package js_of_ocaml-lwt

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Module Lwt_log_jsSource

include module type of Lwt_log_core with type level = Lwt_log_core.level and type logger = Lwt_log_core.logger and type section = Lwt_log_core.section and type template = Lwt_log_core.template and module Section = Lwt_log_core.Section

This module provides functions to deal with logging. It support:

  • logging to multiple destination at the same time
  • filtering logs per destination

Types

Sourcetype level = Lwt_log_core.level =
  1. | Debug
    (*

    Debugging message. They can be automatically removed by the syntax extension.

    *)
  2. | Info
    (*

    Informational message. Suitable to be displayed when the program is in verbose mode.

    *)
  3. | Notice
    (*

    Same as Info, but is displayed by default.

    *)
  4. | Warning
    (*

    Something strange happend

    *)
  5. | Error
    (*

    An error message, which should not means the end of the program.

    *)
  6. | Fatal
    (*

    A fatal error happened, in most cases the program will end after a fatal error.

    *)

Type of log levels. A level determines the importance of a message

Type of a logger. A logger is responsible for dispatching messages and storing them somewhere.

Each logging message has a section. Sections can be used to structure your logs. For example you can choose different loggers according to the section.

Each section carries a level, and messages with a lower log level than than the section level will be dropped.

Section levels are initialised using the contents of the LWT_LOG environment variable, which must contain one or more rules of the form pattern -> level separated by ";". Where pattern is a string that may contain *.

For example, if LWT_LOG contains:

  access -> warning;
  foo[*] -> error

then the level of the section "access" is Warning and the level of any section matching "foo[*]" is Error.

If the pattern is omited in a rule then the pattern "*" is used instead, so LWT_LOG may just contain "debug" for instance.

By default, the following rule apply : "* -> notice"

Sourceval string_of_level : level -> string
Sourceval level_of_string : string -> level option
Sourceval load_rules : ?fail_on_error:bool -> string -> unit

Reset the rules set when parsing the LWT_LOG environment variable using this string.

  • parameter fail_on_error

    defines if the function will raise Failure if it encounters a malformed rule

  • raises Failure

    if an invalid rule is found and fail_on_error is true

load_rules parses the rules string and validates the rules before loading them. If fail_on_error is true, invalid rules will cause this function to raise Failure and leave existing rules unchanged. If fail_on_error is false (this is the default), it tries to load as many rules as possible and ignore invalid ones. If the rules string itself cannot be parsed, existing rules are always left unchanged.

Example:

Lwt_log_core.load_rules ~fail_on_error:true "* -> nosuchlevel" (* Raises Failure *)
Lwt_log_core.load_rules "* -> info"
Sourceval add_rule : string -> level -> unit

add_rule pattern level adds a rule for sections logging levels. The rule is added before all other rules. It takes effect immediately and affects all sections for which the level has not been set explicitly with Section.set_level. pattern may contains *. For example:

  Lwt_log_core.add_rule "lwt*" Lwt_log_core.Info
Sourceval append_rule : string -> level -> unit

append_rule pattern level adds the given rule after all other rules. For example to set the default fallback rule:

  Lwt_log_core.append_rule "*" Lwt_log_core.Info
Sourceval reset_rules : unit -> unit

removes all rules.

Logging functions

The following functions are the same as log except that their name determines which level is used.

For example info msg is the same as log ~level:Info msg.

Sections

Log templates

A template is for generating log messages.

It is a string which may contains variables of the form $(var), where var is one of:

  • message which will be replaced by the message emited
  • level which will be replaced by a string representation of the level
  • section which will be replaced by the name of the message's section
  • loc-file which will be replaced by the file name of the calling logging function
  • loc-line which will be replaced by the line number of the calling logging function
  • loc-column which will be replaced by the column number of the calling logging function

For example:

  • "$(name): $(message)"
  • "$(name): $(loc-file): $(loc-line): $(loc-column): $(message)"
Sourceval render : buffer:Buffer.t -> template:template -> section:section -> level:level -> message:string -> unit

render ~buffer ~template ~section ~level ~message instantiate all variables of template, and store the result in buffer. The location is obtained from threads local storage.

Sourceval location_key : (string * int * int) Lwt.key

The key for storing current location.

