emqx/src/emqx_session.erl

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%%--------------------------------------------------------------------
%% Copyright (c) 2019 EMQ Technologies Co., Ltd. All Rights Reserved.
%%
%% Licensed under the Apache License, Version 2.0 (the "License");
%% you may not use this file except in compliance with the License.
%% You may obtain a copy of the License at
%%
%% http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.
%%--------------------------------------------------------------------
%%--------------------------------------------------------------------
%% @doc
%% A stateful interaction between a Client and a Server. Some Sessions
%% last only as long as the Network Connection, others can span multiple
%% consecutive Network Connections between a Client and a Server.
%%
%% The Session State in the Server consists of:
%%
%% The existence of a Session, even if the rest of the Session State is empty.
%%
%% The Clients subscriptions, including any Subscription Identifiers.
%%
%% QoS 1 and QoS 2 messages which have been sent to the Client, but have not
%% been completely acknowledged.
%%
%% QoS 1 and QoS 2 messages pending transmission to the Client and OPTIONALLY
%% QoS 0 messages pending transmission to the Client.
%%
%% QoS 2 messages which have been received from the Client, but have not been
%% completely acknowledged.The Will Message and the Will Delay Interval
%%
%% If the Session is currently not connected, the time at which the Session
%% will end and Session State will be discarded.
%% @end
%%--------------------------------------------------------------------
%% MQTT Session
-module(emqx_session).
-include("emqx.hrl").
-include("emqx_mqtt.hrl").
-include("logger.hrl").
-include("types.hrl").
-logger_header("[Session]").
-ifdef(TEST).
-compile(export_all).
-compile(nowarn_export_all).
-endif.
-export([init/2]).
-export([ info/1
, info/2
, attrs/1
, stats/1
]).
-export([ subscribe/4
, unsubscribe/3
]).
-export([ publish/3
, puback/2
, pubrec/2
, pubrel/2
, pubcomp/2
]).
-export([ deliver/2
, enqueue/2
, retry/1
]).
-export([ takeover/1
, resume/2
, redeliver/1
]).
-export([expire/2]).
%% export for ct
-export([set_field/3]).
-export_type([session/0]).
-import(emqx_zone, [get_env/3]).
-record(session, {
%% Clients Subscriptions.
subscriptions :: map(),
%% Max subscriptions allowed
max_subscriptions :: non_neg_integer(),
%% Upgrade QoS?
upgrade_qos :: boolean(),
%% Client <- Broker: QoS1/2 messages sent to the client but unacked.
inflight :: emqx_inflight:inflight(),
%% All QoS1/2 messages published to when client is disconnected,
%% or QoS1/2 messages pending transmission to the Client.
%%
%% Optionally, QoS0 messages pending transmission to the Client.
mqueue :: emqx_mqueue:mqueue(),
%% Next packet id of the session
next_pkt_id = 1 :: emqx_types:packet_id(),
%% Retry interval for redelivering QoS1/2 messages
retry_interval :: timeout(),
%% Client -> Broker: QoS2 messages received from client and waiting for pubrel.
awaiting_rel :: map(),
%% Max Packets Awaiting PUBREL
max_awaiting_rel :: non_neg_integer(),
%% Awaiting PUBREL Timeout
awaiting_rel_timeout :: timeout(),
%% Deliver Stats
deliver_stats :: emqx_types:stats(),
%% Created at
created_at :: pos_integer()
}).
-opaque(session() :: #session{}).
-type(publish() :: {publish, emqx_types:packet_id(), emqx_types:message()}).
-define(DEFAULT_BATCH_N, 1000).
-define(ATTR_KEYS, [inflight_cnt,
inflight_max,
mqueue_len,
mqueue_max,
retry_interval,
awaiting_rel_max,
awaiting_rel_timeout,
created_at
]).
-define(INFO_KEYS, [subscriptions,
subscriptions_max,
upgrade_qos,
inflight,
inflight_max,
retry_interval,
mqueue_len,
mqueue_max,
mqueue_dropped,
next_pkt_id,
awaiting_rel,
awaiting_rel_max,
awaiting_rel_timeout,
created_at
]).
-define(STATS_KEYS, [subscriptions_cnt,
subscriptions_max,
inflight_cnt,
inflight_max,
mqueue_len,
mqueue_max,
mqueue_dropped,
awaiting_rel,
awaiting_rel_max,
enqueue_cnt
]).
%%--------------------------------------------------------------------
%% Init a Session
%%--------------------------------------------------------------------
%% @doc Init a session.
