vlt 0.1 · OCaml Package

This module defines the concept of logger.

Loggers are arranged in a hierarchy, according to their names. Logger names are dot-separated identifiers akin to OCaml module names, the hierarchy between loggers is defined the same way as it is defined between modules. It is thus considered good practice to define a logger per module and to have the logger name equal to the module name. The parent of all loggers with no dot is the logger named "" (empty string).

Another good practice is to never call directly the functions of this module. Indeed, registration of loggers should be done by setting either the environment variable "BOLT_CONFIG" (for the new configuration format), or the environment variable "BOLT_FILE" (for the old configuration format). The formats of such files are defined respectively in modules ConfigurationNew, and ConfigurationOld. More information can be found in the Bolt user manual.

Also, actual logging should be done using the camlp4 syntax extension named bolt_pp; it allows to easily turn logging off to avoid any runtime penalty for production use.

Bolt writes error messages on the standard error, except if the environment variable "BOLT_SILENT" is set to either "YES" or "ON" (case insensitive), defaulting to "NO".

val register : 
  string ->
  Level.t ->
  string ->
  string ->
  string ->
  Mode.t ->
  string ->
  (string * Output.rotation) ->
  unit

register nm lv fl ps ly m out (n, r) registers a logger with name nm, level lv, filter named fl, pass filter named ps, mode m, layout named ly, and output named out. n and r are the parameter passed for output instance creation. The logger will write any event with a level below or equal to lv that also make the filter fl return true. Such events are written to output out through mode m, using layout ly.

val log : 
  string ->
  Level.t ->
  ?file:string ->
  ?line:int ->
  ?column:int ->
  ?properties:(string * string) list ->
  ?error:exn option ->
  string ->
  unit

log nm lv ~file:f ~line:l ~column:c ~properties:p ~error:e msg produces an event of level lv, file f, line l, column c, properties p, error e, and message msg. The event is presented to the logger named nm if it exists as well as to all its existing parents. Each logger will decide if it records the event according to its level and filter.

val logf : 
  string ->
  Level.t ->
  ?file:string ->
  ?line:int ->
  ?column:int ->
  ?properties:(string * string) list ->
  ?error:exn option ->
  ('a, unit, string, unit) format4 ->
  'a

log nm lv ~file:f ~line:l ~column:c ~properties:p ~error:e fmt produces an event of level lv, file f, line l, column c, properties p, error e, and message format fmt. The event is presented to the logger named nm if it exists as well as to all its existing parents. Each logger will decide if it records the event according to its level and filter.

val check_level : string -> Level.t -> bool

check_level nm lv checks if an event of level lv is recorded by the logger named nm or its ancestors.

val prepare : string -> unit

prepare nm indicates that a module is about to use a logger with name nm. It is not mandatory to call this function before using a logger, but doing so allows the runtime to setup the appropriate elements for faster accesses.

package vlt