Module 为什么我的主管在启动undef儿童时失败？

我正在尝试运行一个

simple\u one\u for\u one supervisor

，其中

supervisor

和

worker

被放置在不同的模块中，使用

supervisor时，我不断收到以下错误：启动子项

：

>A=sup:start_link().
>B=supervisor:start_child(A,[]).
{error,{'EXIT',{undef,[{worker,start_link,[],[]},
                       {supervisor,do_start_child_i,3,
                                   [{file,"supervisor.erl"},{line,379}]},
                       {supervisor,handle_call,3,
                                   [{file,"supervisor.erl"},{line,404}]},
                       {gen_server,try_handle_call,4,
                                   [{file,"gen_server.erl"},{line,661}]},
                       {gen_server,handle_msg,6,
                                   [{file,"gen_server.erl"},{line,690}]},
                       {proc_lib,init_p_do_apply,3,
                                 [{file,"proc_lib.erl"},{line,249}]}]}}}

主管

-module(sup).
-behaviour(supervisor).
-compile([export_all]).

start_link()->
    {ok,Pid}=supervisor:start_link(?MODULE,[]),
    io:format("sugi pl"),
    Pid.



init(_Args) ->
     RestartStrategy = {simple_one_for_one, 10, 60},
     ChildSpec = {
                  worker, 
                  {worker, start_link, []},  //tried adding here a parameter in the A
                  permanent,
                  brutal_kill, 
                  worker,
                  [sup]
                },
    {ok, {RestartStrategy,[ChildSpec]}}.

-module(worker).
-compile(export_all).


start_link([Arg])->  //tried both [Arg] and Arg
    {ok,Pid}=spawn_link(?MODULE,init,[]),
    Pid.


init([Time])->
    receive->
        {From,Msg}->From !{Time,Msg},
                     init(Time)
    end.

-module(sup).
-behaviour(supervisor).
-compile([export_all]).

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

init(_Args) ->
     RestartStrategy = {simple_one_for_one, 10, 60},
     ChildSpec = {
                  worker,
                  {worker, start_link, []},
                  permanent,
                  brutal_kill,
                  worker,
                  [worker]
                },
    {ok, {RestartStrategy,[ChildSpec]}}.

-module(worker).
-compile(export_all).

start_link()->
    Pid = spawn_link(?MODULE,init,[os:timestamp()]),
    {ok, Pid}.

init(Time) ->
    receive
        {From,Msg} ->
            From ! {Time,Msg},
            init(Time)
    end.

工人

-module(sup).
-behaviour(supervisor).
-compile([export_all]).

start_link()->
    {ok,Pid}=supervisor:start_link(?MODULE,[]),
    io:format("sugi pl"),
    Pid.



init(_Args) ->
     RestartStrategy = {simple_one_for_one, 10, 60},
     ChildSpec = {
                  worker, 
                  {worker, start_link, []},  //tried adding here a parameter in the A
                  permanent,
                  brutal_kill, 
                  worker,
                  [sup]
                },
    {ok, {RestartStrategy,[ChildSpec]}}.

-module(worker).
-compile(export_all).


start_link([Arg])->  //tried both [Arg] and Arg
    {ok,Pid}=spawn_link(?MODULE,init,[]),
    Pid.


init([Time])->
    receive->
        {From,Msg}->From !{Time,Msg},
                     init(Time)
    end.

-module(sup).
-behaviour(supervisor).
-compile([export_all]).

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

init(_Args) ->
     RestartStrategy = {simple_one_for_one, 10, 60},
     ChildSpec = {
                  worker,
                  {worker, start_link, []},
                  permanent,
                  brutal_kill,
                  worker,
                  [worker]
                },
    {ok, {RestartStrategy,[ChildSpec]}}.

-module(worker).
-compile(export_all).

start_link()->
    Pid = spawn_link(?MODULE,init,[os:timestamp()]),
    {ok, Pid}.

init(Time) ->
    receive
        {From,Msg} ->
            From ! {Time,Msg},
            init(Time)
    end.

命令

>c("[somepath]/sup.erl"),A=sup:start_link(),B=supervisor:start_child(A,[]).

