Merge in default

14 files changed, 164 insertions, 103 deletions

diff --git a/include/rabbit.hrl b/include/rabbit.hrl
index 9f483c30..db4773b8 100644
--- a/include/rabbit.hrl
+++ b/include/rabbit.hrl
@@ -43,6 +43,7 @@
 -record(resource, {virtual_host, kind, name}).
 
 -record(exchange, {name, type, durable, auto_delete, internal, arguments}).
+-record(exchange_serial, {name, next}).
 
 -record(amqqueue, {name, durable, auto_delete, exclusive_owner = none,
                    arguments, pid}).
diff --git a/include/rabbit_exchange_type_spec.hrl b/include/rabbit_exchange_type_spec.hrl
index c80cc196..f6283ef7 100644
--- a/include/rabbit_exchange_type_spec.hrl
+++ b/include/rabbit_exchange_type_spec.hrl
@@ -16,16 +16,20 @@
 
 -ifdef(use_specs).
 
+-type(tx() :: 'transaction' | 'none').
+-type(serial() :: pos_integer() | tx()).
+
 -spec(description/0 :: () -> [{atom(), any()}]).
+-spec(serialise_events/0 :: () -> boolean()).
 -spec(route/2 :: (rabbit_types:exchange(), rabbit_types:delivery())
                  -> rabbit_router:match_result()).
 -spec(validate/1 :: (rabbit_types:exchange()) -> 'ok').
--spec(create/2 :: (boolean(), rabbit_types:exchange()) -> 'ok').
--spec(delete/3 :: (boolean(), rabbit_types:exchange(),
+-spec(create/2 :: (tx(), rabbit_types:exchange()) -> 'ok').
+-spec(delete/3 :: (tx(), rabbit_types:exchange(),
                    [rabbit_types:binding()]) -> 'ok').
--spec(add_binding/3 :: (boolean(), rabbit_types:exchange(),
+-spec(add_binding/3 :: (serial(), rabbit_types:exchange(),
                         rabbit_types:binding()) -> 'ok').
--spec(remove_bindings/3 :: (boolean(), rabbit_types:exchange(),
+-spec(remove_bindings/3 :: (serial(), rabbit_types:exchange(),
                             [rabbit_types:binding()]) -> 'ok').
 -spec(assert_args_equivalence/2 ::
         (rabbit_types:exchange(), rabbit_framing:amqp_table())
diff --git a/src/rabbit_amqqueue.erl b/src/rabbit_amqqueue.erl
index 7bb90fd9..e58e67ad 100644
--- a/src/rabbit_amqqueue.erl
+++ b/src/rabbit_amqqueue.erl
@@ -139,8 +139,8 @@
 -spec(internal_delete/1 ::
         (name()) -> rabbit_types:ok_or_error('not_found') |
                     rabbit_types:connection_exit() |
-                    fun ((boolean()) -> rabbit_types:ok_or_error('not_found') |
-                                        rabbit_types:connection_exit())).
+                    fun (() -> rabbit_types:ok_or_error('not_found') |
+                               rabbit_types:connection_exit())).
 -spec(run_backing_queue/3 ::
         (pid(), atom(),
          (fun ((atom(), A) -> {[rabbit_types:msg_id()], A}))) -> 'ok').
@@ -215,7 +215,7 @@ internal_declare(Q = #amqqueue{name = QueueName}, false) ->
                       case mnesia:read({rabbit_durable_queue, QueueName}) of
                           []  -> ok = store_queue(Q),
                                  B = add_default_binding(Q),
-                                 fun (Tx) -> B(Tx), Q end;
+                                 fun () -> B(), Q end;
                           %% Q exists on stopped node
                           [_] -> rabbit_misc:const(not_found)
                       end;
@@ -223,7 +223,7 @@ internal_declare(Q = #amqqueue{name = QueueName}, false) ->
                       case rabbit_misc:is_process_alive(QPid) of
                           true  -> rabbit_misc:const(ExistingQ);
                           false -> TailFun = internal_delete(QueueName),
-                                   fun (Tx) -> TailFun(Tx), ExistingQ end
+                                   fun () -> TailFun(), ExistingQ end
                       end
               end
       end).
@@ -434,9 +434,7 @@ internal_delete(QueueName) ->
               case mnesia:wread({rabbit_queue, QueueName}) of
                   []  -> rabbit_misc:const({error, not_found});
                   [_] -> Deletions = internal_delete1(QueueName),
-                         fun (Tx) -> ok = rabbit_binding:process_deletions(
-                                            Deletions, Tx)
-                         end
+                         rabbit_binding:process_deletions(Deletions)
               end
       end).
 
