Supervisors

Basic supervisor with one worker process

This example uses the map format introduced in Erlang/OTP 18.0.
%% A module implementing a supervisor usually has a name ending with `_sup`.
-module(my_sup).

-behaviour(supervisor).

%% API exports
-export([start_link/0]).

%% Behaviour exports
-export([init/1]).

start_link() ->
    %% If needed, we can pass an argument to the init callback function.
    Args = [],
    supervisor:start_link({local, ?MODULE}, ?MODULE, Args).

%% The init callback function is called by the 'supervisor' module.
init(_Args) ->
    %% Configuration options common to all children.
    %% If a child process crashes, restart only that one (one_for_one).
    %% If there is more than 1 crash ('intensity') in
    %% 5 seconds ('period'), the entire supervisor crashes
    %% with all its children.
    SupFlags = #{strategy => one_for_one,
                 intensity => 1,
                 period => 5},

    %% Specify a child process, including a start function.
    %% Normally the module my_worker would be a gen_server
    %% or a gen_fsm.
    Child = #{id => my_worker,
              start => {my_worker, start_link, []}},

    %% In this case, there is only one child.
    Children = [Child],

    %% Return the supervisor flags and the child specifications
    %% to the 'supervisor' module.
    {ok, {SupFlags, Children}}.