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emqx_persistent_session_ds.erl
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emqx_persistent_session_ds.erl
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%%--------------------------------------------------------------------
%% Copyright (c) 2021-2024 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.
%%--------------------------------------------------------------------
-module(emqx_persistent_session_ds).
-behaviour(emqx_session).
-include("emqx.hrl").
-include_lib("emqx/include/logger.hrl").
-include_lib("snabbkaffe/include/trace.hrl").
-include_lib("stdlib/include/ms_transform.hrl").
-include("emqx_mqtt.hrl").
-include("emqx_persistent_session_ds.hrl").
-ifdef(TEST).
-include_lib("proper/include/proper.hrl").
-include_lib("eunit/include/eunit.hrl").
-endif.
%% Session API
-export([
create/3,
open/3,
destroy/1
]).
-export([
info/2,
stats/1
]).
-export([
subscribe/3,
unsubscribe/2,
get_subscription/2
]).
-export([
publish/3,
puback/3,
pubrec/2,
pubrel/2,
pubcomp/3
]).
-export([
deliver/3,
replay/3,
handle_timeout/3,
disconnect/2,
terminate/2
]).
%% Managment APIs:
-export([
list_client_subscriptions/1
]).
%% session table operations
-export([create_tables/0, sync/1]).
%% internal export used by session GC process
-export([destroy_session/1]).
%% Remove me later (satisfy checks for an unused BPAPI)
-export([
do_open_iterator/3,
do_ensure_iterator_closed/1,
do_ensure_all_iterators_closed/1
]).
-export([print_session/1, seqno_diff/4]).
-ifdef(TEST).
-export([
session_open/2,
list_all_sessions/0
]).
-endif.
-export_type([
id/0,
seqno/0,
timestamp/0,
topic_filter/0,
subscription_id/0,
subscription/0,
session/0,
stream_state/0
]).
-type seqno() :: non_neg_integer().
%% Currently, this is the clientid. We avoid `emqx_types:clientid()' because that can be
%% an atom, in theory (?).
-type id() :: binary().
-type topic_filter() :: emqx_types:topic().
-type subscription_id() :: integer().
-type subscription() :: #{
id := subscription_id(),
start_time := emqx_ds:time(),
props := map(),
deleted := boolean()
}.
-define(TIMER_PULL, timer_pull).
-define(TIMER_GET_STREAMS, timer_get_streams).
-define(TIMER_BUMP_LAST_ALIVE_AT, timer_bump_last_alive_at).
-type timer() :: ?TIMER_PULL | ?TIMER_GET_STREAMS | ?TIMER_BUMP_LAST_ALIVE_AT.
-type session() :: #{
%% Client ID
id := id(),
%% Configuration:
props := map(),
%% Persistent state:
s := emqx_persistent_session_ds_state:t(),
%% Buffer:
inflight := emqx_persistent_session_ds_inflight:t(),
%% Timers:
timer() => reference()
}.
-record(req_sync, {
from :: pid(),
ref :: reference()
}).
-type stream_state() :: #srs{}.
-type timestamp() :: emqx_utils_calendar:epoch_millisecond().
-type millisecond() :: non_neg_integer().
-type clientinfo() :: emqx_types:clientinfo().
-type conninfo() :: emqx_session:conninfo().
-type replies() :: emqx_session:replies().
-define(STATS_KEYS, [
subscriptions_cnt,
subscriptions_max,
inflight_cnt,
inflight_max,
mqueue_len,
mqueue_dropped
]).
%%
-spec create(clientinfo(), conninfo(), emqx_session:conf()) ->
session().
create(#{clientid := ClientID}, ConnInfo, Conf) ->
ensure_timers(session_ensure_new(ClientID, ConnInfo, Conf)).
-spec open(clientinfo(), conninfo(), emqx_session:conf()) ->
{_IsPresent :: true, session(), []} | false.
open(#{clientid := ClientID} = _ClientInfo, ConnInfo, Conf) ->
%% NOTE
%% The fact that we need to concern about discarding all live channels here
%% is essentially a consequence of the in-memory session design, where we
%% have disconnected channels holding onto session state. Ideally, we should
%% somehow isolate those idling not-yet-expired sessions into a separate process
%% space, and move this call back into `emqx_cm` where it belongs.
ok = emqx_cm:discard_session(ClientID),
case session_open(ClientID, ConnInfo) of
Session0 = #{} ->
Session = Session0#{props => Conf},
{true, ensure_timers(Session), []};
false ->
false
end.
-spec destroy(session() | clientinfo()) -> ok.
destroy(#{id := ClientID}) ->
destroy_session(ClientID);
destroy(#{clientid := ClientID}) ->
destroy_session(ClientID).
destroy_session(ClientID) ->
session_drop(ClientID, destroy).
