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Fix double counting of reclaimable bytes in rabbit_fifo (backport #15844) #15847

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Merged
ansd merged 1 commit into from
Mar 26, 2026
Merged

Fix double counting of reclaimable bytes in rabbit_fifo (backport #15844) #15847

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35 changes: 16 additions & 19 deletions deps/rabbit/src/rabbit_fifo.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -2929,7 +2929,7 @@ expire_shallow(Ts, #?STATE{cfg = #cfg{dead_letter_handler = DLH},
messages = Messages0,
delayed = Delayed0,
dlx = DlxState0,
reclaimable_bytes = ReclaimableBytes0,
reclaimable_bytes = ReclaimableBytes,
messages_total = Tot,
msg_bytes_enqueue = MsgBytesEnqueue} = State0) ->

Expand All @@ -2956,7 +2956,7 @@ expire_shallow(Ts, #?STATE{cfg = #cfg{dead_letter_handler = DLH},

ExpMsgs = Expired0 ++ Expired,

{DlxState, _RetainedBytes, DlxEffects} =
{DlxState, RetainedBytes, DlxEffects} =
discard_or_dead_letter(ExpMsgs, expired, DLH, DlxState0),

NumExpired = length(ExpMsgs),
Expand All @@ -2967,13 +2967,13 @@ expire_shallow(Ts, #?STATE{cfg = #cfg{dead_letter_handler = DLH},
Acc + get_header(size, Header)
end, 0, ExpMsgs),

DiscardedSize = Size + (NumExpired * ?ENQ_OVERHEAD_B),
DiscardedSize = Size + (NumExpired * ?ENQ_OVERHEAD_B) - RetainedBytes,
State = State0#?STATE{dlx = DlxState,
returns = Returns,
messages = Messages,
delayed = Delayed,
messages_total = Tot - NumExpired,
reclaimable_bytes = ReclaimableBytes0 + DiscardedSize,
reclaimable_bytes = ReclaimableBytes + DiscardedSize,
msg_bytes_enqueue = MsgBytesEnqueue - Size},
{State, DlxEffects}.

Expand All @@ -2982,18 +2982,18 @@ expire(RaCmdTs, State0, Effects) ->
#?STATE{cfg = #cfg{dead_letter_handler = DLH},
dlx = DlxState0,
messages_total = Tot,
reclaimable_bytes = ReclaimablBytes0,
reclaimable_bytes = ReclaimableBytes,
msg_bytes_enqueue = MsgBytesEnqueue
} = State1} =
take_next_msg(State0),
{DlxState, _RetainedBytes, DlxEffects} =
{DlxState, RetainedBytes, DlxEffects} =
discard_or_dead_letter([Msg], expired, DLH, DlxState0),
Header = get_msg_header(Msg),
Size = get_header(size, Header),
DiscardedSize = Size + ?ENQ_OVERHEAD_B,
DiscardedSize = Size + ?ENQ_OVERHEAD_B - RetainedBytes,
State = State1#?STATE{dlx = DlxState,
messages_total = Tot - 1,
reclaimable_bytes = ReclaimablBytes0 + DiscardedSize,
reclaimable_bytes = ReclaimableBytes + DiscardedSize,
msg_bytes_enqueue = MsgBytesEnqueue - Size},
expire_msgs(RaCmdTs, true, State, Effects ++ DlxEffects).

Expand Down Expand Up @@ -4193,17 +4193,14 @@ discard_or_dead_letter(Msgs0, Reason, {at_most_once, {Mod, Fun, Args}}, State) -
{State, 0, [Effect]};
discard_or_dead_letter(Msgs, Reason, at_least_once, State0)
when Reason =/= maxlen ->
RetainedBytes = lists:foldl(fun (M, Acc) ->
Acc + size_in_bytes(M) + ?ENQ_OVERHEAD_B
end, 0, Msgs),
State = lists:foldl(fun(Msg, #?DLX{discards = D0,
msg_bytes = B0} = S0) ->
MsgSize = size_in_bytes(Msg),
D = lqueue:in(?TUPLE(Reason, Msg), D0),
B = B0 + MsgSize,
S0#?DLX{discards = D,
msg_bytes = B}
end, State0, Msgs),
{State, RetainedBytes} = lists:foldl(
fun(Msg, {#?DLX{discards = D,
msg_bytes = B} = S, R}) ->
MsgSize = size_in_bytes(Msg),
{S#?DLX{discards = lqueue:in(?TUPLE(Reason, Msg), D),
msg_bytes = B + MsgSize},
R + MsgSize + ?ENQ_OVERHEAD_B}
end, {State0, 0}, Msgs),
{State, RetainedBytes,
[{mod_call, rabbit_global_counters, messages_dead_lettered,
[Reason, rabbit_quorum_queue, at_least_once, length(Msgs)]}]}.
Expand Down
18 changes: 16 additions & 2 deletions deps/rabbit/test/rabbit_fifo_SUITE.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -278,6 +278,7 @@ reclaimable_bytes_test(Config) ->
reclaimable_bytes_count := _DiscBytes27} = rabbit_fifo:overview(State27),

Conf5 = Conf4#{msg_ttl => 1000,
dead_letter_handler => at_least_once,
max_length => undefined},
{State28, ok, _} = apply(meta(Config, ?LINE),
rabbit_fifo:make_update_config(Conf5), State27),
Expand All @@ -287,9 +288,22 @@ reclaimable_bytes_test(Config) ->
{State30, _} = enq_ts(Config, ?LINE, 10, Msg, 3000, State29),
% {State31, _} = enq_ts(Config, ?LINE, 11, Msg, 5000, State30),

#{num_messages := 1,
#{num_messages := 2,
reclaimable_bytes_count := DiscBytes30} = rabbit_fifo:overview(State30),
?assert(DiscBytes30 - DiscBytes29 > 1000),
%% The message is dead-lettered at_least_once, so its bytes are retained
%% in the DLX state and should not be added to reclaimable_bytes yet.
?assert(DiscBytes30 - DiscBytes29 < 1000),

%% Now process the DLX message
{State31, _, _} = apply(meta(Config, ?LINE),
rabbit_fifo_dlx:make_checkout(DlxPid, 1),
State30),
{State32, _, _} = apply(meta(Config, ?LINE),
rabbit_fifo_dlx:make_settle([0]),
State31),
#{reclaimable_bytes_count := DiscBytes32} = rabbit_fifo:overview(State32),
%% After settling the DLX message, the bytes should finally be reclaimable
?assert(DiscBytes32 - DiscBytes30 > 1000),
ok.

enq_enq_checkout_test(Config, Spec) ->
Expand Down
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