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)

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, pseudo_queue/3, 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, deliver/3, requeue/4, ack/4, reject/5]).
@@ -488,6 +488,11 @@ 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) ->

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, count/0]).
@@ -219,19 +219,22 @@ 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().