如何接收发送到在 gen_server 内运行的 PID 的消息

Question

• 我有一个 ejabberd 服务器

• 我有一个自定义模块，my_apns_module.erl，它由 ejabberd 服务器运行，如下所示：

  start_link(Host, Opts) ->
    Proc = gen_mod:get_module_proc(Host, ?PROCNAME),
    ?GEN_SERVER:start_link({local, Proc}, ?MODULE,
                           [Host, Opts], []).
  start(Host, Opts) ->
    Proc = gen_mod:get_module_proc(Host, ?PROCNAME),
    ChildSpec = {Proc, {?MODULE, start_link, [Host, Opts]},
                 temporary, 1000, worker, [?MODULE]},
    supervisor:start_child(ejabberd_sup, ChildSpec).
  
  stop(Host) ->
    Proc = gen_mod:get_module_proc(Host, ?PROCNAME),
    ?GEN_SERVER:call(Proc, stop),
    supervisor:delete_child(ejabberd_sup, Proc),
    ok.
  
  init([Host, _Opts]) ->
     ...
  
  handle_call(stop, _From, State) ->
    {stop, normal, ok, State}.
  
  handle_cast(_Msg, State) -> {noreply, State}.
  
  handle_info(#offline_msg{us = _UserServer,
            from = From, to = To, packet = Packet} = _Msg, State) ->
    ...
  
  handle_info(_Info, State) ->
    {noreply, State}.
  
  terminate(_Reason, State) ->
    Host = State#state.host,
    ok.
  
  code_change(_OldVsn, State, _Extra) -> {ok, State}.
  

• 在 init 中，我运行另一个 APNs 应用程序来发送推送通知。 https://github.com/inaka/apns4erl

  init([Host, _Opts]) ->
        apns:start(),
        case apns:connect(cert, ?APNS_CONNECTION) of
             {ok, PID} -> ?INFO_MSG("apns connection successful with PID ~p~n", [PID]);
             {error, timeout} -> ?ERROR_MSG("apns connection unsuccessful reason timed out", [])
        end,
        {ok, #state{host = Host}}.
  

• 这是有效的，因为我可以发送通知。

• 现在文档 (https://github.com/inaka/apns4erl) 说：

如果网络出现故障或发生意外情况，枪 与 APN 的连接将断开。在这种情况下，apns4erl 将发送一个 向客户端进程发送消息{reconnecting, ServerPid}，这意味着 apns4erl 失去了连接，它正在尝试重新连接。一旦 连接已恢复 {connection_up, ServerPid} 消息将 发送。

我的问题是：

• 我应该在my_apns_module.erl 中写什么代码来接收{reconnecting, ServerPid} 或{connection_up, ServerPid}？

Answer 1

发送到 gen_server 进程的消息，例如GenServerPid ! {ok, 10}}，由：

handle_info(Msg, State)

所以，你可以这样做：

handle_info({reconnecting, ServerPid}=Msg, State) ->
     %%do something here, like log Msg or change State;
handl_info({connection_up, ServerPid}=Msg, State) ->
     %%do something here, like log Msg or change State;   
handle_info(#offline_msg{us = _UserServer,
          from = From, to = To, packet = Packet} = _Msg, State) ->
     %%do something.

对评论的回应：

这是您当前的代码：

init([Host, _Opts]) ->
      apns:start(),
      case apns:connect(cert, ?APNS_CONNECTION) of
           {ok, PID} -> ?INFO_MSG("apns connection successful with PID ~p~n", [PID]);
           {error, timeout} -> ?ERROR_MSG("apns connection unsuccessful reason timed out", [])
      end,
      {ok, #state{host = Host}}.

你可以把它改成这样：

init([Host, _Opts]) ->
    spawn(?MODULE, start_apns, []),
    ...


start_apns() ->

          apns:start(),
          case apns:connect(cert, ?APNS_CONNECTION) of
               {ok, PID} -> ?INFO_MSG("apns connection successful with PID ~p~n", [PID]);
               {error, timeout} -> ?ERROR_MSG("apns connection unsuccessful reason timed out", [])
          end,
          apns_loop().

apns_loop() ->
    receive
        {reconnecting, ServerPid} -> %%do something;
        {connection_up, ServerPid} -> %% do something;
        Other -> %% do something
    end,
    apns_loop().
  

启动apns进程后，apns进程会进入循环等待消息。