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-%%--------------------------------------------------------------------
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-%% Copyright (c) 2019 EMQ Technologies Co., Ltd. All Rights Reserved.
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-%%
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-%% Licensed under the Apache License, Version 2.0 (the "License");
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-%% you may not use this file except in compliance with the License.
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-%% You may obtain 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, software
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-%% distributed under the License is distributed on an "AS IS" BASIS,
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-%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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-%% See the License for the specific language governing permissions and
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-%% limitations under the License.
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-%%--------------------------------------------------------------------
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-
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-%% @doc This module implements a request handler based on emqx_client.
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-%% A request handler is a MQTT client which subscribes to a request topic,
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-%% processes the requests then send response to another topic which is
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-%% subscribed by the request sender.
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-%% This code is in test directory because request and response are pure
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-%% client-side behaviours.
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-
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--module(emqx_request_handler).
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-
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--export([start_link/4, stop/1]).
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-
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--type qos() :: emqx_mqtt_types:qos_name() | emqx_mqtt_types:qos().
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--type topic() :: emqx_topic:topic().
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--type handler() :: fun((CorrData :: binary(), ReqPayload :: binary()) -> RspPayload :: binary()).
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-
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--spec start_link(topic(), qos(), handler(), emqx_client:options()) ->
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- {ok, pid()} | {error, any()}.
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-start_link(RequestTopic, QoS, RequestHandler, Options0) ->
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- Parent = self(),
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- MsgHandler = make_msg_handler(RequestHandler, Parent),
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- Options = [{msg_handler, MsgHandler} | Options0],
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- case emqx_client:start_link(Options) of
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- {ok, Pid} ->
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- {ok, _} = emqx_client:connect(Pid),
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- try subscribe(Pid, RequestTopic, QoS) of
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- ok -> {ok, Pid};
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- {error, _} = Error -> Error
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- catch
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- C : E : S ->
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- emqx_client:stop(Pid),
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- {error, {C, E, S}}
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- end;
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- {error, _} = Error -> Error
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- end.
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-
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-stop(Pid) ->
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- emqx_client:disconnect(Pid).
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-
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-make_msg_handler(RequestHandler, Parent) ->
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- #{publish => fun(Msg) -> handle_msg(Msg, RequestHandler, Parent) end,
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- puback => fun(_Ack) -> ok end,
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- disconnected => fun(_Reason) -> ok end
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- }.
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-
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-handle_msg(ReqMsg, RequestHandler, Parent) ->
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- #{qos := QoS, properties := Props, payload := ReqPayload} = ReqMsg,
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- case maps:find('Response-Topic', Props) of
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- {ok, RspTopic} when RspTopic =/= <<>> ->
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- CorrData = maps:get('Correlation-Data', Props),
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- RspProps = maps:without(['Response-Topic'], Props),
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- RspPayload = RequestHandler(CorrData, ReqPayload),
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- emqx_logger:debug("~p sending response msg to topic ~s with~n"
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- "corr-data=~p~npayload=~p",
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- [?MODULE, RspTopic, CorrData, RspPayload]),
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- ok = send_response(RspTopic, RspProps, RspPayload, QoS);
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- _ ->
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- Parent ! {discarded, ReqPayload},
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- ok
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- end.
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-
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-send_response(Topic, Properties, Payload, QoS) ->
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- %% This function is evaluated by emqx_client itself.
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- %% hence delegate to another temp process for the loopback gen_statem call.
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- Client = self(),
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- _ = spawn_link(fun() ->
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- case emqx_client:publish(Client, Topic, Properties, Payload, [{qos, QoS}]) of
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- ok -> ok;
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- {ok, _} -> ok;
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- {error, Reason} -> exit({failed_to_publish_response, Reason})
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- end
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- end),
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- ok.
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-
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-subscribe(Client, Topic, QoS) ->
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- {ok, _Props, _QoS} =
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- emqx_client:subscribe(Client, [{Topic, [{rh, 2}, {rap, false},
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- {nl, true}, {qos, QoS}]}]),
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- ok.
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-
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-
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-
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