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Fix quorum queue drop-head dead letter order #14926

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960918e
Fix quorum queue `drop-head` dead letter order
ansd Nov 10, 2025
422cc2e
Drop large number of messages more efficiently
ansd Nov 10, 2025
42d208d
Simplify
ansd Nov 11, 2025
59fdd73
Add release notes
ansd Nov 11, 2025
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70 changes: 37 additions & 33 deletions deps/rabbit/src/rabbit_fifo.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -411,16 +411,16 @@ apply(#{index := Index,
Effects2 = [reply_log_effect(RaftIdx, MsgId, Header,
messages_ready(State4), From)
| Effects1],
{State, _DroppedMsg, Effects} =
evaluate_limit(Index, false, State0, State4, Effects2),
{State, Effects} = evaluate_limit(Index, State0,
State4, Effects2),
{State, '$ra_no_reply', Effects};
{nochange, _ExpiredMsg = true, State2, Effects0} ->
%% All ready messages expired.
State3 = State2#?STATE{consumers =
maps:remove(ConsumerId,
State2#?STATE.consumers)},
{State, _, Effects} = evaluate_limit(Index, false, State0,
State3, Effects0),
{State, Effects} = evaluate_limit(Index, State0,
State3, Effects0),
{State, {dequeue, empty}, Effects}
end
end;
Expand Down Expand Up @@ -515,8 +515,7 @@ apply(#{index := Index}, #purge{},
},
Effects0 = [{aux, force_checkpoint}, garbage_collection],
Reply = {purge, NumReady},
{State, _, Effects} = evaluate_limit(Index, false, State0,
State1, Effects0),
{State, Effects} = evaluate_limit(Index, State0, State1, Effects0),
{State, Reply, Effects};
apply(#{index := _Idx}, #garbage_collection{}, State) ->
{State, ok, [{aux, garbage_collection}]};
Expand Down Expand Up @@ -1662,7 +1661,6 @@ combine_effects([{mod_call,
combine_effects(New, Old) ->
New ++ Old.


maybe_set_msg_ttl(Msg, RaCmdTs, Header,
#?STATE{cfg = #cfg{msg_ttl = MsgTTL}}) ->
case mc:is(Msg) of
Expand Down Expand Up @@ -1994,10 +1992,8 @@ checkout(#{index := Index} = Meta,
State2 = State1#?STATE{msg_cache = undefined,
dlx = DlxState},
Effects2 = DlxDeliveryEffects ++ Effects1,
case evaluate_limit(Index, false, OldState, State2, Effects2) of
{State, _, Effects} ->
{State, Reply, Effects}
end.
{State, Effects} = evaluate_limit(Index, OldState, State2, Effects2),
{State, Reply, Effects}.

checkout0(Meta, {success, ConsumerKey, MsgId,
?MSG(_, _) = Msg, ExpiredMsg, State, Effects},
Expand All @@ -2014,29 +2010,37 @@ checkout0(_Meta, {_Activity, ExpiredMsg, State0, Effects0}, SendAcc) ->
Effects = add_delivery_effects(Effects0, SendAcc, State0),
{State0, ExpiredMsg, lists:reverse(Effects)}.

evaluate_limit(_Index, Result,
#?STATE{cfg = #cfg{max_length = undefined,
max_bytes = undefined}},
#?STATE{cfg = #cfg{max_length = undefined,
max_bytes = undefined}} = State,
Effects) ->
{State, Result, Effects};
evaluate_limit(_Index, Result, _BeforeState,
#?STATE{cfg = #cfg{max_length = undefined,
max_bytes = undefined},
enqueuers = Enqs0} = State0,
Effects0) ->
evaluate_limit(Idx, State1, State2, OuterEffects) ->
case evaluate_limit0(Idx, State1, State2, []) of
{State, []} ->
{State, OuterEffects};
{State, Effects} ->
{State, OuterEffects ++ lists:reverse(Effects)}
end.

evaluate_limit0(_Index,
#?STATE{cfg = #cfg{max_length = undefined,
max_bytes = undefined}},
#?STATE{cfg = #cfg{max_length = undefined,
max_bytes = undefined}} = State,
Effects) ->
{State, Effects};
evaluate_limit0(_Index, _BeforeState,
#?STATE{cfg = #cfg{max_length = undefined,
max_bytes = undefined},
enqueuers = Enqs0} = State0,
Effects0) ->
%% max_length and/or max_bytes policies have just been deleted
{Enqs, Effects} = unblock_enqueuers(Enqs0, Effects0),
{State0#?STATE{enqueuers = Enqs}, Result, Effects};
evaluate_limit(Index, Result, BeforeState,
#?STATE{cfg = #cfg{overflow_strategy = Strategy},
enqueuers = Enqs0} = State0,
Effects0) ->
{State0#?STATE{enqueuers = Enqs}, Effects};
evaluate_limit0(Index, BeforeState,
#?STATE{cfg = #cfg{overflow_strategy = Strategy},
enqueuers = Enqs0} = State0,
Effects0) ->
case is_over_limit(State0) of
true when Strategy == drop_head ->
{State, Effects} = drop_head(State0, Effects0),
evaluate_limit(Index, true, BeforeState, State, Effects);
evaluate_limit0(Index, BeforeState, State, Effects);
true when Strategy == reject_publish ->
%% generate send_msg effect for each enqueuer to let them know
%% they need to block
Expand All @@ -2050,7 +2054,7 @@ evaluate_limit(Index, Result, BeforeState,
(_P, _E, Acc) ->
Acc
end, {Enqs0, Effects0}, Enqs0),
{State0#?STATE{enqueuers = Enqs}, Result, Effects};
{State0#?STATE{enqueuers = Enqs}, Effects};
false when Strategy == reject_publish ->
%% TODO: optimise as this case gets called for every command
%% pretty much
Expand All @@ -2059,12 +2063,12 @@ evaluate_limit(Index, Result, BeforeState,
{false, true} ->
%% we have moved below the lower limit
{Enqs, Effects} = unblock_enqueuers(Enqs0, Effects0),
{State0#?STATE{enqueuers = Enqs}, Result, Effects};
{State0#?STATE{enqueuers = Enqs}, Effects};
_ ->
{State0, Result, Effects0}
{State0, Effects0}
end;
false ->
{State0, Result, Effects0}
{State0, Effects0}
end.

