1 files changed, 29 insertions, 58 deletions

diff --git a/src/rabbit.erl b/src/rabbit.erl
index 8c36a9f0..a1dd2c2e 100644
--- a/src/rabbit.erl
+++ b/src/rabbit.erl
@@ -301,49 +301,38 @@ run_boot_step({StepName, Attributes}) ->
             ok
     end.
 
-module_attributes(Module) ->
-    case catch Module:module_info(attributes) of
-        {'EXIT', {undef, [{Module, module_info, _} | _]}} ->
-            io:format("WARNING: module ~p not found, so not scanned for boot steps.~n",
-                      [Module]),
-            [];
-        {'EXIT', Reason} ->
-            exit(Reason);
-        V ->
-            V
-    end.
-
 boot_steps() ->
-    AllApps = [App || {App, _, _} <- application:loaded_applications()],
-    Modules = lists:usort(
-                lists:append([Modules
-                              || {ok, Modules} <-
-                                     [application:get_key(App, modules)
-                                      || App <- AllApps]])),
-    UnsortedSteps =
-        lists:flatmap(fun (Module) ->
-                              [{StepName, Attributes}
-                               || {rabbit_boot_step, [{StepName, Attributes}]}
-                                      <- module_attributes(Module)]
-                      end, Modules),
-    sort_boot_steps(UnsortedSteps).
+    sort_boot_steps(rabbit_misc:all_module_attributes(rabbit_boot_step)).
+
+vertices(_Module, Steps) ->
+    [{StepName, {StepName, Atts}} || {StepName, Atts} <- Steps].
+
+edges(_Module, Steps) ->
+    [case Key of
+         requires -> {StepName, OtherStep};
+         enables  -> {OtherStep, StepName}
+     end || {StepName, Atts} <- Steps,
+            {Key, OtherStep} <- Atts,
+            Key =:= requires orelse Key =:= enables].
+
+graph_build_error({vertex, duplicate, StepName}) ->
+    boot_error("Duplicate boot step name: ~w~n", [StepName]);
+graph_build_error({edge, Reason, From, To}) ->
+    boot_error(
+      "Could not add boot step dependency of ~w on ~w:~n~s",
+      [To, From,
+       case Reason of
+           {bad_vertex, V} ->
+               io_lib:format("Boot step not registered: ~w~n", [V]);
+           {bad_edge, [First | Rest]} ->
+               [io_lib:format("Cyclic dependency: ~w", [First]),
+                [io_lib:format(" depends on ~w", [Next]) || Next <- Rest],
+                io_lib:format(" depends on ~w~n", [First])]
+       end]).
 
 sort_boot_steps(UnsortedSteps) ->
-    G = digraph:new([acyclic]),
-
-    %% Add vertices, with duplicate checking.
-    [case digraph:vertex(G, StepName) of
-         false -> digraph:add_vertex(G, StepName, Step);
-         _     -> boot_error("Duplicate boot step name: ~w~n", [StepName])
-     end || Step = {StepName, _Attrs} <- UnsortedSteps],
-
-    %% Add edges, detecting cycles and missing vertices.
-    lists:foreach(fun ({StepName, Attributes}) ->
-                          [add_boot_step_dep(G, StepName, PrecedingStepName)
-                           || {requires, PrecedingStepName} <- Attributes],
-                          [add_boot_step_dep(G, SucceedingStepName, StepName)
-                           || {enables, SucceedingStepName} <- Attributes]
-                  end, UnsortedSteps),
+    G = rabbit_misc:build_acyclic_graph(
+          fun vertices/2, fun edges/2, fun graph_build_error/1, UnsortedSteps),
 
     %% Use topological sort to find a consistent ordering (if there is
     %% one, otherwise fail).
@@ -365,24 +354,6 @@ sort_boot_steps(UnsortedSteps) ->
                                        [MissingFunctions])
     end.
 
-add_boot_step_dep(G, RunsSecond, RunsFirst) ->
-    case digraph:add_edge(G, RunsSecond, RunsFirst) of
-        {error, Reason} ->
-            boot_error("Could not add boot step dependency of ~w on ~w:~n~s",
-              [RunsSecond, RunsFirst,
-               case Reason of
-                   {bad_vertex, V} ->
-                       io_lib:format("Boot step not registered: ~w~n", [V]);
-                   {bad_edge, [First | Rest]} ->
-                       [io_lib:format("Cyclic dependency: ~w", [First]),
-                        [io_lib:format(" depends on ~w", [Next])
-                         || Next <- Rest],
-                        io_lib:format(" depends on ~w~n", [First])]
-               end]);
-        _ ->
-            ok
-    end.
-
 %%---------------------------------------------------------------------------
 
 log_location(Type) ->