我可以清楚地看到问题是在尝试添加子项时。不知何故，

init

函数调用不正确，但我不明白原因。（Badmatch）

---

我已尝试在

ChildSpec

的

MFA

的

a

中添加一个参数，但没有效果

您的代码存在许多问题

• sup:start\u link/0

  的返回值错误；返回的是Pid而不是

  {ok，Pid}

• 虽然这并不是真的不正确，但您使用的是

  supervisor:start\u link/2

  ，它没有注册supervisor名称。有这个名字很方便，所以最好使用

  supervisor:start\u link/3

  ：

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

  这将模块名称与其进程id相关联，允许您在shell命令中使用进程名称，而不是使用pid变量

• 您有一个

  io:format/2

  调用

  sup:start\u link/0

  ，可能是为了调试。一种更好的调试方法是在启动

  sup

  监控程序后，从shell调用

  sys:trace（sup，true）

  。通过指定

  false

  而不是

  true

  作为第二个参数，也可以从shell中关闭它

修复上述问题将使用以下定义的

sup:start\u link/0

：

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

让我们重新编译，启动主管，然后编译

worker

（修复其语法错误后），然后在尝试启动子级时跟踪主管：

1> c(sup).
sup.erl:3: Warning: export_all flag enabled - all functions will be exported
{ok,sup}
2> sup:start_link().
{ok,<0.94.0>}
3> sys:trace(sup, true).
ok
4> c(worker).
worker.erl:2: Warning: export_all flag enabled - all functions will be exported
worker.erl:5: Warning: variable 'Arg' is unused
{ok,worker}
5> supervisor:start_child(sup, []).
*DBG* sup got call {start_child,[]} from <0.81.0>
*DBG* sup sent {error,
                   {'EXIT',
                       {undef,
                           [{worker,start_link,[],[]},
                            {supervisor,do_start_child_i,3,
                                [{file,"supervisor.erl"},{line,379}]},
...

我们通过

supervisor:start\u child（sup，[]）

启动了这个孩子。对于

simple\u one\u For_one

子函数，发送到其start函数的参数由子规范中的参数列表和调用

supervisor:start\u child/2

中指定的参数组成；在本例中，这相当于

[]+[]

，与

[]]

相同，表示没有参数。让我们将

worker:start\u link/1

函数改为

worker:start\u link/0

，重新编译它，然后重试：

6> c(worker).
worker.erl:2: Warning: export_all flag enabled - all functions will be exported
{ok,worker}
7> supervisor:start_child(sup, []).
*DBG* sup got call {start_child,[]} from <0.81.0>
*DBG* sup sent {error,
                   {'EXIT',
                       {{badmatch,<0.94.0>},
                        [{worker,start_link,0,[{file,"worker.erl"},{line,6}]},
...

8> c(worker).
worker.erl:2: Warning: export_all flag enabled - all functions will be exported
{ok,worker}
9> supervisor:start_child(sup, []).
*DBG* sup got call {start_child,[]} from <0.81.0>
*DBG* sup sent {ok,<0.106.0>} to <0.81.0>, new state {state,
                                                      {local,sup},
                                                      simple_one_for_one,
                                                      {[worker],
                                                       #{worker =>
                                                          {child,undefined,
                                                           worker,
                                                           {worker,
                                                            start_link,[]},
                                                           permanent,
                                                           brutal_kill,worker,
                                                           [sup]}}},
                                                      {maps,
                                                       #{<0.106.0> => []}},
                                                      10,60,[],0,sup,[]}
*DBG* sup got {'EXIT',<0.106.0>,{undef,[{worker,init,[],[]}]}}

10> sup:start_link().
{ok,<0.119.0>}
11> sys:trace(sup, true).
ok
12> c(worker).
worker.erl:2: Warning: export_all flag enabled - all functions will be exported
{ok,worker}
13> {ok, Child} = supervisor:start_child(sup, []).
*DBG* sup got call {start_child,[]} from <0.118.0>
*DBG* sup sent {ok,<0.127.0>} to <0.118.0>, new state {state,
                                                       {local,sup},
                                                       simple_one_for_one,
                                                       {[worker],
                                                        #{worker =>
                                                           {child,undefined,
                                                            worker,
                                                            {worker,
                                                             start_link,[]},
                                                            permanent,
                                                            brutal_kill,
                                                            worker,
                                                            [sup]}}},
                                                       {maps,
                                                        #{<0.127.0> => []}},
                                                       10,60,[],0,sup,[]}
{ok,<0.127.0>}

然后让我们重新编译并重试：

6> c(worker).
worker.erl:2: Warning: export_all flag enabled - all functions will be exported
{ok,worker}
7> supervisor:start_child(sup, []).
*DBG* sup got call {start_child,[]} from <0.81.0>
*DBG* sup sent {error,
                   {'EXIT',
                       {{badmatch,<0.94.0>},
                        [{worker,start_link,0,[{file,"worker.erl"},{line,6}]},
...

