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  • 《Erlang程序设计》第十八章 构造基于OTP的系统

    第十八章 构造基于OTP的系统

    第十八章 构造基于OTP的系统

    18.1 通用的事件处理

    %% 创建一个注册名为Name的进程, 这个进程执行my_handler函数 
    make(Name) ->
        register(Name, spawn(fun() ->my_handler(fun no_op/1) end)).
    
    
    %% 等待事件处理
    %% 如果是{event, _}类型则调用Fun处理
    %% 如果是{add, _}类型则更新处理函数 
    my_handler(Fun) ->
        receive
            {add, Fun1} ->
                my_handler(Fun1);
            {event, Any} ->
                (catch Fun(Any)),
                my_handler(Fun)
        end.
    
    %% 更新Name进程的处理函数为Fun
    add_handler(Name, Fun) ->Name ! {add, Fun}.
    
    %% 向Name进程发送事件X
    event(Name, X) ->Name ! {event, X}.
    
    %% 事件处理函数, 什么都不做
    no_op(_) ->void.
    

      运行结果:

    1> c(event_handler).
    {ok,event_handler}
    2> event_handler:make(errors).
    true
    3> event_handler:event(errors, hi).
    {event,hi}
    

      为处理程序添加一个简单的回调模块

    -module(motor_controller).
    
    -export([add_event_handler/0]).
    
    %% 更新errors进程的处理函数
    add_event_handler() ->
        event_handler:add_handler(errors, fun controller/1).
    
    %% 具体处理, 一些简单的输出
    controller(too_hot) ->
        io:format("Turn off the motor~n");
    controller(X) ->
        io:format("~w ignored event: ~p~n",[?MODULE, X]).
    

      运行结果:

    4> c(motor_controller).
    {ok,motor_controller}
    5> motor_controller:add_event_handler().
    {add,#Fun<motor_controller.0.125151531>}
    6> event_handler:event(errors, cool).   
    motor_controller ignored event: cool
    {event,cool}
    7> event_handler:event(errors, too_hot).
    Turn off the motor
    {event,too_hot}
    

    从这个简单的例子可以看到Erlang的强大之处:非常延迟的绑定^_^, 正如作者所说:使用这个机制, 我们可以构造一个可以随着时间推移不断演化的系统, 而演化的过程无需停机, 甚至也不需要升级代码。

    18.2 错误日志

    错误日志的三种视角:如何调用函数记录错误日志; 如何配置错误日志的存储; 如何对错误日志进行分析。

    18.2.1 记录一个错误

    # 错误日志的API 
    
    # 向错误日志发送一个错误消息
    # error_logger:error_msg(String) -> ok
    8> error_logger:error_msg("An error has occurred
    ").
    ok
    9> 
    =ERROR REPORT==== 8-Nov-2013::13:22:42 ===
    An error has occurred
    
    # 向错误日志发送一个带参数的错误消息 
    # error_logger:error_msg(Format, Data) -> ok
    10> error_logger:error_msg("~s, An error has occurred
    ", ["Joe"]).
    
    =ERROR REPORT==== 8-Nov-2013::13:25:39 ===
    Joe, An error has occurred
    ok
    
    # 向错误日志发送一个标准错误报告
    # error_logger:error_report(Report) -> ok
    # @type Report = [{Tag, Data} | term()] | string() | term()
    # @type Tag = term()
    # @type Data = term()
    11> error_logger:error_report([{tag1, data1}, a_term, {tag2, data}]). 
    
    =ERROR REPORT==== 8-Nov-2013::13:29:14 ===
        tag1: data1
        a_term
        tag2: data
    ok 
    

    18.2.2 配置错误日志

    • 1. 标准错误日志
      # 适合程序开发的环境
      $ erl -boot start_clean
      
      # 适合产品化系统的环境
      $ erl -boot start_sasl 
      
    • 2. 不进行配置的SASL
      matrix@MBP:18 $ erl -boot start_sasl
      Erlang R15B01 (erts-5.9.1) [source] [64-bit] [smp:4:4] [async-threads:0] [hipe] [kernel-poll:false]
      
      
      =PROGRESS REPORT==== 8-Nov-2013::13:32:52 ===
                supervisor: {local,sasl_safe_sup}
                   started: [{pid,<0.34.0>},
                             {name,alarm_handler},
                             {mfargs,{alarm_handler,start_link,[]}},
                             {restart_type,permanent},
                             {shutdown,2000},
                             {child_type,worker}]
      
