diff --git a/apps/emqttd/include/emqttd_protocol.hrl b/apps/emqttd/include/emqttd_protocol.hrl
index 5266fae54..35637e3d5 100644
--- a/apps/emqttd/include/emqttd_protocol.hrl
+++ b/apps/emqttd/include/emqttd_protocol.hrl
@@ -196,6 +196,11 @@
                                                  packet_id  = PacketId},
                  payload = Payload}).
 
+-define(PUBLISH(Qos, PacketId),
+    #mqtt_packet{header = #mqtt_packet_header{type = ?PUBLISH,
+                                              qos = Qos},
+                 variable = #mqtt_packet_publish{packet_id  = PacketId}}).
+
 -define(PUBACK_PACKET(Type, PacketId),
     #mqtt_packet{header = #mqtt_packet_header{type = Type},
                  variable = #mqtt_packet_puback{packet_id = PacketId}}).
diff --git a/apps/emqttd/src/emqttd_protocol.erl b/apps/emqttd/src/emqttd_protocol.erl
index 2c4f9568c..7bdc1d67c 100644
--- a/apps/emqttd/src/emqttd_protocol.erl
+++ b/apps/emqttd/src/emqttd_protocol.erl
@@ -170,37 +170,18 @@ handle(Packet = ?CONNECT_PACKET(Var), State0 = #proto_state{peername = Peername}
     %% Send connack
     send(?CONNACK_PACKET(ReturnCode1), State3);
 
-handle(Packet = ?PUBLISH_PACKET(?QOS_0, Topic, _PacketId, _Payload),
-       State = #proto_state{clientid = ClientId, session = Session}) ->
+handle(Packet = ?PUBLISH_PACKET(_Qos, Topic, _PacketId, _Payload),
+           State = #proto_state{clientid = ClientId}) ->
+
     case check_acl(publish, Topic, State) of
-        allow -> 
-            do_publish(Session, ClientId, Packet);
+        allow ->
+            publish(Packet, State);
         deny -> 
             lager:error("ACL Deny: ~s cannot publish to ~s", [ClientId, Topic])
     end,
 	{ok, State};
 
-handle(Packet = ?PUBLISH_PACKET(?QOS_1, Topic, PacketId, _Payload),
-         State = #proto_state{clientid = ClientId, session = Session}) ->
-    case check_acl(publish, Topic, State) of
-        allow -> 
-            do_publish(Session, ClientId, Packet),
-            send(?PUBACK_PACKET(?PUBACK, PacketId), State);
-        deny -> 
-            lager:error("ACL Deny: ~s cannot publish to ~s", [ClientId, Topic]),
-            {ok, State}
-    end;
 
-handle(Packet = ?PUBLISH_PACKET(?QOS_2, Topic, PacketId, _Payload),
-         State = #proto_state{clientid = ClientId, session = Session}) ->
-    case check_acl(publish, Topic, State) of
-        allow -> 
-            do_publish(Session, ClientId, Packet), 
-            send(?PUBACK_PACKET(?PUBREC, PacketId), State);
-        deny -> 
-            lager:error("ACL Deny: ~s cannot publish to ~s", [ClientId, Topic]),
-            {ok, State}
-    end;
 
 handle(?PUBACK_PACKET(?PUBACK, PacketId), State = #proto_state{session = Session}) ->
     emqttd_session:puback(Session, PacketId),
@@ -256,10 +237,26 @@ handle(?PACKET(?DISCONNECT), State) ->
     % clean willmsg
     {stop, normal, State#proto_state{will_msg = undefined}}.
 