-spec(init(emqx_types:clientinfo(), emqx_types:conninfo()) -> session()).
init(#{zone := Zone}, #{receive_maximum := MaxInflight}) ->
#session{max_subscriptions = get_env(Zone, max_subscriptions, 0),
subscriptions = #{},
upgrade_qos = get_env(Zone, upgrade_qos, false),
inflight = emqx_inflight:new(MaxInflight),
mqueue = init_mqueue(Zone),
next_pkt_id = 1,
retry_interval = get_env(Zone, retry_interval, 0),
awaiting_rel = #{},
max_awaiting_rel = get_env(Zone, max_awaiting_rel, 100),
awaiting_rel_timeout = get_env(Zone, awaiting_rel_timeout, 3600*1000),
created_at = erlang:system_time(second)
}.
%% @private init mq
init_mqueue(Zone) ->
emqx_mqueue:init(#{max_len => get_env(Zone, max_mqueue_len, 1000),
store_qos0 => get_env(Zone, mqueue_store_qos0, true),
priorities => get_env(Zone, mqueue_priorities, none),
default_priority => get_env(Zone, mqueue_default_priority, lowest)
}).
%% @doc Get infos of the session.
-spec(info(session()) -> emqx_types:infos()).
info(Session) ->
maps:from_list(info(?INFO_KEYS, Session)).
%% Get attrs of the session.
-spec(attrs(session()) -> emqx_types:attrs()).
attrs(Session) ->
maps:from_list(info(?ATTR_KEYS, Session)).
%% @doc Get stats of the session.
-spec(stats(session()) -> emqx_types:stats()).
stats(Session) -> info(?STATS_KEYS, Session).
info(Keys, Session) when is_list(Keys) ->
[{Key, info(Key, Session)} || Key <- Keys];
info(subscriptions, #session{subscriptions = Subs}) ->
Subs;
info(subscriptions_cnt, #session{subscriptions = Subs}) ->
maps:size(Subs);
info(subscriptions_max, #session{max_subscriptions = MaxSubs}) ->
MaxSubs;
info(upgrade_qos, #session{upgrade_qos = UpgradeQoS}) ->
UpgradeQoS;
info(inflight, #session{inflight = Inflight}) ->
Inflight;
info(inflight_cnt, #session{inflight = Inflight}) ->
emqx_inflight:size(Inflight);
info(inflight_max, #session{inflight = Inflight}) ->
emqx_inflight:max_size(Inflight);
info(retry_interval, #session{retry_interval = Interval}) ->
Interval;
info(mqueue_len, #session{mqueue = MQueue}) ->
emqx_mqueue:len(MQueue);
info(mqueue_max, #session{mqueue = MQueue}) ->
emqx_mqueue:max_len(MQueue);
info(mqueue_dropped, #session{mqueue = MQueue}) ->
emqx_mqueue:dropped(MQueue);
info(next_pkt_id, #session{next_pkt_id = PacketId}) ->
PacketId;
info(awaiting_rel, #session{awaiting_rel = AwaitingRel}) ->
AwaitingRel;
info(awaiting_rel_cnt, #session{awaiting_rel = AwaitingRel}) ->
maps:size(AwaitingRel);
info(awaiting_rel_max, #session{max_awaiting_rel = MaxAwaitingRel}) ->
MaxAwaitingRel;
info(awaiting_rel_timeout, #session{awaiting_rel_timeout = Timeout}) ->
Timeout;
info(enqueue_cnt, #session{deliver_stats = undefined}) ->
0;
info(enqueue_cnt, #session{deliver_stats = Stats}) ->
maps:get(enqueue_cnt, Stats, 0);
info(deliver_stats, #session{deliver_stats = Stats}) ->
Stats;
info(created_at, #session{created_at = CreatedAt}) ->
CreatedAt.
%% For tests
set_field(Name, Val, Channel) ->
Fields = record_info(fields, session),
Pos = emqx_misc:index_of(Name, Fields),
setelement(Pos+1, Channel, Val).
-spec(takeover(session()) -> ok).
takeover(#session{subscriptions = Subs}) ->
lists:foreach(fun({TopicFilter, _SubOpts}) ->
ok = emqx_broker:unsubscribe(TopicFilter)
end, maps:to_list(Subs)).
