Add relative memory endpoint

Author: Diana Corbacho

src/rabbit_mgmt_dispatcher.erl

@@ -41,7 +41,8 @@ dispatcher() ->
      {["cluster-name"],                                            rabbit_mgmt_wm_cluster_name, []},
      {["nodes"],                                                   rabbit_mgmt_wm_nodes, []},
      {["nodes", node],                                             rabbit_mgmt_wm_node, []},
-     {["nodes", node, "memory"],                                   rabbit_mgmt_wm_node_memory, []},
+     {["nodes", node, "memory"],                                   rabbit_mgmt_wm_node_memory, [absolute]},
+     {["nodes", node, "memory", "relative"],                       rabbit_mgmt_wm_node_memory, [relative]},
      {["extensions"],                                              rabbit_mgmt_wm_extensions, []},
      {["all-configuration"],                                       rabbit_mgmt_wm_definitions, []}, %% This was the old name, let's not break things gratuitously.
      {["definitions"],                                             rabbit_mgmt_wm_definitions, []},

src/rabbit_mgmt_wm_node_memory.erl

@@ -27,10 +27,10 @@
 
 %%--------------------------------------------------------------------
 
-init(_Config) -> {ok, #context{}}.
+init([Mode]) -> {ok, {Mode, #context{}}}.
 
-finish_request(ReqData, Context) ->
-    {ok, rabbit_mgmt_cors:set_headers(ReqData, Context), Context}.
+finish_request(ReqData, {Mode, Context}) ->
+    {ok, rabbit_mgmt_cors:set_headers(ReqData, Context), {Mode, Context}}.
 
 allowed_methods(ReqData, Context) ->
     {['HEAD', 'GET', 'OPTIONS'], ReqData, Context}.
@@ -45,11 +45,12 @@ encodings_provided(ReqData, Context) ->
 resource_exists(ReqData, Context) ->
     {node_exists(ReqData, get_node(ReqData)), ReqData, Context}.
 
-to_json(ReqData, Context) ->
-    rabbit_mgmt_util:reply(augment(ReqData), ReqData, Context).
+to_json(ReqData, {Mode, Context}) ->
+    rabbit_mgmt_util:reply(augment(Mode, ReqData), ReqData, {Mode, Context}).
 
-is_authorized(ReqData, Context) ->
-    rabbit_mgmt_util:is_authorized_monitor(ReqData, Context).
+is_authorized(ReqData, {Mode, Context}) ->
+    {Res, RD, C} = rabbit_mgmt_util:is_authorized_monitor(ReqData, Context),
+    {Res, RD, {Mode, C}}.
 
 %%--------------------------------------------------------------------
 get_node(ReqData) ->
@@ -62,14 +63,30 @@ node_exists(ReqData, Node) ->
         [_] -> true
     end.
 
-augment(ReqData) ->
+augment(Mode, ReqData) ->
     Node = get_node(ReqData),
     case node_exists(ReqData, Node) of
         false ->
             not_found;
         true ->
             case rpc:call(Node, rabbit_vm, memory, [], infinity) of
                 {badrpc, _} -> [{memory, not_available}];
-                Result      -> [{memory, Result}]
+                Result      -> [{memory, format(Mode, Result)}]
             end
     end.
+
+format(absolute, Result) ->
+    Result;
+format(relative, Result) ->
+    {[{total, Total}], Rest} = lists:splitwith(fun({Key, _}) ->
+                                                       Key == total
+                                               end, Result),
+    [{total, Total} | [{K, percentage(V, Total)} || {K, V} <- Rest]].
+
+percentage(Part, Total) ->
+    case round((Part/Total) * 100) of
+        0 when Part =/= 0 ->
+            1;
+        Int ->
+            Int
+    end.

test/src/rabbit_mgmt_test_http.erl

@@ -116,8 +116,27 @@ memory_test() ->
             atom, other_system],
     assert_keys(Keys, pget(memory, Result)),
     http_get("/nodes/nonode/memory", ?NOT_FOUND),
+    %% Relative memory as a percentage of the total
+    Result1 = http_get(Path ++ "/relative", ?OK),
+    assert_keys([memory], Result1),
+    Breakdown = pget(memory, Result1),
+    assert_keys(Keys, Breakdown),
+    assert_percentage(Breakdown),
+    http_get("/nodes/nonode/memory/relative", ?NOT_FOUND),
     ok.
 
+assert_percentage(Breakdown) ->
+    Total = lists:sum([P || {K, P} <- Breakdown, K =/= total]),
+    Count = length(Breakdown) - 1,
+    %% Rounding up and down can lose some digits. Never more than the number
+    %% of items in the breakdown.
+    case ((Total =< 100 + Count) andalso (Total >= 100 - Count)) of
+        false ->
+            throw({bad_percentage, Total, Breakdown});
+        true ->
+            ok
+    end.
+
 auth_test() ->
     http_put("/users/user", [{password, <<"user">>},
                              {tags, <<"">>}], [?CREATED, ?NO_CONTENT]),