-do_publish(Session, ClientId, Packet) ->
-    Msg = emqttd_message:from_packet(ClientId, Packet),
-    Msg1 = emqttd_broker:foldl_hooks(client_publish, [], Msg),
-    emqttd_session:publish(Session, Msg1).
+publish(Packet = ?PUBLISH(?QOS_0, _PacketId), #proto_state{clientid = ClientId, session = Session}) ->
+    emqttd_session:publish(Session, emqttd_message:from_packet(ClientId, Packet));
+
+publish(Packet = ?PUBLISH(?QOS_1, PacketId), State = #proto_state{clientid = ClientId, session = Session}) ->
+    case emqttd_session:publish(Session, emqttd_message:from_packet(ClientId, Packet)) of
+        ok ->
+            send(?PUBACK_PACKET(?PUBACK, PacketId), State);
+        {error, Error} ->
+            %%TODO: log format...
+            lager:error("Client ~s: publish qos1 error ~p", [ClientId, Error])
+    end;
+
+publish(Packet = ?PUBLISH(?QOS_2, PacketId), State = #proto_state{clientid = ClientId, session = Session}) ->
+    case emqttd_session:publish(Session, emqttd_message:from_packet(ClientId, Packet)) of
+        ok ->
+            send(?PUBACK_PACKET(?PUBREC, PacketId), State);
+        {error, Error} ->
+            %%TODO: log format...
+            lager:error("Client ~s: publish qos2 error ~p", [ClientId, Error])
+    end.
 
 -spec send(mqtt_message() | mqtt_packet(), proto_state()) -> {ok, proto_state()}.
 send(Msg, State) when is_record(Msg, mqtt_message) ->
@@ -323,7 +320,7 @@ send_willmsg(_ClientId, undefined) ->
     ignore;
 send_willmsg(ClientId, WillMsg) -> 
     lager:info("Client ~s send willmsg: ~p", [ClientId, WillMsg]),
-    emqttd_pubsub:publish(ClientId, WillMsg).
+    emqttd_pubsub:publish(WillMsg#mqtt_message{from = ClientId}).
 
 start_keepalive(0) -> ignore;
 
diff --git a/apps/emqttd/src/emqttd_pubsub.erl b/apps/emqttd/src/emqttd_pubsub.erl
index 1e1304d1a..3699bfc9f 100644
--- a/apps/emqttd/src/emqttd_pubsub.erl
+++ b/apps/emqttd/src/emqttd_pubsub.erl
@@ -47,7 +47,7 @@
 -export([create/1,
          subscribe/1,
          unsubscribe/1,
-         publish/2,
+         publish/1,
          %local node
          dispatch/2, match/1]).
 
@@ -81,7 +81,7 @@ mnesia(boot) ->
                 {ram_copies, [node()]},
                 {record_name, mqtt_subscriber},
                 {attributes, record_info(fields, mqtt_subscriber)},
-                {index, [pid]},
+                {index, [subpid]},
                 {local_content, true}]);
 
 mnesia(copy) ->
@@ -156,19 +156,23 @@ cast(Msg) ->
 %% @doc Publish to cluster nodes
 %% @end
 %%------------------------------------------------------------------------------
--spec publish(From :: mqtt_clientid() | atom(), Msg :: mqtt_message()) -> ok.
-publish(From, #mqtt_message{topic=Topic} = Msg) ->
+-spec publish(Msg :: mqtt_message()) -> ok.
+publish(#mqtt_message{topic=Topic, from = From} = Msg) ->
     trace(publish, From, Msg),
+
+    %%TODO:call hooks here...
+    %%Msg1 = emqttd_broker:foldl_hooks(client_publish, [], Msg),
+
     %% Retain message first. Don't create retained topic.
     case emqttd_msg_store:retain(Msg) of
         ok ->
             %TODO: why unset 'retain' flag?
-            publish(From, Topic, emqttd_message:unset_flag(Msg));
+            publish(Topic, emqttd_message:unset_flag(Msg));
         ignore ->
-            publish(From, Topic, Msg)
+            publish(Topic, Msg)
      end.
 