-spec(resume(emqx_types:clientid(), session()) -> ok).
resume(ClientId, #session{subscriptions = Subs}) ->
%% 1. Subscribe again.
lists:foreach(fun({TopicFilter, SubOpts}) ->
ok = emqx_broker:subscribe(TopicFilter, ClientId, SubOpts)
end, maps:to_list(Subs)).
%% 2. Run hooks.
%% ok = emqx_hooks:run('session.resumed', [#{clientid => ClientId}, attrs(Session)]),
%% TODO: 3. Redeliver: Replay delivery and Dequeue pending messages
%%Session.
redeliver(Session = #session{inflight = Inflight}) ->
Publishes = lists:map(fun({PacketId, {pubrel, _Ts}}) ->
{pubrel, PacketId, ?RC_SUCCESS};
({PacketId, {Msg, _Ts}}) ->
{publish, PacketId, Msg}
end, emqx_inflight:to_list(Inflight)),
case dequeue(Session) of
{ok, NSession} ->
{ok, Publishes, NSession};
{ok, More, NSession} ->
{ok, lists:append(Publishes, More), NSession}
end.
%%--------------------------------------------------------------------
%% Client -> Broker: SUBSCRIBE
%%--------------------------------------------------------------------
-spec(subscribe(emqx_types:clientinfo(), emqx_types:topic(), emqx_types:subopts(), session())
-> {ok, session()} | {error, emqx_types:reason_code()}).
subscribe(ClientInfo, TopicFilter, SubOpts, Session = #session{subscriptions = Subs}) ->
case is_subscriptions_full(Session)
andalso (not maps:is_key(TopicFilter, Subs)) of
true -> {error, ?RC_QUOTA_EXCEEDED};
false ->
do_subscribe(ClientInfo, TopicFilter, SubOpts, Session)
end.
is_subscriptions_full(#session{max_subscriptions = 0}) ->
false;
is_subscriptions_full(#session{max_subscriptions = MaxLimit,
subscriptions = Subs}) ->
maps:size(Subs) >= MaxLimit.
-compile({inline, [do_subscribe/4]}).
do_subscribe(Client = #{clientid := ClientId}, TopicFilter, SubOpts,
Session = #session{subscriptions = Subs}) ->
case IsNew = (not maps:is_key(TopicFilter, Subs)) of
true ->
ok = emqx_broker:subscribe(TopicFilter, ClientId, SubOpts);
false ->
_ = emqx_broker:set_subopts(TopicFilter, SubOpts)
end,
ok = emqx_hooks:run('session.subscribed',
[Client, TopicFilter, SubOpts#{is_new => IsNew}]),
{ok, Session#session{subscriptions = maps:put(TopicFilter, SubOpts, Subs)}}.
%%--------------------------------------------------------------------
%% Client -> Broker: UNSUBSCRIBE
%%--------------------------------------------------------------------
-spec(unsubscribe(emqx_types:clientinfo(), emqx_types:topic(), session())
-> {ok, session()} | {error, emqx_types:reason_code()}).
unsubscribe(ClientInfo, TopicFilter, Session = #session{subscriptions = Subs}) ->
case maps:find(TopicFilter, Subs) of
{ok, SubOpts} ->
ok = emqx_broker:unsubscribe(TopicFilter),
ok = emqx_hooks:run('session.unsubscribed', [ClientInfo, TopicFilter, SubOpts]),
{ok, Session#session{subscriptions = maps:remove(TopicFilter, Subs)}};
error ->
{error, ?RC_NO_SUBSCRIPTION_EXISTED}
end.
%%--------------------------------------------------------------------
%% Client -> Broker: PUBLISH
%%--------------------------------------------------------------------
-spec(publish(emqx_types:packet_id(), emqx_types:message(), session())
-> {ok, emqx_types:publish_result(), session()} |
{error, emqx_types:reason_code()}).
publish(PacketId, Msg = #message{qos = ?QOS_2}, Session) ->
case is_awaiting_full(Session) of
false ->
do_publish(PacketId, Msg, Session);
true ->
{error, ?RC_RECEIVE_MAXIMUM_EXCEEDED}
end;
%% Publish QoS0/1 directly
publish(_PacketId, Msg, Session) ->
{ok, emqx_broker:publish(Msg), Session}.
is_awaiting_full(#session{max_awaiting_rel = 0}) ->
false;
is_awaiting_full(#session{awaiting_rel = AwaitingRel,
max_awaiting_rel = MaxLimit}) ->
maps:size(AwaitingRel) >= MaxLimit.
