Merge in bug25725.

7 files changed, 139 insertions, 18 deletions

diff --git a/include/rabbit.hrl b/include/rabbit.hrl
index 6df44bea..a764855e 100644
--- a/include/rabbit.hrl
+++ b/include/rabbit.hrl
@@ -45,7 +45,7 @@
 
 -record(amqqueue, {name, durable, auto_delete, exclusive_owner = none,
                    arguments, pid, slave_pids, sync_slave_pids, policy,
-                   gm_pids}).
+                   gm_pids, decorators}).
 
 %% mnesia doesn't like unary records, so we add a dummy 'value' field
 -record(route, {binding, value = const}).
diff --git a/src/rabbit_amqqueue.erl b/src/rabbit_amqqueue.erl
index 0673ff8e..38d72479 100644
--- a/src/rabbit_amqqueue.erl
+++ b/src/rabbit_amqqueue.erl
@@ -26,7 +26,7 @@
 -export([list/0, list/1, info_keys/0, info/1, info/2, info_all/1, info_all/2]).
 -export([force_event_refresh/0, wake_up/1]).
 -export([consumers/1, consumers_all/1, consumer_info_keys/0]).
--export([basic_get/4, basic_consume/10, basic_cancel/4]).
+-export([basic_get/4, basic_consume/10, basic_cancel/4, notify_decorators/1]).
 -export([notify_sent/2, notify_sent_queue_down/1, resume/2, flush_all/2]).
 -export([notify_down_all/2, activate_limit_all/2, credit/5]).
 -export([on_node_down/1]).
@@ -79,7 +79,8 @@
         -> queue_or_absent() | rabbit_misc:thunk(queue_or_absent())).
 -spec(update/2 ::
         (name(),
-         fun((rabbit_types:amqqueue()) -> rabbit_types:amqqueue())) -> 'ok').
+         fun((rabbit_types:amqqueue()) -> rabbit_types:amqqueue()))
+         -> 'not_found' | rabbit_types:amqqueue()).
 -spec(lookup/1 ::
         (name()) -> rabbit_types:ok(rabbit_types:amqqueue()) |
                     rabbit_types:error('not_found');
@@ -155,6 +156,7 @@
         -> rabbit_types:ok_or_error('exclusive_consume_unavailable')).
 -spec(basic_cancel/4 ::
         (rabbit_types:amqqueue(), pid(), rabbit_types:ctag(), any()) -> 'ok').
+-spec(notify_decorators/1 :: (rabbit_types:amqqueue()) -> 'ok').
 -spec(notify_sent/2 :: (pid(), pid()) -> 'ok').
 -spec(notify_sent_queue_down/1 :: (pid()) -> 'ok').
 -spec(resume/2 :: (pid(), pid()) -> 'ok').
@@ -278,9 +280,10 @@ update(Name, Fun) ->
             case Durable of
                 true -> ok = mnesia:write(rabbit_durable_queue, Q1, write);
                 _    -> ok
-            end;
+            end,
+            Q1;
         [] ->
-            ok
+            not_found
     end.
 
 store_queue(Q = #amqqueue{durable = true}) ->
@@ -294,8 +297,12 @@ store_queue(Q = #amqqueue{durable = false}) ->
     ok = mnesia:write(rabbit_queue, Q, write),
     ok.
 
-policy_changed(Q1, Q2) ->
+policy_changed(Q1 = #amqqueue{decorators = Decorators1},
+               Q2 = #amqqueue{decorators = Decorators2}) ->
     rabbit_mirror_queue_misc:update_mirrors(Q1, Q2),
+    D1 = rabbit_queue_decorator:select(Decorators1),
+    D2 = rabbit_queue_decorator:select(Decorators2),
+    [ok = M:policy_changed(Q1, Q2) || M <- lists:usort(D1 ++ D2)],
     %% Make sure we emit a stats event even if nothing
     %% mirroring-related has changed - the policy may have changed anyway.
     wake_up(Q1).
@@ -568,6 +575,9 @@ basic_consume(#amqqueue{pid = QPid, name = QName}, NoAck, ChPid,
 basic_cancel(#amqqueue{pid = QPid}, ChPid, ConsumerTag, OkMsg) ->
     delegate:call(QPid, {basic_cancel, ChPid, ConsumerTag, OkMsg}).
 
