Implementation of hook mechanism using ETS table for storage of hooks, along with test cases to validate functionality

3 files changed, 106 insertions, 0 deletions

diff --git a/src/rabbit.erl b/src/rabbit.erl
index 088fa436..b0d62b5a 100644
--- a/src/rabbit.erl
+++ b/src/rabbit.erl
@@ -133,6 +133,7 @@ start(normal, []) ->
        {"core processes",
         fun () ->
                 ok = start_child(rabbit_log),
+                ok = rabbit_hooks:start(),
 
                 ok = rabbit_amqqueue:start(),
 
diff --git a/src/rabbit_hooks.erl b/src/rabbit_hooks.erl
new file mode 100644
index 00000000..454171ca
--- /dev/null
+++ b/src/rabbit_hooks.erl
@@ -0,0 +1,70 @@
+%%   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 Developers of the Original Code are LShift Ltd,
+%%   Cohesive Financial Technologies LLC, and Rabbit Technologies Ltd.
+%%
+%%   Portions created before 22-Nov-2008 00:00:00 GMT by LShift Ltd,
+%%   Cohesive Financial Technologies LLC, or Rabbit Technologies Ltd
+%%   are Copyright (C) 2007-2008 LShift Ltd, Cohesive Financial
+%%   Technologies LLC, and Rabbit Technologies Ltd.
+%%
+%%   Portions created by LShift Ltd are Copyright (C) 2007-2009 LShift
+%%   Ltd. Portions created by Cohesive Financial Technologies LLC are
+%%   Copyright (C) 2007-2009 Cohesive Financial Technologies
+%%   LLC. Portions created by Rabbit Technologies Ltd are Copyright
+%%   (C) 2007-2009 Rabbit Technologies Ltd.
+%%
+%%   All Rights Reserved.
+%%
+%%   Contributor(s): ______________________________________.
+%%
+
+-module(rabbit_hooks).
+
+-export([start/0]).
+-export([subscribe/3, unsubscribe/2, trigger/2]).
+
+-define(TableName, rabbit_hooks).
+
+-ifdef(use_specs).
+
+-type(hookfun() :: fun((list()) -> 'ok')).
+
+-spec(start/0 :: () -> 'ok').
+-spec(subscribe/3 :: (atom(), atom(), hookfun()) -> 'ok').
+-spec(unsubscribe/2 :: (atom(), atom()) -> 'ok').
+-spec(trigger/2 :: (atom(), list()) -> 'ok').
+
+-endif.
+
+start() ->
+    ets:new(?TableName, [bag, public, named_table]),
+    ok.
+
+subscribe(Hook, HandlerName, Handler) ->
+    ets:insert(?TableName, {Hook, HandlerName, Handler}),
+    ok.
+
+unsubscribe(Hook, HandlerName) ->
+    ets:match_delete(?TableName, {Hook, HandlerName, '_'}),
+    ok.
+
+trigger(Hook, Args) ->
+    Hooks = ets:lookup(?TableName, Hook),
+    [case catch H(Args) of
+        {'EXIT', Reason} -> 
+            rabbit_log:warning("Failed to execute handler ~p for hook ~p: ~p", 
+                               [Name, Hook, Reason]);
+        _ -> ok
+     end || {_, Name, H} <- Hooks],
+    ok.
diff --git a/src/rabbit_tests.erl b/src/rabbit_tests.erl
index 01757509..aef8c9d8 100644
--- a/src/rabbit_tests.erl
+++ b/src/rabbit_tests.erl
@@ -54,6 +54,7 @@ all_tests() ->
     passed = test_cluster_management(),
     passed = test_user_management(),
     passed = test_server_status(),
+    passed = test_hooks(),
     passed.
 
 test_priority_queue() ->
@@ -601,6 +602,40 @@ test_server_status() ->
 
     passed.
 
+test_hooks() ->
+    %% Firing of hooks calls all hooks in an isolated manner
+    rabbit_hooks:subscribe(test_hook, test, 
+                           fun(Args) -> 
+                               put(fired_testhook_handler, Args) 
+                           end),
+    rabbit_hooks:subscribe(test_hook, test2, 
+                           fun(Args) -> 
+                               put(fired_testhook_handler2, Args) 
+                           end),
+    rabbit_hooks:subscribe(test_hook2, test2,
+                           fun(Args) ->
+                               put(fired_testhook2_handler, Args)
+                           end),
+    rabbit_hooks:trigger(test_hook, [arg1, arg2]),
+    [arg1, arg2] = get(fired_testhook_handler),
+    [arg1, arg2] = get(fired_testhook_handler2),
+    undefined = get(fired_testhook2_handler),
+
+    %% Hook Deletion works
+    put(fired_testhook_handler, undefined),
+    put(fired_testhook_handler2, undefined),
+    rabbit_hooks:unsubscribe(test_hook, test),
+    rabbit_hooks:trigger(test_hook, [arg3, arg4]),
+    undefined = get(fired_testhook_handler),
+    [arg3, arg4] = get(fired_testhook_handler2),
+    undefined = get(fired_testhook2_handler),
+
+    %% Catches exceptions from bad hooks
+    rabbit_hooks:subscribe(test_hook3, test, fun(Args) -> bad:bad() end),
+    ok = rabbit_hooks:trigger(test_hook3, []),
+
+    passed.
+
 %---------------------------------------------------------------------
 
 control_action(Command, Args) -> control_action(Command, node(), Args).