[racket] Hierarchical loggers

Matthew Flatt <mflatt at cs.utah.edu> writes:
> Every once in a while, I find that option 2 works well with the pattern
>
>  foo.rkt:
>    #lang racket
>    (define-logger foo) ; uses `(current-logger)`
>
>  bar.rkt:
>    #lang racket
>    (define-logger bar) ; uses `(current-logger)`
>
>  main.rkt:
>    #lang racket
>    (require "foo.rkt"
>             "bar.rkt")
>
>    (module configure-runtime racket/base
>      (define-logger main)
>      (current-logger main-logger) ; sets `(current-logger)` early
>      ....)
>
>    (require (submod "." configure-runtime))
>
> The `configure-runtime` submodule name is special: when "main.rkt" is
> run as a program, then `configure-runtime` is loaded and instantiated
> first --- before the result of "main.rkt", and before the imported
> "foo.rkt" and "bar.rkt" modules.
>
> This strategy only makes sense for configuration that is especially
> main-like, though. It doesn't compose for larger things that are built
> on "main.rkt".

Excellent, thanks!  This will work well for part of my program.  I
recently discovered submodules, but did not know about
configure-runtime.  One thing is missing from the pattern above:
(provide main-logger).

Thanks,
Aidan