+notify_decorators(#amqqueue{pid = QPid}) ->
+    delegate:cast(QPid, notify_decorators).
+
 notify_sent(QPid, ChPid) ->
     Key = {consumer_credit_to, QPid},
     put(Key, case get(Key) of
diff --git a/src/rabbit_amqqueue_process.erl b/src/rabbit_amqqueue_process.erl
index 972e6be0..8f2dbc84 100644
--- a/src/rabbit_amqqueue_process.erl
+++ b/src/rabbit_amqqueue_process.erl
@@ -137,9 +137,11 @@ init_with_backing_queue_state(Q = #amqqueue{exclusive_owner = Owner}, BQ, BQS,
                      senders             = Senders,
                      msg_id_to_channel   = MTC},
     State2 = process_args(State1),
-    lists:foldl(fun (Delivery, StateN) ->
-                        deliver_or_enqueue(Delivery, true, StateN)
-                end, State2, Deliveries).
+    State3 = lists:foldl(fun (Delivery, StateN) ->
+                                 deliver_or_enqueue(Delivery, true, StateN)
+                         end, State2, Deliveries),
+    notify_decorators(startup, [], State3),
+    State3.
 
 init_state(Q) ->
     State = #q{q                   = Q,
@@ -198,6 +200,7 @@ declare(Recover, From, State = #q{q                   = Q,
                     recovery_barrier(Recover),
                     State1 = process_args(State#q{backing_queue       = BQ,
                                                   backing_queue_state = BQS}),
+                    notify_decorators(startup, [], State),
                     rabbit_event:notify(queue_created,
                                         infos(?CREATION_EVENT_KEYS, State1)),
                     rabbit_event:if_enabled(State1, #q.stats_timer,
@@ -222,6 +225,27 @@ matches(new, Q1, Q2) ->
 matches(_,  Q,   Q) -> true;
 matches(_, _Q, _Q1) -> false.
 
+notify_decorators(Event, Props, State) when Event =:= startup;
+                                            Event =:= shutdown ->
+    decorator_callback(qname(State), Event, Props);
+
+notify_decorators(Event, Props, State = #q{active_consumers    = ACs,
+                                           backing_queue       = BQ,
+                                           backing_queue_state = BQS}) ->
+    decorator_callback(
+      qname(State), notify,
+      [Event, [{max_active_consumer_priority, priority_queue:highest(ACs)},
+               {is_empty,                     BQ:is_empty(BQS)} | Props]]).
+
+decorator_callback(QName, F, A) ->
+    %% Look up again in case policy and hence decorators have changed
+    case rabbit_amqqueue:lookup(QName) of
+        {ok, Q = #amqqueue{decorators = Ds}} ->
+            [ok = apply(M, F, [Q|A]) || M <- rabbit_queue_decorator:select(Ds)];
+        {error, not_found} ->
+            ok
+    end.
+
 bq_init(BQ, Q, Recover) ->
     Self = self(),
     BQ:init(Q, Recover =/= new,
@@ -275,6 +299,7 @@ terminate_shutdown(Fun, State) ->
         undefined -> State1;
         _         -> ok = rabbit_memory_monitor:deregister(self()),
                      QName = qname(State),
+                     notify_decorators(shutdown, [], State),
                      [emit_consumer_deleted(Ch, CTag, QName)
                       || {Ch, CTag, _} <- consumers(State1)],
                      State1#q{backing_queue_state = Fun(BQS)}
@@ -405,15 +430,18 @@ erase_ch_record(#cr{ch_pid = ChPid, monitor_ref = MonitorRef}) ->
 
 all_ch_record() -> [C || {{ch, _}, C} <- get()].
 
-block_consumer(C = #cr{blocked_consumers = Blocked}, QEntry) ->
-    update_ch_record(C#cr{blocked_consumers = add_consumer(QEntry, Blocked)}).
+block_consumer(C = #cr{blocked_consumers = Blocked},
+               {_ChPid, #consumer{tag = CTag}} = QEntry, State) ->
+    update_ch_record(C#cr{blocked_consumers = add_consumer(QEntry, Blocked)}),
+    notify_decorators(consumer_blocked, [{consumer_tag, CTag}], State).
 
 is_ch_blocked(#cr{unsent_message_count = Count, limiter = Limiter}) ->
     Count >= ?UNSENT_MESSAGE_LIMIT orelse rabbit_limiter:is_suspended(Limiter).
 