-publish(From, <<"$Q/", _/binary>> = Queue, #mqtt_message{qos = Qos} = Msg) ->
+publish(<<"$Q/", _/binary>> = Queue, #mqtt_message{qos = Qos} = Msg) ->
     lists:foreach(
         fun(#mqtt_queue{subpid = SubPid, qos = SubQos}) -> 
             Msg1 = if
@@ -178,7 +182,7 @@ publish(From, <<"$Q/", _/binary>> = Queue, #mqtt_message{qos = Qos} = Msg) ->
             SubPid ! {dispatch, Msg1}
         end, mnesia:dirty_read(queue, Queue));
     
-publish(_From, Topic, Msg) when is_binary(Topic) ->
+publish(Topic, Msg) when is_binary(Topic) ->
 	lists:foreach(fun(#mqtt_topic{topic=Name, node=Node}) ->
         case Node =:= node() of
             true -> dispatch(Name, Msg);
diff --git a/apps/emqttd/src/emqttd_session.erl b/apps/emqttd/src/emqttd_session.erl
index d4e8f081d..384e49ae1 100644
--- a/apps/emqttd/src/emqttd_session.erl
+++ b/apps/emqttd/src/emqttd_session.erl
@@ -21,13 +21,13 @@
 %%%-----------------------------------------------------------------------------
 %%% @doc
 %%%
-%%% emqttd session for persistent client.
+%%% Session for persistent MQTT client.
 %%%
 %%% Session State in the broker consists of:
 %%%
 %%% 1. The Client’s subscriptions.
 %%%
-%%% 2. inflight qos1, qos2 messages sent to the client but unacked, QoS 1 and QoS 2
+%%% 2. inflight qos1/2 messages sent to the client but unacked, QoS 1 and QoS 2
 %%%    messages which have been sent to the Client, but have not been completely
 %%%    acknowledged.
 %%%
@@ -59,6 +59,8 @@
          puback/2, pubrec/2, pubrel/2, pubcomp/2,
          subscribe/2, unsubscribe/2]).
 
+-behaviour(gen_server).
+
 %% gen_server Function Exports
 -export([init/1, handle_call/3, handle_cast/2, handle_info/2,
          terminate/2, code_change/3]).
@@ -116,7 +118,7 @@
         max_awaiting_rel = 100,
 
         %% session expired after 48 hours
-        expired_after = 172800,
+        expired_after = 48,
 
         expired_timer,
         
@@ -126,6 +128,7 @@
 %% @doc Start a session.
 %% @end
 %%------------------------------------------------------------------------------
+-spec start_link(boolean(), binary(), pid()) -> {ok, pid()} | {error, any()}.
 start_link(CleanSess, ClientId, ClientPid) ->
     gen_server:start_link(?MODULE, [CleanSess, ClientId, ClientPid], []).
 
@@ -133,7 +136,8 @@ start_link(CleanSess, ClientId, ClientPid) ->
 %% @doc Resume a session.
 %% @end
 %%------------------------------------------------------------------------------
-resume(Session, ClientId, ClientPid) when is_pid(Session) ->
+-spec resume(pid(), binary(), pid()) -> ok.
+resume(Session, ClientId, ClientPid) ->
     gen_server:cast(Session, {resume, ClientId, ClientPid}).
 
 %%------------------------------------------------------------------------------
@@ -141,73 +145,69 @@ resume(Session, ClientId, ClientPid) when is_pid(Session) ->
 %% @end
 %%------------------------------------------------------------------------------
 -spec destroy(Session:: pid(), ClientId :: binary()) -> ok.
-destroy(Session, ClientId)  when is_pid(Session) ->
+destroy(Session, ClientId) ->
     gen_server:call(Session, {destroy, ClientId}).
 
