[racket] Callback on shutdown

On 05/04/2014 03:55 PM, Spencer Florence wrote:
> Would something like dynamic-wind work for you?
> http://docs.racket-lang.org/reference/cont.html?q=dynamic-wind#%28def._%28%28quote._~23~25kernel%29._dynamic-wind%29%29

Thanks for the suggestion, but unfortunately that won't work for me: the
idea is to be able to write, in client code (rather than library code)

  (start-some-background-service)
  ...
  ...
  (use-background-service-repeatedly)
  ...
  ...

and not have to explicitly (shutdown-background-service-cleanly).

This becomes particularly important when the service is used by multiple
libraries, from multiple threads.

An example of this kind of service is Racket's logging facility. If you
had to (shutdown-logging!) explicitly, there'd either be boilerplate in
every program, or a lot of unnecessary shutdowning-and-restarting as
each library tried to guess an appropriate moment.

Regards,
  Tony


> 
> 
> On Sun, May 4, 2014 at 2:29 PM, Tony Garnock-Jones <tonyg at ccs.neu.edu
> <mailto:tonyg at ccs.neu.edu>> wrote:
> 
>     Hi all,
> 
>     I'm looking for an atexit()-like facility for Racket.
> 
>     I've tried setting the exit-handler, but it only seems to be called when
>     I explicitly call exit, and not implicitly when Racket shuts down when
>     control flows off the end of the main program.
> 
>     The problem I'm facing is to buffer rows to insert into a database, and
>     every few tens of milliseconds flush the buffer, thereby increasing
>     insertion performance.
> 
>     However, I don't want to have waiting buffered rows lost at the end of
>     the program.
> 
>     I'd like to be able to avoid having to explicitly flush the buffer
>     before exiting the program, so I'd like to make some kind of
>     atexit()-alike do it for me.
> 
>     Any suggestions?
> 
>     Tony
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