@@ -465,18 +463,14 @@ drop_expired(QPid) ->
     gen_server2:cast(QPid, drop_expired).
 
 on_node_down(Node) ->
-    rabbit_misc:execute_mnesia_transaction(
-      fun () -> qlc:e(qlc:q([delete_queue(QueueName) ||
-                                #amqqueue{name = QueueName, pid = Pid}
-                                    <- mnesia:table(rabbit_queue),
-                                node(Pid) == Node]))
-      end,
-      fun (Deletions, Tx) ->
-              rabbit_binding:process_deletions(
-                lists:foldl(fun rabbit_binding:combine_deletions/2,
-                            rabbit_binding:new_deletions(),
-                            Deletions),
-                Tx)
+    rabbit_misc:execute_mnesia_tx_with_tail(
+      fun () -> Dels = qlc:e(qlc:q([delete_queue(QueueName) ||
+                                       #amqqueue{name = QueueName, pid = Pid}
+                                           <- mnesia:table(rabbit_queue),
+                                       node(Pid) == Node])),
+                rabbit_binding:process_deletions(
+                  lists:foldl(fun rabbit_binding:combine_deletions/2,
+                              rabbit_binding:new_deletions(), Dels))
       end).
 
 delete_queue(QueueName) ->
diff --git a/src/rabbit_binding.erl b/src/rabbit_binding.erl
index dc119fbd..1944792e 100644
--- a/src/rabbit_binding.erl
+++ b/src/rabbit_binding.erl
@@ -21,7 +21,7 @@
 -export([list_for_source/1, list_for_destination/1,
          list_for_source_and_destination/2]).
 -export([new_deletions/0, combine_deletions/2, add_deletion/3,
-         process_deletions/2]).
+         process_deletions/1]).
 -export([info_keys/0, info/1, info/2, info_all/1, info_all/2]).
 %% these must all be run inside a mnesia tx
 -export([has_for_source/1, remove_for_source/1,
@@ -77,7 +77,7 @@
         (rabbit_types:binding_destination()) -> deletions()).
 -spec(remove_transient_for_destination/1 ::
         (rabbit_types:binding_destination()) -> deletions()).
--spec(process_deletions/2 :: (deletions(), boolean()) -> 'ok').
+-spec(process_deletions/1 :: (deletions()) -> rabbit_misc:thunk('ok')).
 -spec(combine_deletions/2 :: (deletions(), deletions()) -> deletions()).
 -spec(add_deletion/3 :: (rabbit_exchange:name(),
                          {'undefined' | rabbit_types:exchange(),
@@ -114,12 +114,14 @@ recover(XNames, QNames) ->
                                    end)
       end,
       fun (R = #route{binding = B = #binding{source = Src}}, Tx) ->
-              case Tx of
-                  true  -> ok = sync_transient_route(R, fun mnesia:write/3);
-                  false -> ok
-              end,
               {ok, X} = rabbit_exchange:lookup(Src),
-              rabbit_exchange:callback(X, add_binding, [Tx, X, B])
+              Serial = case Tx of
+                           true  -> ok = sync_transient_route(
+                                           R, fun mnesia:write/3),
+                                    transaction;
+                           false -> rabbit_exchange:serial(X)
+                       end,
+              rabbit_exchange:callback(X, add_binding, [Serial, X, B])
       end,
       rabbit_semi_durable_route),
     ok.
@@ -142,7 +144,7 @@ add(Binding, InnerFun) ->
               case InnerFun(Src, Dst) of
                   ok               -> case mnesia:read({rabbit_route, B}) of
                                           []  -> add(Src, Dst, B);
-                                          [_] -> fun rabbit_misc:const_ok/1
+                                          [_] -> fun rabbit_misc:const_ok/0
                                       end;
                   {error, _} = Err -> rabbit_misc:const(Err)
               end
@@ -154,10 +156,11 @@ add(Src, Dst, B) ->
           mnesia:read({rabbit_durable_route, B}) =:= []) of
         true  -> ok = sync_route(#route{binding = B}, SrcDurable, DstDurable,
                                  fun mnesia:write/3),
-                 fun (Tx) -> ok = rabbit_exchange:callback(Src, add_binding,
-                                                           [Tx, Src, B]),
-                             rabbit_event:notify_if(not Tx, binding_created,
-                                                    info(B))
+                 ok = rabbit_exchange:callback(Src, add_binding, [transaction, Src, B]),
+                 Serial = rabbit_exchange:serial(Src),
+                 fun () ->
+                     ok = rabbit_exchange:callback(Src, add_binding, [Serial, Src, B]),
+                     ok = rabbit_event:notify(binding_created, info(B))
                  end;
         false -> rabbit_misc:const({error, binding_not_found})
     end.
@@ -181,7 +184,7 @@ remove(Src, Dst, B) ->
     ok = sync_route(#route{binding = B}, durable(Src), durable(Dst),
                     fun mnesia:delete_object/3),
     Deletions = maybe_auto_delete(B#binding.source, [B], new_deletions()),
-    fun (Tx) -> ok = process_deletions(Deletions, Tx) end.
+    process_deletions(Deletions).
 