+%%------------------------------------------------------------------------------
+%% @doc Subscribe Topics
+%% @end
+%%------------------------------------------------------------------------------
+-spec subscribe(pid(), [{binary(), mqtt_qos()}]) -> {ok, [mqtt_qos()]}.
+subscribe(Session, TopicTable) ->
+    gen_server:call(Session, {subscribe, TopicTable}).
+
 %%------------------------------------------------------------------------------
 %% @doc Publish message
 %% @end
 %%------------------------------------------------------------------------------
 -spec publish(Session :: pid(), {mqtt_qos(), mqtt_message()}) -> ok.
-publish(Session, Msg = #mqtt_message{qos = ?QOS_0}) when is_pid(Session) ->
+publish(_Session, Msg = #mqtt_message{qos = ?QOS_0}) ->
     %% publish qos0 directly
     emqttd_pubsub:publish(Msg);
 
-publish(Session, Msg = #mqtt_message{qos = ?QOS_1}) when is_pid(Session) ->
-    %% publish qos1 directly, and client will puback
+publish(_Session, Msg = #mqtt_message{qos = ?QOS_1}) ->
+    %% publish qos1 directly, and client will puback automatically
 	emqttd_pubsub:publish(Msg);
 
-publish(Session, Msg = #mqtt_message{qos = ?QOS_2}) when is_pid(Session) ->
+publish(Session, Msg = #mqtt_message{qos = ?QOS_2}) ->
     %% publish qos2 by session 
-    gen_server:cast(Session, {publish, Msg}).
+    gen_server:call(Session, {publish, Msg}).
 
 %%------------------------------------------------------------------------------
 %% @doc PubAck message
 %% @end
 %%------------------------------------------------------------------------------
--spec puback(Session :: pid(), MsgId :: mqtt_packet_id()) -> ok.
-puback(Session, MsgId) when is_pid(Session) ->
+-spec puback(pid(), mqtt_msgid()) -> ok.
+puback(Session, MsgId) ->
     gen_server:cast(Session, {puback, MsgId}).
 
--spec pubrec(Session :: pid(), MsgId :: mqtt_packet_id()) -> ok.
-pubrec(Session, MsgId) when is_pid(Session) ->
+-spec pubrec(pid(), mqtt_msgid()) -> ok.
+pubrec(Session, MsgId) ->
     gen_server:cast(Session, {pubrec, MsgId}).
 
--spec pubrel(Session :: pid(), MsgId :: mqtt_packet_id()) -> ok.
-pubrel(Session, MsgId) when is_pid(Session) ->
+-spec pubrel(pid(), mqtt_msgid()) -> ok.
+pubrel(Session, MsgId) ->
     gen_server:cast(Session, {pubrel, MsgId}).
 
--spec pubcomp(Session :: pid(), MsgId :: mqtt_packet_id()) -> ok.
-pubcomp(Session, MsgId) when is_pid(Session) ->
+-spec pubcomp(pid(), mqtt_msgid()) -> ok.
+pubcomp(Session, MsgId) ->
     gen_server:cast(Session, {pubcomp, MsgId}).
 
-%%------------------------------------------------------------------------------
-%% @doc Subscribe Topics
-%% @end
-%%------------------------------------------------------------------------------
--spec subscribe(Session :: pid(), [{binary(), mqtt_qos()}]) -> {ok, [mqtt_qos()]}.
-subscribe(Session, Topics) when is_pid(Session) ->
-    gen_server:call(Session, {subscribe, Topics}).
-
 %%------------------------------------------------------------------------------
 %% @doc Unsubscribe Topics
 %% @end
 %%------------------------------------------------------------------------------
--spec unsubscribe(Session :: pid(), [Topic :: binary()]) -> ok.
-unsubscribe(Session, Topics) when is_pid(Session) ->
+-spec unsubscribe(pid(), [binary()]) -> ok.
+unsubscribe(Session, Topics) ->
     gen_server:call(Session, {unsubscribe, Topics}).
 
