eLog/src/eRum_app.erl

-module(eRum_app).

-behaviour(application).

-include("rumCom.hrl").
-include("rumDef.hrl").
-include("eRum.hrl").

-export([
   start/2
   , stop/1
   , doStart/0
   , startSink/1
   , startSink/2
   , startHandler/3
]).

start(_StartType, _StartArgs) ->
   {ok, Pid} = eRum_sup:start_link(),
   SavedHandlers = doStart(),
   doStartExtraSink(),
   doStartTraces(),
   ?eRumInit(),
   {ok, Pid, SavedHandlers}.

%% 启动默认的接收器(sink)
doStart() ->
   %% 尝试起送异步管理者
   tryStartAsyncMgr(rumUtil:get_env(asyncThreshold, undefined), rumUtil:get_env(asyncThresholdWindow, undefined), ?RumDefSink),

   %%尝试安装killer
   tryInstallKiller(rumUtil:get_env(killerHwm, undefined), rumUtil:get_env(killerReTime, undefined), ?RumDefSink),

   %%尝试启动各个handler
   tryStartHandlers(rumUtil:get_env(handlers, ?RumDefHandler), ?RumDefSink),

   %% 尝试替换error logger
   SavedHandlers = tryStartErrLoggerHandler(rumUtil:get_env(errLoggerRedirect, true), rumUtil:get_env(errLoggerHwm, 0), rumUtil:get_env(errLoggerWhitelist, [])),
   eRum:updateLogevelCfg(?RumDefSink),
   SavedHandlers.

startSink(?RumDefSink) -> doStart();
startSink(Sink) ->
   AllSinksDef = rumUtil:get_env(extraSinks, []),
   SinkValue = lists:keyfind(Sink, 1, AllSinksDef),
   SinkOpts = ?IIF(SinkValue == false, [], element(2, SinkValue)),
   startSink(Sink, SinkOpts).

startSink(Sink, Opts) ->
   rumConfig:initSink(Sink),
   ChildId = rumUtil:makeInnerSinkName(Sink),
   SinkSpec = #{
      id => ChildId,
      start => {gen_event, start_link, [{local, Sink}]},
      restart => permanent,
      shutdown => 5000,
      type => worker,
      modules => [dynamic]},
   _ = supervisor:start_child(eRum_sup, SinkSpec),
   tryStartAsyncMgr(proplists:get_value(asyncThreshold, Opts, undefined), proplists:get_value(asyncThresholdWindow, Opts, undefined), Sink),
   tryInstallKiller(proplists:get_value(killerHwm, Opts, undefined), proplists:get_value(killerReTime, Opts, undefined), Sink),
   tryStartHandlers(proplists:get_value(handlers, Opts, []), Sink),
   eRum:updateLogevelCfg(Sink).

doStartExtraSink() ->
   doStartExtraSinks(rumUtil:get_env(extraSinks, [])).

doStartExtraSinks(Sinks) ->
   [startSink(Sink, Opts) || {Sink, Opts} <- Sinks],
   ok.

doStartTraces() ->
   _ = rumUtil:trace_filter(none),
   ok = addTraces().

addTraces() ->
   Traces = rumUtil:get_env(traces, []),
   [startTrace(One) || One <- Traces],
   ok.

startTrace({Handler, Filter}) ->
   {ok, _} = eRum:trace(Handler, Filter);
startTrace({Handler, Filter, Level}) when is_atom(Level) ->
   {ok, _} = eRum:trace(Handler, Filter, Level).

stop(Handlers) ->
   [error_logger:add_report_handler(Handler) || Handler <- Handlers],
   rumConfig:cleanup().

tryStartAsyncMgr(undefined, _Window, _Sink) ->
   ignore;
tryStartAsyncMgr(Threshold, Window, Sink) ->
   case Window of
      undefined ->
         supervisor:start_child(rumHWatcherSup, [Sink, rumBkdThrottle, [Threshold, erlang:trunc(Threshold * 0.2)]]);
      _ ->
         supervisor:start_child(rumHWatcherSup, [Sink, rumBkdThrottle, [Threshold, Window]])
   end,
   ok.

tryInstallKiller(undefined, _ReTime, _Sink) -> ok;
tryInstallKiller(HWM, ReTime, Sink) ->
   case ReTime of
      undefined ->
         _ = supervisor:start_child(rumHWatcherSup, [Sink, rumMgrKiller, [HWM, 5000]]);
      _ ->
         _ = supervisor:start_child(rumHWatcherSup, [Sink, rumMgrKiller, [HWM, ReTime]])
   end,
   ok.