      =PROGRESS REPORT==== 8-Nov-2013::13:32:52 ===
                supervisor: {local,sasl_safe_sup}
                   started: [{pid,<0.35.0>},
                             {name,overload},
                             {mfargs,{overload,start_link,[]}},
                             {restart_type,permanent},
                             {shutdown,2000},
                             {child_type,worker}]
      
      =PROGRESS REPORT==== 8-Nov-2013::13:32:52 ===
                supervisor: {local,sasl_sup}
                   started: [{pid,<0.33.0>},
                             {name,sasl_safe_sup},
                             {mfargs,
                                 {supervisor,start_link,
                                     [{local,sasl_safe_sup},sasl,safe]}},
                             {restart_type,permanent},
                             {shutdown,infinity},
                             {child_type,supervisor}]
      
      =PROGRESS REPORT==== 8-Nov-2013::13:32:52 ===
                supervisor: {local,sasl_sup}
                   started: [{pid,<0.36.0>},
                             {name,release_handler},
                             {mfargs,{release_handler,start_link,[]}},
                             {restart_type,permanent},
                             {shutdown,2000},
                             {child_type,worker}]
      
      =PROGRESS REPORT==== 8-Nov-2013::13:32:52 ===
               application: sasl
                started_at: nonode@nohost
      Eshell V5.9.1  (abort with ^G)
      1> error_logger:error_msg("This is an error
      ").
      ok
      2> 
      =ERROR REPORT==== 8-Nov-2013::13:33:45 ===
      This is an error
      
    • 3. 控制记录何种日志
      监管报告, 在监管进程启动或者停止被监管的进程时;进程报告, 每次OTP监管进程启动或者停止的时候;崩溃报告, 当被监管的进程退出时, 如果退出原因不是normal或者shutdown则产生此报告。
      %% elog1.config
      [{sasl, [{sasl_error_logger, false}]}].
      

        运行结果:

      matrix@MBP:18 $ erl -boot start_sasl -config elog1
      Erlang R15B01 (erts-5.9.1) [source] [64-bit] [smp:4:4] [async-threads:0] [hipe] [kernel-poll:false]
      
      Eshell V5.9.1  (abort with ^G)
      1> error_logger:error_msg("This is an error
      ").
      ok
      
      =ERROR REPORT==== 8-Nov-2013::13:40:09 ===
      This is an error
      
    • 4. 文本文件和shell
      %% elog2.config
      [{sasl, [{sasl_error_logger, {file, "/Users/matrix/Documents/Erlang/erlp/18/error_logs/THELOG"}}]}].
      

        运行结果:

      matrix@MBP:18 $ cat error_logs/THELOG 
      
      =PROGRESS REPORT==== 8-Nov-2013::13:45:27 ===
                supervisor: {local,sasl_safe_sup}
                   started: [{pid,<0.35.0>},
                             {name,alarm_handler},
                             {mfargs,{alarm_handler,start_link,[]}},
                             {restart_type,permanent},
                             {shutdown,2000},
                             {child_type,worker}]
      
      =PROGRESS REPORT==== 8-Nov-2013::13:45:27 ===
                supervisor: {local,sasl_safe_sup}
                   started: [{pid,<0.36.0>},
                             {name,overload},
                             {mfargs,{overload,start_link,[]}},
                             {restart_type,permanent},
                             {shutdown,2000},
                             {child_type,worker}]
      
      =PROGRESS REPORT==== 8-Nov-2013::13:45:27 ===
                supervisor: {local,sasl_sup}
                   started: [{pid,<0.34.0>},
                             {name,sasl_safe_sup},
                             {mfargs,
                                 {supervisor,start_link,
                                     [{local,sasl_safe_sup},sasl,safe]}},
                             {restart_type,permanent},
                             {shutdown,infinity},
                             {child_type,supervisor}]
      
      =PROGRESS REPORT==== 8-Nov-2013::13:45:27 ===
                supervisor: {local,sasl_sup}
                   started: [{pid,<0.37.0>},
                             {name,release_handler},
                             {mfargs,{release_handler,start_link,[]}},
                             {restart_type,permanent},
                             {shutdown,2000},
                             {child_type,worker}]
      
      =PROGRESS REPORT==== 8-Nov-2013::13:45:27 ===
               application: sasl
                started_at: nonode@nohost
      
    • 5. 循环日志和shell
      %% elog3.config
      [{sasl, [
               {sasl_error_logger, false},
               %% 指定输出目录
               {error_logger_mf_dir, "/Users/matrix/Documents/Erlang/erlp/18/error_logs"},
               %% 指定单个文件最大值
               {error_logger_mf_maxbytes, 10485760},
               %% 指定文件最大数量
               {error_logger_mf_maxfiles, 10}
              ]}].
      

