erlang日志功能。

用cowboy这个库，没有日志功能，所以研究了otp提供的日志功能。

1.启动SASL的方式

erl –boot start_sasl 默认配置文件下启动SASL， {env, [{sasl_error_logger, tty},{errlog_type, all}]},，见源码 sasl.app文件。

erl -boot start_sasl -config xxxx.config 启动指定配置文件例如 elog1.config ，elog2.config 。。。配置文件默认目录是ebin，可自己指定目录。

还可以用 application:start(sasl). 在代码里启动应用。默认会读取代码ebin下的sasl.app，可去源码复制一份sasl.app然后修改 env参数。

sasl是通过application:get_env(sasl,xxx) 获得配置信息。

2、sasl配置文件：

{env, [{sasl_error_logger, {file,"../../logs/error_logs/THELOG"}},%将sasl信息输出到文件中（不记录error_logger发送的信息）。另外，tty ：输出sasl信息到shell中（默认配置），false：不输出sasl信息。

     {errlog_type, all}, %过滤sasl_error_logger中的输出信息（error,progress）

     {error_logger_mf_dir,"../../logs/error_logs"}, %循环日志路径（记录sasl信息以及error_logger发送的信息）。

     {error_logger_mf_maxbytes,10485760},  %限定单个日志大小。

     {error_logger_mf_maxfiles,10}  %限定日志个数。

 ]}

3、error_logger：

参考官方文档

设置日志error_logger输出日志到文件：error_logger:logfile({open,Filename}).

注: 每次执行error_logger:logfile({open,Filename}).都会删掉之前Filename文件。

4、自定义日志功能：

由于业务需要，我想按照日期切分日志，该日志主要是为了记录业务操作。

思路:每次写日志到日志文件，先判断日志文件的最新修改日期是否跟当前日期一致，不一致就对该日志文件重命名（后缀添加日期)，并重新创建日志文件。

daylog_app.erl：

-module(daylog_app).

-behaviour(application).

-export([init/1]).

-export([start/0,start/2,stop/1]).

-define(SERVER,?MODULE).

-define(LOGFILE,"info.log").

start() ->

 application:start(daylog).

start(_StartType,_StartArgs) ->

 LogFile = get_app_env(log_file,?LOGFILE),

 supervisor:start_link({local,?SERVER},?MODULE,[daylog,LogFile]).

stop(_State) ->

 ok.

init([Module,LogFile]) ->

 Element = {Module,{Module,start_link,[LogFile]},

 temporary,2000,worker,[Module]}, %%如何启动和管理子进程

 Children = [Element] ,

 RestartStrategy = {one_for_one,0,1}, %%重启策略

 {ok,{RestartStrategy,Children}}. %%监督规范

%%----------------------------------------------------------------------

%% Internal functions

%%----------------------------------------------------------------------

get_app_env(Opt, Default) ->

 case application:get_env(daylog, Opt) of

 {ok, Val} -> Val;

 _ ->

 case init:get_argument(Opt) of

 [[Val | _]] -> Val;

 error -> Default

 end

 end.

daylog.erl

%%%-------------------------------------------------------------------

%%% Author : kingson <kingsoncai2013@gmail.com>

%%% Description : Cutting logs every day.

%%%

%%% Created : 4 Mar 2015 by kingson <kingsoncai2013@gmail.com>

%%%-------------------------------------------------------------------

-module(daylog).

-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]).

-export([add_logfiles/1,info_log/1,info_log/2,logger/2,logger/3]).

-define(SERVER,?MODULE).

-record(state, {filename,other_files}).

add_logfiles(Files) ->

 gen_server:cast(?SERVER,{add_logfile,Files}).

info_log(Msg) -> %通知类型日志(默认)

 info_log(Msg,[]).

info_log(Format,Data) ->

 gen_server:cast(?SERVER,{accept,Format,Data}).

logger(FileName,Msg) ->

 logger(FileName,Msg,[]).

logger(FileName,Format,Data) ->

 gen_server:cast(?SERVER,{accept,FileName,Format,Data}).

%%====================================================================

%% API

%%====================================================================

%%--------------------------------------------------------------------

%% Function: start_link() -> {ok,Pid} | ignore | {error,Error}

%% Description: Starts the server

%%--------------------------------------------------------------------

start_link(LogFile) when is_list(LogFile) ->

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

%%====================================================================

%% gen_server callbacks

%%====================================================================

%%--------------------------------------------------------------------

%% Function: init(Args) -> {ok, State} |

%% {ok, State, Timeout} |

%% ignore |

%% {stop, Reason}

%% Description: Initiates the server

%%--------------------------------------------------------------------

init([LogFile]) ->

 process_flag(trap_exit, true),

 {ok,F} = file:open(LogFile,[append]),

 put(LogFile,F),

 {ok, #state{filename=LogFile},0}.

