~outputs:[ env#stdout ] ~level:`Debug @@ fun () ->
  Nloge.debug
    ~__LOC__
    ~metadata:[ "now_posix", `Float (Eio.Time.now env#clock) ]
    (fun m -> m "hello")

(* {"log_level":"DEBUG","message":"hello","label":"File \"examples/hello.ml\", line 9, characters 5-12","now_posix":1683056241.957986} *)
;;

see https://github.com/nymphium/nloge/blob/master/examples
for more examples

Writing logs

Nloge writes logs, given by Emit effect, to Eio.Flow.sink

type Effect.t +=

| Write : string * Level.t -> unit Effect.t

val write : Level.t -> string -> unit

module Trans : sig ... end

val run : 
  clock:Eio.Time.clock ->
  sw:Eio.Switch.t ->
  outputs:Eio.Flow.sink list ->
  level:Level.t ->
  ?trans:((unit -> 'r) -> 'r) ->
  (unit -> 'r) ->
  'r

run is the handler to write logs to given outputs.

parameter clock
Eio.Time.clock clock objet

parameter sw
Eio.Switch.t switch object to write output asynchronously

parameter outputs
Eio.Flow.sink list the targets to write logs

parameter level
Level.t option

Emitting log

Nloge "emit"s logs to Writing logs by "perform"ing Emit.

type 'a msgf = (('a, Format.formatter, unit, unit) format4 -> 'a) -> unit

type metadata = (string * Yojson.Safe.t) list

type 'a t = Level.t * string option * metadata * 'a msgf

type Effect.t +=

| Emit : 'a t -> unit Effect.t

Emit is aimed to emit log objects. Writing logs can be injected to handle the effect.

type 'a logger = ?metadata:metadata -> ?__LOC__:string -> 'a msgf -> unit

Log functions

val emit : Level.t -> 'a msgf -> string option -> metadata -> unit

emit level ?metadata ?loc msgf sends msgf message object with level level. metadata and loc can be sent optionally.

emit `Debug @@ fun m -> m "hello, %s" "world" (* -> hello, world *)

And the following emg, alert, etc. are wrapper for emit with correspondng level.

debug ~metadata:["Key", `String "Val" ] ~__LOC__ @@ fun m -> m "the answer: %d" 42

val emg : 'a logger

val alert : 'a logger

val crit : 'a logger

val err : 'a logger

val warn : 'a logger

val notice : 'a logger

val info : 'a logger

val debug : 'a logger

Utilities

val make_emit_handler : 
  (unit -> 'r) ->
  (float -> Level.t -> string option -> metadata -> string -> unit) ->
  'r

make_emit_handler is a utility to build a handler for Emit.

let plain_transformer f =
  Nloge.make_emit_handler f
  @@ fun now level loc metadata msg ->
  let json = Nloge.Trans.insert_info now level loc msg metadata in
  let len = List.length json in
  let k0 = Format.kasprintf (Nloge.write level) "%a:\n%s" Nloge.Level.pp level in
  let k, _ =
    ListLabels.fold_left json ~init:(k0, 0) ~f:(fun (k, idx) (label, v) ->
      let idx' = idx + 1 in
      let comma = if idx' = len then "" else "\n" in
      ( Format.kasprintf
          k
          "\t%-10s = %a%s%s"
          label
          (Yojson.Safe.pretty_print ~std:true)
          v
          comma
      , idx' ))
  in
  k "\n"
;;

Log Level and utilities

module Level : sig ... end

package nloge

Writing logs

Emitting log

Log functions

Utilities

Log Level and utilities