erldns

%% Copyright (c) 2012-2020, DNSimple Corporation
%%
%% Permission to use, copy, modify, and/or distribute this software for any
%% purpose with or without fee is hereby granted, provided that the above
%% copyright notice and this permission notice appear in all copies.
%%
%% THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
%% WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
%% MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
%% ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
%% WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
%% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
%% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

%% @doc Application event handler implementation.
-module(erldns_event_handler).

-behavior(gen_event).

-export([
    init/1,
    handle_event/2,
    handle_call/2,
    handle_info/2,
    code_change/3,
    terminate/2
]).

-record(state, {servers_running = false}).

init(_Args) ->
    {ok, #state{}}.

handle_event({_M, start_servers}, State) ->
    case State#state.servers_running of
        false ->
            % Start up the UDP and TCP servers
            lager:info("Starting the UDP and TCP supervisor"),
            supervisor:start_child(
                erldns_sup,
                #{
                    id => erldns_sup,
                    start => {erldns_server_sup, start_link, []},
                    restart => permanent,
                    shutdown => 5000,
                    type => supervisor
                }
            ),
            erldns_events:notify({?MODULE, servers_started}),
            {ok, State#state{servers_running = true}};
        _ ->
            erldns_events:notify({?MODULE, servers_already_started}),
            {ok, State}
    end;
handle_event({_M, end_udp, [{host, _Host}]}, State) ->
    folsom_metrics:notify({udp_request_meter, 1}),
    folsom_metrics:notify({udp_request_counter, {inc, 1}}),
    {ok, State};
handle_event({_M, end_tcp, [{host, _Host}]}, State) ->
    folsom_metrics:notify({tcp_request_meter, 1}),
    folsom_metrics:notify({tcp_request_counter, {inc, 1}}),
    {ok, State};
handle_event({_M, udp_error, Reason}, State) ->
    folsom_metrics:notify({udp_error_meter, 1}),
    folsom_metrics:notify({udp_error_history, Reason}),
    {ok, State};
handle_event({_M, tcp_error, Reason}, State) ->
    folsom_metrics:notify({tcp_error_meter, 1}),
    folsom_metrics:notify({tcp_error_history, Reason}),
    {ok, State};
handle_event({_M, dnssec_request, _Host, _Qname}, State) ->
    folsom_metrics:notify(dnssec_request_counter, {inc, 1}),
    folsom_metrics:notify(dnssec_request_meter, 1),
    {ok, State};
handle_event({_M = erldns_handler, _E = refused_response, _Questions}, State) ->
    folsom_metrics:notify({refused_response_meter, 1}),
    folsom_metrics:notify({refused_response_counter, {inc, 1}}),
    {ok, State};
handle_event({_M = erldns_handler, _E = empty_response, _Message}, State) ->
    folsom_metrics:notify({empty_response_meter, 1}),
    folsom_metrics:notify({empty_response_counter, {inc, 1}}),
    {ok, State};
handle_event({_M = erldns_handler, _E = resolve_error, {_Exception, _Reason, _Message, _Stacktrace}}, State) ->
    folsom_metrics:notify({erldns_handler_error_counter, {inc, 1}}),
    folsom_metrics:notify({erldns_handler_error_meter, 1}),
    {ok, State};
handle_event({M = erldns_zone_encoder, E = unsupported_rrdata_type, Data}, State) ->
    lager:info("Unable to encode rrdata (module: ~p, event: ~p, data: ~p)", [M, E, Data]),
    {ok, State};
handle_event({M = erldns_zone_loader, E = read_file_error, Reason}, State) ->
    lager:error("Failed to load zones (module: ~p, event: ~p, reason: ~p)", [M, E, Reason]),
    {ok, State};
handle_event({M = erldns_zone_loader, E = put_zone_error, {JsonZone, Reason}}, State) ->
    lager:error("Failed to load zones (module: ~p, event: ~p, reason: ~p, json: ~p)", [M, E, Reason, JsonZone]),
    {ok, State};
handle_event({M = erldns_zone_parser, E = error, {Name, Type, Data, Reason}}, State) ->
    lager:error("Error parsing record (module: ~p, event: ~p, name: ~p, type: ~p, data: ~p, reason: ~p)", [M, E, Name, Type, Data, Reason]),
    {ok, State};
handle_event({M = erldns_zone_parser, E = error, {Name, Type, Data, Exception, Reason}}, State) ->
    lager:error(
        "Error parsing record (module: ~p, event: ~p, name: ~p, type: ~p, data: ~p, exception: ~p, reason: ~p)",
        [M, E, Name, Type, Data, Exception, Reason]
    ),
    {ok, State};
handle_event({M = erldns_zone_parser, E = unsupported_record, Data}, State) ->
    lager:warning("Unsupported record (module: ~p, event: ~p, data: ~p)", [M, E, Data]),
    {ok, State};
handle_event({M = erldns_decoder, E = decode_message_error, {Exception, Reason, Bin}}, State) ->
    lager:error("Error decoding message (module: ~p, event: ~p, data: ~p, exception: ~p, reason: ~p)", [M, E, Bin, Exception, Reason]),
    {ok, State};
handle_event({M = eldns_encoder, E = encode_message_error, {Exception, Reason, Response}}, State) ->
    lager:error("Error encoding message (module: ~p, event: ~p, response: ~p, exception: ~p, reason: ~p)", [
        M, E, Response, Exception, Reason
    ]),
    {ok, State};
handle_event({M = erldns_encoder, E = encode_message_error, {Exception, Reason, Response, Opts}}, State) ->
    lager:error(
        "Error encoding with opts (module: ~p, event: ~p, response: ~p, opts: ~p, exception: ~p, reason: ~p)",
        [M, E, Response, Opts, Exception, Reason]
    ),
    {ok, State};
handle_event({M = erldns_storage, E = failed_zones_load, Reason}, State) ->
    lager:error("Failed to load zones (module: ~p, event: ~p, reason: ~p)", [M, E, Reason]),
    {ok, State};
handle_event({_M = erldns_worker, _E = timeout}, State) ->
    folsom_metrics:notify({worker_timeout_counter, {inc, 1}}),
    folsom_metrics:notify({worker_timeout_meter, 1}),
    {ok, State};
handle_event({M = erldns_worker, E = restart_failed, Error}, State) ->
    lager:error("Restart failed (module: ~p, event: ~p, error: ~p)", [M, E, Error]),
    {ok, State};
handle_event(_Event, State) ->
    {ok, State}.

handle_call(_Message, State) ->
    {ok, ok, State}.

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

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

terminate(_Reason, _State) ->
    ok.