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Auto widen session incoming-window in AMQP 1.0 client #13574

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Mar 19, 2025
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Auto widen session incoming-window in AMQP 1.0 client #13574

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4 changes: 2 additions & 2 deletions deps/amqp10_client/src/amqp10_client.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -339,7 +339,7 @@ flow_link_credit(#link_ref{role = receiver, session = Session,
RenewWhenBelow =< Credit) ->
Flow = #'v1_0.flow'{link_credit = {uint, Credit},
drain = Drain},
ok = amqp10_client_session:flow(Session, Handle, Flow, RenewWhenBelow).
ok = amqp10_client_session:flow_link(Session, Handle, Flow, RenewWhenBelow).

%% @doc Stop a receiving link.
%% See AMQP 1.0 spec §2.6.10.
Expand All @@ -348,7 +348,7 @@ stop_receiver_link(#link_ref{role = receiver,
link_handle = Handle}) ->
Flow = #'v1_0.flow'{link_credit = {uint, 0},
echo = true},
ok = amqp10_client_session:flow(Session, Handle, Flow, never).
ok = amqp10_client_session:flow_link(Session, Handle, Flow, never).

%%% messages

Expand Down
132 changes: 90 additions & 42 deletions deps/amqp10_client/src/amqp10_client_session.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -20,10 +20,13 @@
attach/2,
detach/2,
transfer/3,
flow/4,
disposition/5
disposition/5,
flow_link/4
]).

%% Manual session flow control is currently only used in tests.
-export([flow/3]).

%% Private API
-export([start_link/4,
socket_ready/2
Expand Down Expand Up @@ -51,7 +54,8 @@
[add/2,
diff/2]).

-define(MAX_SESSION_WINDOW_SIZE, 65535).
%% By default, we want to keep the server's remote-incoming-window large at all times.
-define(DEFAULT_MAX_INCOMING_WINDOW, 100_000).
-define(UINT_OUTGOING_WINDOW, {uint, ?UINT_MAX}).
-define(INITIAL_OUTGOING_DELIVERY_ID, ?UINT_MAX).
%% "The next-outgoing-id MAY be initialized to an arbitrary value" [2.5.6]
Expand Down Expand Up @@ -129,7 +133,8 @@
available = 0 :: non_neg_integer(),
drain = false :: boolean(),
partial_transfers :: undefined | {#'v1_0.transfer'{}, [binary()]},
auto_flow :: never | {auto, RenewWhenBelow :: pos_integer(), Credit :: pos_integer()},
auto_flow :: never | {RenewWhenBelow :: pos_integer(),
Credit :: pos_integer()},
incoming_unsettled = #{} :: #{delivery_number() => ok},
footer_opt :: footer_opt() | undefined
}).
Expand All @@ -140,7 +145,10 @@

%% session flow control, see section 2.5.6
next_incoming_id :: transfer_number() | undefined,
incoming_window = ?MAX_SESSION_WINDOW_SIZE :: non_neg_integer(),
%% Can become negative if the peer overshoots our window.
incoming_window :: integer(),
auto_flow :: never | {RenewWhenBelow :: pos_integer(),
NewWindowSize :: pos_integer()},
next_outgoing_id = ?INITIAL_OUTGOING_TRANSFER_ID :: transfer_number(),
remote_incoming_window = 0 :: non_neg_integer(),
remote_outgoing_window = 0 :: non_neg_integer(),
Expand Down Expand Up @@ -200,7 +208,17 @@ transfer(Session, Amqp10Msg, Timeout) ->
[Transfer | Sections] = amqp10_msg:to_amqp_records(Amqp10Msg),
gen_statem:call(Session, {transfer, Transfer, Sections}, Timeout).

flow(Session, Handle, Flow, RenewWhenBelow) ->
-spec flow(pid(), non_neg_integer(), never | pos_integer()) -> ok.
flow(Session, IncomingWindow, RenewWhenBelow) when
%% Check that the RenewWhenBelow value make sense.
RenewWhenBelow =:= never orelse
is_integer(RenewWhenBelow) andalso
RenewWhenBelow > 0 andalso
RenewWhenBelow =< IncomingWindow ->
gen_statem:cast(Session, {flow_session, IncomingWindow, RenewWhenBelow}).