%%--------------------------------------------------------------------
%% Info, Stats
%%--------------------------------------------------------------------
info(Keys, Session) when is_list(Keys) ->
[{Key, info(Key, Session)} || Key <- Keys];
info(id, #{id := ClientID}) ->
ClientID;
info(clientid, #{id := ClientID}) ->
ClientID;
info(created_at, #{s := S}) ->
emqx_persistent_session_ds_state:get_created_at(S);
info(is_persistent, #{}) ->
true;
info(subscriptions, #{s := S}) ->
emqx_persistent_session_ds_subs:to_map(S);
info(subscriptions_cnt, #{s := S}) ->
emqx_topic_gbt:size(emqx_persistent_session_ds_state:get_subscriptions(S));
info(subscriptions_max, #{props := Conf}) ->
maps:get(max_subscriptions, Conf);
info(upgrade_qos, #{props := Conf}) ->
maps:get(upgrade_qos, Conf);
info(inflight, #{inflight := Inflight}) ->
Inflight;
info(inflight_cnt, #{inflight := Inflight}) ->
emqx_persistent_session_ds_inflight:n_inflight(Inflight);
info(inflight_max, #{inflight := Inflight}) ->
emqx_persistent_session_ds_inflight:receive_maximum(Inflight);
info(retry_interval, #{props := Conf}) ->
maps:get(retry_interval, Conf);
% info(mqueue, #sessmem{mqueue = MQueue}) ->
% MQueue;
info(mqueue_len, #{inflight := Inflight}) ->
emqx_persistent_session_ds_inflight:n_buffered(all, Inflight);
% info(mqueue_max, #sessmem{mqueue = MQueue}) ->
% emqx_mqueue:max_len(MQueue);
info(mqueue_dropped, _Session) ->
0;
%% info(next_pkt_id, #{s := S}) ->
%% {PacketId, _} = emqx_persistent_message_ds_replayer:next_packet_id(S),
%% PacketId;
% info(awaiting_rel, #sessmem{awaiting_rel = AwaitingRel}) ->
% AwaitingRel;
%% info(awaiting_rel_cnt, #{s := S}) ->
%% seqno_diff(?QOS_2, ?rec, ?committed(?QOS_2), S);
info(awaiting_rel_max, #{props := Conf}) ->
maps:get(max_awaiting_rel, Conf);
info(await_rel_timeout, #{props := _Conf}) ->
%% TODO: currently this setting is ignored:
%% maps:get(await_rel_timeout, Conf).
0.
-spec stats(session()) -> emqx_types:stats().
stats(Session) ->
info(?STATS_KEYS, Session).
%% Used by management API
-spec print_session(emqx_types:clientid()) -> map() | undefined.
print_session(ClientId) ->
case try_get_live_session(ClientId) of
{Pid, SessionState} ->
maps:update_with(
s, fun emqx_persistent_session_ds_state:format/1, SessionState#{
'_alive' => {true, Pid}
}
);
not_found ->
case emqx_persistent_session_ds_state:print_session(ClientId) of
undefined ->
undefined;
S ->
#{s => S, '_alive' => false}
end;
not_persistent ->
undefined
end.
%%--------------------------------------------------------------------
%% Client -> Broker: SUBSCRIBE / UNSUBSCRIBE
%%--------------------------------------------------------------------
-spec subscribe(topic_filter(), emqx_types:subopts(), session()) ->
{ok, session()} | {error, emqx_types:reason_code()}.
subscribe(
TopicFilter,
SubOpts,
Session = #{id := ID, s := S0}
) ->
case emqx_persistent_session_ds_subs:lookup(TopicFilter, S0) of
undefined ->
%% TODO: max subscriptions
%% N.B.: we chose to update the router before adding the
%% subscription to the session/iterator table. The
%% reasoning for this is as follows:
%%
%% Messages matching this topic filter should start to be
%% persisted as soon as possible to avoid missing
%% messages. If this is the first such persistent session
%% subscription, it's important to do so early on.
%%
%% This could, in turn, lead to some inconsistency: if
%% such a route gets created but the session/iterator data
%% fails to be updated accordingly, we have a dangling
%% route. To remove such dangling routes, we may have a
%% periodic GC process that removes routes that do not
%% have a matching persistent subscription. Also, route
%% operations use dirty mnesia operations, which
%% inherently have room for inconsistencies.
