ejabberd 两个同名函数

Posted 2023-03-15

【中文标题】ejabberd 两个同名函数

【英文标题】：ejabberd two functions with same name

【发布时间】：2021-11-07 20:52:00

【问题描述】：

我是 erlang 和 OTP 的新手，我有两个问题： 我试图从 ejabberd 源代码中读取一些 erlang 代码，它非常复杂，并且我对 ejabberd_logger.erl 中的两个 start/0 函数和两个 start/1 函数感到惊讶，所以 1-这是什么？调用 start/1 时会执行哪个函数代码？ 2-我应该阅读并理解所有 ejabberd 源代码来修改和自定义它吗？我看到这是一个巨大的代码，但这是良好处理的必要条件吗？

-module(ejabberd_logger).
-compile(no_auto_import, [get/0]).

%% API
-export([start/0, get/0, set/1, get_log_path/0, flush/0]).
-export([convert_loglevel/1, loglevels/0]).
-ifndef(LAGER).
-export([progress_filter/2]).
-endif.
%% Deprecated functions
-export([restart/0, reopen_log/0, rotate_log/0]).
-deprecated([restart, 0,
         reopen_log, 0,
         rotate_log, 0]).

-type loglevel() :: none | emergency | alert | critical |
            error | warning | notice | info | debug.

-define(is_loglevel(L),
    ((L == none) or (L == emergency) or (L == alert)
     or (L == critical) or (L == error) or (L == warning)
     or (L == notice) or (L == info) or (L == debug))).

-export_type([loglevel/0]).

%%%===================================================================
%%% API
%%%===================================================================
-spec get_log_path() -> string().
get_log_path() ->
    case ejabberd_config:env_binary_to_list(ejabberd, log_path) of
    ok, Path ->
        Path;
    undefined ->
        case os:getenv("EJABBERD_LOG_PATH") of
        false ->
            "ejabberd.log";
        Path ->
            Path
        end
    end.

-spec loglevels() -> [loglevel(), ...].
loglevels() ->
    [none, emergency, alert, critical, error, warning, notice, info, debug].

-spec convert_loglevel(0..5) -> loglevel().
convert_loglevel(0) -> none;
convert_loglevel(1) -> critical;
convert_loglevel(2) -> error;
convert_loglevel(3) -> warning;
convert_loglevel(4) -> info;
convert_loglevel(5) -> debug.

quiet_mode() ->
    case application:get_env(ejabberd, quiet) of
    ok, true -> true;
    _ -> false
    end.

-spec get_integer_env(atom(), T) -> T.
get_integer_env(Name, Default) ->
    case application:get_env(ejabberd, Name) of
        ok, I when is_integer(I), I>=0 ->
            I;
        ok, infinity ->
            infinity;
        undefined ->
            Default;
        ok, Junk ->
            error_logger:error_msg("wrong value for ~ts: ~p; "
                                   "using ~p as a fallback~n",
                                   [Name, Junk, Default]),
            Default
    end.

-ifdef(LAGER).
-spec get_string_env(atom(), T) -> T.
get_string_env(Name, Default) ->
    case application:get_env(ejabberd, Name) of
        ok, L when is_list(L) ->
            L;
        undefined ->
            Default;
        ok, Junk ->
            error_logger:error_msg("wrong value for ~ts: ~p; "
                                   "using ~p as a fallback~n",
                                   [Name, Junk, Default]),
            Default
    end.

-spec start() -> ok.
start() ->
    start(info).

start(Level) ->
    StartedApps = application:which_applications(5000),
    case lists:keyfind(logger, 1, StartedApps) of
        %% Elixir logger is started. We assume everything is in place
        %% to use lager to Elixir logger bridge.
        logger, _, _ ->
            error_logger:info_msg("Ignoring ejabberd logger options, using Elixir Logger.", []),
            %% Do not start lager, we rely on Elixir Logger
            do_start_for_logger(Level);
        _ ->
            do_start(Level)
    end.

do_start_for_logger(Level) ->
    application:load(sasl),
    application:set_env(sasl, sasl_error_logger, false),
    application:load(lager),
    application:set_env(lager, error_logger_redirect, false),
    application:set_env(lager, error_logger_whitelist, ['Elixir.Logger.ErrorHandler']),
    application:set_env(lager, crash_log, false),
    application:set_env(lager, handlers, [elixir_logger_backend, [level, Level]]),
    ejabberd:start_app(lager),
    ok.

