Avoid filling towards the past when we have older values available

deps/rabbitmq_management_agent/src/exometer_slide.erl

@@ -66,6 +66,9 @@
          sum/5,
          optimize/1]).
 
+%% For testing
+-export([buffer/1]).
+
 -compile(inline).
 -compile(inline_list_funcs).
 
@@ -461,7 +464,8 @@ take_since([{DropTS, drop} | T], Now, Start, N, [{TS, Evt} | _] = Acc,
                                                        -Interval, N)],
             {undefined, lists:reverse(Fill) ++ Acc};
         [{TS0, _} = E | Rest] when TS0 >= Start, N > 0 ->
-            Fill = [{TS1, Evt} || TS1 <- truncated_seq(TS0 + Interval, TS - Interval,
+            Fill = [{TS1, Evt} || TS1 <- truncated_seq(TS0 + Interval,
+                                                       max(TS0 + Interval, TS - Interval),
                                                        Interval, N)],
             take_since(Rest, Now, Start, decr(N), [E | Fill ++ Acc], Interval);
         [Prev | _] -> % next sample is out of range so needs to be filled from Start
@@ -502,3 +506,5 @@ map_timestamp(TS, Start, Interval, Round) ->
     Factor = Round((TS - Start) / Interval),
     Start + Interval * Factor.
 
+buffer(#slide{buf1 = Buf1, buf2 = Buf2}) ->
+    Buf1 ++ Buf2.

deps/rabbitmq_management_agent/test/exometer_slide_SUITE.erl

@@ -47,7 +47,8 @@ groups() ->
                   to_normalized_list,
                   to_normalized_list_no_padding,
                   to_list_in_the_past,
-                  sum_mgmt_352
+                  sum_mgmt_352,
+                  sum_mgmt_352_extra
                  ]}
     ].
 
@@ -500,13 +501,31 @@ to_list_in_the_past(_Config) ->
     [] = exometer_slide:to_list(50, 10, S).
 
 sum_mgmt_352(_Config) ->
+    %% In bug mgmt#352 all the samples returned have the same vale
     Slide = sum_mgmt_352_slide(),
     Last = 1487689330000,
     First = 1487689270000,
     Incr = 5000,
     Empty = {0},
     Sum = exometer_slide:sum(Last, First, Incr, [Slide], Empty),
-    ct:pal("SUM is ~p~n", [Sum]),
+    Values = sets:to_list(sets:from_list(
+                            [V || {_, V} <- exometer_slide:buffer(Sum)])),
+    true = (length(Values) == 12),
+    ok.
+
+sum_mgmt_352_extra(_Config) ->
+    %% Testing previous case clause to the one that fixes mgmt_352
+    %% exometer_slide.erl#L463
+    %% In the buggy version, all but the last sample are the same
+    Slide = sum_mgmt_352_slide_extra(),
+    Last = 1487689330000,
+    First = 1487689260000,
+    Incr = 5000,
+    Empty = {0},
+    Sum = exometer_slide:sum(Last, First, Incr, [Slide], Empty),
+    Values = sets:to_list(sets:from_list(
+                            [V || {_, V} <- exometer_slide:buffer(Sum)])),
+    true = (length(Values) == 13),
     ok.
 
 %% -------------------------------------------------------------------
@@ -537,3 +556,22 @@ sum_mgmt_352_slide() ->
       {1487689257486,{1205600}}],
      [],
      {1591000}}.
+
+sum_mgmt_352_slide_extra() ->
+    {slide,610000,45,122,true,5000,1487689328468,1487689106834,
+     [{1487689328468,{1574200}},
+      {1487689323467,{1538800}},
+      {1487689318466,{1500800}},
+      {1487689313465,{1459138}},
+      {1487689308463,{1419200}},
+      {1487689303462,{1379600}},
+      {1487689298461,{1340000}},
+      {1487689293460,{1303400}},
+      {1487689288460,{1265600}},
+      {1487689283458,{1231400}},
+      {1487689278457,{1215800}},
+      {1487689273456,{1215200}},
+      {1487689272487,drop},
+      {1487689269486,{1205600}}],
+     [],
+     {1591000}}.