tryStartHandlers(undefined, _Sink) -> ok;
tryStartHandlers(Handlers, Sink) ->
   %% 启动失败的处理程序将在handler_watcher中处理
   NewHandler = doStartHandlers(Handlers, Sink, [], []),
   rumConfig:global_set(handlers, rumConfig:global_get(handlers, []) ++ NewHandler),
   ok.

doStartHandlers([], _Sink, _NameAcc, HandlerAcc) ->
   HandlerAcc;
doStartHandlers([OneHandler | Handlers], Sink, NameAcc, HandlerAcc) ->
   {Module, Options} = parseHandlers(OneHandler),
   NewNameAcc =
      case Module of
         {rumBkFile, F} ->
            case lists:member(F, NameAcc) of
               true ->
                  error_logger:error_msg("Cannot have same file (~p) in multiple file backends~n", [F]),
                  throw({error, bad_config});
               _ ->
                  [F | NameAcc]
            end;
         _ ->
            NameAcc
      end,

   HandlerRet = startHandler(Sink, Module, Options),
   doStartHandlers(Handlers, Sink, NewNameAcc, [HandlerRet | HandlerAcc]).

startHandler(Sink, Module, Config) ->
   {ok, Watcher} = supervisor:start_child(rumHWatcherSup, [Sink, Module, Config]),
   {Module, Watcher, Sink}.

-spec tryStartErrLoggerHandler(boolean(), pos_integer(), list()) -> list().
tryStartErrLoggerHandler(false, _HWM, _Whitelist) -> [];
tryStartErrLoggerHandler(_ErrLoggerRedirect, HWM, WhiteList) ->
   case whereis(error_logger) of
      undefined ->
         %% 在OTP 21及以上版本中，error_logger已弃用，而改用 'logger'
         %% 作为一个修补, 启动error_logger并将其安装为 logger handler
         %% 我们不能使用 error_logger:add_report_handler 因为我们想要监视这个handler
         %% 因此，我们必须手动添加这个 logger handler
         %%
         %% 从长远来看，我们应该安装一个日志处理程序, but this will bridge the gap for now.
         _ = error_logger:start(),
         _ = logger:add_handler(error_logger, error_logger, #{level => info, filter_default => log}),
         ok = tryRemoveLoggerHandler();
      _ ->
         ok
   end,

   %% capture which handlers we removed from error_logger so we can restore them when lager stops
   %% 捕获从error_logger中删除的处理程序，以便在lager停止时恢复它们
   OldHandlers =
      case supervisor:start_child(rumHWatcherSup, [error_logger, rumErrLoggerH, [HWM, rumUtil:get_env(errLoggerGroupLeaderStrategy, handle)]]) of
         {ok, _} ->
            [begin error_logger:delete_report_handler(X), X end || X <- gen_event:which_handlers(error_logger) -- [rumErrLoggerH | WhiteList]];
         {error, _} ->
            []
      end,
   OldHandlers.

%% 在OTP 21.1及更高版本上，我们需要删除`default' handler。但是它可能不存在，因此我们将其包装在try-catch块中
tryRemoveLoggerHandler() ->
   try
      ok = logger:remove_handler(default)
   catch
      error:undef -> ok;
      Err:Reason ->
         error_logger:error_msg("calling logger:remove_handler(default) failed: ~p ~p", [Err, Reason])
   end.

parseHandlers([]) ->
   [];
parseHandlers({rumBkdFile, Config}) ->
   %% this is definitely a new-style config, no expansion needed
   maybe_make_handler_id(rumBkdFile, Config);
parseHandlers({Mod, Config}) ->
   maybe_make_handler_id(Mod, Config).

maybe_make_handler_id(Mod, Config) ->
   %% Allow the backend to generate a gen_event handler id, if it wants to.
   %% We don't use erlang:function_exported here because that requires the module
   %% already be loaded, which is unlikely at this phase of startup. Using code:load
   %% caused undesirable side-effects with generating code-coverage reports.

   %%允许后端生成gen_event处理程序id，如果它愿意的话。
   %%这里我们没有使用erlang:function_exported，因为这需要用到模块
   %%已经加载，这在启动阶段是不太可能的。使用代码:负载
   %%会在生成代码覆盖率报告时产生不良的副作用。

   try Mod:configToId(Config) of
      Id ->
         {Id, Config}
   catch
      error:undef ->
         {Mod, Config}
   end.