 list(VHostPath) ->
     VHostResource = rabbit_misc:r(VHostPath, '_'),
@@ -407,19 +410,29 @@ merge_entry({X1, Deleted1, Bindings1}, {X2, Deleted2, Bindings2}) ->
      anything_but(not_deleted, Deleted1, Deleted2),
      [Bindings1 | Bindings2]}.
 
-process_deletions(Deletions, Tx) ->
-    dict:fold(
-      fun (_XName, {X, Deleted, Bindings}, ok) ->
-              FlatBindings = lists:flatten(Bindings),
-              [rabbit_event:notify_if(not Tx, binding_deleted, info(B)) ||
-                  B <- FlatBindings],
-              case Deleted of
-                  not_deleted ->
-                      rabbit_exchange:callback(X, remove_bindings,
-                                               [Tx, X, FlatBindings]);
-                  deleted ->
-                      rabbit_event:notify_if(not Tx, exchange_deleted,
-                                             [{name, X#exchange.name}]),
-                      rabbit_exchange:callback(X, delete, [Tx, X, FlatBindings])
-              end
-      end, ok, Deletions).
+process_deletions(Deletions) ->
+    AugmentedDeletions =
+        dict:map(fun (_XName, {X, deleted, Bindings}) ->
+                         Bs = lists:flatten(Bindings),
+                         x_callback(transaction, X, delete, Bs),
+                         {X, deleted, Bs, none};
+                     (_XName, {X, not_deleted, Bindings}) ->
+                         Bs = lists:flatten(Bindings),
+                         x_callback(transaction, X, remove_bindings, Bs),
+                         {X, not_deleted, Bs, rabbit_exchange:serial(X)}
+                 end, Deletions),
+    fun() ->
+            dict:fold(fun (XName, {X, deleted, Bs, Serial}, ok) ->
+                              ok = rabbit_event:notify(
+                                     exchange_deleted, [{name, XName}]),
+                              del_notify(Bs),
+                              x_callback(Serial, X, delete, Bs);
+                          (_XName, {X, not_deleted, Bs, Serial}, ok) ->
+                              del_notify(Bs),
+                              x_callback(Serial, X, remove_bindings, Bs)
+                      end, ok, AugmentedDeletions)
+    end.
+
+del_notify(Bs) -> [rabbit_event:notify(binding_deleted, info(B)) || B <- Bs].
+
+x_callback(Arg, X, F, Bs) -> ok = rabbit_exchange:callback(X, F, [Arg, X, Bs]).
diff --git a/src/rabbit_exchange.erl b/src/rabbit_exchange.erl
index 42111773..28a639ac 100644
--- a/src/rabbit_exchange.erl
+++ b/src/rabbit_exchange.erl
@@ -23,8 +23,8 @@
          lookup/1, lookup_or_die/1, list/1,
          info_keys/0, info/1, info/2, info_all/1, info_all/2,
          publish/2, delete/2]).
-%% this must be run inside a mnesia tx
--export([maybe_auto_delete/1]).
+%% these must be run inside a mnesia tx
+-export([maybe_auto_delete/1, serial/1]).
 
