[erlang-questions] OTP application design

Vlad Dumitrescu <>
Tue Jun 12 20:33:37 CEST 2007


Hi,

On 6/12/07, Kirill Zaborski <> wrote:
> Thanks, quite reasonable.
> But implementing  an emulator for worker seems a bit ugly - I won't be able
> use "normal" behavior so I will need gen_server with
> handle_call({work,Data}) (taken from your example).

Mmm, that's not an emulator or wrapper for the worker. The
gen_server:call has two arguments: a reference to the process running
the code, and the message to be sent.

For your dispatcher, the reference is ?MODULE, presumably because the
process was registered with that name (dispatcher). Since the name is
known at compile time, the external API need not include it (i.e
dispatcher:action needs only one argument)

For the workers, the reference  will have to be the Pid of the
process. The API will have to reflect that, worker:action has two
arguments, the identity of the process and the message.

Behind the scenes, the gen_server:call will take the {work, Data}
message, wrap it up in an internal strucure and send that. The
gen_server behaviour unpacks it and dispatches it to the appropriate
handler (handle_call, handle_cast, handle_info).

I hope this is clearer.
Regards,
Vlad



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