-compile({inline, [do_publish/3]}).
do_publish(PacketId, Msg = #message{timestamp = Ts},
Session = #session{awaiting_rel = AwaitingRel}) ->
case maps:is_key(PacketId, AwaitingRel) of
false ->
DeliverResults = emqx_broker:publish(Msg),
AwaitingRel1 = maps:put(PacketId, Ts, AwaitingRel),
Session1 = Session#session{awaiting_rel = AwaitingRel1},
{ok, DeliverResults, Session1};
true ->
{error, ?RC_PACKET_IDENTIFIER_IN_USE}
end.
%%--------------------------------------------------------------------
%% Client -> Broker: PUBACK
%%--------------------------------------------------------------------
-spec(puback(emqx_types:packet_id(), session())
-> {ok, emqx_types:message(), session()}
| {ok, emqx_types:message(), list(publish()), session()}
| {error, emqx_types:reason_code()}).
puback(PacketId, Session = #session{inflight = Inflight}) ->
case emqx_inflight:lookup(PacketId, Inflight) of
{value, {Msg, _Ts}} when is_record(Msg, message) ->
Inflight1 = emqx_inflight:delete(PacketId, Inflight),
return_with(Msg, dequeue(Session#session{inflight = Inflight1}));
{value, {_Pubrel, _Ts}} ->
{error, ?RC_PACKET_IDENTIFIER_IN_USE};
none ->
{error, ?RC_PACKET_IDENTIFIER_NOT_FOUND}
end.
return_with(Msg, {ok, Session}) ->
{ok, Msg, Session};
return_with(Msg, {ok, Publishes, Session}) ->
{ok, Msg, Publishes, Session}.
%%--------------------------------------------------------------------
%% Client -> Broker: PUBREC
%%--------------------------------------------------------------------
-spec(pubrec(emqx_types:packet_id(), session())
-> {ok, emqx_types:message(), session()} | {error, emqx_types:reason_code()}).
pubrec(PacketId, Session = #session{inflight = Inflight}) ->
case emqx_inflight:lookup(PacketId, Inflight) of
{value, {Msg, _Ts}} when is_record(Msg, message) ->
Inflight1 = emqx_inflight:update(PacketId, {pubrel, os:timestamp()}, Inflight),
{ok, Msg, Session#session{inflight = Inflight1}};
{value, {pubrel, _Ts}} ->
{error, ?RC_PACKET_IDENTIFIER_IN_USE};
none ->
{error, ?RC_PACKET_IDENTIFIER_NOT_FOUND}
end.
%%--------------------------------------------------------------------
%% Client -> Broker: PUBREL
%%--------------------------------------------------------------------
-spec(pubrel(emqx_types:packet_id(), session())
-> {ok, session()} | {error, emqx_types:reason_code()}).
pubrel(PacketId, Session = #session{awaiting_rel = AwaitingRel}) ->
case maps:take(PacketId, AwaitingRel) of
{_Ts, AwaitingRel1} ->
{ok, Session#session{awaiting_rel = AwaitingRel1}};
error ->
{error, ?RC_PACKET_IDENTIFIER_NOT_FOUND}
end.
%%--------------------------------------------------------------------
%% Client -> Broker: PUBCOMP
%%--------------------------------------------------------------------
-spec(pubcomp(emqx_types:packet_id(), session())
-> {ok, session()} | {ok, list(publish()), session()}
| {error, emqx_types:reason_code()}).
pubcomp(PacketId, Session = #session{inflight = Inflight}) ->
case emqx_inflight:contain(PacketId, Inflight) of
true ->
Inflight1 = emqx_inflight:delete(PacketId, Inflight),
dequeue(Session#session{inflight = Inflight1});
false ->
{error, ?RC_PACKET_IDENTIFIER_NOT_FOUND}
end.
%%--------------------------------------------------------------------
%% Dequeue Msgs
%%--------------------------------------------------------------------
dequeue(Session = #session{inflight = Inflight, mqueue = Q}) ->
case emqx_mqueue:is_empty(Q) of
true -> {ok, Session};
false ->
{Msgs, Q1} = dequeue(batch_n(Inflight), [], Q),
deliver(lists:reverse(Msgs), [], Session#session{mqueue = Q1})
end.
dequeue(Cnt, Msgs, Q) when Cnt =< 0 ->
{Msgs, Q};
dequeue(Cnt, Msgs, Q) ->
case emqx_mqueue:out(Q) of
{empty, _Q} -> {Msgs, Q};
{{value, Msg}, Q1} ->
case emqx_message:is_expired(Msg) of
true ->
ok = emqx_metrics:inc('messages.expired'),
dequeue(Cnt-1, Msgs, Q1);
false ->
dequeue(Cnt-1, [Msg|Msgs], Q1)
end
end.
batch_n(Inflight) ->
case emqx_inflight:max_size(Inflight) of
0 -> ?DEFAULT_BATCH_N;
Sz -> Sz - emqx_inflight:size(Inflight)
end.