-spec flow_link(pid(), link_handle(), #'v1_0.flow'{}, never | pos_integer()) -> ok.
flow_link(Session, Handle, Flow, RenewWhenBelow) ->
gen_statem:cast(Session, {flow_link, Handle, Flow, RenewWhenBelow}).

%% Sending a disposition on a sender link (with receiver-settle-mode = second)
Expand Down Expand Up @@ -239,6 +257,9 @@ init([FromPid, Channel, Reader, ConnConfig]) ->
channel = Channel,
reader = Reader,
connection_config = ConnConfig,
incoming_window = ?DEFAULT_MAX_INCOMING_WINDOW,
auto_flow = {?DEFAULT_MAX_INCOMING_WINDOW div 2,
?DEFAULT_MAX_INCOMING_WINDOW},
early_attach_requests = []},
{ok, unmapped, State}.

Expand Down Expand Up @@ -282,15 +303,15 @@ mapped(cast, 'end', State) ->
mapped(cast, {flow_link, OutHandle, Flow0, RenewWhenBelow}, State0) ->
State = send_flow_link(OutHandle, Flow0, RenewWhenBelow, State0),
{keep_state, State};
mapped(cast, {flow_session, Flow0 = #'v1_0.flow'{incoming_window = {uint, IncomingWindow}}},
#state{next_incoming_id = NII,
next_outgoing_id = NOI} = State) ->
Flow = Flow0#'v1_0.flow'{
next_incoming_id = maybe_uint(NII),
next_outgoing_id = uint(NOI),
outgoing_window = ?UINT_OUTGOING_WINDOW},
ok = send(Flow, State),
{keep_state, State#state{incoming_window = IncomingWindow}};
mapped(cast, {flow_session, IncomingWindow, RenewWhenBelow}, State0) ->
AutoFlow = case RenewWhenBelow of
never -> never;
_ -> {RenewWhenBelow, IncomingWindow}
end,
State = State0#state{incoming_window = IncomingWindow,
auto_flow = AutoFlow},
send_flow_session(State),
{keep_state, State};
mapped(cast, #'v1_0.end'{} = End, State) ->
%% We receive the first end frame, reply and terminate.
_ = send_end(State),
Expand Down Expand Up @@ -656,35 +677,44 @@ is_bare_message_section(_Section) ->

send_flow_link(OutHandle,
#'v1_0.flow'{link_credit = {uint, Credit}} = Flow0, RenewWhenBelow,
#state{links = Links,
next_incoming_id = NII,
next_outgoing_id = NOI,
incoming_window = InWin} = State) ->
#state{links = Links} = State) ->
AutoFlow = case RenewWhenBelow of
never -> never;
Limit -> {auto, Limit, Credit}
_ -> {RenewWhenBelow, Credit}
end,
#{OutHandle := #link{output_handle = H,
role = receiver,
delivery_count = DeliveryCount,
available = Available} = Link} = Links,
Flow = Flow0#'v1_0.flow'{
handle = uint(H),
%% "This value MUST be set if the peer has received the begin
%% frame for the session, and MUST NOT be set if it has not." [2.7.4]
next_incoming_id = maybe_uint(NII),
next_outgoing_id = uint(NOI),
outgoing_window = ?UINT_OUTGOING_WINDOW,
incoming_window = uint(InWin),
%% "In the event that the receiving link endpoint has not yet seen the
%% initial attach frame from the sender this field MUST NOT be set." [2.7.4]
delivery_count = maybe_uint(DeliveryCount),
available = uint(Available)},
Flow1 = Flow0#'v1_0.flow'{
handle = uint(H),
%% "In the event that the receiving link endpoint has not yet seen the
%% initial attach frame from the sender this field MUST NOT be set." [2.7.4]
delivery_count = maybe_uint(DeliveryCount),
available = uint(Available)},
Flow = set_flow_session_fields(Flow1, State),
ok = send(Flow, State),
State#state{links = Links#{OutHandle =>
Link#link{link_credit = Credit,
auto_flow = AutoFlow}}}.

send_flow_session(State) ->
Flow = set_flow_session_fields(#'v1_0.flow'{}, State),
ok = send(Flow, State).

