[erlang-questions] How to identify the process which died and restart it?

[Harit Himanshu]

Yes, because I am not on the chapter which teaches about it yet. My
understanding is that the same semantics could be reaching without using it
as well.

Having said that, I do believe supervisor would be the best solution, but
 this problem has to be used without Supervisor. I guess the exercise is
given to understand the semantics of Supervisor works

Thank you
+ Harit Himanshu

On Wed, Jan 14, 2015 at 1:02 AM, Roberto Ostinelli <roberto@REDACTED>
wrote:

> Is there any reason why you're not considering a supervisor [1]?
>
> Best,
> r.
>
> [1] http://erlang.org/doc/man/supervisor.html
>
> On Wed, Jan 14, 2015 at 4:52 AM, Harit Himanshu <
> harit.subscriptions@REDACTED> wrote:
>
>> I was working on the following problem and wrote the code that works, but
>> I have conceptual questions which are still bothering me. So I thought to
>> put them in community and seek recommendations and guidance
>>
>> *Question*
>> Write a function that starts and monitors several worker processes. If
>> any of the worker processes dies abnormally, restart it.
>>
>> My attempt looks like
>> monitor_workers(F, NumberOfWorkers) ->
>>   spawn(error_handling, monitor_workers_loop, [F, NumberOfWorkers]).
>>
>>
>> monitor_workers_loop(F, NumberOfWorkers) ->
>>   Workers = [spawn_monitor(F) || _Worker <- lists:seq(1,
>> NumberOfWorkers)],
>>   io:format("started workers: ~p.~n", [Workers]),
>>   receive
>>     {'DOWN', _, process, _, _} ->
>>       io:format("one of workers killed, starting one.~n"),
>>       monitor_workers_loop(F, 1)
>>   end.
>>
>> and when I run, I see
>>
>> 1> c(error_handling).
>> {ok,error_handling}
>> 2>
>> 2> error_handling:monitor_workers(fun()-> area_server0:loop() end, 2).
>> started workers: [{<0.40.0>,#Ref<0.0.0.81>},{<0.41.0>,#Ref<0.0.0.82>}].
>> <0.39.0>
>> 3>
>> 3>  Worker1 = list_to_pid("<0.40.0>").
>> <0.40.0>
>> 4>
>> 4> Worker2 = list_to_pid("<0.41.0>").
>> <0.41.0>
>> 5>
>> 5> exit(Worker1, kill).
>> one of workers killed, starting one.
>> started workers: [{<0.45.0>,#Ref<0.0.0.98>}].
>> true
>> 6> exit(Worker2, kill).
>> one of workers killed, starting one.
>> started workers: [{<0.47.0>,#Ref<0.0.0.105>}].
>> true
>> 7>
>>
>> *Problem(s)?*
>>
>>    1. A better way to solve this would be pass in different
>>    functions(than same, what I did) and let workers work on different
>>    problems. In such a scenario all we know if Pid and Ref to the workers.
>>    2. When any process fails, it matches {'DOWN', Ref, process, Pid,
>>    Why}, and given this context how could I identify what function this
>>    process was running?
>>
>> I am very new to Erlang so have not much knowledge to solve such problems.
>>
>> Thank you
>> + Harit Himanshu
>>
>> _______________________________________________
>> erlang-questions mailing list
>> erlang-questions@REDACTED
>> http://erlang.org/mailman/listinfo/erlang-questions
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://erlang.org/pipermail/erlang-questions/attachments/20150114/75388e85/attachment.htm>