fix issue#42: Redelivery on reconnect

apps/emqtt/src/emqtt_client.erl

@@ -37,6 +37,8 @@
 
 -include("emqtt.hrl").
 
+-include("emqtt_packet.hrl").
+
 %%Client State...
 -record(state, { 
         socket, 
@@ -103,6 +105,10 @@ handle_info({dispatch, {From, Message}}, #state{proto_state = ProtoState} = Stat
     {ok, ProtoState1} = emqtt_protocol:send_message({From, Message}, ProtoState),
     {noreply, State#state{proto_state = ProtoState1}};
 
+handle_info({redeliver, {?PUBREL, PacketId}}, #state{proto_state = ProtoState} = State) ->
+    {ok, ProtoState1} = emqtt_protocol:redeliver({?PUBREL, PacketId}, ProtoState),
+    {noreply, State#state{proto_state = ProtoState1}};
+
 handle_info({inet_reply, _Ref, ok}, State) ->
     {noreply, State, hibernate};
 

apps/emqtt/src/emqtt_protocol.erl

@@ -32,7 +32,7 @@
 
 -export([initial_state/2, client_id/1]).
 
--export([handle_packet/2, send_message/2, send_packet/2, shutdown/2]).
+-export([handle_packet/2, send_message/2, send_packet/2, redeliver/2, shutdown/2]).
 
 -export([info/1]).
 
@@ -253,6 +253,12 @@ send_packet(Packet, State = #proto_state{socket = Sock, peer_name = PeerName, cl
     erlang:port_command(Sock, Data),
     {ok, State}.
 
+%%
+%% @doc redeliver PUBREL PacketId
+%%
+redeliver({?PUBREL, PacketId}, State) ->
+    send_packet( make_packet(?PUBREL, PacketId), State).
+
 shutdown(Error, #proto_state{peer_name = PeerName, client_id = ClientId, will_msg = WillMsg}) ->
     send_willmsg(WillMsg),
     try_unregister(ClientId, self()),

apps/emqtt/src/emqtt_session.erl

@@ -228,14 +228,28 @@ handle_call(Req, _From, State) ->
     {stop, {badreq, Req}, State}.
 
 handle_cast({resume, ClientId, ClientPid}, State = #session_state { 
-        client_id = ClientId, 
-        client_pid = undefined, 
-        msg_queue = Queue,
-        expire_timer = ETimer}) ->
-    lager:info("Session: client ~s resumed by ~p", [ClientId, ClientPid]),
+                                                client_id = ClientId, 
+                                                client_pid = undefined, 
+                                                msg_queue = Queue,
+                                                awaiting_ack = AwaitingAck,
+                                                awaiting_comp = AwaitingComp,
+                                                expire_timer = ETimer}) ->
+    lager:info("Session ~s resumed by ~p", [ClientId, ClientPid]),
     erlang:cancel_timer(ETimer),
+
+    %% redelivery PUBREL
+    [ ClientPid ! {redeliver, {?PUBREL, PacketId}} || PacketId <- maps:keys(AwaitingComp) ],
+
+    %% redelivery messages that awaiting PUBACK or PUBREC
+    Dup = fun(Msg) -> Msg#mqtt_message{ dup = true } end,
+    [ ClientPid ! {dispatch, {self(), Dup(Message)}} || Message <- maps:values(AwaitingAck) ],
+
+    %% send offline messages
     [ClientPid ! {dispatch, {self(), Message}} || Message <- emqtt_queue:all(Queue)],
-    NewState = State#session_state{ client_pid = ClientPid, msg_queue = emqtt_queue:clear(Queue), expire_timer = undefined},
+
+    NewState = State#session_state{ client_pid = ClientPid, 
+                                    msg_queue = emqtt_queue:clear(Queue), 
+                                    expire_timer = undefined},
     {noreply, NewState, hibernate};
 
 handle_cast({publish, ?QOS_2, Message}, State) ->