Erlang Dynamic supervisor launches gen_server

Question

I have a root supervisor that creates another supervisor:

start_link() ->
    supervisor:start_link({local, ?MODULE}, ?MODULE, []).

init([]) ->
    RestartStrategy = {one_for_one, 5, 600},
    ListenerSup =
            {popd_listener_sup,
            {popd_listener_sup, start_link, []},
             permanent, 2000, supervisor, [popd_listener]},

    Children = [ListenerSup],

    {ok, {RestartStrategy, Children}}.

And I have a gen_server - listener. How can I run this gen_server using popd_listener_supsupervisor when the supervisor is created?

Thank.

Answer 1

Root supervisor

-module(root_sup).
-behaviour(supervisor).
-export([start_link/0]).
-export([init/1, shutdown/0]).

start_link() ->
     supervisor:start_link({local,?MODULE}, ?MODULE, []).

init(_Args) ->
     RestartStrategy = {one_for_one, 10, 60},
     ListenerSup = {popd_listener_sup,
          {popd_listener_sup, start_link, []},
          permanent, infinity, supervisor, [popd_listener_sup]},
     Children = [ListenerSup],
     {ok, {RestartStrategy, Children}}.    

% supervisor can be shutdown by calling exit(SupPid,shutdown)
% or, if it linked to its parent, by parent calling exit/1.
shutdown() ->
     exit(whereis(?MODULE), shutdown).
     % or
     % exit(normal).

If the child process is another supervisor, Shutdownthe specification for children should be set to infinityto give the subtree enough time to turn off, and Typeshould be set to supervisor, and what we did.

Children's leader

-module(popd_listener_sup).
-behaviour(supervisor).
-export([start_link/0]).
-export([init/1]).

start_link() ->
    supervisor:start_link({local,?MODULE}, ?MODULE, []).

init(_Args) ->
    RestartStrategy = {one_for_one, 10, 60},
    Listener = {ch1, {ch1, start_link, []},
            permanent, 2000, worker, [ch1]},
    Children = [Listener],
    {ok, {RestartStrategy, Children}}.

Shutdown 2000. , , exit(Child,shutdown), .

-module(ch1).
-behaviour(gen_server).

% Callback functions which should be exported
-export([init/1]).
-export([handle_cast/2, terminate/2]).

% user-defined interface functions
-export([start_link/0]).

start_link() ->
     gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).

init(_Args) ->
     erlang:process_flag(trap_exit, true),
     io:format("ch1 has started (~w)~n", [self()]),
     % If the initialization is successful, the function
     % should return {ok,State}, {ok,State,Timeout} ..
     {ok, []}.

handle_cast(calc, State) ->
     io:format("result 2+2=4~n"),
     {noreply, State};
handle_cast(calcbad, State) ->
     io:format("result 1/0~n"),
     1 / 0,
     {noreply, State}.

terminate(_Reason, _State) ->
     io:format("ch1: terminating.~n"),
     ok.

Erlang/OTP:

gen_server , Module:terminate(Reason, State) Reason=shutdown, :

• gen_server ,
• ,
  -, brutal_kill.

erlang:process_flag(trap_exit, true) Module:init(Args).

:

1> root_sup:start_link().
ch1 has started (<0.35.0>)
{ok,<0.33.0>}

, . - ; ch1.

make ch1 :

2> gen_server:cast(ch1, calc).
result 2+2=4
ok

:

3> gen_server:cast(ch1, calcbad).
result 1/0
ok
ch1: terminating.

=ERROR REPORT==== 31-Jan-2011::01:38:44 ===
** Generic server ch1 terminating 
** Last message in was {'$gen_cast',calcbad}
** When Server state == []
** Reason for termination == 
** {badarith,[{ch1,handle_cast,2},
              {gen_server,handle_msg,5},
              {proc_lib,init_p_do_apply,3}]}
ch1 has started (<0.39.0>)
4> exit(normal).
ch1: terminating.
** exception exit: normal

, ch1 popd_listener_sup ( ch1 has started (<0.39.0>)).

( supervisor:start_link, supervisor:start root start_link/0)), exit(normal) root, .