Set deleting exchange status

* Avoids race condition between declare and delete

2 files changed, 73 insertions, 19 deletions

diff --git a/src/rabbit_exchange.erl b/src/rabbit_exchange.erl
index 9502f3a78a..842aff9b19 100644
--- a/src/rabbit_exchange.erl
+++ b/src/rabbit_exchange.erl
@@ -166,24 +166,32 @@ declare(XName, Type, Durable, AutoDelete, Internal, Args) ->
     XT = type_to_module(Type),
     %% We want to upset things if it isn't ok
     ok = XT:validate(X),
-    rabbit_misc:execute_mnesia_transaction(
-      fun () ->
-              case mnesia:wread({rabbit_exchange, XName}) of
-                  [] ->
-                      {new, store(X)};
-                  [ExistingX] ->
-                      {existing, ExistingX}
-              end
-      end,
-      fun ({new, Exchange}, Tx) ->
-              ok = callback(X, create, map_create_tx(Tx), [Exchange]),
-              rabbit_event:notify_if(not Tx, exchange_created, info(Exchange)),
-              Exchange;
-          ({existing, Exchange}, _Tx) ->
-              Exchange;
-          (Err, _Tx) ->
-              Err
-      end).
+    case rabbit_runtime_parameters:lookup(XName#resource.virtual_host,
+                                          <<"exchange-delete">>,
+                                          XName#resource.name) of
+        not_found ->
+            rabbit_misc:execute_mnesia_transaction(
+              fun () ->
+                      case mnesia:wread({rabbit_exchange, XName}) of
+                          [] ->
+                              {new, store(X)};
+                          [ExistingX] ->
+                              {existing, ExistingX}
+                      end
+              end,
+              fun ({new, Exchange}, Tx) ->
+                      ok = callback(X, create, map_create_tx(Tx), [Exchange]),
+                      rabbit_event:notify_if(not Tx, exchange_created, info(Exchange)),
+                      Exchange;
+                  ({existing, Exchange}, _Tx) ->
+                      Exchange;
+                  (Err, _Tx) ->
+                      Err
+              end);
+        _ ->
+            rabbit_log:warning("Delete in progress ~p.~n.", [XName]),
+            X
+    end.
 
 map_create_tx(true)  -> transaction;
 map_create_tx(false) -> none.
@@ -427,6 +435,9 @@ delete(XName, IfUnused) ->
               true  -> fun conditional_delete/2;
               false -> fun unconditional_delete/2
           end,
+    rabbit_runtime_parameters:set(XName#resource.virtual_host,
+                                  <<"exchange-delete">>,
+                                  XName#resource.name, true, none),
     call_with_exchange(
       XName,
       fun (X) ->
@@ -438,7 +449,10 @@ delete(XName, IfUnused) ->
                   {error, _InUseOrNotFound} = E ->
                       rabbit_misc:const(E)
               end
-      end).
+      end),
+    rabbit_runtime_parameters:clear(XName#resource.virtual_host,
+                                    <<"exchange-delete">>,
+                                    XName#resource.name).
 
 validate_binding(X = #exchange{type = XType}, Binding) ->
     Module = type_to_module(XType),
diff --git a/src/rabbit_exchange_parameters.erl b/src/rabbit_exchange_parameters.erl
new file mode 100644
index 0000000000..793c06007a
--- /dev/null
+++ b/src/rabbit_exchange_parameters.erl
@@ -0,0 +1,40 @@
+%% The contents of this file are subject to the Mozilla Public License
+%% Version 1.1 (the "License"); you may not use this file except in
+%% compliance with the License. You may obtain a copy of the License
+%% at http://www.mozilla.org/MPL/
+%%
+%% Software distributed under the License is distributed on an "AS IS"
+%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+%% the License for the specific language governing rights and
+%% limitations under the License.
+%%
+%% The Original Code is RabbitMQ.
+%%
+%% The Initial Developer of the Original Code is GoPivotal, Inc.
+%% Copyright (c) 2007-2016 Pivotal Software, Inc.  All rights reserved.
+%%
+
+-module(rabbit_exchange_parameters).
+
+-behaviour(rabbit_runtime_parameter).
+
+-export([register/0]).
+-export([validate/5, notify/4, notify_clear/3]).
+
+-rabbit_boot_step({?MODULE,
+                   [{description, "exchange parameters"},
+                    {mfa, {rabbit_exchange_parameters, register, []}},
+                    {requires, rabbit_registry},
+                    {enables, recovery}]}).
+
+register() ->
+    rabbit_registry:register(runtime_parameter, <<"exchange-delete">>, ?MODULE).
+
+validate(_VHost, <<"exchange-delete">>, _Name, _Term, _User) ->
+    ok.
+
+notify(_VHost, <<"exchange-delete">>, _Name, _Term) ->
+    ok.
+
+notify_clear(_VHost, <<"exchange-delete">>, _Name) ->
+    ok.