我正在学习Erlang文档，尝试理解设置OTP gen_server和supervisor的基础知识。每当我的gen_server崩溃时，我的supervisor也会崩溃。实际上，每当我在命令行上出现错误时，我的supervisor都会崩溃。
我期望gen_server在崩溃时被重启。我期望命令行错误对我的服务器组件完全没有影响。我的supervisor根本不应该崩溃。
我正在使用一个基本的“回声服务器”代码，它将回复任何你发送的内容，并且一个supervisor每分钟最多重新启动echo_server 5次（one_for_one）。我的代码：
echo_server.erl
-module(echo_server).
-behaviour(gen_server).
-export([start_link/0]).
-export([echo/1, crash/0]).
-export([init/1, handle_call/3, handle_cast/2]).
start_link() ->
gen_server:start_link({local, echo_server}, echo_server, [], []).
%% public api
echo(Text) ->
gen_server:call(echo_server, {echo, Text}).
crash() ->
gen_server:call(echo_server, crash)..
%% behaviours
init(_Args) ->
{ok, none}.
handle_call(crash, _From, State) ->
X=1,
{reply, X=2, State}.
handle_call({echo, Text}, _From, State) ->
{reply, Text, State}.
handle_cast(_, State) ->
{noreply, State}.
echo_sup.erl
-module(echo_sup).
-behaviour(supervisor).
-export([start_link/0]).
-export([init/1]).
start_link() ->
supervisor:start_link(echo_sup, []).
init(_Args) ->
{ok, {{one_for_one, 5, 60},
[{echo_server, {echo_server, start_link, []},
permanent, brutal_kill, worker, [echo_server]}]}}.
使用erlc *.erl编译，这是一个示例运行：
Erlang R13B01 (erts-5.7.2) [source] [smp:2:2] [rq:2] [async-threads:0] [kernel-p
oll:false]
Eshell V5.7.2 (abort with ^G)
1> echo_sup:start_link().
{ok,<0.37.0>}
2> echo_server:echo("hi").
"hi"
3> echo_server:crash().
=ERROR REPORT==== 5-May-2010::10:05:54 ===
** Generic server echo_server terminating
** Last message in was crash
** When Server state == none
** Reason for termination ==
** {'function not exported',
[{echo_server,terminate,
[{{badmatch,2},
[{echo_server,handle_call,3},
{gen_server,handle_msg,5},
{proc_lib,init_p_do_apply,3}]},
none]},
{gen_server,terminate,6},
{proc_lib,init_p_do_apply,3}]}
=ERROR REPORT==== 5-May-2010::10:05:54 ===
** Generic server <0.37.0> terminating
** Last message in was {'EXIT',<0.35.0>,
{{{undef,
[{echo_server,terminate,
[{{badmatch,2},
[{echo_server,handle_call,3},
{gen_server,handle_msg,5},
{proc_lib,init_p_do_apply,3}]},
none]},
{gen_server,terminate,6},
{proc_lib,init_p_do_apply,3}]},
{gen_server,call,[echo_server,crash]}},
[{gen_server,call,2},
{erl_eval,do_apply,5},
{shell,exprs,6},
{shell,eval_exprs,6},
{shell,eval_loop,3}]}}
** When Server state == {state,
{<0.37.0>,echo_sup},
one_for_one,
[{child,<0.41.0>,echo_server,
{echo_server,start_link,[]},
permanent,brutal_kill,worker,
[echo_server]}],
{dict,0,16,16,8,80,48,
{[],[],[],[],[],[],[],[],[],[],[],[],[],[],[],
[]},
{{[],[],[],[],[],[],[],[],[],[],[],[],[],[],
[],[]}}},
5,60,
[{1273,79154,701110}],
echo_sup,[]}
** Reason for termination ==
** {{{undef,[{echo_server,terminate,
[{{badmatch,2},
[{echo_server,handle_call,3},
{gen_server,handle_msg,5},
{proc_lib,init_p_do_apply,3}]},
none]},
{gen_server,terminate,6},
{proc_lib,init_p_do_apply,3}]},
{gen_server,call,[echo_server,crash]}},
[{gen_server,call,2},
{erl_eval,do_apply,5},
{shell,exprs,6},
{shell,eval_exprs,6},
{shell,eval_loop,3}]}
** exception exit: {{undef,
[{echo_server,terminate,
[{{badmatch,2},
[{echo_server,handle_call,3},
{gen_server,handle_msg,5},
{proc_lib,init_p_do_apply,3}]},
none]},
{gen_server,terminate,6},
{proc_lib,init_p_do_apply,3}]},
{gen_server,call,[echo_server,crash]}}
in function gen_server:call/2
4> echo_server:echo("hi").
** exception exit: {noproc,{gen_server,call,[echo_server,{echo,"hi"}]}}
in function gen_server:call/2
5>