Racket

simple-log🔗ℹ

A small logging layer on top of Racket’s logger system. A log definition creates a logger plus five convenience procedures. Messages are formatted with format, timestamped, and dispatched asynchronously to the registered callbacks.

1 API🔗ℹ

(require "simple-log")

package: simple-log

syntax
(sl-def-log id)
(sl-def-log id name)
(sl-def-log id name parent)

Defines a logger with topic 'id and creates:

dbg-id
info-id
warn-id
err-id
fatal-id

Note. If name is given, id dbg-prefix, etc. will be generated instead of dbg-id, etc.

Each procedure has shape:

(proc msg arg ...)

The message is formatted via format and emitted with a timestamp (YYYY-MM-DDTHH:MM:SS) and topic 'id.

If parent is omitted, the #f is used as "parent logger".

A background thread is started that receives log events and forwards them to the registered callbacks.

syntax
(sl-log-to name callback)

Registers callback under the symbolic name derived from name.

name is an identifier (not a runtime value). It is converted at macro expansion time to a symbol and used as key in the callback registry.

Invocation shape:

(callback topic level timestamp message)

with:

topic — logger topic (symbol)
level — level (symbol)
timestamp — YYYY-MM-DDTHH:MM:SS
message — formatted string

An existing callback with the same name is replaced.

procedure
(sl-log-to-file filename) → void?
filename : path-string?

Registers a callback that writes log lines to filename. The file is opened with 'replace.

Format:

"<topic>:<level>:<timestamp>:<message>"

procedure
(sl-log-to-display) → void?

Registers a callback that writes log lines to the current output port using displayln.

Format:

"<topic>:<level>:<timestamp>:<message>"

procedure
(sl-log-to-file&display filename) → void?
filename : path-string?

Equivalent to combining sl-log-to-display and sl-log-to-file.

procedure
(sl-set-log-level l) → symbol?
   l :
(or/c 'debug 'dbg
      'info
      'warning 'warn
      'error 'err
      'fatal)

Sets the module-wide log level and returns the normalized symbol.

Aliases:

'dbg → 'debug
'warn → 'warning
'err → 'error

Other values raise an exception.

Note: this value is stored globally. The receiver installed by sl-def-log itself operates at level 'debug.

procedure
(sl-log-level) → symbol?

Returns the current module-wide log level (default 'debug).

2 Generated procedures🔗ℹ

A call to sl-def-log creates five procedures. For example:

(sl-def-log my-module)

creates:

procedure
(dbg-my-module msg arg ...) → void?
msg : string?
arg : any/c

Debug log.

procedure
(info-my-module msg arg ...) → void?
msg : string?
arg : any/c

Info log.

procedure
(warn-my-module msg arg ...) → void?
msg : string?
arg : any/c

Warning log.

procedure
(err-my-module msg arg ...) → void?
msg : string?
arg : any/c

Error log.

procedure
(fatal-my-module msg arg ...) → void?
msg : string?
arg : any/c

Fatal log.

All use format and emit asynchronously.