Erlang Tracing - プロセスを処理するメッセージを無視する方法

Question

[send 'receive']のプロセスをトレースしているアプリケーションがあります。ただし、アプリケーションは、トレースされたプロセスがメッセージ{code_server,{module,random}}などのメッセージでプロセスcode_serverと交換しているというトレースメッセージを受信して​​います。

"システムプロセス"との間でこれらのメッセージをフィルタリングする方法はありますか？

Answer 1

独自のイベントハンドラを作成し、error_loggerイベントマネージャに追加することができます。あなたのメッセージをフィルタリングするためのイベント処理関数。

二例えばCouchDBのオープンソースプロジェクトからコピーしたファイル、couch_log.erl、couch_event_sup.erl

couch_event_sup.erl
 

% Licensed under the Apache License, Version 2.0 (the "License"); you may not 
% use this file except in compliance with the License. You may obtain a copy of 
% the License at 
% 
% http://www.apache.org/licenses/LICENSE-2.0 
% 
% Unless required by applicable law or agreed to in writing, software 
% distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 
% WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the 
% License for the specific language governing permissions and limitations under 
% the License. 

-module(couch_log). 
-behaviour(gen_event). 

-export([start_link/0,stop/0]). 
-export([debug/2, info/2, error/2]). 
-export([debug_on/0,info_on/0,get_level/0,get_level_integer/0, set_level/1]). 
-export([init/1, handle_event/2, terminate/2, code_change/3, handle_info/2, handle_call/2]). 
-export([read/2]). 

-define(LEVEL_ERROR, 3). 
-define(LEVEL_INFO, 2). 
-define(LEVEL_DEBUG, 1). 
-define(LEVEL_TMI, 0). 

debug(Format, Args) -> 
    {ConsoleMsg, FileMsg} = get_log_messages(self(), debug, Format, Args), 
    gen_event:sync_notify(error_logger, {couch_debug, ConsoleMsg, FileMsg}). 

info(Format, Args) -> 
    {ConsoleMsg, FileMsg} = get_log_messages(self(), info, Format, Args), 
    gen_event:sync_notify(error_logger, {couch_info, ConsoleMsg, FileMsg}). 

error(Format, Args) -> 
    {ConsoleMsg, FileMsg} = get_log_messages(self(), error, Format, Args), 
    gen_event:sync_notify(error_logger, {couch_error, ConsoleMsg, FileMsg}). 


level_integer(error) -> ?LEVEL_ERROR; 
level_integer(info)  -> ?LEVEL_INFO; 
level_integer(debug) -> ?LEVEL_DEBUG; 
level_integer(tmi)  -> ?LEVEL_TMI; 
level_integer(_Else) -> ?LEVEL_ERROR. % anything else default to ERROR level 

level_atom(?LEVEL_ERROR) -> error; 
level_atom(?LEVEL_INFO) -> info; 
level_atom(?LEVEL_DEBUG) -> debug; 
level_atom(?LEVEL_TMI) -> tmi. 


start_link() -> 
    couch_event_sup:start_link({local, couch_log}, error_logger, couch_log, []). 

stop() -> 
    couch_event_sup:stop(couch_log). 

init([]) -> 
    % read config and register for configuration changes 

    % just stop if one of the config settings change. couch_server_sup 
    % will restart us and then we will pick up the new settings. 
    ok = couch_config:register(
     fun("log", "file") -> 
      ?MODULE:stop(); 
     ("log", "level") -> 
      ?MODULE:stop(); 
     ("log", "include_sasl") -> 
      ?MODULE:stop() 
     end), 

    Filename = couch_config:get("log", "file", "couchdb.log"), 
    Level = level_integer(list_to_atom(couch_config:get("log", "level", "info"))), 
    Sasl = list_to_atom(couch_config:get("log", "include_sasl", "true")), 

    case ets:info(?MODULE) of 
    undefined -> ets:new(?MODULE, [named_table]); 
    _ -> ok 
    end, 
    ets:insert(?MODULE, {level, Level}), 

    case file:open(Filename, [append]) of 
    {ok, Fd} -> 
     {ok, {Fd, Level, Sasl}}; 
    {error, eacces} -> 
     {stop, {file_permission_error, Filename}}; 
    Error -> 
     {stop, Error} 
    end. 

debug_on() -> 
    get_level_integer() =< ?LEVEL_DEBUG. 

info_on() -> 
    get_level_integer() =< ?LEVEL_INFO. 

set_level(LevelAtom) -> 
    set_level_integer(level_integer(LevelAtom)). 

get_level() -> 
    level_atom(get_level_integer()). 

get_level_integer() -> 
    try 
     ets:lookup_element(?MODULE, level, 2) 
    catch error:badarg -> 
     ?LEVEL_ERROR 
    end. 

set_level_integer(Int) -> 
    gen_event:call(error_logger, couch_log, {set_level_integer, Int}). 

