eredis_proxy.erl

%%%-------------------------------------------------------------------
%%% @author linbo
%%% @copyright (C) 2015, <COMPANY>
%%% @doc
%%%
%%% @end
%%% Created : 14. 四月 2015 下午5:27
%%%-------------------------------------------------------------------
-module(eredis_proxy).
-author("linbo").

-behaviour(gen_server).

%% API
-export([start_link/1]).

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

-define(SERVER, ?MODULE).

-compile({parse_transform, lager_transform}).

-record(state, {
    connect_args,
    pid
}).

%%%===================================================================
%%% API
%%%===================================================================

%%--------------------------------------------------------------------
%% @doc
%% Starts the server
%%
%% @end
%%--------------------------------------------------------------------

-spec(start_link(Args :: term()) ->
    {ok, Pid :: pid()} | ignore | {error, Reason :: term()}).
start_link(Args) ->
    gen_server:start_link(?MODULE, Args, []).

%%%===================================================================
%%% gen_server callbacks
%%%===================================================================

%%--------------------------------------------------------------------
%% @private
%% @doc
%% Initializes the server
%%
%% @spec init(Args) -> {ok, State} |
%%                     {ok, State, Timeout} |
%%                     ignore |
%%                     {stop, Reason}
%% @end
%%--------------------------------------------------------------------
-spec(init(Args :: term()) ->
    {ok, State :: #state{}} | {ok, State :: #state{}, timeout() | hibernate} |
    {stop, Reason :: term()} | ignore).
init(Args) ->
    process_flag(trap_exit, true),
    {ok, #state{connect_args = Args}}.

%%--------------------------------------------------------------------
%% @private
%% @doc
%% Handling call messages
%%
%% @end
%%--------------------------------------------------------------------
-spec(handle_call(Request :: term(), From :: {pid(), Tag :: term()},
    State :: #state{}) ->
    {reply, Reply :: term(), NewState :: #state{}} |
    {reply, Reply :: term(), NewState :: #state{}, timeout() | hibernate} |
    {noreply, NewState :: #state{}} |
    {noreply, NewState :: #state{}, timeout() | hibernate} |
    {stop, Reason :: term(), Reply :: term(), NewState :: #state{}} |
    {stop, Reason :: term(), NewState :: #state{}}).
handle_call(connect, _From, State=#state{pid=undefined}) ->
    case eredis:start_link(State#state.connect_args) of
        {ok, Pid} ->
            {reply, {ok, Pid}, State#state{pid = Pid}};
        {error, Error} ->
            lager:error("start eredis failed, reason: ~p~n", [Error]),
            {reply, {error, Error}, State}
    end;

handle_call(connect, _From, State=#state{pid=Pid}) ->
    {reply, {ok, Pid}, State};

handle_call(_Request, _From, State) ->
    {reply, ok, State}.

%%--------------------------------------------------------------------
%% @private
%% @doc
%% Handling cast messages
%%
%% @end
%%--------------------------------------------------------------------
-spec(handle_cast(Request :: term(), State :: #state{}) ->
    {noreply, NewState :: #state{}} |
    {noreply, NewState :: #state{}, timeout() | hibernate} |
    {stop, Reason :: term(), NewState :: #state{}}).
handle_cast(_Request, State) ->
    {noreply, State}.

%%--------------------------------------------------------------------
%% @private
%% @doc
%% Handling all non call/cast messages
%%
%% @spec handle_info(Info, State) -> {noreply, State} |
%%                                   {noreply, State, Timeout} |
%%                                   {stop, Reason, State}
%% @end
%%--------------------------------------------------------------------
-spec(handle_info(Info :: timeout() | term(), State :: #state{}) ->
    {noreply, NewState :: #state{}} |
    {noreply, NewState :: #state{}, timeout() | hibernate} |
    {stop, Reason :: term(), NewState :: #state{}}).
handle_info({'EXIT', Pid, _}, State=#state{pid=Pid}) ->
    lager:error("eredis_proxy recv exit siganl Pid ~p~n", [Pid]),
    {noreply, State#state{pid=undefined}};

handle_info(_Info, State) ->
    lager:debug("eredis_proxy recv unknow ~p~n", [_Info]),
    {noreply, State}.

%%--------------------------------------------------------------------
%% @private
%% @doc
%% This function is called by a gen_server when it is about to
%% terminate. It should be the opposite of Module:init/1 and do any
%% necessary cleaning up. When it returns, the gen_server terminates
%% with Reason. The return value is ignored.
%%
%% @spec terminate(Reason, State) -> void()
%% @end
%%--------------------------------------------------------------------
-spec(terminate(Reason :: (normal | shutdown | {shutdown, term()} | term()),
    State :: #state{}) -> term()).
terminate(Reason, #state{pid = undefined}) ->
    lager:critical("eredis_proxy terminate ~p~n", [Reason]),
    ok;

terminate(_Reason, #state{pid = Pid}) ->
    eredis:stop(Pid).

%%--------------------------------------------------------------------
%% @private
%% @doc
%% Convert process state when code is changed
%%
%% @spec code_change(OldVsn, State, Extra) -> {ok, NewState}
%% @end
%%--------------------------------------------------------------------
-spec(code_change(OldVsn :: term() | {down, term()}, State :: #state{},
    Extra :: term()) ->
    {ok, NewState :: #state{}} | {error, Reason :: term()}).
code_change(_OldVsn, State, _Extra) ->
    {ok, State}.

%%%===================================================================
%%% Internal functions
%%%===================================================================