 %%----------------------------------------------------------------------------
 
@@ -36,7 +36,7 @@
 -type(type() :: atom()).
 -type(fun_name() :: atom()).
 
--spec(recover/0 :: () -> [name()]).
+-spec(recover/0 :: () -> [rabbit_types:resource()]).
 -spec(callback/3:: (rabbit_types:exchange(), fun_name(), [any()]) -> 'ok').
 -spec(declare/6 ::
         (name(), type(), boolean(), boolean(), boolean(),
@@ -75,6 +75,7 @@
 -spec(maybe_auto_delete/1::
         (rabbit_types:exchange())
         -> 'not_deleted' | {'deleted', rabbit_binding:deletions()}).
+-spec(serial/1:: (rabbit_types:exchange()) -> 'none' | pos_integer()).
 
 -endif.
 
@@ -89,7 +90,7 @@ recover() ->
            end,
            fun (X, Tx) ->
                    case Tx of
-                       true  -> ok = mnesia:write(rabbit_exchange, X, write);
+                       true  -> store(X);
                        false -> ok
                    end,
                    rabbit_exchange:callback(X, create, [Tx, X])
@@ -97,8 +98,8 @@ recover() ->
            rabbit_durable_exchange),
     [XName || #exchange{name = XName} <- Xs].
 
-callback(#exchange{type = XType}, Fun, Args) ->
-    apply(type_to_module(XType), Fun, Args).
+callback(#exchange{type = Type}, Fun, Args) ->
+    apply(type_to_module(Type), Fun, Args).
 
 declare(XName, Type, Durable, AutoDelete, Internal, Args) ->
     X = #exchange{name        = XName,
@@ -107,13 +108,14 @@ declare(XName, Type, Durable, AutoDelete, Internal, Args) ->
                   auto_delete = AutoDelete,
                   internal    = Internal,
                   arguments   = Args},
+    XT = type_to_module(Type),
     %% We want to upset things if it isn't ok
-    ok = (type_to_module(Type)):validate(X),
+    ok = XT:validate(X),
     rabbit_misc:execute_mnesia_transaction(
       fun () ->
               case mnesia:wread({rabbit_exchange, XName}) of
                   [] ->
-                      ok = mnesia:write(rabbit_exchange, X, write),
+                      store(X),
                       ok = case Durable of
                                true  -> mnesia:write(rabbit_durable_exchange,
                                                      X, write);
@@ -125,7 +127,10 @@ declare(XName, Type, Durable, AutoDelete, Internal, Args) ->
               end
       end,
       fun ({new, Exchange}, Tx) ->
-              ok = (type_to_module(Type)):create(Tx, Exchange),
+              ok = XT:create(case Tx of
+                                 true  -> transaction;
+                                 false -> none
+                             end, Exchange),
               rabbit_event:notify_if(not Tx, exchange_created, info(Exchange)),
               Exchange;
           ({existing, Exchange}, _Tx) ->
@@ -134,6 +139,14 @@ declare(XName, Type, Durable, AutoDelete, Internal, Args) ->
               Err
       end).
 