unblock_enqueuers(Enqs0, Effects0) ->
Expand Down
45 changes: 45 additions & 0 deletions deps/rabbit/test/quorum_queue_SUITE.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -167,6 +167,7 @@ all_tests() ->
subscribe_redelivery_count,
message_bytes_metrics,
queue_length_limit_drop_head,
queue_length_bytes_limit_drop_head,
queue_length_limit_reject_publish,
queue_length_limit_policy_cleared,
subscribe_redelivery_limit,
Expand Down Expand Up @@ -3669,6 +3670,50 @@ queue_length_limit_drop_head(Config) ->
amqp_channel:call(Ch, #'basic.get'{queue = QQ,
no_ack = true})).

queue_length_bytes_limit_drop_head(Config) ->
[Server | _] = Servers = rabbit_ct_broker_helpers:get_node_configs(Config, nodename),

Ch = rabbit_ct_client_helpers:open_channel(Config, Server),
QQ = ?config(queue_name, Config),
DLQ = <<"dead letter queue">>,

?assertEqual({'queue.declare_ok', DLQ, 0, 0},
declare(Ch, DLQ, [{<<"x-queue-type">>, longstr, <<"quorum">>}])),
?assertEqual({'queue.declare_ok', QQ, 0, 0},
declare(Ch, QQ, [{<<"x-queue-type">>, longstr, <<"quorum">>},
{<<"x-overflow">>, longstr, <<"drop-head">>},
{<<"x-max-length-bytes">>, long, 1000},
{<<"x-dead-letter-exchange">>, longstr, <<>>},
{<<"x-dead-letter-routing-key">>, longstr, DLQ}])),

LargePayload = binary:copy(<<"x">>, 1500),
ok = amqp_channel:cast(Ch,
#'basic.publish'{routing_key = QQ},
#amqp_msg{payload = <<"m1">>}),
ok = amqp_channel:cast(Ch,
#'basic.publish'{routing_key = QQ},
#amqp_msg{payload = <<"m2">>}),
ok = amqp_channel:cast(Ch,
#'basic.publish'{routing_key = QQ},
#amqp_msg{payload = LargePayload}),
wait_for_consensus(QQ, Config),
wait_for_consensus(DLQ, Config),
RaName = ra_name(DLQ),
wait_for_messages_ready(Servers, RaName, 3),
?assertMatch({#'basic.get_ok'{}, #amqp_msg{payload = <<"m1">>}},
amqp_channel:call(Ch, #'basic.get'{queue = DLQ,
no_ack = true})),
?assertMatch({#'basic.get_ok'{}, #amqp_msg{payload = <<"m2">>}},
amqp_channel:call(Ch, #'basic.get'{queue = DLQ,
no_ack = true})),
?assertMatch({#'basic.get_ok'{}, #amqp_msg{payload = LargePayload}},
amqp_channel:call(Ch, #'basic.get'{queue = DLQ,
no_ack = true})),

[?assertEqual(#'queue.delete_ok'{message_count = 0},
amqp_channel:call(Ch, #'queue.delete'{queue = Q}))
|| Q <- [QQ, DLQ]].

queue_length_limit_reject_publish(Config) ->
[Server | _] = Servers = rabbit_ct_broker_helpers:get_node_configs(Config, nodename),

Expand Down
11 changes: 11 additions & 0 deletions release-notes/4.2.1.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
## RabbitMQ 4.2.1

RabbitMQ `4.2.1` is a maintenance release in the `4.2.x` [release series](https://www.rabbitmq.com/release-information).

### Core Server

#### Bug Fixes

* Quorum queue at-most-once dead lettering for the overflow behaviour `drop-head` now happens in the correct order.

GitHub issue: [#14926](https://github.com/rabbitmq/rabbitmq-server/pull/14926)
6 changes: 6 additions & 0 deletions release-notes/4.3.0.md
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Expand Up @@ -57,6 +57,12 @@ compared to other versions.

### Core Server

#### Bug Fixes

* Quorum queue at-most-once dead lettering for the overflow behaviour `drop-head` now happens in the correct order.

GitHub issue: [#14926](https://github.com/rabbitmq/rabbitmq-server/pull/14926)

#### Enhancements

TBD
Expand Down
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