      运行后会在错误日志存储目录下发现已经生成了名字为1的日志文件。

    • 6. 产品化环境
      %% elog4.config
      [{sasl, [
               {sasl_error_logger, false},
               %% 只记录错误日志
               {errorlog_type, error},
               %% 指定输出目录
               {error_logger_mf_dir, "/Users/matrix/Documents/Erlang/erlp/18/error_logs"},
               %% 指定单个文件最大值
               {error_logger_mf_maxbytes, 10485760},
               %% 指定文件最大数量
               {error_logger_mf_maxfiles, 10}
              ]}].
      

    18.2.3 分析错误

    使用rb模块读取错误日志

    18.3 警报管理

    -module(my_alarm_handler).
    -behaviour(gen_event).
    
    %% 需要自定义的gen_event的回调函数
    -export([init/1, handle_event/2, handle_call/2, 
         handle_info/2, terminate/2]).
    
    %% 完成初始化, 必须返回{ok, State}
    init(Args) ->
        io:format("*** my_alarm_handler init:~p~n",[Args]),
        {ok, 0}.
    
    %% handle_event(Event, State) -> {ok, NewState}
    %% 其中Event是形如{EventType, EventArgs}的元组
    %% EventType可以是set_event或clear_event
    %% EventArgs是用户提供的参数
    
    %% 设置警报 
    handle_event({set_alarm, tooHot}, N) ->
        error_logger:error_msg("*** Tell the Engineer to turn on the fan~n"),
        {ok, N+1};
    
    %% 清除警报
    handle_event({clear_alarm, tooHot}, N) ->
        error_logger:error_msg("*** Danger over. Turn off the fan~n"),
        {ok, N};
    
    %% 其它类型的警报
    handle_event(Event, N) ->
        io:format("*** unmatched event:~p~n",[Event]),
        {ok, N}.
    
    %% 其它需要实现的回调函数 
    handle_call(_Request, N) ->Reply = N, {ok, Reply,  N}.
    
    handle_info(_Info, N)    ->{ok, N}.
    
    terminate(_Reason, _N)   ->ok.
    
    

      运行结果:

    matrix@MBP:18 $ erl -boot start_sasl -config elog3
    Erlang R15B01 (erts-5.9.1) [source] [64-bit] [smp:4:4] [async-threads:0] [hipe] [kernel-poll:false]
    
    Eshell V5.9.1  (abort with ^G)
    1> c(my_alarm_handler).
    {ok,my_alarm_handler}
    
    # 普通的警报
    2> alarm_handler:set_alarm(tooHot).
    ok
    3> 
    =INFO REPORT==== 8-Nov-2013::14:02:43 ===
        alarm_handler: {set,tooHot}
    
    # 使用自定义的警报 
    3> gen_event:swap_handler(alarm_handler, {alarm_handler, swap}, {my_alarm_handler, xyz}).
    *** my_alarm_handler init:{xyz,{alarm_handler,[tooHot]}}
    ok
    
    # 触发警报
    4> alarm_handler:set_alarm(tooHot).                                                      
    
    =ERROR REPORT==== 8-Nov-2013::14:03:51 ===
    *** Tell the Engineer to turn on the fan
    ok
    
    # 清除警报 
    5> alarm_handler:clear_alarm(tooHot).
    
    =ERROR REPORT==== 8-Nov-2013::14:04:07 ===
    *** Danger over. Turn off the fan
    ok
    
    # 查看错误日志报告
    6> rb:start([{max, 20}]).
    rb: reading report...done.
    rb: reading report...done.
    rb: reading report...done.
    {ok,<0.51.0>}
    7> rb:list().
      No                Type   Process       Date     Time
      ==                ====   =======       ====     ====
      20            progress  <0.30.0> 2013-11-08 13:51:15
      19            progress  <0.30.0> 2013-11-08 13:51:15
      18            progress  <0.23.0> 2013-11-08 13:51:15
      17               error  <0.24.0> 2013-11-08 13:51:25
      16            progress  <0.30.0> 2013-11-08 13:55:08
      15            progress  <0.30.0> 2013-11-08 13:55:08
      14            progress  <0.30.0> 2013-11-08 13:55:08
      13            progress  <0.30.0> 2013-11-08 13:55:08
      12            progress  <0.23.0> 2013-11-08 13:55:08
      11        crash_report        rb 2013-11-08 13:55:23
      10               error  <0.24.0> 2013-11-08 13:56:16
       9        crash_report        rb 2013-11-08 13:56:20
       8            progress  <0.30.0> 2013-11-08 14:01:19
       7            progress  <0.30.0> 2013-11-08 14:01:19
       6            progress  <0.30.0> 2013-11-08 14:01:19
       5            progress  <0.30.0> 2013-11-08 14:01:19
       4            progress  <0.23.0> 2013-11-08 14:01:19
       3         info_report  <0.30.0> 2013-11-08 14:02:43
       2               error  <0.30.0> 2013-11-08 14:03:51
       1               error  <0.30.0> 2013-11-08 14:04:07
    ok
    8> rb:show(1).
    