+store(X = #exchange{name = Name, type = Type}) ->
+    ok = mnesia:write(rabbit_exchange, X, write),
+    case (type_to_module(Type)):serialise_events() of
+        true  -> S = #exchange_serial{name = Name, next = 1},
+                 ok = mnesia:write(rabbit_exchange_serial, S, write);
+        false -> ok
+    end.
+
 %% Used with binaries sent over the wire; the type may not exist.
 check_type(TypeBin) ->
     case rabbit_registry:binary_to_type(TypeBin) of
@@ -257,27 +270,30 @@ process_route(#resource{kind = queue} = QName,
               {WorkList, SeenXs, QNames}) ->
     {WorkList, SeenXs, [QName | QNames]}.
 
-call_with_exchange(XName, Fun, PrePostCommitFun) ->
-    rabbit_misc:execute_mnesia_transaction(
+call_with_exchange(XName, Fun) ->
+    rabbit_misc:execute_mnesia_tx_with_tail(
       fun () -> case mnesia:read({rabbit_exchange, XName}) of
-                    []  -> {error, not_found};
+                    []  -> rabbit_misc:const({error, not_found});
                     [X] -> Fun(X)
                 end
-      end, PrePostCommitFun).
+      end).
 
 delete(XName, IfUnused) ->
+    Fun = case IfUnused of
+              true  -> fun conditional_delete/1;
+              false -> fun unconditional_delete/1
+          end,
     call_with_exchange(
       XName,
-      case IfUnused of
-          true  -> fun conditional_delete/1;
-          false -> fun unconditional_delete/1
-      end,
-      fun ({deleted, X, Bs, Deletions}, Tx) ->
-              ok = rabbit_binding:process_deletions(
-                     rabbit_binding:add_deletion(
-                       XName, {X, deleted, Bs}, Deletions), Tx);
-          (Error = {error, _InUseOrNotFound}, _Tx) ->
-              Error
+      fun (X) ->
+              case Fun(X) of
+                  {deleted, X, Bs, Deletions} ->
+                      rabbit_binding:process_deletions(
+                        rabbit_binding:add_deletion(
+                          XName, {X, deleted, Bs}, Deletions));
+                  {error, _InUseOrNotFound} = E ->
+                      rabbit_misc:const(E)
+              end
       end).
 
 maybe_auto_delete(#exchange{auto_delete = false}) ->
@@ -297,9 +313,23 @@ conditional_delete(X = #exchange{name = XName}) ->
 unconditional_delete(X = #exchange{name = XName}) ->
     ok = mnesia:delete({rabbit_durable_exchange, XName}),
     ok = mnesia:delete({rabbit_exchange, XName}),
+    ok = mnesia:delete({rabbit_exchange_serial, XName}),
     Bindings = rabbit_binding:remove_for_source(XName),
     {deleted, X, Bindings, rabbit_binding:remove_for_destination(XName)}.
 
+serial(#exchange{name = XName, type = Type}) ->
+    case (type_to_module(Type)):serialise_events() of
+        true  -> next_serial(XName);
+        false -> none
+    end.
+
+next_serial(XName) ->
+    [#exchange_serial{next = Serial}] =
+        mnesia:read(rabbit_exchange_serial, XName, write),
+    ok = mnesia:write(rabbit_exchange_serial,
+                      #exchange_serial{name = XName, next = Serial + 1}, write),
+    Serial.
+
 %% Used with atoms from records; e.g., the type is expected to exist.
 type_to_module(T) ->
     {ok, Module} = rabbit_registry:lookup_module(exchange, T),
diff --git a/src/rabbit_exchange_type.erl b/src/rabbit_exchange_type.erl
index cd96407c..ab3d00dc 100644
--- a/src/rabbit_exchange_type.erl
+++ b/src/rabbit_exchange_type.erl
@@ -21,6 +21,13 @@
 behaviour_info(callbacks) ->
     [
      {description, 0},
+
+     %% Should Rabbit ensure that all binding events that are
+     %% delivered to an individual exchange can be serialised? (they
+     %% might still be delivered out of order, but there'll be a
+     %% serial number).
+     {serialise_events, 0},
+
      {route, 2},
 
      %% called BEFORE declaration, to check args etc; may exit with #amqp_error{}
diff --git a/src/rabbit_exchange_type_direct.erl b/src/rabbit_exchange_type_direct.erl
index 40078b1a..b485e31f 100644
--- a/src/rabbit_exchange_type_direct.erl
+++ b/src/rabbit_exchange_type_direct.erl
@@ -19,7 +19,7 @@
 
 -behaviour(rabbit_exchange_type).
 
