[erlang-questions] diameter callback module

S X <>
Mon Apr 15 23:02:38 CEST 2013

I think the first question is clear. The diameter library maintains the
diameter_app callback module properly with each client calling process.  In
erlang, each process behaves like an object comparing with the OO
programming language. On the other hand, in order to deliver variables, has
to pass the values through a series of function calls or through message
box. Sometimes it is bit difficult to organize the code nicely.

But how to establish a nice notification mechanism, i.e. when the
diameter_app callback module "client_cb_ccra" receives the response from
the diameter server, how to notify the master process? By using ets table
or some generic behaviours?



On Sun, Apr 14, 2013 at 1:01 PM, S X <> wrote:

> Hello,
> Based on the erlang diameter library and the sample code, I want to start
> multiple diameter client processes in one erlang node(one client IP), and
> the client needs to define a diameter_app callback module for certain
> application, for example:
> -define(SERVICE(Name), [{'Origin-Host', ?L(Name) ++ ".example.com"},
>                         {'Origin-Realm', "example.com"},
>                         {'Vendor-Id', 193},
>                         {'Product-Name', "Client"},
>                         {'Auth-Application-Id', [?DIAMETER_APP_ID_COMMON,
>                         {application, [{alias, ?APP_CCR_ALIAS},
>                                        {dictionary, ?DIAMETER_DICT_CCRA},
>                                        {module, client_cb_ccra}]}]).
> First question:
> how the diameter library handles this situation? Will all diameter client
> processes share one single diameter_app callback module "client_cb_ccra" or
> it will automatically attach different instance of the callback module
> (process) to the different client process by using spawn_monitor? So from
> the callback handle_answer in "client_cb_ccra" I can notify the proper
> client proce by just calling client:notify() something.
> Second question:
> Notice that diameter:call allows to set extra arguments, so I was
> wondering I could set some data like:
> diameter:call(Name, ?APP_CCR_ALIAS, CCR, [{extra, [self()]}]).
> which sets the client process ID and I hope to deliver to the callback
> module "client_cb_ccra" and when the callback module knows which client
> process sends request and response accordingly, for example using the
> client process ID in the callback function handle_answer.
> However, I don't want pack the extra arguments into the diameter packet
> since the diameter server doesn't know what they are and the extra ones are
> not part of standard diameter packet.
> Now I changed the pick_peer callback signatures to allow extra arguments,
> pick_peer([Peer | _], _, _SvcName, _State, A)
> But I got encoding error in the callback prepare_request
> =ERROR REPORT==== 14-Apr-2013::11:40:41 ===
> Error in process <0.175.0> with exit value:
> {undef,[{client_cb_ccra,prepare_request,[{diameter_packet,{diameter_header,1,undefined,undefined,undefined,3958849953,3958849953,undefined,undefined,undefined,undefined},undefined,{diameter_rfc4006_cc_CCR,["who",";","142745567...
> {error,encode}
> In overall, I read the online documents, which have limited information on
> how to use the extra arguments in the library and  don't quite get how to
> utilize the extra arguments to do something tricky,
> Are there any suggestions on how to deal with multiple client processes?
> Thanks a lot!
> Samuel
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