%%--------------------------------------------------------------------
%% Broker -> Client: Publish | Msg
%%--------------------------------------------------------------------
deliver(Delivers, Session = #session{subscriptions = Subs})
when is_list(Delivers) ->
Msgs = [enrich_subopt(get_subopts(Topic, Subs), Msg, Session)
|| {deliver, Topic, Msg} <- Delivers],
deliver(Msgs, [], Session).
deliver([], Publishes, Session) ->
{ok, lists:reverse(Publishes), Session};
deliver([Msg = #message{qos = ?QOS_0}|More], Acc, Session) ->
deliver(More, [{publish, undefined, Msg}|Acc], Session);
deliver([Msg = #message{qos = QoS}|More], Acc,
Session = #session{next_pkt_id = PacketId, inflight = Inflight})
when QoS =:= ?QOS_1 orelse QoS =:= ?QOS_2 ->
case emqx_inflight:is_full(Inflight) of
true ->
deliver(More, Acc, enqueue(Msg, Session));
false ->
Publish = {publish, PacketId, Msg},
Session1 = await(PacketId, Msg, Session),
deliver(More, [Publish|Acc], next_pkt_id(Session1))
end.
enqueue(Delivers, Session = #session{subscriptions = Subs}) when is_list(Delivers) ->
Msgs = [enrich_subopt(get_subopts(Topic, Subs), Msg, Session)
|| {deliver, Topic, Msg} <- Delivers],
lists:foldl(fun enqueue/2, Session, Msgs);
enqueue(Msg, Session = #session{mqueue = Q})
when is_record(Msg, message) ->
{Dropped, NewQ} = emqx_mqueue:in(Msg, Q),
if is_record(Dropped, message) ->
?LOG(warning, "Dropped msg due to mqueue is full: ~s",
[emqx_message:format(Dropped)]);
true -> ok
end,
inc_deliver_stats(enqueue_cnt, Session#session{mqueue = NewQ}).
%%--------------------------------------------------------------------
%% Awaiting ACK for QoS1/QoS2 Messages
%%--------------------------------------------------------------------
await(PacketId, Msg, Session = #session{inflight = Inflight}) ->
Inflight1 = emqx_inflight:insert(PacketId, {Msg, os:timestamp()}, Inflight),
Session#session{inflight = Inflight1}.
get_subopts(Topic, SubMap) ->
case maps:find(Topic, SubMap) of
{ok, #{nl := Nl, qos := QoS, rap := Rap, subid := SubId}} ->
[{nl, Nl}, {qos, QoS}, {rap, Rap}, {subid, SubId}];
{ok, #{nl := Nl, qos := QoS, rap := Rap}} ->
[{nl, Nl}, {qos, QoS}, {rap, Rap}];
error -> []
end.
enrich_subopt([], Msg, _Session) -> Msg;
enrich_subopt([{nl, 1}|Opts], Msg, Session) ->
enrich_subopt(Opts, emqx_message:set_flag(nl, Msg), Session);
enrich_subopt([{nl, 0}|Opts], Msg, Session) ->
enrich_subopt(Opts, Msg, Session);
enrich_subopt([{qos, SubQoS}|Opts], Msg = #message{qos = PubQoS},
Session = #session{upgrade_qos= true}) ->
enrich_subopt(Opts, Msg#message{qos = max(SubQoS, PubQoS)}, Session);
enrich_subopt([{qos, SubQoS}|Opts], Msg = #message{qos = PubQoS},
Session = #session{upgrade_qos= false}) ->
enrich_subopt(Opts, Msg#message{qos = min(SubQoS, PubQoS)}, Session);
enrich_subopt([{rap, _}|Opts], Msg = #message{headers = #{retained := true}}, Session) ->
enrich_subopt(Opts, emqx_message:set_flag(retain, true, Msg), Session);
enrich_subopt([{rap, 0}|Opts], Msg, Session) ->
enrich_subopt(Opts, emqx_message:set_flag(retain, false, Msg), Session);
enrich_subopt([{rap, 1}|Opts], Msg, Session) ->
enrich_subopt(Opts, Msg, Session);
enrich_subopt([{subid, SubId}|Opts], Msg, Session) ->
Msg1 = emqx_message:set_header('Subscription-Identifier', SubId, Msg),
enrich_subopt(Opts, Msg1, Session).