%%
%% In practice, we use the iterator reference table as a
%% source of truth, since it is guarded by a transaction
%% context: we consider a subscription operation to be
%% successful if it ended up changing this table. Both
%% router and iterator information can be reconstructed
%% from this table, if needed.
ok = emqx_persistent_session_ds_router:do_add_route(TopicFilter, ID),
{SubId, S1} = emqx_persistent_session_ds_state:new_id(S0),
Subscription = #{
start_time => now_ms(),
props => SubOpts,
id => SubId,
deleted => false
},
IsNew = true;
Subscription0 = #{} ->
Subscription = Subscription0#{props => SubOpts},
IsNew = false,
S1 = S0
end,
S = emqx_persistent_session_ds_subs:on_subscribe(TopicFilter, Subscription, S1),
?tp(persistent_session_ds_subscription_added, #{
topic_filter => TopicFilter, sub => Subscription, is_new => IsNew
}),
{ok, Session#{s => S}}.
-spec unsubscribe(topic_filter(), session()) ->
{ok, session(), emqx_types:subopts()} | {error, emqx_types:reason_code()}.
unsubscribe(
TopicFilter,
Session = #{id := ID, s := S0}
) ->
case emqx_persistent_session_ds_subs:lookup(TopicFilter, S0) of
undefined ->
{error, ?RC_NO_SUBSCRIPTION_EXISTED};
Subscription = #{props := SubOpts} ->
S = do_unsubscribe(ID, TopicFilter, Subscription, S0),
{ok, Session#{s => S}, SubOpts}
end.
-spec do_unsubscribe(id(), topic_filter(), subscription(), emqx_persistent_session_ds_state:t()) ->
emqx_persistent_session_ds_state:t().
do_unsubscribe(SessionId, TopicFilter, Subscription = #{id := SubId}, S0) ->
S1 = emqx_persistent_session_ds_subs:on_unsubscribe(TopicFilter, Subscription, S0),
?tp(persistent_session_ds_subscription_delete, #{
session_id => SessionId, topic_filter => TopicFilter
}),
S = emqx_persistent_session_ds_stream_scheduler:on_unsubscribe(SubId, S1),
?tp_span(
persistent_session_ds_subscription_route_delete,
#{session_id => SessionId, topic_filter => TopicFilter},
ok = emqx_persistent_session_ds_router:do_delete_route(TopicFilter, SessionId)
),
S.
-spec get_subscription(topic_filter(), session()) ->
emqx_types:subopts() | undefined.
get_subscription(TopicFilter, #{s := S}) ->
case emqx_persistent_session_ds_subs:lookup(TopicFilter, S) of
_Subscription = #{props := SubOpts} ->
SubOpts;
undefined ->
undefined
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, Session) ->
%% TODO: QoS2
Result = emqx_broker:publish(Msg),
{ok, Result, Session}.
%%--------------------------------------------------------------------
%% Client -> Broker: PUBACK
%%--------------------------------------------------------------------
-spec puback(clientinfo(), emqx_types:packet_id(), session()) ->
{ok, emqx_types:message(), replies(), session()}
| {error, emqx_types:reason_code()}.
puback(_ClientInfo, PacketId, Session0) ->
case update_seqno(puback, PacketId, Session0) of
{ok, Msg, Session} ->
{ok, Msg, [], pull_now(Session)};
Error ->
Error
end.
%%--------------------------------------------------------------------
%% Client -> Broker: PUBREC
%%--------------------------------------------------------------------
-spec pubrec(emqx_types:packet_id(), session()) ->
{ok, emqx_types:message(), session()}
| {error, emqx_types:reason_code()}.
pubrec(PacketId, Session0) ->
case update_seqno(pubrec, PacketId, Session0) of
{ok, Msg, Session} ->
{ok, Msg, Session};
Error = {error, _} ->
Error
end.
%%--------------------------------------------------------------------
%% Client -> Broker: PUBREL
%%--------------------------------------------------------------------
-spec pubrel(emqx_types:packet_id(), session()) ->
{ok, session()} | {error, emqx_types:reason_code()}.
pubrel(_PacketId, Session = #{}) ->
% TODO: stub
{ok, Session}.
%%--------------------------------------------------------------------
%% Client -> Broker: PUBCOMP
%%--------------------------------------------------------------------
-spec pubcomp(clientinfo(), emqx_types:packet_id(), session()) ->
{ok, emqx_types:message(), replies(), session()}
| {error, emqx_types:reason_code()}.
pubcomp(_ClientInfo, PacketId, Session0) ->
case update_seqno(pubcomp, PacketId, Session0) of
{ok, Msg, Session} ->
{ok, Msg, [], pull_now(Session)};
Error = {error, _} ->
Error
end.
