Ensures pending counter in rabbit_shovel_status is always an integer

deps/rabbitmq_shovel/src/rabbit_amqp091_shovel.erl

@@ -33,7 +33,8 @@
          ack/3,
          nack/3,
          status/1,
-         forward/3
+         forward/3,
+         pending_count/1
         ]).
 
 %% Function references should not be stored on the metadata store.
@@ -360,6 +361,10 @@ status(#{dest := #{blocked_by := BlockReasons}}) when BlockReasons =/= [] ->
 status(_) ->
     running.
 
+pending_count(#{dest := Dest}) ->
+    Pending = maps:get(pending, Dest, queue:new()),
+    queue:len(Pending).
+
 add_pending(Elem, State = #{dest := Dest}) ->
     Pending = maps:get(pending, Dest, queue:new()),
     State#{dest => Dest#{pending => queue:in(Elem, Pending)}}.

deps/rabbitmq_shovel/src/rabbit_amqp10_shovel.erl

@@ -32,7 +32,8 @@
          ack/3,
          nack/3,
          status/1,
-         forward/3
+         forward/3,
+         pending_count/1
         ]).
 
 -import(rabbit_misc, [pget/2, pget/3]).
@@ -317,6 +318,10 @@ status(_) ->
     %% Destination not yet connected
     ignore.
 
+pending_count(#{dest := Dest}) ->
+    Pending = maps:get(pending, Dest, []),
+    length(Pending).
+
 -spec forward(Tag :: tag(), Mc :: mc:state(), state()) ->
     state() | {stop, any()}.
 forward(_Tag, _Mc,

deps/rabbitmq_shovel/src/rabbit_local_shovel.erl

@@ -42,7 +42,8 @@
          ack/3,
          nack/3,
          forward/3,
-         status/1
+         status/1,
+         pending_count/1
         ]).
 
 -export([
@@ -437,6 +438,11 @@ add_routing(Msg0, Dest) ->
 status(_) ->
     running.
 
+pending_count(#{source := #{current := #{unacked_message_q := UAMQ}}}) ->
+    ?QUEUE:len(UAMQ);
+pending_count(_State) ->
+    0.
+
 %% Internal
 
 parse_parameter(_, _, none) ->

deps/rabbitmq_shovel/src/rabbit_shovel_behaviour.erl

@@ -85,6 +85,7 @@
 -callback forward(Tag :: tag(), Msg :: mc:state(), state()) ->
     state() | {stop, any()}.
 -callback status(state()) -> rabbit_shovel_status:shovel_status().
+-callback pending_count(state()) -> non_neg_integer().
 
 -spec parse(atom(), binary(), {source | destination, proplists:proplist()}) ->
     source_config() | dest_config().
@@ -164,12 +165,12 @@ incr_forwarded(State = #{dest := Dest}) ->
     State#{dest => maps:put(forwarded, maps:get(forwarded, Dest, 0) + 1, Dest)}.
 
 -spec metrics(state()) -> rabbit_shovel_status:metrics().
-metrics(_State = #{source := Source,
-                   dest := Dest}) ->
+metrics(#{source := Source,
+          dest := #{module := Mod}} = State) ->
     #{remaining => maps:get(remaining, Source, unlimited),
-     remaining_unacked => maps:get(remaining_unacked, Source, 0),
-      pending => maps:get(pending, Dest, 0),
-      forwarded => maps:get(forwarded, Dest, 0)}.
+      remaining_unacked => maps:get(remaining_unacked, Source, 0),
+      pending => Mod:pending_count(State),
+      forwarded => maps:get(forwarded, maps:get(dest, State), 0)}.
 