handle_event({couch_error, ConMsg, FileMsg}, {Fd, _LogLevel, _Sasl}=State) -> 
    log(Fd, ConMsg, FileMsg), 
    {ok, State}; 
handle_event({couch_info, ConMsg, FileMsg}, {Fd, LogLevel, _Sasl}=State) 
when LogLevel =< ?LEVEL_INFO -> 
    log(Fd, ConMsg, FileMsg), 
    {ok, State}; 
handle_event({couch_debug, ConMsg, FileMsg}, {Fd, LogLevel, _Sasl}=State) 
when LogLevel =< ?LEVEL_DEBUG -> 
    log(Fd, ConMsg, FileMsg), 
    {ok, State}; 
handle_event({error_report, _, {Pid, _, _}}=Event, {Fd, _LogLevel, Sasl}=State) 
when Sasl =/= false -> 
    {ConMsg, FileMsg} = get_log_messages(Pid, error, "~p", [Event]), 
    log(Fd, ConMsg, FileMsg), 
    {ok, State}; 
handle_event({error, _, {Pid, Format, Args}}, {Fd, _LogLevel, Sasl}=State) 
when Sasl =/= false -> 
    {ConMsg, FileMsg} = get_log_messages(Pid, error, Format, Args), 
    log(Fd, ConMsg, FileMsg), 
    {ok, State}; 
handle_event({_, _, {Pid, _, _}}=Event, {Fd, LogLevel, _Sasl}=State) 
when LogLevel =< ?LEVEL_TMI -> 
    % log every remaining event if tmi! 
    log(Fd, Pid, tmi, "~p", [Event]), 
    {ok, State}; 
handle_event(_Event, State) -> 
    {ok, State}. 

handle_call({set_level_integer, NewLevel}, {Fd, _LogLevel, Sasl}) -> 
    ets:insert(?MODULE, {level, NewLevel}), 
    {ok, ok, {Fd, NewLevel, Sasl}}. 

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

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

terminate(_Arg, {Fd, _LoggingLevel, _Sasl}) -> 
    file:close(Fd). 

log(Fd, Pid, Level, Format, Args) -> 
    Msg = io_lib:format(Format, Args), 
    ok = io:format("[~s] [~p] ~s~n", [Level, Pid, Msg]), % dump to console too 
    Msg2 = re:replace(lists:flatten(Msg),"\\r\\n|\\r|\\n", "\r\n", 
     [global, {return, list}]), 
    ok = io:format(Fd, "[~s] [~s] [~p] ~s\r~n", [httpd_util:rfc1123_date(), Level, Pid, Msg2]). 

log(Fd, ConsoleMsg, FileMsg) -> 
    ok = io:put_chars(ConsoleMsg), 
    ok = io:put_chars(Fd, FileMsg). 

get_log_messages(Pid, Level, Format, Args) -> 
    ConsoleMsg = unicode:characters_to_binary(io_lib:format(
     "[~s] [~p] " ++ Format ++ "~n", [Level, Pid | Args])), 
    FileMsg = ["[", httpd_util:rfc1123_date(), "] ", ConsoleMsg], 
    {ConsoleMsg, iolist_to_binary(FileMsg)}. 

read(Bytes, Offset) -> 
    LogFileName = couch_config:get("log", "file"), 
    LogFileSize = filelib:file_size(LogFileName), 
    MaxChunkSize = list_to_integer(
     couch_config:get("httpd", "log_max_chunk_size", "1000000")), 
    case Bytes > MaxChunkSize of 
    true -> 
     throw({bad_request, "'bytes' cannot exceed " ++ 
      integer_to_list(MaxChunkSize)}); 
    false -> 
     ok 
    end, 

    {ok, Fd} = file:open(LogFileName, [read]), 
    Start = lists:max([LogFileSize - Bytes, 0]) + Offset, 

    % TODO: truncate chopped first line 
    % TODO: make streaming 

    {ok, Chunk} = file:pread(Fd, Start, LogFileSize), 
    ok = file:close(Fd), 
    Chunk. 

%%%couch_event_sup.erl 
% Licensed under the Apache License, Version 2.0 (the "License"); you may not 
% use this file except in compliance with the License. You may obtain a copy of 
% the License at 
% 
% http://www.apache.org/licenses/LICENSE-2.0 
% 
% Unless required by applicable law or agreed to in writing, software 
% distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 
% WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the 
% License for the specific language governing permissions and limitations under 
% the License. 

%% The purpose of this module is to allow event handlers to particpate in Erlang 
%% supervisor trees. It provide a monitorable process that crashes if the event 
%% handler fails. The process, when shutdown, deregisters the event handler. 

-module(couch_event_sup). 
-behaviour(gen_server). 

-include("couch_db.hrl"). 

-export([start_link/3,start_link/4, stop/1]). 
-export([init/1, terminate/2, handle_call/3, handle_cast/2, handle_info/2,code_change/3]). 

% 
% Instead calling the 
% ok = gen_event:add_sup_handler(error_logger, my_log, Args) 
% 
% do this: 
% {ok, LinkedPid} = couch_event_sup:start_link(error_logger, my_log, Args) 
% 
% The benefit is the event is now part of the process tree, and can be 
% started, restarted and shutdown consistently like the rest of the server 
% components. 
% 
% And now if the "event" crashes, the supervisor is notified and can restart 
% the event handler. 
% 
% Use this form to named process: 
% {ok, LinkedPid} = couch_event_sup:start_link({local, my_log}, error_logger, my_log, Args) 
% 

start_link(EventMgr, EventHandler, Args) -> 
    gen_server:start_link(couch_event_sup, {EventMgr, EventHandler, Args}, []). 

start_link(ServerName, EventMgr, EventHandler, Args) -> 
    gen_server:start_link(ServerName, couch_event_sup, {EventMgr, EventHandler, Args}, []). 

stop(Pid) -> 
    gen_server:cast(Pid, stop). 

init({EventMgr, EventHandler, Args}) -> 
    case gen_event:add_sup_handler(EventMgr, EventHandler, Args) of 
    ok -> 
     {ok, {EventMgr, EventHandler}}; 
    {stop, Error} -> 
     {stop, Error} 
    end. 

terminate(_Reason, _State) -> 
    ok. 

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

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

handle_info({gen_event_EXIT, _Handler, Reason}, State) -> 
    {stop, Reason, State}. 

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