Loggers

Sourceexception Logger_closed

Exception raised when trying to use a closed logger

Sourceval make : output:(section -> level -> string list -> unit Lwt.t) -> close:(unit -> unit Lwt.t) -> logger

make ~output ~close creates a new logger.

  • parameter output

    is used to write logs. It is a function which receive a section, a level and a list lines that must be logged together.

  • parameter close

    is used to close the logger.

Sourceval close : logger -> unit Lwt.t

Close the given logger

Sourceval default : logger ref

The default logger. It is used as default when no one is specified. If Lwt_core is linked (in the package lwt.unix) the default logger sends all messages to standard error. Otherwise the default logger is null.

Sourceval broadcast : logger list -> logger

broadcast loggers is a logger which send messages to all the given loggers.

Note: closing a broadcast logger does not close its components.

Sourceval dispatch : (section -> level -> logger) -> logger

dispatch f is a logger which dispatch logging instructions to different logger according to their level and/or section.

Here is an example:

  let access_logger = Lwt_log.file "access.log"
  and error_logger = Lwt_log.file "error.log" in

  Lwt_log_core.dispatch
    (fun section level ->
      match Lwt_log_core.Section.name section, level with
        | "access", _ -> access_logger
        | _, Lwt_log_core.Error -> error_logger)

Predefined loggers

Sourceval null : logger

Logger which drops everything

Lwt logger for js_of_ocaml

Predefined logger

Logger that use the javascript console object.

Logging functions

Sourceval log : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> level:level -> string -> unit Lwt.t

log ?section ?logger ~level message logs a message.

section defaults to Section.main. If logger is not specified, then the default one is used instead (see default).

If exn is provided, then its string representation (= Printexc.to_string exn) will be append to the message, and if possible the backtrace will also be logged.

If inspect is provided, it will be append to the message.

location contains the location of the logging directive, it is of the form (file_name, line, column).

Sourceval log_f : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> level:level -> ('a, unit, string, unit Lwt.t) format4 -> 'a

log_f is the same as log except that it takes a format string

Sourceval ign_log : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> level:level -> string -> unit

Same as log but ignore the resulting thread.

Sourceval ign_log_f : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> level:level -> ('a, unit, string, unit) format4 -> 'a

Same as log_f but ignore the resulting thread.

The following functions are the same as log except that their name determines which level is used.

For example info msg is the same as log ~level:Info msg.

Sourceval debug : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> string -> unit Lwt.t
Sourceval debug_f : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> ('a, unit, string, unit Lwt.t) format4 -> 'a
Sourceval ign_debug : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> string -> unit
Sourceval ign_debug_f : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> ('a, unit, string, unit) format4 -> 'a
Sourceval info : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> string -> unit Lwt.t
Sourceval info_f : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> ('a, unit, string, unit Lwt.t) format4 -> 'a
Sourceval ign_info : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> string -> unit
Sourceval ign_info_f : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> ('a, unit, string, unit) format4 -> 'a
Sourceval notice : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> string -> unit Lwt.t
Sourceval notice_f : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> ('a, unit, string, unit Lwt.t) format4 -> 'a
Sourceval ign_notice : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> string -> unit
Sourceval ign_notice_f : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> ('a, unit, string, unit) format4 -> 'a
Sourceval warning : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> string -> unit Lwt.t
Sourceval warning_f : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> ('a, unit, string, unit Lwt.t) format4 -> 'a
Sourceval ign_warning : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> string -> unit
Sourceval ign_warning_f : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> ('a, unit, string, unit) format4 -> 'a
Sourceval error : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> string -> unit Lwt.t
Sourceval error_f : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> ('a, unit, string, unit Lwt.t) format4 -> 'a
Sourceval ign_error : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> string -> unit
Sourceval ign_error_f : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> ('a, unit, string, unit) format4 -> 'a
Sourceval fatal : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> string -> unit Lwt.t
Sourceval fatal_f : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> ('a, unit, string, unit Lwt.t) format4 -> 'a
Sourceval ign_fatal : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> string -> unit
Sourceval ign_fatal_f : ?inspect:'v -> ?exn:exn -> ?section:section -> ?location:(string * int * int) -> ?logger:logger -> ('a, unit, string, unit) format4 -> 'a