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%% -------------------------------------------------------------------
%% Copyright (c) 2007-2010 Basho Technologies, Inc. All Rights Reserved.
%% Copyright (c) 2018-2020 VMware, Inc. or its affiliates. All rights reserved.
%%
%% This file is provided to you 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
%%
%% https://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(rabbit_sysmon_minder).
-behaviour(gen_server).
%% API
-export([start_link/0]).
%% gen_server callbacks
-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
terminate/2, code_change/3]).
-record(state, {}).
%%%===================================================================
%%% API
%%%===================================================================
%%--------------------------------------------------------------------
%% @doc
%% Starts the server
%%
%% @spec start_link() -> {ok, Pid} | ignore | {error, Error}
%% @end
%%--------------------------------------------------------------------
start_link() ->
gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
%%%===================================================================
%%% gen_server callbacks
%%%===================================================================
%%--------------------------------------------------------------------
%% @private
%% @doc
%% Initializes the server
%%
%% @spec init(Args) -> {ok, State} |
%% {ok, State, Timeout} |
%% ignore |
%% {stop, Reason}
%% @end
%%--------------------------------------------------------------------
init([]) ->
%% Add our system_monitor event handler. We do that here because
%% we have a process at our disposal (i.e. ourself) to receive the
%% notification in the very unlikely event that the
%% sysmon_handler has crashed and been removed from the
%% sysmon_handler gen_event server. (If we had a supervisor
%% or app-starting process add the handler, then if the handler
%% crashes, nobody will act on the crash notification.)
rabbit_sysmon_handler:add_handler(),
{ok, #state{}}.
%%--------------------------------------------------------------------
%% @private
%% @doc
%% Handling call messages
%%
%% @spec handle_call(Request, From, State) ->
%% {reply, Reply, State} |
%% {reply, Reply, State, Timeout} |
%% {noreply, State} |
%% {noreply, State, Timeout} |
%% {stop, Reason, Reply, State} |
%% {stop, Reason, State}
%% @end
%%--------------------------------------------------------------------
handle_call(_Request, _From, State) ->
Reply = ok,
{reply, Reply, State}.
%%--------------------------------------------------------------------
%% @private
%% @doc
%% Handling cast messages
%%
%% @spec handle_cast(Msg, State) -> {noreply, State} |
%% {noreply, State, Timeout} |
%% {stop, Reason, State}
%% @end
%%--------------------------------------------------------------------
handle_cast(_Msg, State) ->
{noreply, State}.
%%--------------------------------------------------------------------
%% @private
%% @doc
%% Handling all non call/cast messages
%%
%% @spec handle_info(Info, State) -> {noreply, State} |
%% {noreply, State, Timeout} |
%% {stop, Reason, State}
%% @end
%%--------------------------------------------------------------------
handle_info({gen_event_EXIT, rabbit_sysmon_handler, _}, State) ->
%% SASL will create an error message, no need for us to duplicate it.
%%
%% Our handler should never crash, but it did indeed crash. If
%% there's a pathological condition somewhere that's generating
%% lots of unforseen things that crash core's custom handler, we
%% could make things worse by jumping back into the exploding
%% volcano. Wait a little bit before jumping back. Besides, the
%% system_monitor data is nice but is not critical: there is no
%% need to make things worse if things are indeed bad, and if we
%% miss a few seconds of system_monitor events, the world will not
%% end.
timer:sleep(2*1000),
rabbit_sysmon_handler:add_handler(),
{noreply, State};
handle_info(_Info, State) ->
{noreply, State}.
%%--------------------------------------------------------------------
%% @private
%% @doc
%% 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.
%%
%% @spec terminate(Reason, State) -> void()
%% @end
%%--------------------------------------------------------------------
terminate(_Reason, _State) ->
ok.
%%--------------------------------------------------------------------
%% @private
%% @doc
%% Convert process state when code is changed
%%
%% @spec code_change(OldVsn, State, Extra) -> {ok, NewState}
%% @end
%%--------------------------------------------------------------------
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
|