%%--------------------------------------------------------------------
-spec deliver(clientinfo(), [emqx_types:deliver()], session()) ->
{ok, replies(), session()}.
deliver(ClientInfo, Delivers, Session0) ->
%% Durable sessions still have to handle some transient messages.
%% For example, retainer sends messages to the session directly.
Session = lists:foldl(
fun(Msg, Acc) -> enqueue_transient(ClientInfo, Msg, Acc) end, Session0, Delivers
),
{ok, [], pull_now(Session)}.
-spec handle_timeout(clientinfo(), _Timeout, session()) ->
{ok, replies(), session()} | {ok, replies(), timeout(), session()}.
handle_timeout(
ClientInfo,
?TIMER_PULL,
Session0
) ->
{Publishes, Session1} = drain_buffer(fetch_new_messages(Session0, ClientInfo)),
Timeout =
case Publishes of
[] ->
emqx_config:get([session_persistence, idle_poll_interval]);
[_ | _] ->
0
end,
Session = emqx_session:ensure_timer(?TIMER_PULL, Timeout, Session1),
{ok, Publishes, Session};
handle_timeout(_ClientInfo, ?TIMER_GET_STREAMS, Session0 = #{s := S0}) ->
S1 = emqx_persistent_session_ds_subs:gc(S0),
S = emqx_persistent_session_ds_stream_scheduler:renew_streams(S1),
Interval = emqx_config:get([session_persistence, renew_streams_interval]),
Session = emqx_session:ensure_timer(
?TIMER_GET_STREAMS,
Interval,
Session0#{s => S}
),
{ok, [], Session};
handle_timeout(_ClientInfo, ?TIMER_BUMP_LAST_ALIVE_AT, Session0 = #{s := S0}) ->
S = emqx_persistent_session_ds_state:commit(bump_last_alive(S0)),
Session = emqx_session:ensure_timer(
?TIMER_BUMP_LAST_ALIVE_AT,
bump_interval(),
Session0#{s => S}
),
{ok, [], Session};
handle_timeout(_ClientInfo, #req_sync{from = From, ref = Ref}, Session = #{s := S0}) ->
S = emqx_persistent_session_ds_state:commit(S0),
From ! Ref,
{ok, [], Session#{s => S}};
handle_timeout(_ClientInfo, Timeout, Session) ->
?SLOG(warning, #{msg => "unknown_ds_timeout", timeout => Timeout}),
{ok, [], Session}.
bump_last_alive(S0) ->
%% Note: we take a pessimistic approach here and assume that the client will be alive
%% until the next bump timeout. With this, we avoid garbage collecting this session
%% too early in case the session/connection/node crashes earlier without having time
%% to commit the time.
EstimatedLastAliveAt = now_ms() + bump_interval(),
emqx_persistent_session_ds_state:set_last_alive_at(EstimatedLastAliveAt, S0).
-spec replay(clientinfo(), [], session()) ->
{ok, replies(), session()}.
replay(ClientInfo, [], Session0 = #{s := S0}) ->
Streams = emqx_persistent_session_ds_stream_scheduler:find_replay_streams(S0),
Session = lists:foldl(
fun({_StreamKey, Stream}, SessionAcc) ->
replay_batch(Stream, SessionAcc, ClientInfo)
end,
Session0,
Streams
),
%% Note: we filled the buffer with the historical messages, and
%% from now on we'll rely on the normal inflight/flow control
%% mechanisms to replay them:
{ok, [], pull_now(Session)}.
-spec replay_batch(stream_state(), session(), clientinfo()) -> session().
replay_batch(Srs0, Session, ClientInfo) ->
#srs{batch_size = BatchSize} = Srs0,
%% TODO: retry on errors:
{Srs, Inflight} = enqueue_batch(true, BatchSize, Srs0, Session, ClientInfo),
%% Assert:
Srs =:= Srs0 orelse
?tp(warning, emqx_persistent_session_ds_replay_inconsistency, #{
expected => Srs0,
got => Srs
}),
Session#{inflight => Inflight}.
%%--------------------------------------------------------------------
-spec disconnect(session(), emqx_types:conninfo()) -> {shutdown, session()}.
disconnect(Session = #{s := S0}, ConnInfo) ->
S1 = emqx_persistent_session_ds_state:set_last_alive_at(now_ms(), S0),
S2 =
case ConnInfo of
#{expiry_interval := EI} when is_number(EI) ->
emqx_persistent_session_ds_state:set_expiry_interval(EI, S1);
_ ->
S1
end,
S = emqx_persistent_session_ds_state:commit(S2),
{shutdown, Session#{s => S}}.
