erlang OTP Supervisor崩溃

时间:2010-05-05 16:39:04

标签: erlang otp supervisor gen-server

我正在研究Erlang文档,试图了解设置OTP gen_server和supervisor的基础知识。每当我的gen_server崩溃时,我的主管也会崩溃。事实上,每当我在命令行上出错时,我的主管就会崩溃。

我希望gen_server在崩溃时重新启动。我希望命令行错误在我的服务器组件上无任何。我的主管不应该崩溃。

我正在使用的代码是一个基本的“回显服务器”,它回复你发送的任何内容,以及一个主管,它最多每分钟重启一次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>

3 个答案:

答案 0 :(得分:15)

来自shell的测试主管的问题是主管进程链接到shell进程。当gen_server进程崩溃时,退出信号会传播到崩溃并重新启动的shell。

为避免此问题,请向主管添加以下内容:

start_in_shell_for_testing() ->
    {ok, Pid} = supervisor:start_link(echo_sup, []),
    unlink(Pid).

答案 1 :(得分:9)

我建议您调试/跟踪您的应用程序以检查发生了什么。这对了解OTP中的工作原理非常有帮助。

在您的情况下,您可能希望执行以下操作。

启动示踪剂:

dbg:tracer().

跟踪您的主管和gen_server的所有函数调用:

dbg:p(all,c).
dbg:tpl(echo_server, x).
dbg:tpl(echo_sup, x).

检查进程传递的消息:

dbg:p(new, m).

了解您的流程发生了什么(崩溃等):

dbg:p(new, p).

有关跟踪的更多信息:

http://www.erlang.org/doc/man/dbg.html

http://aloiroberto.wordpress.com/2009/02/23/tracing-erlang-functions/

希望这对今后的情况有所帮助。

提示: gen_server行为期望定义并导出回调终止/ 2;)

更新: terminate / 2 的定义之后,跟踪中可以看出崩溃的原因。这是它的外观:

我们(75)调用crash / 0函数。这是由gen_server(78)接收的。

(<0.75.0>) call echo_server:crash()
(<0.75.0>) <0.78.0> ! {'$gen_call',{<0.75.0>,#Ref<0.0.0.358>},crash}
(<0.78.0>) << {'$gen_call',{<0.75.0>,#Ref<0.0.0.358>},crash}
(<0.78.0>) call echo_server:handle_call(crash,{<0.75.0>,#Ref<0.0.0.358>},none)

呃,句柄调用问题。我们有一个糟糕的地方......

(<0.78.0>) exception_from {echo_server,handle_call,3} {error,{badmatch,2}}

终止函数被称为。服务器退出并取消注册。

(<0.78.0>) call echo_server:terminate({{badmatch,2},
 [{echo_server,handle_call,3},
  {gen_server,handle_msg,5},
  {proc_lib,init_p_do_apply,3}]},none)
(<0.78.0>) returned from echo_server:terminate/2 -> ok
(<0.78.0>) exit {{badmatch,2},
 [{echo_server,handle_call,3},
  {gen_server,handle_msg,5},
  {proc_lib,init_p_do_apply,3}]}
(<0.78.0>) unregister echo_server

Supervisor(77)从gen_server接收退出信号并完成其工作:

(<0.77.0>) << {'EXIT',<0.78.0>,
                      {{badmatch,2},
                       [{echo_server,handle_call,3},
                        {gen_server,handle_msg,5},
                        {proc_lib,init_p_do_apply,3}]}}
(<0.77.0>) getting_unlinked <0.78.0>
(<0.75.0>) << {'DOWN',#Ref<0.0.0.358>,process,<0.78.0>,
                      {{badmatch,2},
                       [{echo_server,handle_call,3},
                        {gen_server,handle_msg,5},
                        {proc_lib,init_p_do_apply,3}]}}
(<0.77.0>) call echo_server:start_link()

嗯,它尝试......因为它发生在菲利波所说的......

答案 2 :(得分:1)

另一方面,如果必须在控制台内测试restart-strategy,请使用console启动主管并检查pman以终止该过程。

您会看到pman使用相同的主管Pid刷新,但具有不同的工作者Pids,具体取决于您在restart-strategy中设置的MaxR和MaxT。