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184 lines
6.9 KiB
184 lines
6.9 KiB
%% Copyright (c) 2011-2012 Basho Technologies, Inc. All Rights Reserved.
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%%
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%% This file is provided to you under the Apache License,
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%% Version 2.0 (the "License"); you may not use this file
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%% except in compliance with the License. You may obtain
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%% a copy of the License at
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%%
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%% http://www.apache.org/licenses/LICENSE-2.0
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%%
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%% Unless required by applicable law or agreed to in writing,
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%% software distributed under the License is distributed on an
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%% "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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%% KIND, either express or implied. See the License for the
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%% specific language governing permissions and limitations
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%% under the License.
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%% @doc A process that does a gen_event:add_sup_handler and attempts to re-add
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%% event handlers when they exit.
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%% @private
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-module(lager_handler_watcher).
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-behaviour(gen_server).
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-include("lager.hrl").
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-ifdef(TEST).
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-include_lib("eunit/include/eunit.hrl").
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-endif.
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%% callbacks
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-export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2,
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code_change/3]).
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-export([start_link/3, start/3]).
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-record(state, {
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module :: atom(),
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config :: any(),
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sink :: pid() | atom()
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}).
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start_link(Sink, Module, Config) ->
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gen_server:start_link(?MODULE, [Sink, Module, Config], []).
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start(Sink, Module, Config) ->
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gen_server:start(?MODULE, [Sink, Module, Config], []).
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init([Sink, Module, Config]) ->
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install_handler(Sink, Module, Config),
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{ok, #state{sink=Sink, module=Module, config=Config}}.
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handle_call(_Call, _From, State) ->
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{reply, ok, State}.
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handle_cast(_Request, State) ->
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{noreply, State}.
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handle_info({gen_event_EXIT, Module, normal}, #state{module=Module} = State) ->
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{stop, normal, State};
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handle_info({gen_event_EXIT, Module, shutdown}, #state{module=Module} = State) ->
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{stop, normal, State};
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handle_info({gen_event_EXIT, Module, Reason}, #state{module=Module,
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config=Config, sink=Sink} = State) ->
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case lager:log(error, self(), "Lager event handler ~p exited with reason ~s",
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[Module, error_logger_lager_h:format_reason(Reason)]) of
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ok ->
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install_handler(Sink, Module, Config);
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{error, _} ->
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%% lager is not working, so installing a handler won't work
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ok
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end,
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{noreply, State};
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handle_info(reinstall_handler, #state{module=Module, config=Config, sink=Sink} = State) ->
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install_handler(Sink, Module, Config),
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{noreply, State};
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handle_info(stop, State) ->
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{stop, normal, State};
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handle_info(_Info, State) ->
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{noreply, State}.
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terminate(_Reason, _State) ->
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ok.
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code_change(_OldVsn, State, _Extra) ->
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{ok, State}.
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%% internal
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install_handler(Sink, lager_backend_throttle, Config) ->
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%% The lager_backend_throttle needs to know to which sink it is
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%% attached, hence this admittedly ugly workaround. Handlers are
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%% sensitive to the structure of the configuration sent to `init',
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%% sadly, so it's not trivial to add a configuration item to be
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%% ignored to backends without breaking 3rd party handlers.
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install_handler2(Sink, lager_backend_throttle, [{sink, Sink}|Config]);
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install_handler(Sink, Module, Config) ->
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install_handler2(Sink, Module, Config).
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%% private
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install_handler2(Sink, Module, Config) ->
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case gen_event:add_sup_handler(Sink, Module, Config) of
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ok ->
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?INT_LOG(debug, "Lager installed handler ~p into ~p", [Module, Sink]),
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lager:update_loglevel_config(Sink),
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ok;
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{error, {fatal, Reason}} ->
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?INT_LOG(error, "Lager fatally failed to install handler ~p into"
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" ~p, NOT retrying: ~p", [Module, Sink, Reason]),
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%% tell ourselves to stop
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self() ! stop,
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ok;
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Error ->
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%% try to reinstall it later
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?INT_LOG(error, "Lager failed to install handler ~p into"
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" ~p, retrying later : ~p", [Module, Sink, Error]),
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erlang:send_after(5000, self(), reinstall_handler),
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ok
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end.
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-ifdef(TEST).
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from_now(Seconds) ->
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{Mega, Secs, Micro} = os:timestamp(),
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{Mega, Secs + Seconds, Micro}.
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reinstall_on_initial_failure_test_() ->
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{timeout, 60000,
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[
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fun() ->
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error_logger:tty(false),
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application:load(lager),
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application:set_env(lager, handlers, [{lager_test_backend, info}, {lager_crash_backend, [from_now(2), undefined]}]),
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application:set_env(lager, error_logger_redirect, false),
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application:unset_env(lager, crash_log),
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lager:start(),
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try
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?assertEqual(1, lager_test_backend:count()),
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{_Level, _Time, Message, _Metadata} = lager_test_backend:pop(),
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?assertMatch("Lager failed to install handler lager_crash_backend into lager_event, retrying later :"++_, lists:flatten(Message)),
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?assertEqual(0, lager_test_backend:count()),
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timer:sleep(6000),
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?assertEqual(0, lager_test_backend:count()),
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?assert(lists:member(lager_crash_backend, gen_event:which_handlers(lager_event)))
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after
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application:stop(lager),
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application:stop(goldrush),
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error_logger:tty(true)
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end
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end
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]
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}.
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reinstall_on_runtime_failure_test_() ->
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{timeout, 60000,
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[
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fun() ->
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error_logger:tty(false),
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application:load(lager),
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application:set_env(lager, handlers, [{lager_test_backend, info}, {lager_crash_backend, [undefined, from_now(5)]}]),
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application:set_env(lager, error_logger_redirect, false),
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application:unset_env(lager, crash_log),
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lager:start(),
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try
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?assertEqual(0, lager_test_backend:count()),
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?assert(lists:member(lager_crash_backend, gen_event:which_handlers(lager_event))),
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timer:sleep(6000),
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?assertEqual(2, lager_test_backend:count()),
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{_Severity, _Date, Msg, _Metadata} = lager_test_backend:pop(),
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?assertEqual("Lager event handler lager_crash_backend exited with reason crash", lists:flatten(Msg)),
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{_Severity2, _Date2, Msg2, _Metadata2} = lager_test_backend:pop(),
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?assertMatch("Lager failed to install handler lager_crash_backend into lager_event, retrying later :"++_, lists:flatten(Msg2)),
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?assertEqual(false, lists:member(lager_crash_backend, gen_event:which_handlers(lager_event)))
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after
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application:stop(lager),
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application:stop(goldrush),
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error_logger:tty(true)
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end
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end
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]
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}.
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-endif.
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