-spec terminate(Reason :: term(), session()) -> ok.
terminate(_Reason, _Session = #{id := Id, s := S}) ->
_ = emqx_persistent_session_ds_state:commit(S),
?tp(debug, persistent_session_ds_terminate, #{id => Id}),
ok.
%%--------------------------------------------------------------------
%% Management APIs (dashboard)
%%--------------------------------------------------------------------
-spec list_client_subscriptions(emqx_types:clientid()) ->
{node() | undefined, [{emqx_types:topic() | emqx_types:share(), emqx_types:subopts()}]}
| {error, not_found}.
list_client_subscriptions(ClientId) ->
case emqx_persistent_message:is_persistence_enabled() of
true ->
%% TODO: this is not the most optimal implementation, since it
%% should be possible to avoid reading extra data (streams, etc.)
case print_session(ClientId) of
Sess = #{s := #{subscriptions := Subs}} ->
Node =
case Sess of
#{'_alive' := {true, Pid}} ->
node(Pid);
_ ->
undefined
end,
SubList =
maps:fold(
fun(Topic, #{props := SubProps}, Acc) ->
Elem = {Topic, SubProps},
[Elem | Acc]
end,
[],
Subs
),
{Node, SubList};
undefined ->
{error, not_found}
end;
false ->
{error, not_found}
end.
%%--------------------------------------------------------------------
%% Session tables operations
%%--------------------------------------------------------------------
create_tables() ->
emqx_persistent_session_ds_state:create_tables().
%% @doc Force syncing of the transient state to persistent storage
sync(ClientId) ->
case emqx_cm:lookup_channels(ClientId) of
[Pid] ->
Ref = monitor(process, Pid),
Pid ! {emqx_session, #req_sync{from = self(), ref = Ref}},
receive
{'DOWN', Ref, process, _Pid, Reason} ->
{error, Reason};
Ref ->
demonitor(Ref, [flush]),
ok
end;
[] ->
{error, noproc}
end.
%% @doc Called when a client connects. This function looks up a
%% session or returns `false` if previous one couldn't be found.
%%
%% Note: session API doesn't handle session takeovers, it's the job of
%% the broker.
-spec session_open(id(), emqx_types:conninfo()) ->
session() | false.
session_open(SessionId, NewConnInfo) ->
NowMS = now_ms(),
case emqx_persistent_session_ds_state:open(SessionId) of
{ok, S0} ->
EI = emqx_persistent_session_ds_state:get_expiry_interval(S0),
LastAliveAt = emqx_persistent_session_ds_state:get_last_alive_at(S0),
case NowMS >= LastAliveAt + EI of
true ->
session_drop(SessionId, expired),
false;
false ->
?tp(open_session, #{ei => EI, now => NowMS, laa => LastAliveAt}),
%% New connection being established
S1 = emqx_persistent_session_ds_state:set_expiry_interval(EI, S0),
S2 = emqx_persistent_session_ds_state:set_last_alive_at(NowMS, S1),
S = emqx_persistent_session_ds_state:commit(S2),
Inflight = emqx_persistent_session_ds_inflight:new(
receive_maximum(NewConnInfo)
),
#{
id => SessionId,
s => S,
inflight => Inflight,
props => #{}
}
end;
undefined ->
false
end.
-spec session_ensure_new(id(), emqx_types:conninfo(), emqx_session:conf()) ->
session().
session_ensure_new(Id, ConnInfo, Conf) ->
?tp(debug, persistent_session_ds_ensure_new, #{id => Id}),
Now = now_ms(),
S0 = emqx_persistent_session_ds_state:create_new(Id),
S1 = emqx_persistent_session_ds_state:set_expiry_interval(expiry_interval(ConnInfo), S0),
S2 = bump_last_alive(S1),
S3 = emqx_persistent_session_ds_state:set_created_at(Now, S2),
S4 = lists:foldl(
fun(Track, Acc) ->
emqx_persistent_session_ds_state:put_seqno(Track, 0, Acc)
end,
S3,
[
?next(?QOS_1),
?dup(?QOS_1),
?committed(?QOS_1),
?next(?QOS_2),
?dup(?QOS_2),
?rec,
?committed(?QOS_2)
]
),
S = emqx_persistent_session_ds_state:commit(S4),
#{
id => Id,
props => Conf,
s => S,
inflight => emqx_persistent_session_ds_inflight:new(receive_maximum(ConnInfo))
}.
