[erlang-questions] Implement standard API (was process hierarchy and passing references)

Frans Schneider schneider@REDACTED
Fri Aug 15 16:16:50 CEST 2014

Yes, I guess defining my own behaviour is what I am looking for.
Found Cascading Behaviours 
which seems to do the trick.
It is a little dated and still uses behaviour_info(). Is it possible to 
reuse the callback definitions from gen_server?


On 08/15/2014 04:02 PM, Ladislav Lenart wrote:
> Hello.
> On 15.8.2014 11:49, Frans Schneider wrote:
>> Hi list,
>> Now that I got the supervision working, I am looking for a way to
>> implement a standard API for every "main" server. The API implements a
>> way for the main gen_server to call the RPC middleman and should also
>> define standard callbacks for the main server the middleman can use. The
>> API would also use some internal state. In a previous life, I would have
>> used inheritance to accomplish this, but how can I do this in Erlang?
>> I had a look at the supervisor implementation, but was wondering if
>> there is a easier way to accomplish this.
> I am not sure I follow you completely. However, if you want to parametrize
> process behavior in Erlang (i.e. something similar to OO inheritance that you
> mentioned), you can define your own behaviour (a module) and define different
> callback modules that all implement it. The pattern is the same as with a
> gen_server behaviour.
> If this is not what you need, please provide us with a concrete example(s) that
> you currently struggle with.
> HTH,
> Ladislav Lenart
>> Thanks
>> Frans
>> On 08/14/2014 05:16 PM, Ladislav Lenart wrote:
>>> Hello again.
>>> On 14.8.2014 17:00, Ladislav Lenart wrote:
>>>> Hello.
>>>> What about the following solution:
>>>> * Put all three processes under one supervisor.
>>>> * Set its restart strategy to one_for_all.
>>> Or rest_for_one. This one may better suite your needs. For more info, refer to
>>> the official documentation at: http://www.erlang.org/doc/man/supervisor.html
>>>> * Pass supervisor's PID to its children.
>>>> * Each worker process can lookup PID of its relevant sibling via
>>>> supervisor:which_children/1.
>>> HTH,
>>> Ladislav Lenart
>>>> On 14.8.2014 16:48, Schneider wrote:
>>>>> Hi list,
>>>>> Since I am very new to Erlang, I am not sure how to layout process
>>>>> hierarchies in the following case:
>>>>> Besides the domain specific functionality, every program has a RPC
>>>>> middleman and an XML-RPC interface, each implemented as gen_servers. In
>>>>> the current setup, the main gen_server process starts the RPC middleman,
>>>>> passing it its Pid, and the RPC gen_server starts the XML-RPC server
>>>>> which is passed the RPC middleman's Pid.
>>>>> Using the passed in Pid's, the XML-RPC server can do a
>>>>> gen_server:call()/cast() back to the RPC server which on its turn can
>>>>> call the main server. Works ok, but I would like to have the RPC
>>>>> middleman and XML-RPC controller under the control of a supervisor. The
>>>>> main supervisor should start the main gen_server process plus a
>>>>> supervisor that on its turn should start the RPC midleman and the
>>>>> XML-RPC handler.
>>>>> The thing I can't figure out is how the XML-RPC process should find the
>>>>> RPC middleman process and how that process should locate the main server
>>>>> when using supervision. Since there can be many RPC middlemen and
>>>>> XMP-RPC servers around, each belonging to different main servers, naming
>>>>> and registering seems a little hard.
>>>>> So how to pass references around?
>>>>> Any help will be very much appreciated.
>>>>> Frans
>>>>> _______________________________________________
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