Introduce rabbit_{exchange,amqqueue}:lookup_many/1

rabbit_amqqueue:lookup/1 already supports lists of keys
but it makes less sense for rabbit_exchange:lookup/1.

This introduces a uniform API element that can be used to look up
N entities by key while preserving the historically accumulated
difference that stems from the common access patterns
for each entity type.

(cherry picked from commit 4216b2a)

Conflicts:
	src/rabbit_amqqueue.erl
	src/rabbit_exchange.erl

Author: michaelklishin

src/rabbit_amqqueue.erl

@@ -22,7 +22,7 @@
          forget_all_durable/1, delete_crashed/1, delete_crashed/2,
          delete_crashed_internal/2]).
 -export([pseudo_queue/2, immutable/1]).
--export([lookup/1, not_found_or_absent/1, with/2, with/3, with_or_die/2,
+-export([lookup/1, lookup_many/1, not_found_or_absent/1, with/2, with/3, with_or_die/2,
          assert_equivalence/5,
          check_exclusive_access/2, with_exclusive_access_or_die/3,
          stat/1, deliver/2, requeue/3, ack/3, reject/4]).
@@ -94,13 +94,6 @@
 -spec update
         (name(), fun((rabbit_types:amqqueue()) -> rabbit_types:amqqueue())) ->
             'not_found' | rabbit_types:amqqueue().
--spec lookup
-        (name()) ->
-            rabbit_types:ok(rabbit_types:amqqueue()) |
-            rabbit_types:error('not_found');
-        ([name()]) ->
-            [rabbit_types:amqqueue()].
--spec not_found_or_absent(name()) -> not_found_or_absent().
 -spec with(name(), qfun(A)) ->
           A | rabbit_types:error(not_found_or_absent()).
 -spec with(name(), qfun(A), fun((not_found_or_absent()) -> B)) -> A | B.
@@ -436,6 +429,13 @@ add_default_binding(#amqqueue{name = QueueName}) ->
                                 args        = []},
                        ?INTERNAL_USER).
 
+-spec lookup
+        (name()) ->
+            rabbit_types:ok(rabbit_types:amqqueue()) |
+            rabbit_types:error('not_found');
+        ([name()]) ->
+            [rabbit_types:amqqueue()].
+
 lookup([])     -> [];                             %% optimisation
 lookup([Name]) -> ets:lookup(rabbit_queue, Name); %% optimisation
 lookup(Names) when is_list(Names) ->
@@ -445,6 +445,14 @@ lookup(Names) when is_list(Names) ->
 lookup(Name) ->
     rabbit_misc:dirty_read({rabbit_queue, Name}).
 
+
+-spec lookup_many ([name()]) -> [amqqueue:amqqueue()].
+
+lookup_many(Names) when is_list(Names) ->
+    lookup(Names).
+
+-spec not_found_or_absent(name()) -> not_found_or_absent().
+
 not_found_or_absent(Name) ->
     %% NB: we assume that the caller has already performed a lookup on
     %% rabbit_queue and not found anything

src/rabbit_exchange.erl

@@ -20,7 +20,7 @@
 
 -export([recover/1, policy_changed/2, callback/4, declare/7,
          assert_equivalence/6, assert_args_equivalence/2, check_type/1,
-         lookup/1, lookup_or_die/1, list/0, list/1, lookup_scratch/2,
+         lookup/1, lookup_many/1, lookup_or_die/1, list/0, list/1, lookup_scratch/2,
          update_scratch/3, update_decorators/1, immutable/1,
          info_keys/0, info/1, info/2, info_all/1, info_all/2, info_all/4,
          route/2, delete/3, validate_binding/2]).
@@ -55,9 +55,6 @@
 -spec assert_args_equivalence
         (rabbit_types:exchange(), rabbit_framing:amqp_table())
         -> 'ok' | rabbit_types:connection_exit().
--spec lookup_or_die
-        (name()) -> rabbit_types:exchange() |
-                    rabbit_types:channel_exit().
 -spec list() -> [rabbit_types:exchange()].
 -spec list_names() -> [rabbit_exchange:name()].
 -spec list(rabbit_types:vhost()) -> [rabbit_types:exchange()].
@@ -252,19 +249,26 @@ assert_args_equivalence(#exchange{ name = Name, arguments = Args },
 
 -spec lookup
         (name()) -> rabbit_types:ok(rabbit_types:exchange()) |
-                    rabbit_types:error('not_found');
-        ([name()]) ->
-            [rabbit_types:exchange()].
+                    rabbit_types:error('not_found').
 
-lookup([])     -> [];
-lookup([Name]) -> ets:lookup(rabbit_exchange, Name);
-lookup(Names) when is_list(Names) ->
-    %% Normally we'd call mnesia:dirty_read/1 here, but that is quite
-    %% expensive for reasons explained in rabbit_misc:dirty_read/1.
-    lists:append([ets:lookup(rabbit_exchange, Name) || Name <- Names]);
 lookup(Name) ->
     rabbit_misc:dirty_read({rabbit_exchange, Name}).
 
+
+-spec lookup_many([name()]) -> [rabbit_types:exchange()].
+
+lookup_many([])     -> [];
+lookup_many([Name]) -> ets:lookup(rabbit_exchange, Name);
+lookup_many(Names) when is_list(Names) ->
+    %% Normally we'd call mnesia:dirty_read/1 here, but that is quite
+    %% expensive for reasons explained in rabbit_misc:dirty_read/1.
+    lists:append([ets:lookup(rabbit_exchange, Name) || Name <- Names]).
+
+
+-spec lookup_or_die
+        (name()) -> rabbit_types:exchange() |
+                    rabbit_types:channel_exit().
+
 lookup_or_die(Name) ->
     case lookup(Name) of
         {ok, X}            -> X;