8> c(worker).
worker.erl:2: Warning: export_all flag enabled - all functions will be exported
{ok,worker}
9> supervisor:start_child(sup, []).
*DBG* sup got call {start_child,[]} from <0.81.0>
*DBG* sup sent {ok,<0.106.0>} to <0.81.0>, new state {state,
                                                      {local,sup},
                                                      simple_one_for_one,
                                                      {[worker],
                                                       #{worker =>
                                                          {child,undefined,
                                                           worker,
                                                           {worker,
                                                            start_link,[]},
                                                           permanent,
                                                           brutal_kill,worker,
                                                           [sup]}}},
                                                      {maps,
                                                       #{<0.106.0> => []}},
                                                      10,60,[],0,sup,[]}
*DBG* sup got {'EXIT',<0.106.0>,{undef,[{worker,init,[],[]}]}}

10> sup:start_link().
{ok,<0.119.0>}
11> sys:trace(sup, true).
ok
12> c(worker).
worker.erl:2: Warning: export_all flag enabled - all functions will be exported
{ok,worker}
13> {ok, Child} = supervisor:start_child(sup, []).
*DBG* sup got call {start_child,[]} from <0.118.0>
*DBG* sup sent {ok,<0.127.0>} to <0.118.0>, new state {state,
                                                       {local,sup},
                                                       simple_one_for_one,
                                                       {[worker],
                                                        #{worker =>
                                                           {child,undefined,
                                                            worker,
                                                            {worker,
                                                             start_link,[]},
                                                            permanent,
                                                            brutal_kill,
                                                            worker,
                                                            [sup]}}},
                                                       {maps,
                                                        #{<0.127.0> => []}},
                                                       10,60,[],0,sup,[]}
{ok,<0.127.0>}

因为这是一个硬错误，它每次都会立即失败，并且在60秒或更短的时间内重新启动10次失败后，管理器就会死亡，就像它应该：

=SUPERVISOR REPORT==== 20-Apr-2020::10:43:43.557307 ===
    supervisor: {local,sup}
    errorContext: shutdown
    reason: reached_max_restart_intensity
    offender: [{pid,<0.117.0>},
               {id,worker},
               {mfargs,{worker,start_link,[]}},
               {restart_type,permanent},
               {shutdown,brutal_kill},
               {child_type,worker}]
** exception error: shutdown

让我们也修复

init/1

以直接获取参数，而不是在列表中：

init(Time) ->
    receive
        {From,Msg} ->
            From ! {Time,Msg},
            init(Time)
end.

让我们重新启动主管，重新编译

工作程序

，然后重试：

6> c(worker).
worker.erl:2: Warning: export_all flag enabled - all functions will be exported
{ok,worker}
7> supervisor:start_child(sup, []).
*DBG* sup got call {start_child,[]} from <0.81.0>
*DBG* sup sent {error,
                   {'EXIT',
                       {{badmatch,<0.94.0>},
                        [{worker,start_link,0,[{file,"worker.erl"},{line,6}]},
...

8> c(worker).
worker.erl:2: Warning: export_all flag enabled - all functions will be exported
{ok,worker}
9> supervisor:start_child(sup, []).
*DBG* sup got call {start_child,[]} from <0.81.0>
*DBG* sup sent {ok,<0.106.0>} to <0.81.0>, new state {state,
                                                      {local,sup},
                                                      simple_one_for_one,
                                                      {[worker],
                                                       #{worker =>
                                                          {child,undefined,
                                                           worker,
                                                           {worker,
                                                            start_link,[]},
                                                           permanent,
                                                           brutal_kill,worker,
                                                           [sup]}}},
                                                      {maps,
                                                       #{<0.106.0> => []}},
                                                      10,60,[],0,sup,[]}
*DBG* sup got {'EXIT',<0.106.0>,{undef,[{worker,init,[],[]}]}}