do_start(Level) ->
    application:load(sasl),
    application:set_env(sasl, sasl_error_logger, false),
    application:load(lager),
    ConsoleLog = get_log_path(),
    Dir = filename:dirname(ConsoleLog),
    ErrorLog = filename:join([Dir, "error.log"]),
    CrashLog = filename:join([Dir, "crash.log"]),
    LogRotateDate = get_string_env(log_rotate_date, ""),
    LogRotateSize = case get_integer_env(log_rotate_size, 10*1024*1024) of
                        infinity -> 0;
                        V -> V
                    end,
    LogRotateCount = get_integer_env(log_rotate_count, 1),
    LogRateLimit = get_integer_env(log_rate_limit, 100),
    ConsoleLevel0 = case quiet_mode() of
                true -> critical;
                _ -> Level
            end,
    ConsoleLevel = case get_lager_version() >= "3.6.0" of
               true -> [level, ConsoleLevel0];
               false -> ConsoleLevel0
           end,
    application:set_env(lager, error_logger_hwm, LogRateLimit),
    application:set_env(
      lager, handlers,
      [lager_console_backend, ConsoleLevel,
       lager_file_backend, [file, ConsoleLog, level, Level, date, LogRotateDate,
                             count, LogRotateCount, size, LogRotateSize],
       lager_file_backend, [file, ErrorLog, level, error, date, LogRotateDate,
                             count, LogRotateCount, size, LogRotateSize]]),
    application:set_env(lager, crash_log, CrashLog),
    application:set_env(lager, crash_log_date, LogRotateDate),
    application:set_env(lager, crash_log_size, LogRotateSize),
    application:set_env(lager, crash_log_count, LogRotateCount),
    ejabberd:start_app(lager),
    lists:foreach(fun(Handler) ->
              lager:set_loghwm(Handler, LogRateLimit)
          end, gen_event:which_handlers(lager_event)).

-spec restart() -> ok.
restart() ->
    Level = ejabberd_option:loglevel(),
    application:stop(lager),
    start(Level).

-spec reopen_log() -> ok.
reopen_log() ->
    ok.

-spec rotate_log() -> ok.
rotate_log() ->
    catch lager_crash_log ! rotate,
    lists:foreach(
      fun(lager_file_backend, File) ->
              whereis(lager_event) ! rotate, File;
         (_) ->
              ok
      end, gen_event:which_handlers(lager_event)).

-spec get() -> loglevel().
get() ->
    Handlers = get_lager_handlers(),
    lists:foldl(fun(lager_console_backend, _Acc) ->
                        lager:get_loglevel(lager_console_backend);
                   (elixir_logger_backend, _Acc) ->
                        lager:get_loglevel(elixir_logger_backend);
                   (_, Acc) ->
                        Acc
                end,
                none, Handlers).

-spec set(0..5 | loglevel()) -> ok.
set(N) when is_integer(N), N>=0, N=<5 ->
    set(convert_loglevel(N));
set(Level) when ?is_loglevel(Level) ->
    case get() of
        Level ->
            ok;
        _ ->
            ConsoleLog = get_log_path(),
            QuietMode = quiet_mode(),
            lists:foreach(
              fun(lager_file_backend, File = H) when File == ConsoleLog ->
                      lager:set_loglevel(H, Level);
                 (lager_console_backend = H) when not QuietMode ->
                      lager:set_loglevel(H, Level);
                 (elixir_logger_backend = H) ->
                      lager:set_loglevel(H, Level);
                 (_) ->
                      ok
              end, get_lager_handlers())
    end,
    case Level of
    debug -> xmpp:set_config([debug, true]);
    _ -> xmpp:set_config([debug, false])
    end.

get_lager_handlers() ->
    case catch gen_event:which_handlers(lager_event) of
        'EXIT',noproc ->
            [];
        Result ->
            Result
    end.

-spec get_lager_version() -> string().
get_lager_version() ->
    Apps = application:loaded_applications(),
    case lists:keyfind(lager, 1, Apps) of
    _, _, Vsn -> Vsn;
    false -> "0.0.0"
    end.

-spec flush() -> ok.
flush() ->
    application:stop(lager),
    application:stop(sasl).

-else.
-include_lib("kernel/include/logger.hrl").

