WIP - Keep running sum

plugins/aggregators/basicstats/basicstats.go

@@ -41,6 +41,7 @@ type basicstats struct {
 	count float64
 	min   float64
 	max   float64
+	sum   float64
 	mean  float64
 	M2    float64 //intermedia value for variance/stdev
 }
@@ -78,6 +79,7 @@ func (m *BasicStats) Add(in telegraf.Metric) {
 					min:   fv,
 					max:   fv,
 					mean:  fv,
+					sum:   fv,
 					M2:    0.0,
 				}
 			}
@@ -93,6 +95,7 @@ func (m *BasicStats) Add(in telegraf.Metric) {
 						min:   fv,
 						max:   fv,
 						mean:  fv,
+						sum:   fv,
 						M2:    0.0,
 					}
 					continue
@@ -120,6 +123,8 @@ func (m *BasicStats) Add(in telegraf.Metric) {
 				} else if fv > tmp.max {
 					tmp.max = fv
 				}
+				//sum compute
+				tmp.sum += fv
 				//store final data
 				m.cache[id].fields[k] = tmp
 			}
@@ -148,7 +153,7 @@ func (m *BasicStats) Push(acc telegraf.Accumulator) {
 				fields[k+"_mean"] = v.mean
 			}
 			if config.sum {
-				fields[k+"_sum"] = (v.mean * v.count)
+				fields[k+"_sum"] = v.sum
 			}
 
 			//v.count always >=1

plugins/aggregators/basicstats/basicstats_test.go

@@ -276,6 +276,58 @@ func TestBasicStatsWithOnlySum(t *testing.T) {
 	acc.AssertContainsTaggedFields(t, "m1", expectedFields, expectedTags)
 }
 
+// Verify that sum doesn't suffer from floating point errors.  Early
+// implementations of sum were calulated from mean and count, which
+// e.g. summed "1, 1, 5, 1" as "7.999999..." instead of 8.
+func TestBasicStatsWithOnlySumFloatingPointErrata(t *testing.T) {
+
+	var sum1, _ = metric.New("m1",
+		map[string]string{},
+		map[string]interface{}{
+			"a": int64(1),
+		},
+		time.Now(),
+	)
+	var sum2, _ = metric.New("m1",
+		map[string]string{},
+		map[string]interface{}{
+			"a": int64(1),
+		},
+		time.Now(),
+	)
+	var sum3, _ = metric.New("m1",
+		map[string]string{},
+		map[string]interface{}{
+			"a": int64(5),
+		},
+		time.Now(),
+	)
+	var sum4, _ = metric.New("m1",
+		map[string]string{},
+		map[string]interface{}{
+			"a": int64(1),
+		},
+		time.Now(),
+	)
+
+	aggregator := NewBasicStats()
+	aggregator.Stats = []string{"sum"}
+
+	aggregator.Add(sum1)
+	aggregator.Add(sum2)
+	aggregator.Add(sum3)
+	aggregator.Add(sum4)
+
+	acc := testutil.Accumulator{}
+	aggregator.Push(&acc)
+
+	expectedFields := map[string]interface{}{
+		"a_sum": float64(8),
+	}
+	expectedTags := map[string]string{}
+	acc.AssertContainsTaggedFields(t, "m1", expectedFields, expectedTags)
+}
+
 // Test only aggregating variance
 func TestBasicStatsWithOnlyVariance(t *testing.T) {