 maybe_send_drained(WasEmpty, State) ->
     case (not WasEmpty) andalso is_empty(State) of
-        true  -> [send_drained(C) || C <- all_ch_record()];
+        true  -> notify_decorators(queue_empty, [], State),
+                 [send_drained(C) || C <- all_ch_record()];
         false -> ok
     end,
     State.
@@ -443,13 +471,13 @@ deliver_msgs_to_consumers(DeliverFun, false,
 deliver_msg_to_consumer(DeliverFun, E = {ChPid, Consumer}, Priority, State) ->
     C = lookup_ch(ChPid),
     case is_ch_blocked(C) of
-        true  -> block_consumer(C, E),
+        true  -> block_consumer(C, E, State),
                  {false, State};
         false -> case rabbit_limiter:can_send(C#cr.limiter,
                                               Consumer#consumer.ack_required,
                                               Consumer#consumer.tag) of
                      {suspend, Limiter} ->
-                         block_consumer(C#cr{limiter = Limiter}, E),
+                         block_consumer(C#cr{limiter = Limiter}, E, State),
                          {false, State};
                      {continue, Limiter} ->
                          AC1 = priority_queue:in(E, Priority,
@@ -674,6 +702,9 @@ unblock(State, C = #cr{limiter = Limiter}) ->
             update_ch_record(C#cr{blocked_consumers = BlockedQ}),
             AC1 = priority_queue:join(State#q.active_consumers, UnblockedQ),
             State1 = State#q{active_consumers = AC1},
+            [notify_decorators(
+               consumer_unblocked, [{consumer_tag, CTag}], State1) ||
+                {_P, {_ChPid, #consumer{tag = CTag}}} <- Unblocked],
             run_message_queue(State1)
     end.
 
@@ -1181,6 +1212,8 @@ handle_call({basic_consume, NoAck, ChPid, LimiterPid, LimiterActive,
                                   not NoAck, qname(State1), OtherArgs),
             AC1 = add_consumer({ChPid, Consumer}, State1#q.active_consumers),
             State2 = State1#q{active_consumers = AC1},
+            notify_decorators(
+              basic_consume, [{consumer_tag, ConsumerTag}], State2),
             reply(ok, run_message_queue(State2))
     end;
 
@@ -1211,6 +1244,8 @@ handle_call({basic_cancel, ChPid, ConsumerTag, OkMsg}, _From,
                        active_consumers   = remove_consumer(
                                               ChPid, ConsumerTag,
                                               State#q.active_consumers)},
+            notify_decorators(
+              basic_cancel, [{consumer_tag, ConsumerTag}], State1),
             case should_auto_delete(State1) of
                 false -> reply(ok, ensure_expiry_timer(State1));
                 true  -> stop(ok, State1)
@@ -1388,6 +1423,10 @@ handle_cast({credit, ChPid, CTag, Credit, Drain},
                          end
             end);
 
+handle_cast(notify_decorators, State) ->
+    notify_decorators(refresh, [], State),
+    noreply(State);
+
 handle_cast(wake_up, State) ->
     noreply(State).
 
diff --git a/src/rabbit_policy.erl b/src/rabbit_policy.erl
index 0785d278..738fa92a 100644
--- a/src/rabbit_policy.erl
+++ b/src/rabbit_policy.erl
@@ -46,7 +46,8 @@ name(#exchange{policy = Policy}) -> name0(Policy).
 name0(undefined) -> none;
 name0(Policy)    -> pget(name, Policy).
 
-set(Q = #amqqueue{name = Name}) -> Q#amqqueue{policy = set0(Name)};
+set(Q = #amqqueue{name = Name}) -> rabbit_queue_decorator:set(
+                                     Q#amqqueue{policy = set0(Name)});
 set(X = #exchange{name = Name}) -> rabbit_exchange_decorator:set(
                                      X#exchange{policy = set0(Name)}).
 
@@ -228,9 +229,14 @@ update_exchange(X = #exchange{name = XName, policy = OldPolicy}, Policies) ->
 update_queue(Q = #amqqueue{name = QName, policy = OldPolicy}, Policies) ->
     case match(QName, Policies) of
         OldPolicy -> no_change;
-        NewPolicy -> rabbit_amqqueue:update(
-                       QName, fun(Q1) -> Q1#amqqueue{policy = NewPolicy} end),
-                     {Q, Q#amqqueue{policy = NewPolicy}}
+        NewPolicy -> case rabbit_amqqueue:update(
+                       QName, fun(Q1) ->
+                                      rabbit_queue_decorator:set(
+                                        Q1#amqqueue{policy = NewPolicy})
+                              end) of
+                         #amqqueue{} = Q1 -> {Q, Q1};
+                         not_found        -> {Q, Q }
+                     end
     end.
 
