193 lines
6 KiB
Erlang
193 lines
6 KiB
Erlang
-module(stomp_worker).
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-behaviour(gen_server).
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%% API.
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-export([start_link/0]).
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%% gen_server.
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-export([init/1]).
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-export([handle_call/3]).
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-export([handle_cast/2]).
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-export([handle_info/2]).
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-export([terminate/2]).
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-export([code_change/3]).
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%% Testing
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-compile(export_all).
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-include("stomp.hrl").
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%% State of a stomp_worker
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-record(state, {connection :: port(),
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next_sub :: sub_id(),
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subscriptions :: #{ destination() => sub_id() },
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subscribers :: #{ destination() => pid() }
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}).
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-type state() :: #state{}.
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%% API implementation
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-spec start_link() -> {ok, pid()}.
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start_link() ->
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{ok, Pid} = gen_server:start_link(?MODULE, [], []),
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register(?MODULE, Pid),
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{ok, Pid}.
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%% gen_server implementation
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-spec init(any()) -> {ok, state()}.
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init(_Args) ->
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%% Fetch configuration from app config
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{ok, Host} = application:get_env(stomp, host),
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Port = application:get_env(stomp, port, 61613),
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Login = application:get_env(stomp, login),
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Pass = application:get_env(stomp, passcode),
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%% Catch exit signals from linked processes (subscribers dying)
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process_flag(trap_exit, true),
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%% Establish connection
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{ok, Conn} = connect(Host, Port, Login, Pass),
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{ok, #state{connection = Conn,
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next_sub = 0,
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subscriptions = #{},
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subscribers = #{}}}.
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%% Handle subscription calls
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handle_call({subscribe, Dest, Ack}, From, State) ->
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%% Subscribe to new destination
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SubId = State#state.next_sub,
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ok = subscribe(State#state.connection, SubId, Dest, Ack),
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%% Add subscription and subscriber to state
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Subscriptions = maps:put(SubId, Dest, State#state.subscriptions),
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Subscribers = maps:put(SubId, From, State#state.subscribers),
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NextSub = SubId + 1,
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NewState = State#state{subscriptions = Subscriptions,
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subscribers = Subscribers,
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next_sub = NextSub },
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{reply, {ok, SubId}, NewState};
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handle_call(_Req, _From, State) ->
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{reply, ignored, State}.
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handle_info({tcp, Conn, Frame}, State) when Conn =:= State#state.connection ->
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handle_frame(Frame, State);
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handle_info(_Msg, State) ->
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{noreply, State}.
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%% Unused gen_server callbacks
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handle_cast(_Msg, 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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%% Private functions
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-spec connect(list(), integer(), any(), any()) -> {ok, port()}.
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connect(Host, Port, Login, Pass) ->
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%% STOMP CONNECT frame
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Connect = connect_frame(Host, Login, Pass),
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%% TODO: Configurable buffer size
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%% Frames larger than the user-level buffer will be truncated, so it should
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%% never be smaller than the largest expected messages.
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{ok, Socket} = gen_tcp:connect(Host, Port, [binary,
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{packet, line},
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{line_delimiter, $\0},
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{buffer, 262144}]),
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ok = gen_tcp:send(Socket, Connect),
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{ok, Socket}.
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-spec subscribe(port(), sub_id(), destination(), ack_mode()) -> ok.
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subscribe(Socket, Id, Queue, Ack) ->
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{ok, SubscribeFrame} = subscribe_frame(Id, Queue, Ack),
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gen_tcp:send(Socket, SubscribeFrame).
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%%% Parsing STOMP frames
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handle_frame(<<"MESSAGE", "\n", _Frame/binary>>, State) ->
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{noreply, State};
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handle_frame(Frame, State) ->
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io:format("Received unknown frame ~p", [Frame]),
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{noreply, State}.
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%% Parse out headers into a map
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-spec parse_headers(binary()) -> headers().
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parse_headers(HeadersBin) ->
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Headers = binary:split(HeadersBin, <<"\n">>, [global]),
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ToPairs = fun(H, M) -> [K,V | []] = binary:split(H, <<":">>),
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maps:put(K, V, M)
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end,
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{ok, lists:mapfoldl(ToPairs, #{}, Headers)}.
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%%% Making STOMP protocol frames
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%% Format a header
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-spec format_header({binary(), binary()}) -> binary().
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format_header({Key, Val}) ->
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<<Key/binary, ":", Val/binary, "\n">>.
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%% Build a single STOMP frame
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-spec make_frame(binary(),
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headers(),
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binary())
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-> {ok, iolist()}.
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make_frame(Command, HeaderMap, Body) ->
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Headers = lists:map(fun format_header/1, maps:to_list(HeaderMap)),
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Frame = [Command, <<"\n">>, Headers, <<"\n">>, Body, <<0>>],
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{ok, Frame}.
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%%% Default frames
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-spec connect_frame(list(), any(), any()) -> iolist().
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connect_frame(Host, {ok, Login}, {ok, Pass}) ->
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make_frame(<<"CONNECT">>,
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#{<<"accept-version">> => <<"1.2">>,
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<<"host">> => Host,
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<<"login">> => Login,
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<<"passcode">> => Pass,
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<<"heart-beat">> => <<"0,5000">>},
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[]);
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connect_frame(Host, _Login, _Pass) ->
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make_frame(<<"CONNECT">>,
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#{<<"accept-version">> => <<"1.2">>,
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<<"host">> => Host,
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%% Expect a server heartbeat every 5 seconds, let the server
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%% expect one every 10. We don't actually check this and just
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%% echo server heartbeats.
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%% TODO: For now the server is told not to expect replies due to
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%% a weird behaviour.
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<<"heart-beat">> => <<"0,5000">>},
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[]).
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-spec subscribe_frame(sub_id(), destination(), ack_mode()) -> iolist().
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subscribe_frame(Id, Queue, Ack) ->
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make_frame(<<"SUBSCRIBE">>,
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#{<<"id">> => integer_to_binary(Id),
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<<"destination">> => Queue,
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<<"ack">> => ack_mode_to_binary(Ack)},
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[]).
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-spec ack_mode_to_binary(ack_mode()) -> binary().
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ack_mode_to_binary(AckMode) ->
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case AckMode of
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auto -> <<"auto">>;
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client -> <<"client">>;
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client_individual -> <<"client-individual">>
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end.
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%% -spec ack_frame(binary()) -> iolist().
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%% ack_frame(MessageID) ->
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%% make_frame(<<"ACK">>,
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%% [{"id", MessageID}],
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%% []).
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