Transplant of bug25152

3 files changed, 50 insertions, 22 deletions

diff --git a/src/rabbit_amqqueue.erl b/src/rabbit_amqqueue.erl
index 8d7ed408..0cdadd0f 100644
--- a/src/rabbit_amqqueue.erl
+++ b/src/rabbit_amqqueue.erl
@@ -548,7 +548,12 @@ flush_all(QPids, ChPid) ->
 
 internal_delete1(QueueName) ->
     ok = mnesia:delete({rabbit_queue, QueueName}),
-    ok = mnesia:delete({rabbit_durable_queue, QueueName}),
+    %% this 'guarded' delete prevents unnecessary writes to the mnesia
+    %% disk log
+    case mnesia:wread({rabbit_durable_queue, QueueName}) of
+        []  -> ok;
+        [_] -> ok = mnesia:delete({rabbit_durable_queue, QueueName})
+    end,
     %% we want to execute some things, as decided by rabbit_exchange,
     %% after the transaction.
     rabbit_binding:remove_for_destination(QueueName).
diff --git a/src/rabbit_binding.erl b/src/rabbit_binding.erl
index bb44797e..0993dfad 100644
--- a/src/rabbit_binding.erl
+++ b/src/rabbit_binding.erl
@@ -279,21 +279,15 @@ has_for_source(SrcName) ->
 remove_for_source(SrcName) ->
     lock_route_tables(),
     Match = #route{binding = #binding{source = SrcName, _ = '_'}},
-    Routes = lists:usort(
-               mnesia:match_object(rabbit_route, Match, write) ++
-                   mnesia:match_object(rabbit_durable_route, Match, write)),
-    [begin
-         sync_route(Route, fun mnesia:delete_object/3),
-         Route#route.binding
-     end || Route <- Routes].
+    remove_routes(
+      lists:usort(mnesia:match_object(rabbit_route, Match, write) ++
+                      mnesia:match_object(rabbit_durable_route, Match, write))).
 
-remove_for_destination(Dst) ->
-    remove_for_destination(
-      Dst, fun (R) -> sync_route(R, fun mnesia:delete_object/3) end).
+remove_for_destination(DstName) ->
+    remove_for_destination(DstName, fun remove_routes/1).
 
-remove_transient_for_destination(Dst) ->
-    remove_for_destination(
-      Dst, fun (R) -> sync_transient_route(R, fun mnesia:delete_object/3) end).
+remove_transient_for_destination(DstName) ->
+    remove_for_destination(DstName, fun remove_transient_routes/1).
 
 %%----------------------------------------------------------------------------
 
@@ -310,6 +304,14 @@ binding_action(Binding = #binding{source      = SrcName,
               Fun(Src, Dst, Binding#binding{args = SortedArgs})
       end).
 
+delete_object(Tab, Record, LockKind) ->
+    %% this 'guarded' delete prevents unnecessary writes to the mnesia
+    %% disk log
+    case mnesia:match_object(Tab, Record, LockKind) of
+        []  -> ok;
+        [_] -> mnesia:delete_object(Tab, Record, LockKind)
+    end.
+
 sync_route(R, Fun) -> sync_route(R, true, true, Fun).
 
 sync_route(Route, true, true, Fun) ->
@@ -372,16 +374,32 @@ lock_route_tables() ->
                                              rabbit_semi_durable_route,
                                              rabbit_durable_route]].
 
-remove_for_destination(DstName, DeleteFun) ->
+remove_routes(Routes) ->
+    %% This partitioning allows us to suppress unnecessary delete
+    %% operations on disk tables, which require an fsync.
+    {TransientRoutes, DurableRoutes} =
+        lists:partition(fun (R) -> mnesia:match_object(
+                                     rabbit_durable_route, R, write) == [] end,
+                        Routes),
+    [ok = sync_transient_route(R, fun mnesia:delete_object/3) ||
+        R <- TransientRoutes],
+    [ok = sync_route(R, fun mnesia:delete_object/3) ||
+        R <- DurableRoutes],
+    [R#route.binding || R <- Routes].
+
+remove_transient_routes(Routes) ->
+    [begin
+         ok = sync_transient_route(R, fun delete_object/3),
+         R#route.binding
+     end || R <- Routes].
+
+remove_for_destination(DstName, Fun) ->
     lock_route_tables(),
     Match = reverse_route(
               #route{binding = #binding{destination = DstName, _ = '_'}}),
-    ReverseRoutes = mnesia:match_object(rabbit_reverse_route, Match, write),
-    Bindings = [begin
-                    Route = reverse_route(ReverseRoute),
-                    ok = DeleteFun(Route),
-                    Route#route.binding
-                end || ReverseRoute <- ReverseRoutes],
+    Routes = [reverse_route(R) || R <- mnesia:match_object(
+                                         rabbit_reverse_route, Match, write)],
+    Bindings = Fun(Routes),
     group_bindings_fold(fun maybe_auto_delete/3, new_deletions(),
                         lists:keysort(#binding.source, Bindings)).
 
diff --git a/src/rabbit_exchange.erl b/src/rabbit_exchange.erl
index 910a89b4..2253cca1 100644
--- a/src/rabbit_exchange.erl
+++ b/src/rabbit_exchange.erl
@@ -335,7 +335,12 @@ conditional_delete(X = #exchange{name = XName}) ->
     end.
 
 unconditional_delete(X = #exchange{name = XName}) ->
-    ok = mnesia:delete({rabbit_durable_exchange, XName}),
+    %% this 'guarded' delete prevents unnecessary writes to the mnesia
+    %% disk log
+    case mnesia:wread({rabbit_durable_exchange, XName}) of
+        []  -> ok;
+        [_] -> ok = mnesia:delete({rabbit_durable_exchange, XName})
+    end,
     ok = mnesia:delete({rabbit_exchange, XName}),
     ok = mnesia:delete({rabbit_exchange_serial, XName}),
     Bindings = rabbit_binding:remove_for_source(XName),