 %%%=============================================================================
 %%% gen_server callbacks
 %%%=============================================================================
+
 init([CleanSess, ClientId, ClientPid]) ->
-    if
-        CleanSess =:= false ->
-            process_flag(trap_exit, true),
-            true = link(ClientPid);
-        CleanSess =:= true ->
-            ok
-    end,
+    process_flag(trap_exit, true),
+    true = link(ClientPid),
     QEnv = emqttd:env(mqtt, queue),
     SessEnv = emqttd:env(mqtt, session),
     PendingQ = emqttd_mqueue:new(ClientId, QEnv),
@@ -227,25 +227,25 @@ init([CleanSess, ClientId, ClientPid]) ->
         await_rel_timeout = emqttd_opts:g(await_rel_timeout, SessEnv),
         max_awaiting_rel  = emqttd_opts:g(max_awaiting_rel, SessEnv),
         expired_after     = emqttd_opts:g(expired_after, SessEnv) * 3600,
-        timestamp         = os:timestamp()
-    },
+        timestamp         = os:timestamp()},
     {ok, Session, hibernate}.
 
-handle_call({subscribe, Topics}, _From, Session = #session{clientid = ClientId, subscriptions = Subscriptions}) ->
+handle_call({subscribe, Topics}, _From, Session = #session{clientid = ClientId,
+                                                           subscriptions = Subscriptions}) ->
 
     %% subscribe first and don't care if the subscriptions have been existed
     {ok, GrantedQos} = emqttd_pubsub:subscribe(Topics),
 
-    lager:info([{client, ClientId}], "Session ~s subscribe ~p. Granted QoS: ~p",
-               [ClientId, Topics, GrantedQos]),
+    lager:info([{client, ClientId}], "Session ~s subscribe ~p, Granted QoS: ~p",
+                   [ClientId, Topics, GrantedQos]),
 
     Subscriptions1 =
     lists:foldl(fun({Topic, Qos}, Acc) ->
                 case lists:keyfind(Topic, 1, Acc) of
                     {Topic, Qos} ->
-                        lager:warning([{client, ClientId}], "~s resubscribe ~p: qos = ~p", [ClientId, Topic, Qos]), Acc;
+                        lager:warning([{client, ClientId}], "Session ~s resubscribe ~p: qos = ~p", [ClientId, Topic, Qos]), Acc;
                     {Topic, Old} ->
-                        lager:warning([{client, ClientId}], "~s resubscribe ~p: old qos=~p, new qos=~p",
+                        lager:warning([{client, ClientId}], "Session ~s resubscribe ~p: old qos=~p, new qos=~p",
                                           [ClientId, Topic, Old, Qos]),
                         lists:keyreplace(Topic, 1, Acc, {Topic, Qos});
                     false ->
@@ -263,7 +263,7 @@ handle_call({unsubscribe, Topics}, _From, Session = #session{clientid = ClientId
 
     %%unsubscribe from topic tree
     ok = emqttd_pubsub:unsubscribe(Topics),
-    lager:info([{client, ClientId}], "Client ~s unsubscribe ~p.", [ClientId, Topics]),
+    lager:info([{client, ClientId}], "Session ~s unsubscribe ~p.", [ClientId, Topics]),
 
     Subscriptions1 =
     lists:foldl(fun(Topic, Acc) ->
@@ -277,12 +277,24 @@ handle_call({unsubscribe, Topics}, _From, Session = #session{clientid = ClientId
 
     {reply, ok, Session#session{subscriptions = Subscriptions1}};
 
+handle_call({publish, Message = #mqtt_message{qos = ?QOS_2, msgid = MsgId}}, _From, 
+            Session = #session{clientid = ClientId, awaiting_rel = AwaitingRel, await_rel_timeout = Timeout}) ->
+    case check_awaiting_rel(Session) of
+        true -> 
+            TRef = timer(Timeout, {timeout, awaiting_rel, MsgId}),
+            {reply, ok, Session#session{awaiting_rel = maps:put(MsgId, {Message, TRef}, AwaitingRel)}};
+        false ->
+            lager:error([{clientid, ClientId}], "Session ~s "
+                                " dropped Qos2 message for too many awaiting_rel: ~p", [ClientId, Message]),
+            {reply, {error, dropped}, Session}
+    end;
+
 handle_call({destroy, ClientId}, _From, Session = #session{clientid = ClientId}) ->
     lager:warning("Session ~s destroyed", [ClientId]),
     {stop, {shutdown, destroy}, ok, Session};
 
 handle_call(Req, _From, State) ->
-    lager:error("Unexpected Request: ~p", [Req]),
+    lager:critical("Unexpected Request: ~p", [Req]),
     {reply, {error, badreq}, State}.
 