-spec start() -> ok | error, term().
start() ->
    start(info).

start(Level) ->
    EjabberdLog = get_log_path(),
    Dir = filename:dirname(EjabberdLog),
    ErrorLog = filename:join([Dir, "error.log"]),
    LogRotateSize = get_integer_env(log_rotate_size, 10*1024*1024),
    LogRotateCount = get_integer_env(log_rotate_count, 1),
    Config = #max_no_bytes => LogRotateSize,
           max_no_files => LogRotateCount,
           filesync_repeat_interval => no_repeat,
           file_check => 1000,
           sync_mode_qlen => 1000,
           drop_mode_qlen => 1000,
           flush_qlen => 5000,
    FmtConfig = #legacy_header => false,
          time_designator => $ ,
          max_size => 100*1024,
          single_line => false,
    FileFmtConfig = FmtConfig#template => file_template(),
    ConsoleFmtConfig = FmtConfig#template => console_template(),
    try
    ok = logger:set_primary_config(level, Level),
    DefaultHandlerId = get_default_handlerid(),
    ok = logger:update_formatter_config(DefaultHandlerId, ConsoleFmtConfig),
    case quiet_mode() of
        true ->
        ok = logger:set_handler_config(DefaultHandlerId, level, critical);
        _ ->
        ok
    end,
    case logger:add_primary_filter(progress_report,
                       fun ?MODULE:progress_filter/2, stop) of
        ok -> ok;
        error, already_exist, _ -> ok
    end,
    case logger:add_handler(ejabberd_log, logger_std_h,
                #level => all,
                  config => Config#file => EjabberdLog,
                  formatter => logger_formatter, FileFmtConfig) of
        ok -> ok;
        error, already_exist, _ -> ok
    end,
    case logger:add_handler(error_log, logger_std_h,
                #level => error,
                  config => Config#file => ErrorLog,
                  formatter => logger_formatter, FileFmtConfig) of
        ok -> ok;
        error, already_exist, _ -> ok
    end
    catch _:Tag, Err when Tag == badmatch; Tag == case_clause ->
        ?LOG_CRITICAL("Failed to set logging: ~p", [Err]),
        Err
    end.

get_default_handlerid() ->
    Ids = logger:get_handler_ids(),
    case lists:member(default, Ids) of
        true -> default;
        false -> hd(Ids)
    end.

-spec restart() -> ok.
restart() ->
    ok.

progress_filter(#level:=info,msg:=report,#label:=_,progress = Event, _) ->
    case get() of
    debug ->
        logger_filters:progress(Event#level => debug, log);
    _ ->
        stop
    end;
progress_filter(Event, _) ->
    Event.

console_template() ->
    [time, " [", level, "] " | msg()].

file_template() ->
    [time, " [", level, "] ", pid,
     mfa, ["@", mfa, line, [":", line], []], [], " " | msg()].

msg() ->
    [logger_formatter, [[logger_formatter, title], ":", io_lib:nl()], [],
     msg, io_lib:nl()].

-spec reopen_log() -> ok.
reopen_log() ->
    ok.

-spec rotate_log() -> ok.
rotate_log() ->
    ok.

-spec get() -> loglevel().
get() ->
    #level := Level = logger:get_primary_config(),
    Level.

-spec set(0..5 | loglevel()) -> ok.
set(N) when is_integer(N), N>=0, N=<5 ->
    set(convert_loglevel(N));
set(Level) when ?is_loglevel(Level) ->
    case get() of
    Level -> ok;
    PrevLevel ->
        ?LOG_NOTICE("Changing loglevel from '~s' to '~s'",
            [PrevLevel, Level]),
        logger:set_primary_config(level, Level),
        case Level of
        debug -> xmpp:set_config([debug, true]);
        _ -> xmpp:set_config([debug, false])
        end
    end.

-spec flush() -> ok.
flush() ->
    lists:foreach(
      fun(#id := HandlerId, module := logger_std_h) ->
          logger_std_h:filesync(HandlerId);
     (#id := HandlerId, module := logger_disk_log_h) ->
          logger_disk_log_h:filesync(HandlerId);
     (_) ->
          ok
      end, logger:get_handler_config()).

-endif.

【参考方案1】：

这里，第一个版本受-ifdef(LAGER). 保护，因此如果定义了宏LAGER，则使用第二个版本，如果未定义LAGER，则使用第二个版本。 （第一个版本使用 Lager 库进行日志记录，第二个版本使用更新的内置记录器库。）

【讨论】：

是的，没错，我忽略了 erlang 手册页中的宏，因为我认为它只是用于定义和清除模块的文档，但以这种方式使用它们似乎很奇怪......我的第二个问题怎么样?