10> sup:start_link().
{ok,<0.119.0>}
11> sys:trace(sup, true).
ok
12> c(worker).
worker.erl:2: Warning: export_all flag enabled - all functions will be exported
{ok,worker}
13> {ok, Child} = supervisor:start_child(sup, []).
*DBG* sup got call {start_child,[]} from <0.118.0>
*DBG* sup sent {ok,<0.127.0>} to <0.118.0>, new state {state,
                                                       {local,sup},
                                                       simple_one_for_one,
                                                       {[worker],
                                                        #{worker =>
                                                           {child,undefined,
                                                            worker,
                                                            {worker,
                                                             start_link,[]},
                                                            permanent,
                                                            brutal_kill,
                                                            worker,
                                                            [sup]}}},
                                                       {maps,
                                                        #{<0.127.0> => []}},
                                                       10,60,[],0,sup,[]}
{ok,<0.127.0>}

正如我们预期的那样，它有一个工人。最后，让我们向worker发送一条消息，看看它是否按预期响应：

15> Child ! {self(), "are you there?"}.
{<0.118.0>,"are you there?"}
16> flush().
Shell got {{1587,394860,258120},"are you there?"}
ok

工人

-module(sup).
-behaviour(supervisor).
-compile([export_all]).

start_link()->
    {ok,Pid}=supervisor:start_link(?MODULE,[]),
    io:format("sugi pl"),
    Pid.



init(_Args) ->
     RestartStrategy = {simple_one_for_one, 10, 60},
     ChildSpec = {
                  worker, 
                  {worker, start_link, []},  //tried adding here a parameter in the A
                  permanent,
                  brutal_kill, 
                  worker,
                  [sup]
                },
    {ok, {RestartStrategy,[ChildSpec]}}.

-module(worker).
-compile(export_all).


start_link([Arg])->  //tried both [Arg] and Arg
    {ok,Pid}=spawn_link(?MODULE,init,[]),
    Pid.


init([Time])->
    receive->
        {From,Msg}->From !{Time,Msg},
                     init(Time)
    end.

-module(sup).
-behaviour(supervisor).
-compile([export_all]).

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

init(_Args) ->
     RestartStrategy = {simple_one_for_one, 10, 60},
     ChildSpec = {
                  worker,
                  {worker, start_link, []},
                  permanent,
                  brutal_kill,
                  worker,
                  [worker]
                },
    {ok, {RestartStrategy,[ChildSpec]}}.

-module(worker).
-compile(export_all).

start_link()->
    Pid = spawn_link(?MODULE,init,[os:timestamp()]),
    {ok, Pid}.

init(Time) ->
    receive
        {From,Msg} ->
            From ! {Time,Msg},
            init(Time)
    end.

---

除了已经发布的优秀答案之外，我想补充几点来解释问题中观察到的行为

childspec中的开始值是一个元组

{Mod，Fun，ArgsList}

，子进程可以通过调用

主管：开始\u子进程（主管，列表）

生成。主管通过调用

erlang:apply（Mod，Fun，List++ArgsList）

启动子进程

在这种情况下，开始值是

{worker，start\u link，[]}

，子项是通过调用

主管：start\u child（A，[]）

生成的。主管试图调用

erlang:apply（worker，start\u link，[]）

。这意味着主管希望在

worker

模块中定义

worker:start\u link/0

。但是

worker

模块定义了

worker:start\u link/1

。因此出现

undef

错误

给出了函数定义

start_link([Arg]) ->
  %% do stuff

最好是生成子进程

• 让子规范中的起始值为

  {worker，start\u link，[]}

• 呼叫

  supervisor:start_child（A，[[Value]]）

将函数定义为

start_link(Arg) ->
  %% so stuff

---

并调用

supervisor:start_child（A，[Value]）

您确定编译并加载了

worker

吗？我正在erlang shell中运行我上面编写的命令。如果

sup

模块使用

worker

模块，是否需要编译它？它们是否都将被编译？

unde，[{worker，start\u link，[

表示worker:start\u link/0不存在，但worker仅定义start\u link/1。这可能是因为您的模块不同步。请确保sup和worker对worker:start\u link使用相同的arity，并在重试之前重新编译这两个模块。