 handle_cast({resume, ClientId, ClientPid}, State = #session{
@@ -331,9 +343,6 @@ handle_cast({resume, ClientId, ClientPid}, State = #session{
                             pending_queue = emqttd_queue:clear(Queue),
                             expired_timer = undefined}, hibernate};
 
-handle_cast({publish, Message = #mqtt_message{qos = ?QOS_2}}, Session) ->
-    {noreply, publish_qos2(Message, Session)};
-
 
 handle_cast({puback, MsgId}, Session = #session{clientid = ClientId, inflight_queue = Q, awaiting_ack = Awaiting}) ->
     case maps:find(MsgId, Awaiting) of
@@ -362,14 +371,14 @@ handle_cast({pubrec, MsgId}, Session = #session{clientid = ClientId,
             {noreply, Session}
     end;
 
-handle_cast({pubrel, MsgId}, Session = #session{clientid = ClientId, awaiting_rel = Awaiting}) ->
-    case maps:find(MsgId, Awaiting) of
+handle_cast({pubrel, MsgId}, Session = #session{clientid = ClientId, awaiting_rel = AwaitingRel}) ->
+    case maps:find(MsgId, AwaitingRel) of
         {ok, {Msg, TRef}} ->
             catch erlang:cancel_timer(TRef),
             emqttd_pubsub:publish(Msg),
-            {noreply, Session#session{awaiting_rel = maps:remove(MsgId, Awaiting)}};
+            {noreply, Session#session{awaiting_rel = maps:remove(MsgId, AwaitingRel)}};
         error ->
-            lager:error("Session ~s cannot find PUBREL'~p'!", [ClientId, MsgId]),
+            lager:error("Session ~s cannot find PUBREL '~p'!", [ClientId, MsgId]),
             {noreply, Session}
     end;
 
@@ -408,6 +417,10 @@ handle_info({'EXIT', ClientPid, Reason}, Session = #session{clean_sess = false,
     TRef = timer(Expires * 1000, session_expired),
     {noreply, Session#session{expired_timer = TRef}};
 
+handle_info({'EXIT', ClientPid, _Reason}, Session = #session{clean_sess = true, client_pid = ClientPid}) ->
+    %%TODO: reason...
+    {stop, normal, Session};
+
 handle_info({'EXIT', ClientPid0, _Reason}, State = #session{client_pid = ClientPid}) ->
     lager:critical("Unexpected Client EXIT: pid=~p, pid(state): ~p", [ClientPid0, ClientPid]),
     {noreply, State};
@@ -456,19 +469,6 @@ code_change(_OldVsn, Session, _Extra) ->
 %% @end
 %%------------------------------------------------------------------------------
 
-publish_qos2(Message = #mqtt_message{qos = ?QOS_2,msgid = MsgId}, Session = #session{clientid = ClientId,
-                                                                                     awaiting_rel = AwaitingRel,
-                                                                                     await_rel_timeout = Timeout}) ->
-
-    case check_awaiting_rel(Session) of
-        true -> 
-            TRef = timer(Timeout, {timeout, awaiting_rel, MsgId}),
-            Session#session{awaiting_rel = maps:put(MsgId, {Message, TRef}, AwaitingRel)};
-        false ->
-            lager:error([{clientid, ClientId}], "Session ~s "
-                                " dropped Qos2 message for too many awaiting_rel: ~p", [ClientId, Message]),
-            Session
-    end.
 
 check_awaiting_rel(#session{max_awaiting_rel = 0}) ->
     true;