--export([description/0, route/2]).
+-export([description/0, serialise_events/0, route/2]).
 -export([validate/1, create/2, delete/3,
          add_binding/3, remove_bindings/3, assert_args_equivalence/2]).
 -include("rabbit_exchange_type_spec.hrl").
@@ -35,6 +35,8 @@ description() ->
     [{name, <<"direct">>},
      {description, <<"AMQP direct exchange, as per the AMQP specification">>}].
 
+serialise_events() -> false.
+
 route(#exchange{name = Name},
       #delivery{message = #basic_message{routing_keys = Routes}}) ->
     rabbit_router:match_routing_key(Name, Routes).
diff --git a/src/rabbit_exchange_type_fanout.erl b/src/rabbit_exchange_type_fanout.erl
index f32ef917..3c029722 100644
--- a/src/rabbit_exchange_type_fanout.erl
+++ b/src/rabbit_exchange_type_fanout.erl
@@ -19,7 +19,7 @@
 
 -behaviour(rabbit_exchange_type).
 
--export([description/0, route/2]).
+-export([description/0, serialise_events/0, route/2]).
 -export([validate/1, create/2, delete/3, add_binding/3,
          remove_bindings/3, assert_args_equivalence/2]).
 -include("rabbit_exchange_type_spec.hrl").
@@ -35,6 +35,8 @@ description() ->
     [{name, <<"fanout">>},
      {description, <<"AMQP fanout exchange, as per the AMQP specification">>}].
 
+serialise_events() -> false.
+
 route(#exchange{name = Name}, _Delivery) ->
     rabbit_router:match_routing_key(Name, ['_']).
 
diff --git a/src/rabbit_exchange_type_headers.erl b/src/rabbit_exchange_type_headers.erl
index 139feb04..f09e4aae 100644
--- a/src/rabbit_exchange_type_headers.erl
+++ b/src/rabbit_exchange_type_headers.erl
@@ -20,7 +20,7 @@
 
 -behaviour(rabbit_exchange_type).
 
--export([description/0, route/2]).
+-export([description/0, serialise_events/0, route/2]).
 -export([validate/1, create/2, delete/3, add_binding/3,
          remove_bindings/3, assert_args_equivalence/2]).
 -include("rabbit_exchange_type_spec.hrl").
@@ -41,6 +41,8 @@ description() ->
     [{name, <<"headers">>},
      {description, <<"AMQP headers exchange, as per the AMQP specification">>}].
 
+serialise_events() -> false.
+
 route(#exchange{name = Name},
       #delivery{message = #basic_message{content = Content}}) ->
     Headers = case (Content#content.properties)#'P_basic'.headers of
diff --git a/src/rabbit_exchange_type_topic.erl b/src/rabbit_exchange_type_topic.erl
index 74c566b8..348655b1 100644
--- a/src/rabbit_exchange_type_topic.erl
+++ b/src/rabbit_exchange_type_topic.erl
@@ -20,7 +20,7 @@
 
 -behaviour(rabbit_exchange_type).
 
--export([description/0, route/2]).
+-export([description/0, serialise_events/0, route/2]).
 -export([validate/1, create/2, delete/3, add_binding/3,
          remove_bindings/3, assert_args_equivalence/2]).
 -include("rabbit_exchange_type_spec.hrl").
@@ -38,6 +38,8 @@ description() ->
     [{name, <<"topic">>},
      {description, <<"AMQP topic exchange, as per the AMQP specification">>}].
 