    ERROR REPORT  <0.34.0>                                      2013-11-08 14:04:07
    ===============================================================================
    
    *** Danger over. Turn off the fan
    ok
    9> rb:show(2).
    
    ERROR REPORT  <0.34.0>                                      2013-11-08 14:03:51
    ===============================================================================
    
    *** Tell the Engineer to turn on the fan
    ok
    

    18.4 应用服务

    18.4.1 素数服务

      使用gen_server模块快速生成代码, 然后添加获取素数的的方法, 并添加警报处理。

    -module(prime_server).
    -behaviour(gen_server).
    
    -export([new_prime/1, start_link/0]).
    
    %% 必须自定义实现的gen_server回调函数
    -export([init/1, handle_call/3, handle_cast/2, handle_info/2,
         terminate/2, code_change/3]).
    
    start_link() ->
        gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
    
    %% 生成素数的服务, 设置了超时时间 
    new_prime(N) ->
        gen_server:call(?MODULE, {prime, N}, 20000).
    
    init([]) ->
        process_flag(trap_exit, true),
        io:format("~p starting~n",[?MODULE]),
        {ok, 0}.
    
    handle_call({prime, K}, _From, N) ->
        {reply, make_new_prime(K), N+1}.
    
    handle_cast(_Msg, N)  ->{noreply, N}.
    
    handle_info(_Info, N)  ->{noreply, N}.
    
    terminate(_Reason, _N) ->
        io:format("~p stopping~n",[?MODULE]),
        ok.
    
    code_change(_OldVsn, N, _Extra) ->{ok, N}.
    
    %% 生成素数时添加了警报处理 
    make_new_prime(K) ->
        if
        K > 100 ->
            alarm_handler:set_alarm(tooHot),
            N = lib_primes:make_prime(K),
            alarm_handler:clear_alarm(tooHot),
            N;
        true ->
            lib_primes:make_prime(K)
        end.
    

    18.4.2 面积服务

    与素数服务代码相差无几, 但是计算面积的函数对于长方形需要提供两个参数而 hadle_call({area, Thing}, …) 只提供了对一个参数的支持。

    18.5 监控树

      监控树有两种类型:one-for-one, 如果一个进程失效, 它的监控进程就会重启它; all-for-one, 如果一个进程失效, 所有的工作进程都会被终止, 然后被重启。
       监控树的形式:

    %% RestartStrategy可以是one-for-one或all-for-one
    %% MaxRestarts, Time限定了在Time时间内最多可以重启MaxRestarts次, 否则将终止所有工作进程, 以防止出现死循环
    init(...) ->
        {ok, {RestartStrategy, MaxRestarts, Time},
             [Worker1, Worker2, ...]}.
    

      实现自己的监控树:

    -module(sellaprime_supervisor).
    -behaviour(supervisor).
    
    -export([start/0, start_in_shell_for_testing/0, start_link/1, init/1]).
    
    %% 调用 supervisor:start_link 启动监控树, 将会调用自定义的init/1函数
    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([]) ->
         %% 使用自定义的警报器 
         gen_event:swap_handler(alarm_handler, 
                                       {alarm_handler, swap},
                       {my_alarm_handler, xyz}),
        %% {ok, {SupFlags, Children}}
        %% SupFlags : {supervision_strategy(), maxR(), maxT()}
        %% supervision_strategy() : one_for_one | one_for_all | simple_one_for_one
        {ok, {{one_for_one, 3, 10},
          %% Children : [ChildStartSpecification]
          %% ChildStartSpecification : {internal_name(),
          %%                            {module(), function(), args()},
          %%                            shutdown_time(),
          %%                            child_type(),
          %%                            modules()}
          [{tag1, 
            {area_server, start_link, []},
            permanent, 
            10000, 
            worker, 
            [area_server]},
           {tag2, 
            {prime_server, start_link, []},
            permanent, 
            10000, 
            worker, 
            [prime_server]}
          ]}}.
    

