Add a proptest checking ra_indexes indices

This is mostly the same as the `messages_total` property test but checks
that the Raft indexes in `ra_indexes` are the set of the indexes checked
out by all consumers union any indexes in the `returns` queue. This is
the intended state of `ra_indexes` and failing this condition could
cause bugs that would prevent snapshotting.

Author: the-mikedavis

deps/rabbit/src/rabbit_fifo_index.erl

@@ -7,7 +7,8 @@
          delete/2,
          size/1,
          smallest/1,
-         map/2
+         map/2,
+         to_list/1
         ]).
 
 -compile({no_auto_import, [size/1]}).
@@ -87,6 +88,10 @@ smallest(#?MODULE{smallest = Smallest}) ->
 map(F, #?MODULE{data = Data} = State) ->
     State#?MODULE{data = maps:map(F, Data)}.
 
+% Note: the ordering of the list is undefined. Sort the list for ordering.
+-spec to_list(state()) -> [integer()].
+to_list(#?MODULE{data = Data}) ->
+    maps:keys(Data).
 
 %% internal
 

deps/rabbit/test/rabbit_fifo_prop_SUITE.erl

@@ -64,6 +64,7 @@ all_tests() ->
      scenario32,
      upgrade,
      messages_total,
+     ra_indexes,
      simple_prefetch,
      simple_prefetch_without_checkout_cancel,
      simple_prefetch_01,
@@ -910,6 +911,30 @@ messages_total(_Config) ->
                       end)
       end, [], Size).
 
+ra_indexes(_Config) ->
+    meck:expect(rabbit_feature_flags, is_enabled, fun (_) -> false end),
+    Size = 256,
+    run_proper(
+      fun () ->
+              ?FORALL({Length, Bytes, DeliveryLimit, SingleActive},
+                      frequency([{5, {undefined, undefined, undefined, false}},
+                                 {5, {oneof([range(1, 10), undefined]),
+                                      oneof([range(1, 1000), undefined]),
+                                      oneof([range(1, 3), undefined]),
+                                      oneof([true, false])
+                                     }}]),
+                      begin
+                          Config  = config(?FUNCTION_NAME,
+                                           Length,
+                                           Bytes,
+                                           SingleActive,
+                                           DeliveryLimit),
+                      ?FORALL(O, ?LET(Ops, log_gen(Size), expand(Ops, Config)),
+                              collect({log_size, length(O)},
+                                      ra_indexes_prop(Config, O)))
+                      end)
+      end, [], Size).
+
 simple_prefetch(_Config) ->
     Size = 500,
     meck:expect(rabbit_feature_flags, is_enabled, fun (_) -> true end),
@@ -1464,6 +1489,38 @@ messages_total_invariant() ->
             end
     end.
 
+ra_indexes_prop(Conf0, Commands) ->
+    Conf = Conf0#{release_cursor_interval => 100},
+    Indexes = lists:seq(1, length(Commands)),
+    Entries = lists:zip(Indexes, Commands),
+    InitState = test_init(Conf),
+    run_log(InitState, Entries, ra_indexes_invariant()),
+    true.
+
+ra_indexes_invariant() ->
+    %% The raft indexes contained in the `ra_indexes` `rabbit_fifo_index` must
+    %% be the same as all indexes checked out by consumers plus those in the
+    %% `returns` queue.
+    fun(#rabbit_fifo{ra_indexes = Index,
+                     consumers = C,
+                     returns = R}) ->
+            RIdxs = lqueue:fold(fun(?MSG(I, _), Acc) -> [I | Acc] end, [], R),
+            CIdxs = maps:fold(fun(_, #consumer{checked_out = Ch}, Acc0) ->
+                                      maps:fold(fun(_, ?MSG(I, _), Acc) ->
+                                                        [I | Acc]
+                                                end, Acc0, Ch)
+                              end, [], C),
+            ActualIdxs = lists:sort(RIdxs ++ CIdxs),
+            IndexIdxs = lists:sort(rabbit_fifo_index:to_list(Index)),
+            case ActualIdxs == IndexIdxs of
+                true -> true;
+                false ->
+                    ct:pal("ra_indexes invariant failed Expected ~b Got ~b",
+                           [ActualIdxs, IndexIdxs]),
+                    false
+            end
+    end.
+
 simple_prefetch_prop(Conf0, Commands, WithCheckoutCancel) ->
     Conf = Conf0#{release_cursor_interval => 100},
     Indexes = lists:seq(1, length(Commands)),