QQ: handle messages_ready() in a mixed-version cluster

Author: mkuratczyk

deps/rabbit/src/rabbit_fifo.erl

@@ -1375,7 +1375,12 @@ is_v4() ->
 
 messages_ready(#?STATE{messages = M,
                        returns = R}) ->
-    rabbit_fifo_q:len(M) + lqueue:len(R).
+    case is_v4() of
+        true ->
+            rabbit_fifo_q:len(M) + lqueue:len(R);
+        false ->
+            lqueue:len(M) + lqueue:len(R)
+    end.
 
 messages_total(#?STATE{messages_total = Total,
                        dlx = DlxState}) ->
@@ -1547,7 +1552,7 @@ activate_next_consumer(#?STATE{consumers = Cons0,
                                   waiting_consumers = Waiting},
             Effects1 = consumer_update_active_effects(State, Active,
                                                       false, waiting,
-                                                      Effects0),                                  
+                                                      Effects0),
             Effects = consumer_update_active_effects(State, Consumer,
                                                      true, single_active,
                                                      Effects1),