分布式监控树

 Erlang中有不同的监督策略，包括一对一监督（one-for-one）、一对多监督（one-for-all）和简单监督（simple-one-for-one）。不同的监督策略适用于不同的故障处理场景。

one-for-one 

如果一个子进程终止了，仅该进程被重启

one-for-all

如果一个子进程终止了，那么所有其他的子进程都被终止然后，所有的子进程都被重启，包括原来被终止的那个。

rest_for_one

如果一个子进程终止了，那么后面的子进程——即在启动顺序上在这个终止了的进程后面的子进程——都被终止。然后该终止的进程和后面的子进程都被重启。

-module(sellaprime_supervisor).
-behaviour(supervisor).    % see erl -man supervisor
-export([start/0, start_in_shell_for_testing/0, start_link/1, init/1]).
 
start() ->
  spawn(fun() ->
    supervisor:start_link({local, ?MODULE}, ?MODULE, _Arg = [])
        end).
start_in_shell_for_testing() ->
  {ok, Pid} = supervisor:start_link({local, ?MODULE}, ?MODULE, _Arg = []),
  unlink(Pid).
start_link(Args) ->
  supervisor:start_link({local, ?MODULE}, ?MODULE, Args).
init([]) ->
  gen_event:swap_handler(alarm_handler,
    {alarm_handler, swap},
    {my_alarm_handler, xyz}),
  {ok, {{one_for_all, 3, 10},
    [
      {tag1,
        {tcp_server, start, []},
        permanent,
        10000,
        worker,
        [area_server]},
 
      {tag2,
        {start_tcp_client, start_link, []},
        permanent,
        10000,
        worker,
        [prime_server]}
    ]}}.

-module(tcp_server).
-author("chen").
 
-behaviour(gen_server).
 
-export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2, code_change/3, start/0]).
 
-define(PORT,8003).
-record(state, {socket}).
 
start() ->
  gen_server:start_link({local, ?MODULE}, ?MODULE, ?PORT, []).
 
init(Port) ->
  {ok, LSocket} = gen_tcp:listen(Port, [binary, {packet, 4}, {active, true}, {reuseaddr, true}]),
  self() ! {to_accept, LSocket},
  io:format("start tcp_server ~n"),
  {ok, #state{socket = LSocket}}.
 
do_accept(LSocket) ->
  {ok, Socket} = gen_tcp:accept(LSocket),
  io:fwrite("Socket connected: ~w ~n", [Socket]),
  {ok, Pid} = gen_server:start_link(server_rec, Socket, []),
  gen_tcp:controlling_process(Socket, Pid),
  do_accept(LSocket).
 
handle_info({to_accept, LSocket}, State) ->
  do_accept(LSocket),
  {noreply, State}.
 
handle_call(stop, _From, Tab) ->
  {stop, normal, stopped, Tab}.
 
handle_cast(_Msg, State) ->
  {noreply, State}.
 
terminate(_Reason, _State) ->
  ok.
code_change(_OldVsn, State, _Extra) ->
  {ok, State}.
 
 

 通过启动一个监督程序，同时启动了两个进程，

 客户端发送消息，tcp接收消息，崩溃。

 服务重新启动。