    18.6 启动整个系统

    1> sellaprime_supervisor:start_in_shell_for_testing().
    *** my_alarm_handler init:{xyz,error}
    area_server starting
    prime_server starting
    true
    
    # 正常计算面积
    2> area_server:area({square, 10}).
    100
    
    # 错误的参数
    3> area_server:area({rectangle, 10, 20}).
    area_server stopping
    area_server starting
    ** exception exit: {{function_clause,[{area_server,compute_area,
                                                       [{rectangle,10,20}],
                                                       [{file,"area_server.erl"},{line,44}]},
                                          {area_server,handle_call,3,
                                                       [{file,"area_server.erl"},{line,32}]},
                                          {gen_server,handle_msg,5,
                                                      [{file,"gen_server.erl"},{line,588}]},
                                          {proc_lib,init_p_do_apply,3,
                                                    [{file,"proc_lib.erl"},{line,227}]}]},
                        {gen_server,call,[area_server,{area,{rectangle,10,20}}]}}
         in function  gen_server:call/2 (gen_server.erl, line 180)
    4> 
    =ERROR REPORT==== 8-Nov-2013::14:52:19 ===
    ** Generic server area_server terminating 
    ** Last message in was {area,{rectangle,10,20}}
    ** When Server state == 1
    ** Reason for termination == 
    ** {function_clause,[{area_server,compute_area,
                                      [{rectangle,10,20}],
                                      [{file,"area_server.erl"},{line,44}]},
                         {area_server,handle_call,3,
                                      [{file,"area_server.erl"},{line,32}]},
                         {gen_server,handle_msg,5,
                                     [{file,"gen_server.erl"},{line,588}]},
                         {proc_lib,init_p_do_apply,3,
                                   [{file,"proc_lib.erl"},{line,227}]}]}
    
    # 求阶乘
    5> prime_server:new_prime(20).  
    Generating a 20 digit prime .................................
    46877940609417488267
    
    # 触发警报 
    6> prime_server:new_prime(120). 
    Generating a 120 digit prime .
    =ERROR REPORT==== 8-Nov-2013::14:58:22 ===
    *** Tell the Engineer to turn on the fan
    
    =ERROR REPORT==== 8-Nov-2013::14:58:22 ===
    *** Tell the Engineer to turn on the fan
    ......................................
    
    =ERROR REPORT==== 8-Nov-2013::14:58:22 ===
    *** Danger over. Turn off the fan
    296183949730132038037133059736194002935394554326329071373943691961695511107247366466697700357121237051115084833162714631
    
    =ERROR REPORT==== 8-Nov-2013::14:58:22 ===
    *** Danger over. Turn off the fan
    
    # 查看错误日志报告
    7> rb:start([{max, 20}]).
    rb: reading report...done.
    {ok,<0.96.0>}
    8> rb:list().            
      No                Type       Process       Date     Time
      ==                ====       =======       ====     ====
      20               error      <0.24.0> 2013-11-08 14:52:19
      19        crash_report   area_server 2013-11-08 14:52:19
      18   supervisor_report      <0.24.0> 2013-11-08 14:52:19
      17            progress      <0.24.0> 2013-11-08 14:52:19
      16               error      <0.24.0> 2013-11-08 14:53:17
      15        crash_report  prime_server 2013-11-08 14:53:17
      14   supervisor_report      <0.24.0> 2013-11-08 14:53:17
      13            progress      <0.24.0> 2013-11-08 14:53:17
      12               error      <0.24.0> 2013-11-08 14:54:48
      11        crash_report  prime_server 2013-11-08 14:54:48
      10   supervisor_report      <0.24.0> 2013-11-08 14:54:48
       9            progress      <0.24.0> 2013-11-08 14:54:48
       8               error      <0.24.0> 2013-11-08 14:57:28
       7        crash_report  prime_server 2013-11-08 14:57:28
       6   supervisor_report      <0.24.0> 2013-11-08 14:57:28
       5            progress      <0.24.0> 2013-11-08 14:57:28
       4               error      <0.30.0> 2013-11-08 14:58:22
       3               error      <0.30.0> 2013-11-08 14:58:22
       2               error      <0.30.0> 2013-11-08 14:58:22
       1               error      <0.30.0> 2013-11-08 14:58:22
    ok
    9> rb:show(19).
    
