[erlang-questions] Erlang way for process-as-library?

Hakan Mattsson <>
Wed Feb 7 16:41:32 CET 2007


On Wed, 7 Feb 2007, Mats Cronqvist wrote:

MC> > Ok it is not safe in that particular regard if the pid
MC> > really is intended to be used, but as Tobbe did not use
MC> > in his example I assumed that that it was not intended
MC> > to be used. 
MC> 
MC>    i think it's clear from tobbes code that he intended
MC> it to return the correct pid. and i think it should.

Feel free to think so... ;-)

MC> > If it is important that the correct pid
MC> > is returned you will need to change the example to:
MC> >   start() ->
MC> >     case whereis(my_service) of
MC> >       Pid when pid(Pid) ->
MC> >         Pid
MC> >       _ ->
MC> >         spawn(my_mod, my_server, []), 
MC> >         whereis(my_service)
MC> >     end.
MC> 
MC>    the second whereis/1 will (likely) run before the
MC> register/2 call (presumably present) in my_mod:my_server/0,
MC> and so will return undefined.

I did not think about that race condition. It
definitely complicates things a bit. Perhaps,
it is time to dust off my good old service_broker
user contribution. It solved that problem.

/Håkan


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