%% @doc Called when a client reconnects with `clean session=true' or
%% during session GC
-spec session_drop(id(), _Reason) -> ok.
session_drop(ID, Reason) ->
case emqx_persistent_session_ds_state:open(ID) of
{ok, S0} ->
?tp(debug, drop_persistent_session, #{client_id => ID, reason => Reason}),
_S = emqx_persistent_session_ds_subs:fold(
fun(TopicFilter, Subscription, S) ->
do_unsubscribe(ID, TopicFilter, Subscription, S)
end,
S0,
S0
),
emqx_persistent_session_ds_state:delete(ID);
undefined ->
ok
end.
now_ms() ->
erlang:system_time(millisecond).
%%--------------------------------------------------------------------
%% RPC targets (v1)
%%--------------------------------------------------------------------
%% RPC target.
-spec do_open_iterator(emqx_types:words(), emqx_ds:time(), emqx_ds:iterator_id()) ->
{ok, emqx_ds_storage_layer:iterator()} | {error, _Reason}.
do_open_iterator(_TopicFilter, _StartMS, _IteratorID) ->
{error, not_implemented}.
%% RPC target.
-spec do_ensure_iterator_closed(emqx_ds:iterator_id()) -> ok.
do_ensure_iterator_closed(_IteratorID) ->
ok.
%% RPC target.
-spec do_ensure_all_iterators_closed(id()) -> ok.
do_ensure_all_iterators_closed(_DSSessionID) ->
ok.
%%--------------------------------------------------------------------
%% Normal replay:
%%--------------------------------------------------------------------
fetch_new_messages(Session = #{s := S}, ClientInfo) ->
Streams = emqx_persistent_session_ds_stream_scheduler:find_new_streams(S),
fetch_new_messages(Streams, Session, ClientInfo).
fetch_new_messages([], Session, _ClientInfo) ->
Session;
fetch_new_messages([I | Streams], Session0 = #{inflight := Inflight}, ClientInfo) ->
BatchSize = emqx_config:get([session_persistence, batch_size]),
case emqx_persistent_session_ds_inflight:n_buffered(all, Inflight) >= BatchSize of
true ->
%% Buffer is full:
Session0;
false ->
Session = new_batch(I, BatchSize, Session0, ClientInfo),
fetch_new_messages(Streams, Session, ClientInfo)
end.
new_batch({StreamKey, Srs0}, BatchSize, Session = #{s := S0}, ClientInfo) ->
SN1 = emqx_persistent_session_ds_state:get_seqno(?next(?QOS_1), S0),
SN2 = emqx_persistent_session_ds_state:get_seqno(?next(?QOS_2), S0),
Srs1 = Srs0#srs{
first_seqno_qos1 = SN1,
first_seqno_qos2 = SN2,
batch_size = 0,
last_seqno_qos1 = SN1,
last_seqno_qos2 = SN2
},
{Srs, Inflight} = enqueue_batch(false, BatchSize, Srs1, Session, ClientInfo),
S1 = emqx_persistent_session_ds_state:put_seqno(?next(?QOS_1), Srs#srs.last_seqno_qos1, S0),
S2 = emqx_persistent_session_ds_state:put_seqno(?next(?QOS_2), Srs#srs.last_seqno_qos2, S1),
S = emqx_persistent_session_ds_state:put_stream(StreamKey, Srs, S2),
Session#{s => S, inflight => Inflight}.
enqueue_batch(IsReplay, BatchSize, Srs0, Session = #{inflight := Inflight0}, ClientInfo) ->
#srs{
it_begin = ItBegin0,
it_end = ItEnd0,
first_seqno_qos1 = FirstSeqnoQos1,
first_seqno_qos2 = FirstSeqnoQos2
} = Srs0,
ItBegin =
case IsReplay of
true -> ItBegin0;
false -> ItEnd0
end,
case emqx_ds:next(?PERSISTENT_MESSAGE_DB, ItBegin, BatchSize) of
{ok, ItEnd, Messages} ->
{Inflight, LastSeqnoQos1, LastSeqnoQos2} = process_batch(
IsReplay, Session, ClientInfo, FirstSeqnoQos1, FirstSeqnoQos2, Messages, Inflight0
),
Srs = Srs0#srs{
it_begin = ItBegin,
it_end = ItEnd,
%% TODO: it should be possible to avoid calling
%% length here by diffing size of inflight before
%% and after inserting messages:
batch_size = length(Messages),
last_seqno_qos1 = LastSeqnoQos1,
last_seqno_qos2 = LastSeqnoQos2
},
{Srs, Inflight};
{ok, end_of_stream} ->
%% No new messages; just update the end iterator:
{Srs0#srs{it_begin = ItBegin, it_end = end_of_stream, batch_size = 0}, Inflight0};
{error, _} when not IsReplay ->
?SLOG(info, #{msg => "failed_to_fetch_batch", iterator => ItBegin}),
{Srs0, Inflight0}
end.