+serialise_events() -> false.
+
 %% NB: This may return duplicate results in some situations (that's ok)
 route(#exchange{name = X},
       #delivery{message = #basic_message{routing_keys = Routes}}) ->
@@ -49,19 +51,19 @@ route(#exchange{name = X},
 validate(_X) -> ok.
 create(_Tx, _X) -> ok.
 
-delete(true, #exchange{name = X}, _Bs) ->
+delete(transaction, #exchange{name = X}, _Bs) ->
     trie_remove_all_edges(X),
     trie_remove_all_bindings(X),
     ok;
-delete(false, _Exchange, _Bs) ->
+delete(none, _Exchange, _Bs) ->
     ok.
 
-add_binding(true, _Exchange, Binding) ->
+add_binding(transaction, _Exchange, Binding) ->
     internal_add_binding(Binding);
-add_binding(false, _Exchange, _Binding) ->
+add_binding(none, _Exchange, _Binding) ->
     ok.
 
-remove_bindings(true, #exchange{name = X}, Bs) ->
+remove_bindings(transaction, #exchange{name = X}, Bs) ->
     %% The remove process is split into two distinct phases. In the
     %% first phase we gather the lists of bindings and edges to
     %% delete, then in the second phase we process all the
@@ -80,7 +82,7 @@ remove_bindings(true, #exchange{name = X}, Bs) ->
     [trie_remove_edge(X, Parent, Node, W) ||
         {Node, {Parent, W, {0, 0}}} <- gb_trees:to_list(Paths)],
     ok;
-remove_bindings(false, _X, _Bs) ->
+remove_bindings(none, _X, _Bs) ->
     ok.
 
 maybe_add_path(_X, [{root, none}], PathAcc) ->
diff --git a/src/rabbit_misc.erl b/src/rabbit_misc.erl
index cec10ff6..d70b0c0b 100644
--- a/src/rabbit_misc.erl
+++ b/src/rabbit_misc.erl
@@ -53,7 +53,7 @@
 -export([all_module_attributes/1, build_acyclic_graph/3]).
 -export([now_ms/0]).
 -export([lock_file/1]).
--export([const_ok/1, const/1]).
+-export([const_ok/0, const/1]).
 -export([ntoa/1, ntoab/1]).
 -export([is_process_alive/1]).
 
@@ -61,11 +61,10 @@
 
 -ifdef(use_specs).
 
--export_type([resource_name/0, thunk/1, const/1]).
+-export_type([resource_name/0, thunk/1]).
 
 -type(ok_or_error() :: rabbit_types:ok_or_error(any())).
 -type(thunk(T) :: fun(() -> T)).
--type(const(T) :: fun((any()) -> T)).
 -type(resource_name() :: binary()).
 -type(optdef() :: {flag, string()} | {option, string(), any()}).
 -type(channel_or_connection_exit()
@@ -190,8 +189,8 @@
                                       digraph:vertex(), digraph:vertex()})).
 -spec(now_ms/0 :: () -> non_neg_integer()).
 -spec(lock_file/1 :: (file:filename()) -> rabbit_types:ok_or_error('eexist')).
--spec(const_ok/1 :: (any()) -> 'ok').
--spec(const/1 :: (A) -> const(A)).
+-spec(const_ok/0 :: () -> 'ok').
+-spec(const/1 :: (A) -> thunk(A)).
 -spec(ntoa/1 :: (inet:ip_address()) -> string()).
 -spec(ntoab/1 :: (inet:ip_address()) -> string()).
 -spec(is_process_alive/1 :: (pid()) -> boolean()).
@@ -404,17 +403,12 @@ execute_mnesia_transaction(TxFun, PrePostCommitFun) ->
                        end), false).
 
 %% Like execute_mnesia_transaction/2, but TxFun is expected to return a
-%% TailFun which gets called immediately before and after the tx commit
+%% TailFun which gets called (only) immediately after the tx commit
 execute_mnesia_tx_with_tail(TxFun) ->
     case mnesia:is_transaction() of
         true  -> execute_mnesia_transaction(TxFun);
-        false -> TailFun = execute_mnesia_transaction(
-                             fun () ->
-                                     TailFun1 = TxFun(),
-                                     TailFun1(true),
-                                     TailFun1
-                             end),
-                 TailFun(false)
+        false -> TailFun = execute_mnesia_transaction(TxFun),
+                 TailFun()
     end.
 
 ensure_ok(ok, _) -> ok;
@@ -843,8 +837,8 @@ lock_file(Path) ->
                  ok = file:close(Lock)
     end.
 