 
 %% Common functions

deps/rabbitmq_shovel/test/pending_count_SUITE.erl

@@ -0,0 +1,175 @@
+%% This Source Code Form is subject to the terms of the Mozilla Public
+%% License, v. 2.0. If a copy of the MPL was not distributed with this
+%% file, You can obtain one at https://mozilla.org/MPL/2.0/.
+%%
+%% Copyright (c) 2007-2025 Broadcom. All Rights Reserved. The term "Broadcom" refers to Broadcom Inc. and/or its subsidiaries. All rights reserved.
+%%
+
+-module(pending_count_SUITE).
+
+-compile(export_all).
+
+-include_lib("eunit/include/eunit.hrl").
+-include_lib("rabbit/include/mc.hrl").
+-include("../include/rabbit_shovel.hrl").
+
+%%%===================================================================
+%%% Common Test callbacks
+%%%===================================================================
+
+all() ->
+    [
+     {group, pending_count_tests}
+    ].
+
+groups() ->
+    [
+     {pending_count_tests, [], [
+         amqp091_pending_count_empty_queue,
+         amqp091_pending_count_with_messages,
+         amqp091_pending_count_after_drain,
+         amqp10_pending_count_empty_list,
+         amqp10_pending_count_with_messages,
+         amqp10_pending_count_after_clear,
+         local_pending_count_empty_queue,
+         local_pending_count_with_messages,
+         local_pending_count_after_settle,
+         behaviour_metrics_includes_pending,
+         behaviour_pending_count_delegation
+        ]}
+    ].
+
+init_per_suite(Config) ->
+    Config.
+
+end_per_suite(_Config) ->
+    ok.
+
+init_per_group(_Group, Config) ->
+    Config.
+
+end_per_group(_Group, _Config) ->
+    ok.
+
+init_per_testcase(_TestCase, Config) ->
+    Config.
+
+end_per_testcase(_TestCase, _Config) ->
+    meck:unload(),
+    ok.
+
+%%%===================================================================
+%%% Test cases
+%%%===================================================================
+
+%% Test AMQP 0.9.1 pending_count functionality
+amqp091_pending_count_empty_queue(_Config) ->
+    %% Test that pending_count returns 0 when no messages are pending
+    State = #{dest => #{}},
+    ?assertEqual(0, rabbit_amqp091_shovel:pending_count(State)).
+
+amqp091_pending_count_with_messages(_Config) ->
+    %% Test that pending_count returns correct count when messages are pending
+    PendingQueue = queue:from_list([{1, msg1}, {2, msg2}, {3, msg3}]),
+    State = #{dest => #{pending => PendingQueue}},
+    ?assertEqual(3, rabbit_amqp091_shovel:pending_count(State)).
+
+amqp091_pending_count_after_drain(_Config) ->
+    %% Test that pending_count returns 0 after messages are drained
+    EmptyQueue = queue:new(),
+    State = #{dest => #{pending => EmptyQueue}},
+    ?assertEqual(0, rabbit_amqp091_shovel:pending_count(State)).
+
+%% Test AMQP 1.0 pending_count functionality
+amqp10_pending_count_empty_list(_Config) ->
+    %% Test that pending_count returns 0 when no messages are pending
+    State = #{dest => #{}},
+    ?assertEqual(0, rabbit_amqp10_shovel:pending_count(State)).
+
+amqp10_pending_count_with_messages(_Config) ->
+    %% Test that pending_count returns correct count when messages are pending
+    PendingList = [{1, msg1}, {2, msg2}],
+    State = #{dest => #{pending => PendingList}},
+    ?assertEqual(2, rabbit_amqp10_shovel:pending_count(State)).
+
+amqp10_pending_count_after_clear(_Config) ->
+    %% Test that pending_count returns 0 after pending list is cleared
+    State = #{dest => #{pending => []}},
+    ?assertEqual(0, rabbit_amqp10_shovel:pending_count(State)).
+
+%% Test Local shovel pending_count functionality
+local_pending_count_empty_queue(_Config) ->
+    %% Test that pending_count returns 0 when unacked message queue is empty
+    EmptyQueue = lqueue:new(),
+    State = #{source => #{current => #{unacked_message_q => EmptyQueue}}},
+    ?assertEqual(0, rabbit_local_shovel:pending_count(State)).
+
+local_pending_count_with_messages(_Config) ->
+    %% Test that pending_count returns correct count from unacked message queue
+    UnackedQueue = lqueue:from_list([msg1, msg2, msg3, msg4]),
+    State = #{source => #{current => #{unacked_message_q => UnackedQueue}}},
+    ?assertEqual(4, rabbit_local_shovel:pending_count(State)).
+
+local_pending_count_after_settle(_Config) ->
+    %% Test that pending_count returns 0 when state doesn't contain unacked queue
+    State = #{source => #{current => #{}}},
+    ?assertEqual(0, rabbit_local_shovel:pending_count(State)).
+
+%% Test behaviour module integration
+behaviour_metrics_includes_pending(_Config) ->
+    %% Mock the destination module's pending_count and status functions
+    meck:new(rabbit_amqp091_shovel, [passthrough]),
+    meck:expect(rabbit_amqp091_shovel, pending_count, fun(_) -> 5 end),
+    meck:expect(rabbit_amqp091_shovel, status, fun(_) -> running end),
+
+    State = #{source => #{remaining => 10, remaining_unacked => 3},
+              dest => #{module => rabbit_amqp091_shovel, forwarded => 7}},
+
+    {_Status, Metrics} = rabbit_shovel_behaviour:status(State),
+
+    ?assertMatch(#{remaining := 10,
+                   remaining_unacked := 3,
+                   pending := 5,
+                   forwarded := 7}, Metrics),
+
+    ?assert(meck:validate(rabbit_amqp091_shovel)).
+
+behaviour_pending_count_delegation(_Config) ->
+    %% Test that the behaviour module correctly delegates to the specific implementation
+    meck:new(rabbit_amqp10_shovel, [passthrough]),
+    meck:expect(rabbit_amqp10_shovel, pending_count, fun(_State) -> 3 end),
+    meck:expect(rabbit_amqp10_shovel, status, fun(_State) -> running end),
+
+    State = #{dest => #{module => rabbit_amqp10_shovel}},
+
+    %% This would be called indirectly through status/1
+    {_Status, Metrics} = rabbit_shovel_behaviour:status(#{source => #{},
+                                                          dest => maps:get(dest, State)}),
+
+    ?assertEqual(3, maps:get(pending, Metrics)),
+    ?assert(meck:validate(rabbit_amqp10_shovel)).
+
+%%%===================================================================
+%%% Integration tests for pending_count behavior in different scenarios
+%%%===================================================================
+
+%% Additional test cases to verify pending_count behavior in realistic scenarios
+%% These could be added if we want to test the actual message flow scenarios
+
+pending_count_during_flow_control(_Config) ->
+    %% Test case outline: Verify pending_count increases when flow control blocks forwarding
+    %% and decreases when flow control is lifted
+    %% This would require more complex setup with actual message handling
+    ok.
+
+pending_count_with_multiple_ack_modes(_Config) ->
+    %% Test case outline: Verify pending_count behaves correctly across different ack modes
+    %% (no_ack, on_publish, on_confirm)
+    ok.
+
+pending_count_edge_cases(_Config) ->
+    %% Test case outline: Test edge cases like:
+    %% - Missing dest/source maps
+    %% - Malformed pending data structures
+    %% - Very large pending counts
+    ok.