Erlang如何查看gen_server内部的状态

方法1、自写个函数，想gen_server发查看的消息。

方法2、利用系统现有的架构。sasl应用带了一个si的东西 全名是status inspector, 这个东西就是设计来帮用户解决这个问题的。

%%%-------------------------------------------------------------------
%%% @author flybird <flybird@flybird>
%%% @copyright (C) 2013, flybird
%%% @doc
%%%
%%% @end
%%% Created : 29 May 2013 by flybird <flybird@flybird>
%%%-------------------------------------------------------------------
-module(wy).

-behaviour(gen_server).

%% API
-export([start_link/0]).
-export([test/0,
	 stop/0,
	 check_msg/0]).

%% gen_server callbacks
-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
	 terminate/2, code_change/3]).

-define(SERVER, ?MODULE). 

-record(state, {a, b}).

test() ->
    gen_server:call(?SERVER, {test, "fuck you!"}).
stop() ->
    gen_server:cast(?SERVER, stop).
check_msg() ->
    gen_server:call(?SERVER, check_msg).

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

init([]) ->
    {ok, #state{a = hello, b = world}}.

handle_call({test, _} = Request, _From, State) ->
    io:format("Got msg:~p~n", [Request]),
    {reply, ok, State};
handle_call(check_msg, _From, State)->  %方法1的实现
    {reply, State, State};
handle_call(_Request, _From, State) ->
    Reply = ok,
    {reply, Reply, State}.

handle_cast(stop, State) ->
    {stop, normal, State};
handle_cast(_Msg, State) ->
    {noreply, State}.

handle_info(_Info, State) ->
    {noreply, State}.

terminate(_Reason, _State) ->
    ok.

code_change(_OldVsn, State, _Extra) ->
    {ok, State}.

第二种方法，详情参考

http://blog.yufeng.info/archives/99