%%--------------------------------------------------------------------
%% Retry Delivery
%%--------------------------------------------------------------------
%% Redeliver at once if force is true
retry(Session = #session{inflight = Inflight}) ->
case emqx_inflight:is_empty(Inflight) of
true -> {ok, Session};
false ->
SortFun = fun({_, {_, Ts1}}, {_, {_, Ts2}}) -> Ts1 < Ts2 end,
Msgs = lists:sort(SortFun, emqx_inflight:to_list(Inflight)),
retry_delivery(Msgs, os:timestamp(), [], Session)
end.
retry_delivery([], _Now, Acc, Session) ->
%% Retry again...
{ok, lists:reverse(Acc), Session};
retry_delivery([{PacketId, {Val, Ts}}|More], Now, Acc,
Session = #session{retry_interval = Interval,
inflight = Inflight}) ->
%% Microseconds -> MilliSeconds
Age = timer:now_diff(Now, Ts) div 1000,
if
Age >= Interval ->
{Acc1, Inflight1} = retry_delivery(PacketId, Val, Now, Acc, Inflight),
retry_delivery(More, Now, Acc1, Session#session{inflight = Inflight1});
true ->
{ok, lists:reverse(Acc), Interval - max(0, Age), Session}
end.
retry_delivery(PacketId, Msg, Now, Acc, Inflight) when is_record(Msg, message) ->
case emqx_message:is_expired(Msg) of
true ->
ok = emqx_metrics:inc('messages.expired'),
{Acc, emqx_inflight:delete(PacketId, Inflight)};
false ->
Msg1 = emqx_message:set_flag(dup, true, Msg),
{[{publish, PacketId, Msg1}|Acc],
emqx_inflight:update(PacketId, {Msg1, Now}, Inflight)}
end;
retry_delivery(PacketId, pubrel, Now, Acc, Inflight) ->
Inflight1 = emqx_inflight:update(PacketId, {pubrel, Now}, Inflight),
{[{pubrel, PacketId}|Acc], Inflight1}.
%%--------------------------------------------------------------------
%% Expire Awaiting Rel
%%--------------------------------------------------------------------
expire(awaiting_rel, Session = #session{awaiting_rel = AwaitingRel}) ->
case maps:size(AwaitingRel) of
0 -> {ok, Session};
_ ->
AwaitingRel1 = lists:keysort(2, maps:to_list(AwaitingRel)),
expire_awaiting_rel(AwaitingRel1, os:timestamp(), Session)
end.
expire_awaiting_rel([], _Now, Session) ->
{ok, Session};
expire_awaiting_rel([{PacketId, Ts} | More], Now,
Session = #session{awaiting_rel = AwaitingRel,
awaiting_rel_timeout = Timeout}) ->
case (timer:now_diff(Now, Ts) div 1000) of
Age when Age >= Timeout ->
ok = emqx_metrics:inc('messages.qos2.expired'),
?LOG(warning, "Dropped qos2 packet ~s for awaiting_rel_timeout", [PacketId]),
Session1 = Session#session{awaiting_rel = maps:remove(PacketId, AwaitingRel)},
expire_awaiting_rel(More, Now, Session1);
Age ->
{ok, Timeout - max(0, Age), Session}
end.
%%--------------------------------------------------------------------
%% Next Packet Id
%%--------------------------------------------------------------------
next_pkt_id(Session = #session{next_pkt_id = 16#FFFF}) ->
Session#session{next_pkt_id = 1};
next_pkt_id(Session = #session{next_pkt_id = Id}) ->
Session#session{next_pkt_id = Id + 1}.
%%--------------------------------------------------------------------
%% Helper functions
%%--------------------------------------------------------------------
inc_deliver_stats(Key, Session) ->
inc_deliver_stats(Key, 1, Session).
inc_deliver_stats(Key, I, Session = #session{deliver_stats = undefined}) ->
Session#session{deliver_stats = #{Key => I}};
inc_deliver_stats(Key, I, Session = #session{deliver_stats = Stats}) ->
NStats = maps:update_with(Key, fun(V) -> V+I end, I, Stats),
Session#session{deliver_stats = NStats}.