-const_ok(_) -> ok.
-const(X) -> fun (_) -> X end.
+const_ok() -> ok.
+const(X) -> fun () -> X end.
 
 %% Format IPv4-mapped IPv6 addresses as IPv4, since they're what we see
 %% when IPv6 is enabled but not used (i.e. 99% of the time).
diff --git a/src/rabbit_mnesia.erl b/src/rabbit_mnesia.erl
index 77b06d0c..2df76d4e 100644
--- a/src/rabbit_mnesia.erl
+++ b/src/rabbit_mnesia.erl
@@ -225,6 +225,10 @@ table_definitions() ->
       [{record_name, exchange},
        {attributes, record_info(fields, exchange)},
        {match, #exchange{name = exchange_name_match(), _='_'}}]},
+     {rabbit_exchange_serial,
+      [{record_name, exchange_serial},
+       {attributes, record_info(fields, exchange_serial)},
+       {match, #exchange_serial{name = exchange_name_match(), _='_'}}]},
      {rabbit_durable_queue,
       [{record_name, amqqueue},
        {attributes, record_info(fields, amqqueue)},
diff --git a/src/rabbit_tests.erl b/src/rabbit_tests.erl
index 524e8e6e..48119fae 100644
--- a/src/rabbit_tests.erl
+++ b/src/rabbit_tests.erl
@@ -691,10 +691,10 @@ test_topic_matching() ->
     test_topic_expect_match(X, [{"a.b.c", []}, {"b.b.c", []}, {"", []}]),
     passed.
 
-exchange_op_callback(X, Fun, ExtraArgs) ->
+exchange_op_callback(X, Fun, Args) ->
     rabbit_misc:execute_mnesia_transaction(
-      fun () -> rabbit_exchange:callback(X, Fun, [true, X] ++ ExtraArgs) end),
-    rabbit_exchange:callback(X, Fun, [false, X] ++ ExtraArgs).
+      fun () -> rabbit_exchange:callback(X, Fun, [transaction, X] ++ Args) end),
+    rabbit_exchange:callback(X, Fun, [none, X] ++ Args).
 
 test_topic_expect_match(X, List) ->
     lists:foreach(
diff --git a/src/rabbit_upgrade_functions.erl b/src/rabbit_upgrade_functions.erl
index 842c3b4f..1bd9a7c3 100644
--- a/src/rabbit_upgrade_functions.erl
+++ b/src/rabbit_upgrade_functions.erl
@@ -27,6 +27,7 @@
 -rabbit_upgrade({user_to_internal_user, mnesia, [hash_passwords]}).
 -rabbit_upgrade({topic_trie,            mnesia, []}).
 -rabbit_upgrade({semi_durable_route,    mnesia, []}).
+-rabbit_upgrade({exchange_event_serial, mnesia, []}).
 
 %% -------------------------------------------------------------------
 
@@ -38,6 +39,7 @@
 -spec(internal_exchanges/0 :: () -> 'ok').
 -spec(user_to_internal_user/0 :: () -> 'ok').
 -spec(topic_trie/0 :: () -> 'ok').
+-spec(exchange_event_serial/0 :: () -> 'ok').
 -spec(semi_durable_route/0 :: () -> 'ok').
 
 -endif.
@@ -106,6 +108,10 @@ topic_trie() ->
 semi_durable_route() ->
     create(rabbit_semi_durable_route, [{record_name, route},
                                        {attributes, [binding, value]}]).
+                                       
+exchange_event_serial() ->
+    create(rabbit_exchange_serial, [{record_name, exchange_serial},
+                                    {attributes, [name, next]}]).
 
 %%--------------------------------------------------------------------