CODEWITHSUNDEEP
debuggingerlangerlang-supervisor
why
why

Reputation: 24851

How to trace function call in Erlang ?

I have a function in my_sup.erl like this:

init([ems_media_sup]) ->
  {ok, {{simple_one_for_one, ?MAX_RESTART, ?MAX_TIME}, [
   {ems_media_sup, {ems_media, start_link, []}, temporary, 2000, worker, [ems_media]}]
}};

But there is no function named start_link/1 in ems_media.erl, I want to know why there is no error when run 

supervisor:start_link(?MODULE, [ems_media_sup])

So, How to know what happened next after call init([ems_media_sup])

Upvotes: 1

Views: 185

Answers (1)

legoscia
legoscia

Reputation: 41528

That's because my_sup is of type simple_one_for_one - so it will only start child processes when explicitly asked to do so through supervisor:start_child/2.

If the supervisor had been of any other type (one_for_one, one_for_all or rest_for_one) it would have attempted to start all children in the child specification at startup, but a simple_one_for_one supervisor is for creating large numbers of children that only vary by their argument list, so in that case the child specification in the init function only plays the role of a template.

Upvotes: 3

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