Support x-death event values from before #78

src/rabbit_dead_letter.erl

@@ -84,36 +84,95 @@ x_death_event_key(Info, Key, KeyType) ->
         {value, {Key, KeyType, Val}} -> Val
     end.
 
+maybe_append_to_event_group(Table, _Key, _SeenKeys, []) ->
+    [Table];
+maybe_append_to_event_group(Table, {_Queue, _Reason} = Key, SeenKeys, Acc) ->
+    case sets:is_element(Key, SeenKeys) of
+        true  -> Acc;
+        false -> [Table | Acc]
+    end.
+
+group_by_queue_and_reason([]) ->
+    [];
+group_by_queue_and_reason([Table]) ->
+    [Table];
+group_by_queue_and_reason(Tables) ->
+    {_, Grouped} =
+        lists:foldl(
+          fun ({table, Info}, {SeenKeys, Acc}) ->
+                  Q = x_death_event_key(Info, <<"queue">>, longstr),
+                  R = x_death_event_key(Info, <<"reason">>, longstr),
+                  Matcher = queue_and_reason_matcher(Q, R),
+                  {Matches, _} = lists:partition(Matcher, Tables),
+                  {Augmented, N} = case Matches of
+                                       [X]        -> {X, 1};
+                                       [X|_] = Xs -> {X, length(Xs)}
+                                   end,
+                  Key = {Q, R},
+                  Acc1 = maybe_append_to_event_group(
+                           ensure_xdeath_event_count(Augmented, N),
+                           Key, SeenKeys, Acc),
+                  {sets:add_element(Key, SeenKeys), Acc1}
+          end, {sets:new(), []}, Tables),
+    Grouped.
+
 update_x_death_header(Info, Headers) ->
     Q = x_death_event_key(Info, <<"queue">>, longstr),
     R = x_death_event_key(Info, <<"reason">>, longstr),
     case rabbit_basic:header(<<"x-death">>, Headers) of
         undefined ->
-            rabbit_basic:prepend_table_header(<<"x-death">>,
+            rabbit_basic:prepend_table_header(
+              <<"x-death">>,
               [{<<"count">>, long, 1} | Info], Headers);
         {<<"x-death">>, array, Tables} ->
+            %% group existing x-death headers in case we have some from
+            %% before rabbitmq-server#78
+            GroupedTables = group_by_queue_and_reason(Tables),
             {Matches, Others} = lists:partition(
-              fun ({table, Info0}) ->
-                  x_death_event_key(Info0, <<"queue">>, longstr) =:= Q
-                  andalso x_death_event_key(Info0, <<"reason">>, longstr) =:= R
-              end, Tables),
+                                  queue_and_reason_matcher(Q, R),
+                                  GroupedTables),
             Info1 = case Matches of
                         [] ->
                             [{<<"count">>, long, 1} | Info];
                         [{table, M}] ->
-                            case x_death_event_key(M, <<"count">>, long) of
-                                undefined ->
-                                    [{<<"count">>, long, 1} | M];
-                                N ->
-                                    lists:keyreplace(
-                                      <<"count">>, 1, M,
-                                      {<<"count">>, long, N + 1})
-                            end
+                            increment_xdeath_event_count(M)
                     end,
-            rabbit_misc:set_table_value(Headers, <<"x-death">>, array,
+            rabbit_misc:set_table_value(
+              Headers, <<"x-death">>, array,
               [{table, rabbit_misc:sort_field_table(Info1)} | Others])
     end.
 
+ensure_xdeath_event_count({table, Info}, InitialVal) when InitialVal >= 1 ->
+    {table, ensure_xdeath_event_count(Info, InitialVal)};
+ensure_xdeath_event_count(Info, InitialVal) when InitialVal >= 1 ->
+    case x_death_event_key(Info, <<"count">>, long) of
+        undefined ->
+            [{<<"count">>, long, InitialVal} | Info];
+        _ ->
+            Info
+    end.
+
+increment_xdeath_event_count(Info) ->
+    case x_death_event_key(Info, <<"count">>, long) of
+        undefined ->
+            [{<<"count">>, long, 1} | Info];
+        N ->
+            lists:keyreplace(
+              <<"count">>, 1, Info,
+              {<<"count">>, long, N + 1})
+    end.
+
+queue_and_reason_matcher(Q, R) ->
+    F = fun(Info) ->
+                x_death_event_key(Info, <<"queue">>, longstr) =:= Q
+                    andalso x_death_event_key(Info, <<"reason">>, longstr) =:= R
+        end,
+    fun({table, Info}) ->
+            F(Info);
+       (Info) when is_list(Info) ->
+            F(Info)
+    end.
+
 per_msg_ttl_header(#'P_basic'{expiration = undefined}) ->
     [];
 per_msg_ttl_header(#'P_basic'{expiration = Expiration}) ->
@@ -178,7 +237,7 @@ log_cycle_once(Queues) ->
         true      -> ok;
         undefined -> rabbit_log:warning(
                        "Message dropped. Dead-letter queues cycle detected" ++
-                       ": ~p~nThis cycle will NOT be reported again.~n",
+                           ": ~p~nThis cycle will NOT be reported again.~n",
                        [Queues]),
                      put(Key, true)
     end.