Erlang OTP Design

OTP としましては。。。
Application(try_app.erl), Supervisor(try_sup.erl), Worker(try_srv.erl) とある。
Application を start すると Supervisor プロセスが起動する。
Supervisor は Worker プロセスを管理する。
Worker プロセスが仕事を行う。

3> lc([try_app, try_sup, try_srv]).
ok
4> application:start(try_app).
ok
5> gen_server:call(try_srv, 1).
{"Hello World!",1}
6> gen_server:call(try_srv, banobion).
{"Hello World!",banobion}

try_app.erl
%%%-------------------------------------------------------------------
%%% File : try_app.erl
%%% Author :
%%% Description : OTPのお試し
%%%
%%% Created : 25 Dec 2006 by
%%%-------------------------------------------------------------------
-module(try_app).

-behaviour(application).

%% Application callbacks
-export([start/2, stop/1]).

%%====================================================================
%% Application callbacks
%%====================================================================
%%--------------------------------------------------------------------
%% Function: start(Type, StartArgs) -> {ok, Pid} |
%% {ok, Pid, State} |
%% {error, Reason}
%% Description: This function is called whenever an application
%% is started using application:start/1,2, and should start the processes
%% of the application. If the application is structured according to the
%% OTP design principles as a supervision tree, this means starting the
%% top supervisor of the tree.
%%--------------------------------------------------------------------
start(_Type, StartArgs) ->
case try_sup:start_link(StartArgs) of
{ok, Pid} ->
{ok, Pid};
Error ->
Error
end.

%%--------------------------------------------------------------------
%% Function: stop(State) -> void()
%% Description: This function is called whenever an application
%% has stopped. It is intended to be the opposite of Module:start/2 and
%% should do any necessary cleaning up. The return value is ignored.
%%--------------------------------------------------------------------
stop(_State) ->
ok.

%%====================================================================
%% Internal functions
%%====================================================================

try_app.app

%% -*-erlang-*-
{application, try_app,
[{description, "OTP のお試し"},
 {vsn, "0.1"},
 {modules, [try_app, try_sup, try_srv]},
 {registered, [try_app]},
 {applications, [kernel, stdlib]},
 {mod, {try_app,[]}}
]}.

try_sup.erl

%%%-------------------------------------------------------------------
%%% File    : try_sup.erl
%%% Author  :
%%% Description : OTP のお試し
%%%
%%% Created : 25 Dec 2006 by
%%%-------------------------------------------------------------------
-module(try_sup).

-behaviour(supervisor).

%% API
-export([start_link/1]).

%% Supervisor callbacks
-export([init/1]).

-define(SERVER, ?MODULE).

%%====================================================================
%% API functions
%%====================================================================
%%--------------------------------------------------------------------
%% Function: start_link() -> {ok,Pid} | ignore | {error,Error}
%% Description: Starts the supervisor
%%--------------------------------------------------------------------
start_link(_StartArgs) ->
   supervisor:start_link({local, ?SERVER}, ?MODULE, []).

%%====================================================================
%% Supervisor callbacks
%%====================================================================
%%--------------------------------------------------------------------
%% Func: init(Args) -> {ok,  {SupFlags,  [ChildSpec]}} |
%%                     ignore                          |
%%                     {error, Reason}
%% Description: Whenever a supervisor is started using
%% supervisor:start_link/[2,3], this function is called by the new process
%% to find out about restart strategy, maximum restart frequency and child
%% specifications.
%%--------------------------------------------------------------------
init([]) ->
   AChild = {try_srv,{try_srv,start_link,[]},
      permanent,2000,worker,[try_srv]},
   {ok,{{one_for_all,0,1}, [AChild]}}.

%%====================================================================
%% Internal functions
%%====================================================================

try_srv.erl

%%%-------------------------------------------------------------------
%%% File    : try_srv.erl
%%% Author  :
%%% Description : OTP のお試し
%%%
%%% Created : 25 Dec 2006 by
%%%-------------------------------------------------------------------
-module(try_srv).

-behaviour(gen_server).

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

%% gen_server callbacks
-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
 terminate/2, code_change/3]).

-define(SERVER, try_srv).

-record(state, {message = "Hello World!"}).

%%====================================================================
%% API
%%====================================================================
%%--------------------------------------------------------------------
%% Function: start_link() -> {ok,Pid} | ignore | {error,Error}
%% Description: Starts the server
%%--------------------------------------------------------------------
start_link() ->
   gen_server:start_link({local, ?SERVER}, ?MODULE, [], []).

%%====================================================================
%% gen_server callbacks
%%====================================================================

%%--------------------------------------------------------------------
%% Function: init(Args) -> {ok, State} |
%%                         {ok, State, Timeout} |
%%                         ignore               |
%%                         {stop, Reason}
%% Description: Initiates the server
%%--------------------------------------------------------------------
init([]) ->
   {ok, #state{}}.

%%--------------------------------------------------------------------
%% Function: %% handle_call(Request, From, State) -> {reply, Reply, State} |
%%                                      {reply, Reply, State, Timeout} |
%%                                      {noreply, State} |
%%                                      {noreply, State, Timeout} |
%%                                      {stop, Reason, Reply, State} |
%%                                      {stop, Reason, State}
%% Description: Handling call messages
%%--------------------------------------------------------------------
handle_call(Request, _From, State) ->
   Reply = {State#state.message, Request},
   {reply, Reply, State}.

%%--------------------------------------------------------------------
%% Function: handle_cast(Msg, State) -> {noreply, State} |
%%                                      {noreply, State, Timeout} |
%%                                      {stop, Reason, State}
%% Description: Handling cast messages
%%--------------------------------------------------------------------
handle_cast(_Msg, State) ->
   {noreply, State}.

%%--------------------------------------------------------------------
%% Function: handle_info(Info, State) -> {noreply, State} |
%%                                       {noreply, State, Timeout} |
%%                                       {stop, Reason, State}
%% Description: Handling all non call/cast messages
%%--------------------------------------------------------------------
handle_info(_Info, State) ->
   {noreply, State}.

%%--------------------------------------------------------------------
%% Function: terminate(Reason, State) -> void()
%% Description: This function is called by a gen_server when it is about to
%% terminate. It should be the opposite of Module:init/1 and do any necessary
%% cleaning up. When it returns, the gen_server terminates with Reason.
%% The return value is ignored.
%%--------------------------------------------------------------------
terminate(_Reason, _State) ->
   ok.

%%--------------------------------------------------------------------
%% Func: code_change(OldVsn, State, Extra) -> {ok, NewState}
%% Description: Convert process state when code is changed
%%--------------------------------------------------------------------
code_change(_OldVsn, State, _Extra) ->
   {ok, State}.

%%--------------------------------------------------------------------
%%% Internal functions
%%--------------------------------------------------------------------