-module(base_super).

-behaviour(supervisor).		% see erl -man supervisor

-export([start_link/0,
	 init/1]).

%% This is the start function for the top supervisor.
%% A common pattern: implement a module that implements a
%% start_link() function. I frown upon the practise of exporting
%% a start() function that e.g. calls supervisor:start_link(), or
%% worse: the other way around.
%%
start_link() ->
    supervisor:start_link({local,?MODULE}, ?MODULE, _Arg = []).

%% When the supervisor is started, it calls init(Arg).
%% This function should return {ok, {SupFlags, Children}}.
%%
%% SupFlags : {supervision_strategy(), maxR(), maxT()}
%% supervision_strategy() : one_for_one | one_for_all | simple_one_for_one
%%
%% Children : [ChildStartSpecification]
%% ChildStartSpecification : {internal_name(),
%%                            {module(), function(), args()},
%%                            shutdown_time(),
%%                            child_type(),
%%                            modules()}
%% See erl -man supervisor for more details.
%%
%% A word on MaxR/MaxT:
%% Choosing a good restart frequency is difficult. The following
%% reasoning might help:
%%
%% - MaxR should be low enough that escalation is not needlessly delayed.
%%   Remember that if you have multiple levels of supervisors, MaxR will
%%   multiply; you might want to set MaxR=0 for most higher supervisors.
%% - MaxT should be low enough that unrelated restarts aren't counted as
%%   looping restart (think: how long does it take for the effects of a
%%   problem to "heal"?); if MaxT is too low, there may not be time enough
%%   for MaxR restarts.
%%
%% In general, think about what should happen if a certain process restars.
%% Some processes may be designed as "kernel processes", such that the only
%% reasonable course of action, should they crash, is to terminate the node.
%%
%% I've chosen three restarts in 10 seconds.
%%
init([]) ->
    SupFlags = {one_for_one, 3, 10},
    {ok, {SupFlags, [{server, {base_server, start_link, []},
		      permanent, 10000, worker, [base_server]}]}}.