%% key_of_iter(#{3 := #{3 := #{5 := K}}}) ->
%% K.
process_batch(_IsReplay, _Session, _ClientInfo, LastSeqNoQos1, LastSeqNoQos2, [], Inflight) ->
{Inflight, LastSeqNoQos1, LastSeqNoQos2};
process_batch(
IsReplay, Session, ClientInfo, FirstSeqNoQos1, FirstSeqNoQos2, [KV | Messages], Inflight0
) ->
#{s := S, props := #{upgrade_qos := UpgradeQoS}} = Session,
{_DsMsgKey, Msg0 = #message{topic = Topic}} = KV,
Comm1 = emqx_persistent_session_ds_state:get_seqno(?committed(?QOS_1), S),
Comm2 = emqx_persistent_session_ds_state:get_seqno(?committed(?QOS_2), S),
Dup1 = emqx_persistent_session_ds_state:get_seqno(?dup(?QOS_1), S),
Dup2 = emqx_persistent_session_ds_state:get_seqno(?dup(?QOS_2), S),
Rec = emqx_persistent_session_ds_state:get_seqno(?rec, S),
Subs = emqx_persistent_session_ds_state:get_subscriptions(S),
Msgs = [
Msg
|| SubMatch <- emqx_topic_gbt:matches(Topic, Subs, []),
Msg <- begin
#{props := SubOpts} = emqx_topic_gbt:get_record(SubMatch, Subs),
emqx_session:enrich_message(ClientInfo, Msg0, SubOpts, UpgradeQoS)
end
],
{Inflight, LastSeqNoQos1, LastSeqNoQos2} = lists:foldl(
fun(Msg = #message{qos = Qos}, {Acc, SeqNoQos10, SeqNoQos20}) ->
case Qos of
?QOS_0 ->
SeqNoQos1 = SeqNoQos10,
SeqNoQos2 = SeqNoQos20;
?QOS_1 ->
SeqNoQos1 = inc_seqno(?QOS_1, SeqNoQos10),
SeqNoQos2 = SeqNoQos20;
?QOS_2 ->
SeqNoQos1 = SeqNoQos10,
SeqNoQos2 = inc_seqno(?QOS_2, SeqNoQos20)
end,
{
case Qos of
?QOS_0 when IsReplay ->
%% We ignore QoS 0 messages during replay:
Acc;
?QOS_0 ->
emqx_persistent_session_ds_inflight:push({undefined, Msg}, Acc);
?QOS_1 when SeqNoQos1 =< Comm1 ->
%% QoS1 message has been acked by the client, ignore:
Acc;
?QOS_1 when SeqNoQos1 =< Dup1 ->
%% QoS1 message has been sent but not
%% acked. Retransmit:
Msg1 = emqx_message:set_flag(dup, true, Msg),
emqx_persistent_session_ds_inflight:push({SeqNoQos1, Msg1}, Acc);
?QOS_1 ->
emqx_persistent_session_ds_inflight:push({SeqNoQos1, Msg}, Acc);
?QOS_2 when SeqNoQos2 =< Comm2 ->
%% QoS2 message has been PUBCOMP'ed by the client, ignore:
Acc;
?QOS_2 when SeqNoQos2 =< Rec ->
%% QoS2 message has been PUBREC'ed by the client, resend PUBREL:
emqx_persistent_session_ds_inflight:push({pubrel, SeqNoQos2}, Acc);
?QOS_2 when SeqNoQos2 =< Dup2 ->
%% QoS2 message has been sent, but we haven't received PUBREC.
%%
%% TODO: According to the MQTT standard 4.3.3:
%% DUP flag is never set for QoS2 messages? We
%% do so for mem sessions, though.
Msg1 = emqx_message:set_flag(dup, true, Msg),
emqx_persistent_session_ds_inflight:push({SeqNoQos2, Msg1}, Acc);
?QOS_2 ->
emqx_persistent_session_ds_inflight:push({SeqNoQos2, Msg}, Acc)
end,
SeqNoQos1,
SeqNoQos2
}
end,
{Inflight0, FirstSeqNoQos1, FirstSeqNoQos2},
Msgs
),
process_batch(
IsReplay, Session, ClientInfo, LastSeqNoQos1, LastSeqNoQos2, Messages, Inflight
).
%%--------------------------------------------------------------------
%% Transient messages
%%--------------------------------------------------------------------
enqueue_transient(ClientInfo, Msg0, Session = #{s := S, props := #{upgrade_qos := UpgradeQoS}}) ->
%% TODO: Such messages won't be retransmitted, should the session
%% reconnect before transient messages are acked.