set_flow_session_fields(Flow, #state{next_incoming_id = NID,
incoming_window = IW,
next_outgoing_id = NOI}) ->
Flow#'v1_0.flow'{
%% "This value MUST be set if the peer has received the begin
%% frame for the session, and MUST NOT be set if it has not." [2.7.4]
next_incoming_id = maybe_uint(NID),
%% IncomingWindow0 can be negative when the sending server overshoots our window.
%% We must set a floor of 0 in the FLOW frame because field incoming-window is an uint.
incoming_window = uint(max(0, IW)),
next_outgoing_id = uint(NOI),
outgoing_window = ?UINT_OUTGOING_WINDOW}.

build_frames(Channel, Trf, Bin, MaxPayloadSize, Acc)
when byte_size(Bin) =< MaxPayloadSize ->
T = amqp10_framing:encode_bin(Trf#'v1_0.transfer'{more = false}),
Expand Down Expand Up @@ -1059,17 +1089,21 @@ book_transfer_send(Num, #link{output_handle = Handle} = Link,
links = Links#{Handle => book_link_transfer_send(Link)}}.

book_partial_transfer_received(#state{next_incoming_id = NID,
remote_outgoing_window = ROW} = State) ->
State#state{next_incoming_id = add(NID, 1),
remote_outgoing_window = ROW - 1}.
incoming_window = IW,
remote_outgoing_window = ROW} = State0) ->
State = State0#state{next_incoming_id = add(NID, 1),
incoming_window = IW - 1,
remote_outgoing_window = ROW - 1},
maybe_widen_incoming_window(State).

book_transfer_received(State = #state{connection_config =
#{transfer_limit_margin := Margin}},
#link{link_credit = Margin} = Link) ->
{transfer_limit_exceeded, Link, State};
book_transfer_received(#state{next_incoming_id = NID,
incoming_window = IW,
remote_outgoing_window = ROW,
links = Links} = State,
links = Links} = State0,
#link{output_handle = OutHandle,
delivery_count = DC,
link_credit = LC,
Expand All @@ -1079,19 +1113,31 @@ book_transfer_received(#state{next_incoming_id = NID,
%% "the receiver MUST maintain a floor of zero in its
%% calculation of the value of available" [2.6.7]
available = max(0, Avail - 1)},
State1 = State#state{links = Links#{OutHandle => Link1},
next_incoming_id = add(NID, 1),
remote_outgoing_window = ROW - 1},
State1 = State0#state{links = Links#{OutHandle => Link1},
next_incoming_id = add(NID, 1),
incoming_window = IW - 1,
remote_outgoing_window = ROW - 1},
State = maybe_widen_incoming_window(State1),
case Link1 of
#link{link_credit = 0,
auto_flow = never} ->
{credit_exhausted, Link1, State1};
{credit_exhausted, Link1, State};
_ ->
{ok, Link1, State1}
{ok, Link1, State}
end.

maybe_widen_incoming_window(
State0 = #state{incoming_window = IncomingWindow,
auto_flow = {RenewWhenBelow, NewWindowSize}})
when IncomingWindow < RenewWhenBelow ->
State = State0#state{incoming_window = NewWindowSize},
send_flow_session(State),
State;
maybe_widen_incoming_window(State) ->
State.

auto_flow(#link{link_credit = LC,
auto_flow = {auto, RenewWhenBelow, Credit},
auto_flow = {RenewWhenBelow, Credit},
output_handle = OutHandle,
incoming_unsettled = Unsettled},
State)
Expand Down Expand Up @@ -1230,6 +1276,7 @@ format_status(Status = #{data := Data0}) ->
remote_channel = RemoteChannel,
next_incoming_id = NextIncomingId,
incoming_window = IncomingWindow,
auto_flow = SessionAutoFlow,
next_outgoing_id = NextOutgoingId,
remote_incoming_window = RemoteIncomingWindow,
remote_outgoing_window = RemoteOutgoingWindow,
Expand Down Expand Up @@ -1294,6 +1341,7 @@ format_status(Status = #{data := Data0}) ->
remote_channel => RemoteChannel,
next_incoming_id => NextIncomingId,
incoming_window => IncomingWindow,
auto_flow => SessionAutoFlow,
next_outgoing_id => NextOutgoingId,
remote_incoming_window => RemoteIncomingWindow,
remote_outgoing_window => RemoteOutgoingWindow,
Expand Down
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