[erlang-questions] Re: Interfaces between distributed OTP applications

Angel <>
Fri Jan 29 20:17:19 CET 2010


On Viernes, 29 de Enero de 2010 17:57:13 Garrett Smith escribió:
> On Fri, Jan 29, 2010 at 10:27 AM, ZZZZZZZZZZZZZZZZ
> 
> <> wrote:
> > I hate to repost, but maybe somebody can answer?
> > thanks in advance
> 
> FWIW, when I first saw your post, I casually interpreted your all-caps
> name as spam that got through the filter. You might want to tweak your
> mail client.

Yeahhh! please change your address format if posible.
> 
> > Zvi
> >
> > On Jan 26, 10:36 am, ZZZZZZZZZZZZZZZZ <> wrote:
> >> Hi,
> >>
> >> the OTP Design Principles states, that OTP Applications are set of
> >> loosely-coupled components, while modules inside single application
> >> are tightly coupled.
> >> Let's say I have two distributed OTP applications:  "client" and
> >> "server", both running on different Erlang nodes/hosts.
> >> Let's say "server" application uses gen_server, which exposes public
> >> function API.
> >> The "client" applications calling functions in public API of
> >> gen_server in "server" application.
> >> What's the proper way to express this in OTP?
> >>
> >> 1. For simplicity, just add dependency on "server" application in
> >> "client" application's .app file. Start both on "server" node.
> 
> Yes, though I'm not sure why the client would need to run on the
> server node. The server would typically be registered globally and
> then accessed from the client through a public API in the server
> module (or an application level module).
> 
> >> 2. Don't use public API functions in "server". Send messages directly
> >> to "server" using gen_server:call / cast.
> 
> No. Look over the API docs for other gen_server implementations in OTP
> -- there's always a public API that wraps the call/cast to the server.
> 
> >> 3. Add third application: "server_api" or "server_if" with single
> >> module defining public API wrappers around gen_server messages
> >> protocol. Then "client" application will be depended on "server_api"
> >> application, and not the "server" itself.
> 
> It's common to provide an application level module that provides all
> public APIs. E.g. look over the mnesia application.
> 
> That said, you still want to provide an API per gen_server, even if
> it's only used within your app.
> 
> >> 4. Any other ideas?
> 
> For learning OTP principles, there's no substitute for reading and
> understanding the way existing OTP apps are implemented. I'd recommend
> spending some time looking over apps (source, .app file, directory
> structure, etc.) like inets and mnesia. I do this all the time to get
> ideas for structuring my Erlang code.
> 
> Garrett
> 
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-- 
Most people know C is not so high level....
                ...Everybody else just got assembler overdose
 


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