 notify(no_change)->
diff --git a/src/rabbit_queue_decorator.erl b/src/rabbit_queue_decorator.erl
new file mode 100644
index 00000000..8f6375a5
--- /dev/null
+++ b/src/rabbit_queue_decorator.erl
@@ -0,0 +1,48 @@
+-module(rabbit_queue_decorator).
+
+-include("rabbit.hrl").
+
+-export([select/1, set/1]).
+
+%%----------------------------------------------------------------------------
+
+-ifdef(use_specs).
+
+-type(notify_event() :: 'consumer_blocked'   |
+                        'consumer_unblocked' |
+                        'queue_empty'        |
+                        'basic_consume'      |
+                        'basic_cancel'       |
+                        'refresh').
+
+-callback startup(rabbit_types:amqqueue()) -> 'ok'.
+
+-callback shutdown(rabbit_types:amqqueue()) -> 'ok'.
+
+-callback policy_changed(rabbit_types:amqqueue(), rabbit_types:amqqueue()) ->
+    'ok'.
+
+-callback active_for(rabbit_types:amqqueue()) -> boolean().
+
+-callback notify(rabbit_types:amqqueue(), notify_event(), any()) -> 'ok'.
+
+-else.
+
+-export([behaviour_info/1]).
+
+behaviour_info(callbacks) ->
+    [{description, 0}, {startup, 1}, {shutdown, 1}, {policy_changed, 2},
+     {active_for, 1}, {notify, 3}];
+behaviour_info(_Other) ->
+    undefined.
+
+-endif.
+
+%%----------------------------------------------------------------------------
+
+select(Modules) ->
+    [M || M <- Modules, code:which(M) =/= non_existing].
+
+set(Q) -> Q#amqqueue{decorators = [D || D <- list(), D:active_for(Q)]}.
+
+list() -> [M || {_, M} <- rabbit_registry:lookup_all(queue_decorator)].
diff --git a/src/rabbit_registry.erl b/src/rabbit_registry.erl
index f933e4e9..3014aeb7 100644
--- a/src/rabbit_registry.erl
+++ b/src/rabbit_registry.erl
@@ -130,6 +130,7 @@ class_module(exchange)           -> rabbit_exchange_type;
 class_module(auth_mechanism)     -> rabbit_auth_mechanism;
 class_module(runtime_parameter)  -> rabbit_runtime_parameter;
 class_module(exchange_decorator) -> rabbit_exchange_decorator;
+class_module(queue_decorator)    -> rabbit_queue_decorator;
 class_module(policy_validator)   -> rabbit_policy_validator;
 class_module(ha_mode)            -> rabbit_mirror_queue_mode.
 
diff --git a/src/rabbit_upgrade_functions.erl b/src/rabbit_upgrade_functions.erl
index d50cb282..6f95ef60 100644
--- a/src/rabbit_upgrade_functions.erl
+++ b/src/rabbit_upgrade_functions.erl
@@ -45,6 +45,7 @@
 -rabbit_upgrade({gm_pids,               mnesia, [no_mirror_nodes]}).
 -rabbit_upgrade({exchange_decorators,   mnesia, [policy]}).
 -rabbit_upgrade({policy_apply_to,       mnesia, [runtime_parameters]}).
+-rabbit_upgrade({queue_decorators,      mnesia, [gm_pids]}).
 
 %% -------------------------------------------------------------------
 
@@ -72,6 +73,7 @@
 -spec(gm_pids/0               :: () -> 'ok').
 -spec(exchange_decorators/0   :: () -> 'ok').
 -spec(policy_apply_to/0       :: () -> 'ok').
+-spec(queue_decorators/0      :: () -> 'ok').
 
 -endif.
 
@@ -323,6 +325,21 @@ apply_to(Def) ->
         [_,         _]         -> <<"all">>
     end.
 
+queue_decorators() ->
+    ok = queue_decorators(rabbit_queue),
+    ok = queue_decorators(rabbit_durable_queue).
+
+queue_decorators(Table) ->
+    transform(
+      Table,
+      fun ({amqqueue, Name, Durable, AutoDelete, ExclusiveOwner, Arguments,
+            Pid, SlavePids, SyncSlavePids, Policy, GmPids}) ->
+              {amqqueue, Name, Durable, AutoDelete, ExclusiveOwner, Arguments,
+               Pid, SlavePids, SyncSlavePids, Policy, GmPids, []}
+      end,
+      [name, durable, auto_delete, exclusive_owner, arguments, pid, slave_pids,
+       sync_slave_pids, policy, gm_pids, decorators]).
+
 %%--------------------------------------------------------------------
 
 transform(TableName, Fun, FieldList) ->