Merge pull request #9161 from rabbitmq/mergify/bp/v3.12.x/pr-9158

QQ: fix bug when subscribing using an already existing consumer tag (backport #9158)

Author: michaelklishin

deps/rabbit/src/rabbit_fifo.erl

@@ -408,6 +408,7 @@ apply(Meta, #checkout{spec = Spec, meta = ConsumerMeta,
               credit = Credit,
               delivery_count = DeliveryCount,
               next_msg_id = NextMsgId} = Consumer,
+
     %% reply with a consumer summary
     Reply = {ok, #{next_msg_id => NextMsgId,
                    credit => Credit,

deps/rabbit/src/rabbit_fifo_client.erl

@@ -46,7 +46,7 @@
                   rabbit_queue_type:action().
 -type actions() :: [action()].
 
--record(consumer, {last_msg_id :: seq() | -1,
+-record(consumer, {last_msg_id :: seq() | -1 | undefined,
                    ack = false :: boolean(),
                    delivery_count = 0 :: non_neg_integer()}).
 
@@ -359,8 +359,20 @@ checkout(ConsumerTag, NumUnsettled, CreditMode, Meta,
                                 %% this is the pre 3.11.1 / 3.10.9
                                 %% reply format
                                 -1;
-                            {ok, #{next_msg_id := NextMsgId}} ->
-                                NextMsgId - 1
+                            {ok, #{num_checked_out := NumChecked,
+                                   next_msg_id := NextMsgId}} ->
+                                case NumChecked > 0 of
+                                    true ->
+                                        %% we cannot know if the pending messages
+                                        %% have been delivered to the client or they
+                                        %% are on their way to the current process.
+                                        %% We set `undefined' to signal this uncertainty
+                                        %% and will just accept the next arriving message
+                                        %% irrespective of message id
+                                        undefined;
+                                    false ->
+                                        NextMsgId - 1
+                                end
                         end,
             SDels = maps:update_with(
                       ConsumerTag, fun (C) -> C#consumer{ack = Ack} end,
@@ -713,7 +725,11 @@ handle_delivery(QName, Leader, {delivery, Tag, [{FstId, _} | _] = IdMsgs},
     %% TODO: remove potential default allocation
     case Consumer of
         #consumer{last_msg_id = Prev} = C
-          when FstId =:= Prev+1 ->
+          when Prev =:= undefined orelse FstId =:= Prev+1 ->
+            %% Prev =:= undefined is a special case where a checkout was done
+            %% for a previously cancelled consumer that still had pending messages
+            %% In this case we can't reliably know what the next expected message
+            %% id should be so have to accept whatever message comes next
             maybe_auto_ack(Ack, Del,
                            State0#state{consumer_deliveries =
                                         update_consumer(Tag, LastId,

deps/rabbit/test/quorum_queue_SUITE.erl

@@ -1726,7 +1726,7 @@ confirm_availability_on_leader_change(Config) ->
 
 flush(T) ->
     receive X ->
-                ct:pal("flushed ~w", [X]),
+                ct:pal("flushed ~p", [X]),
                 flush(T)
     after T ->
               ok
@@ -3057,12 +3057,13 @@ cancel_and_consume_with_same_tag(Config) ->
     DeclareRslt0 = declare(Ch, QQ, [{<<"x-queue-type">>, longstr, <<"quorum">>}]),
     ?assertMatch(ExpectedDeclareRslt0, DeclareRslt0),
 
-    ok = publish(Ch, QQ),
+    ok = publish(Ch, QQ, <<"msg1">>),
 
     ok = subscribe(Ch, QQ, false),
 
     DeliveryTag = receive
-                      {#'basic.deliver'{delivery_tag = D}, _} ->
+                      {#'basic.deliver'{delivery_tag = D},
+                       #amqp_msg{payload = <<"msg1">>}} ->
                           D
                   after 5000 ->
                             flush(100),
@@ -3073,10 +3074,11 @@ cancel_and_consume_with_same_tag(Config) ->
 
     ok = subscribe(Ch, QQ, false),
 
-    ok = publish(Ch, QQ),
+    ok = publish(Ch, QQ, <<"msg2">>),
 
     receive
-        {#'basic.deliver'{delivery_tag = _}, _} ->
+        {#'basic.deliver'{delivery_tag = _},
+         #amqp_msg{payload = <<"msg2">>}} ->
             ok
     after 5000 ->
               flush(100),

deps/rabbit/test/rabbit_fifo_SUITE.erl

@@ -1990,6 +1990,26 @@ chunk_disk_msgs_test(_Config) ->
                  rabbit_fifo:chunk_disk_msgs(TwoBigMsgs, 0, [[]])),
     ok.
 
+checkout_metadata_test(Config) ->
+    Cid = {<<"cid">>, self()},
+    {State00, _} = enq(Config, 1, 1, first, test_init(test)),
+    {State0, _} = enq(Config, 2, 2, second, State00),
+    %% NB: the consumer meta data is taken _before_ it runs a checkout
+    %% so in this case num_checked_out will be 0
+    {State1, {ok, #{next_msg_id := 0,
+                    num_checked_out := 0}}, _} =
+        apply(meta(Config, ?LINE),
+              rabbit_fifo:make_checkout(Cid, {auto, 1, simple_prefetch}, #{}),
+              State0),
+    {State2, _, _} = apply(meta(Config, ?LINE),
+                           rabbit_fifo:make_checkout(Cid, cancel, #{}), State1),
+    {_State3, {ok, #{next_msg_id := 1,
+                     num_checked_out := 1}}, _} =
+        apply(meta(Config, ?LINE),
+              rabbit_fifo:make_checkout(Cid, {auto, 1, simple_prefetch}, #{}),
+              State2),
+    ok.
+
 %% Utility
 
 init(Conf) -> rabbit_fifo:init(Conf).