%%--------------------------------------------------------------------

%% Function: %% handle_call(Request, From, State) -> {reply, Reply, State} |

%% {reply, Reply, State, Timeout} |

%% {noreply, State} |

%% {noreply, State, Timeout} |

%% {stop, Reason, Reply, State} |

%% {stop, Reason, State}

%% Description: Handling call messages

%%--------------------------------------------------------------------

handle_call(_Request, _From, State) ->

 Reply = ok,

 {reply, Reply, State}.

%%--------------------------------------------------------------------

%% Function: handle_cast(Msg, State) -> {noreply, State} |

%% {noreply, State, Timeout} |

%% {stop, Reason, State}

%% Description: Handling cast messages

%%--------------------------------------------------------------------

handle_cast({accept,Format,Data}, #state{filename=FileName}=State) ->

 write(Format,Data,FileName),

 {noreply, State};

handle_cast({accept,FileName,Format,Data},State) ->

 write(Format,Data,FileName),

 {noreply,State};

handle_cast({add_logfile,LogFiles},State) ->

 open_files(LogFiles),

 State2 = State#state{other_files=LogFiles},

 {noreply,State2};

handle_cast(_Msg, State) ->

 {noreply, State}.

%%--------------------------------------------------------------------

%% Function: handle_info(Info, State) -> {noreply, State} |

%% {noreply, State, Timeout} |

%% {stop, Reason, State}

%% Description: Handling all non call/cast messages

%%--------------------------------------------------------------------

handle_info(timeout, State) ->

 gen_server:cast(?SERVER,{accept,"Has started daylog application~n",[]}),

 {noreply, State};

handle_info(_Info, State) ->

 {noreply, State}.

%%--------------------------------------------------------------------

%% Function: terminate(Reason, State) -> void()

%% Description: 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.

%%--------------------------------------------------------------------

terminate(_Reason, State) ->

 #state{filename=FileName,other_files=OtherFiles} = State,

 close_files(OtherFiles),

 F = get(FileName),

 io:format("Has stoped daylog application~n"),

 io:format(F,"Has stoped daylog application~n",[]),

 file:close(F),

 ok.

%%--------------------------------------------------------------------

%% Func: code_change(OldVsn, State, Extra) -> {ok, NewState}

%% Description: Convert process state when code is changed

%%--------------------------------------------------------------------

code_change(_OldVsn, State, _Extra) ->

 {ok, State}.

%%--------------------------------------------------------------------

%%% Internal functions

%%--------------------------------------------------------------------

write(Format,Data,Filename) ->

 LocalTime = calendar:local_time(),

 case filelib:last_modified(Filename) of

 {Last_Modified_Date,_} ->

 {Today,_} = LocalTime,

 {Date_diff,_} = calendar:time_difference({Last_Modified_Date,{0,0,0}},{Today,{0,0,0}}),

 if Date_diff /= 0 -> %not the same date

 {Y,M,D} = Last_Modified_Date,

 Newname = Filename ++ "." ++ integer_to_list(Y) ++ "-" ++ integer_to_list(M) ++ "-" ++ integer_to_list(D),

 file:close(get(Filename)),

 file:rename(Filename,Newname),

 {ok,F} = file:open(Filename,[append]),

 put(Filename,F);

 true -> false

 end;

 0 -> false % the file does not exist.

 end,

 FileHandle = get(Filename),

 {{Year,Month,Day},{Hour,Minute,Second}} = LocalTime,

 do_write(FileHandle,"[~p-~p-~p T ~p:~p:~p] ", [Year,Month,Day,Hour,Minute,Second]),

 Format2 = Format ++ "~n",

 do_write(FileHandle,Format2,Data).

do_write(FileHandle,Format,Data) ->

 io:format(Format, Data),

 io:format(FileHandle,Format,Data).

open_files([]) ->

 ok;

open_files([File|Others]) ->

 {ok,FileHandle} = file:open(File,[append]),

 put(File,FileHandle),

 open_files(Others).

close_files([]) ->

 ok;

close_files([File|Others]) ->

 FileHandle = get(File),

 file:close(FileHandle),

 close_files(Others).

daylog.app

{application,daylog, %%应用名

[ {description,""},

 {vsn,"0.1.0"},

 {modules,[]}, %%应用中的模块,可留空。

 {registered,[]}, %%进程注册名，没进行实际注册操作,用于告知otp系统哪个进程注册了哪个名字,可留空

 {applications,[kernel,stdlib]}, %%先行启动的所有应用,不能留空

 {mod,{daylog_app,[]}}, %%指定应用启动模块,不能留空

 {env,[{log_file,"../../logs/info.log"}]}

]}.

compile.sh

for f in *.erl;do erlc +debug_info -o ../ebin $f;done

reference.txt

API Reference:

Module:daylog

add_logfiles(Files):

 Types:

 Files : a list for filenames 

info_log(Msg):

 Types:

 Msg: string

 descript:output log to default file which is descripted in ebin/daylog.app.

info_log(Format,Datas)

 Types:

 Format: string

 Datas: list for data

logger(FileName,Msg) ->

 Types:

 FileName: string

 Msg: String

logger(FileName,Format,Datas) ->

 Types:

 FileName: string

 Format: string

 Datas: list for data