    CRASH REPORT  <0.56.0>                                      2013-11-08 14:52:19
    ===============================================================================
    Crashing process                                                               
       initial_call                              {area_server,init,['Argument__1']}
       pid                                                                 <0.56.0>
       registered_name                                                  area_server
       error_info
             {exit,
                {function_clause,
                    [{area_server,compute_area,
                         [{rectangle,10,20}],
                         [{file,"area_server.erl"},{line,44}]},
                     {area_server,handle_call,3,
                         [{file,"area_server.erl"},{line,32}]},
                     {gen_server,handle_msg,5,
                         [{file,"gen_server.erl"},{line,588}]},
                     {proc_lib,init_p_do_apply,3,
                         [{file,"proc_lib.erl"},{line,227}]}]},
                [{gen_server,terminate,6,[{file,"gen_server.erl"},{line,747}]},
                 {proc_lib,init_p_do_apply,3,
                     [{file,"proc_lib.erl"},{line,227}]}]}
       ancestors                                   [sellaprime_supervisor,<0.43.0>]
       messages                                                                  []
       links                                                             [<0.55.0>]
       dictionary                                                                []
       trap_exit                                                               true
       status                                                               running
       heap_size                                                                610
       stack_size                                                                24
       reductions                                                               176
    
    ok
    

    18.7 应用程序

      应用程序信息文件

    %% 名称
    {application, sellaprime,
     %% 概述  
     [{description, "The Prime Number Shop"},
      %% 版本 
      {vsn, "1.0"},
      %% 包含的模块
      {modules, [sellaprime_app, sellaprime_supervisor, area_server, 
             prime_server, lib_lin, lib_primes, my_alarm_handler]}, 
      %% 注册进程
      {registered,[area_server, prime_server, sellaprime_super]},
      %% 依赖的应用程序
      {applications, [kernel,stdlib]},
      %% 模块
      {mod, {sellaprime_app,[]}},
      {start_phases, []}
     ]}.
    

      应用程序回调模块

    -module(sellaprime_app).
    -behaviour(application).
    -export([start/2, stop/1]).
    
    
    start(_Type, StartArgs) ->
        sellaprime_supervisor:start_link(StartArgs).
    
    stop(_State) ->
        ok.
    

      运行结果:

    # 显示加载的应用程序 
    1> application:loaded_applications(). 
    [{kernel,"ERTS  CXC 138 10","2.15.1"},
     {sasl,"SASL  CXC 138 11","2.2.1"},
     {stdlib,"ERTS  CXC 138 10","1.18.1"}]
    
    # 加载指定的应用程序
    2> application:load(sellaprime). 
    ok
    3> application:loaded_applications().
    [{kernel,"ERTS  CXC 138 10","2.15.1"},
     {sasl,"SASL  CXC 138 11","2.2.1"},
     {stdlib,"ERTS  CXC 138 10","1.18.1"},
     {sellaprime,"The Prime Number Shop","1.0"}]
    
    # 启动应用程序 
    4> application:start(sellaprime).    
    *** my_alarm_handler init:{xyz,{alarm_handler,[]}}
    area_server starting
    prime_server starting
    ok
    
    # 停止应用程序
    5> application:stop(sellaprime). 
    prime_server stopping
    area_server stopping
    ok
    6> 
    =INFO REPORT==== 8-Nov-2013::15:12:35 ===
        application: sellaprime
        exited: stopped
        type: temporary
    
    # 卸载应用程序
    7> application:unload(sellaprime).
    ok
    8> application:loaded_applications().
    [{kernel,"ERTS  CXC 138 10","2.15.1"},
     {sasl,"SASL  CXC 138 11","2.2.1"},
     {stdlib,"ERTS  CXC 138 10","1.18.1"}]
    

    18.8 文件系统的组织

     
    文件功能
    area_server.erl 面积服务, gen_server回调
    prime_server.erl 素数服务, gen_server回调
    sellaprime_supervisor.erl 监控回调
    sellaprime_app.erl 应用程序回调
    my_alarm_handler.erl gen_event的事件回调
    sellaprime.app 应用程序规范
    elog4.config 错误日志配置文件

    18.9 应用程序监视器

    使用appmon:start()启动图形界面的查看程序。

    Date: 2013-12-07 10:51:32 CST

    Author: matrix

    Org version 7.8.11 with Emacs version 24

    Validate XHTML 1.0
     
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  • 原文地址:https://www.cnblogs.com/scheme/p/3462546.html
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