%%
%% Proper solution could look like this: session publishes
%% transient messages to a separate DS DB that serves as a queue,
%% then subscribes to a special system topic that contains the
%% queued messages. Since streams in this DB are exclusive to the
%% session, messages from the queue can be dropped as soon as they
%% are acked.
Subs = emqx_persistent_session_ds_state:get_subscriptions(S),
Msgs = [
Msg
|| SubMatch <- emqx_topic_gbt:matches(Msg0#message.topic, Subs, []),
Msg <- begin
#{props := SubOpts} = emqx_topic_gbt:get_record(SubMatch, Subs),
emqx_session:enrich_message(ClientInfo, Msg0, SubOpts, UpgradeQoS)
end
],
lists:foldl(fun do_enqueue_transient/2, Session, Msgs).
do_enqueue_transient(Msg = #message{qos = Qos}, Session = #{inflight := Inflight0, s := S0}) ->
case Qos of
?QOS_0 ->
S = S0,
Inflight = emqx_persistent_session_ds_inflight:push({undefined, Msg}, Inflight0);
QoS when QoS =:= ?QOS_1; QoS =:= ?QOS_2 ->
SeqNo = inc_seqno(
QoS, emqx_persistent_session_ds_state:get_seqno(?next(QoS), S0)
),
S = emqx_persistent_session_ds_state:put_seqno(?next(QoS), SeqNo, S0),
Inflight = emqx_persistent_session_ds_inflight:push({SeqNo, Msg}, Inflight0)
end,
Session#{
inflight => Inflight,
s => S
}.
%%--------------------------------------------------------------------
%% Buffer drain
%%--------------------------------------------------------------------
drain_buffer(Session = #{inflight := Inflight0, s := S0}) ->
{Publishes, Inflight, S} = do_drain_buffer(Inflight0, S0, []),
{Publishes, Session#{inflight => Inflight, s := S}}.
do_drain_buffer(Inflight0, S0, Acc) ->
case emqx_persistent_session_ds_inflight:pop(Inflight0) of
undefined ->
{lists:reverse(Acc), Inflight0, S0};
{{pubrel, SeqNo}, Inflight} ->
Publish = {pubrel, seqno_to_packet_id(?QOS_2, SeqNo)},
do_drain_buffer(Inflight, S0, [Publish | Acc]);
{{SeqNo, Msg}, Inflight} ->
case Msg#message.qos of
?QOS_0 ->
do_drain_buffer(Inflight, S0, [{undefined, Msg} | Acc]);
Qos ->
S = emqx_persistent_session_ds_state:put_seqno(?dup(Qos), SeqNo, S0),
Publish = {seqno_to_packet_id(Qos, SeqNo), Msg},
do_drain_buffer(Inflight, S, [Publish | Acc])
end
end.
%%--------------------------------------------------------------------------------
%% TODO: find a more reliable way to perform actions that have side
%% effects. Add `CBM:init' callback to the session behavior?
-spec ensure_timers(session()) -> session().
ensure_timers(Session0) ->
Session1 = emqx_session:ensure_timer(?TIMER_PULL, 100, Session0),
Session2 = emqx_session:ensure_timer(?TIMER_GET_STREAMS, 100, Session1),
emqx_session:ensure_timer(?TIMER_BUMP_LAST_ALIVE_AT, 100, Session2).
-spec pull_now(session()) -> session().
pull_now(Session) ->
emqx_session:reset_timer(?TIMER_PULL, 0, Session).
-spec receive_maximum(conninfo()) -> pos_integer().
receive_maximum(ConnInfo) ->
%% Note: the default value should be always set by the channel
%% with respect to the zone configuration, but the type spec
%% indicates that it's optional.
maps:get(receive_maximum, ConnInfo, 65_535).
-spec expiry_interval(conninfo()) -> millisecond().
expiry_interval(ConnInfo) ->
maps:get(expiry_interval, ConnInfo, 0).
bump_interval() ->
emqx_config:get([session_persistence, last_alive_update_interval]).
-spec try_get_live_session(emqx_types:clientid()) ->
{pid(), session()} | not_found | not_persistent.
try_get_live_session(ClientId) ->
case emqx_cm:lookup_channels(local, ClientId) of
[Pid] ->
try
#{channel := ChanState} = emqx_connection:get_state(Pid),
case emqx_channel:info(impl, ChanState) of
?MODULE ->
{Pid, emqx_channel:info(session_state, ChanState)};
_ ->
not_persistent
end
catch
_:_ ->
not_found
end;
_ ->
not_found
end.
%%--------------------------------------------------------------------
%% SeqNo tracking
%% --------------------------------------------------------------------