Add sum stat to basicstats aggregator (#3797)

plugins/aggregators/basicstats/README.md

 # BasicStats Aggregator Plugin
 
-The BasicStats aggregator plugin give us count,max,min,mean,s2(variance), stdev for a set of values,
+The BasicStats aggregator plugin give us count,max,min,mean,sum,s2(variance), stdev for a set of values,
 emitting the aggregate every `period` seconds.
 
 ### Configuration:
@@ -21,11 +21,11 @@ emitting the aggregate every `period` seconds.
   ## BasicStats Arguments:
 
   ## Configures which basic stats to push as fields
-  stats = ["count","min","max","mean","stdev","s2"]
+  stats = ["count","min","max","mean","stdev","s2","sum"]
 ```
 
 - stats
-    - If not specified, all stats are aggregated and pushed as fields
+    - If not specified, then `count`, `min`, `max`, `mean`, `stdev`, and `s2` are aggregated and pushed as fields.  `sum` is not aggregated by default to maintain backwards compatibility.
     - If empty array, no stats are aggregated
 
 ### Measurements & Fields:
@@ -35,6 +35,7 @@ emitting the aggregate every `period` seconds.
     - field1_max
     - field1_min
     - field1_mean
+    - field1_sum
     - field1_s2 (variance)
     - field1_stdev (standard deviation)
 
@@ -48,8 +49,8 @@ No tags are applied by this aggregator.
 $ telegraf --config telegraf.conf --quiet
 system,host=tars load1=1 1475583980000000000
 system,host=tars load1=1 1475583990000000000
-system,host=tars load1_count=2,load1_max=1,load1_min=1,load1_mean=1,load1_s2=0,load1_stdev=0 1475584010000000000
+system,host=tars load1_count=2,load1_max=1,load1_min=1,load1_mean=1,load1_sum=2,load1_s2=0,load1_stdev=0 1475584010000000000
 system,host=tars load1=1 1475584020000000000
 system,host=tars load1=3 1475584030000000000
-system,host=tars load1_count=2,load1_max=3,load1_min=1,load1_mean=2,load1_s2=2,load1_stdev=1.414162 1475584010000000000
+system,host=tars load1_count=2,load1_max=3,load1_min=1,load1_mean=2,load1_sum=4,load1_s2=2,load1_stdev=1.414162 1475584010000000000
 ```

plugins/aggregators/basicstats/basicstats.go

@@ -22,6 +22,7 @@ type configuredStats struct {
 	mean     bool
 	variance bool
 	stdev    bool
+	sum      bool
 }
 
 func NewBasicStats() *BasicStats {
@@ -40,6 +41,7 @@ type basicstats struct {
 	count float64
 	min   float64
 	max   float64
+	sum   float64
 	mean  float64
 	M2    float64 //intermedia value for variance/stdev
 }
@@ -77,6 +79,7 @@ func (m *BasicStats) Add(in telegraf.Metric) {
 					min:   fv,
 					max:   fv,
 					mean:  fv,
+					sum:   fv,
 					M2:    0.0,
 				}
 			}
@@ -92,6 +95,7 @@ func (m *BasicStats) Add(in telegraf.Metric) {
 						min:   fv,
 						max:   fv,
 						mean:  fv,
+						sum:   fv,
 						M2:    0.0,
 					}
 					continue
@@ -119,6 +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
 			}
@@ -146,6 +152,9 @@ func (m *BasicStats) Push(acc telegraf.Accumulator) {
 			if config.mean {
 				fields[k+"_mean"] = v.mean
 			}
+			if config.sum {
+				fields[k+"_sum"] = v.sum
+			}
 
 			//v.count always >=1
 			if v.count > 1 {
@@ -187,6 +196,8 @@ func parseStats(names []string) *configuredStats {
 			parsed.variance = true
 		case "stdev":
 			parsed.stdev = true
+		case "sum":
+			parsed.sum = true
 
 		default:
 			log.Printf("W! Unrecognized basic stat '%s', ignoring", name)
@@ -206,6 +217,7 @@ func defaultStats() *configuredStats {
 	defaults.mean = true
 	defaults.variance = true
 	defaults.stdev = true
+	defaults.sum = false
 
 	return defaults
 }

plugins/aggregators/basicstats/basicstats_test.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/influxdata/telegraf/metric"
 	"github.com/influxdata/telegraf/testutil"
+	"github.com/stretchr/testify/assert"
 )
 
 var m1, _ = metric.New("m1",
@@ -250,6 +251,83 @@ func TestBasicStatsWithOnlyMean(t *testing.T) {
 	acc.AssertContainsTaggedFields(t, "m1", expectedFields, expectedTags)
 }
 
+// Test only aggregating sum
+func TestBasicStatsWithOnlySum(t *testing.T) {
+
+	aggregator := NewBasicStats()
+	aggregator.Stats = []string{"sum"}
+
+	aggregator.Add(m1)
+	aggregator.Add(m2)
+
+	acc := testutil.Accumulator{}
+	aggregator.Push(&acc)
+
+	expectedFields := map[string]interface{}{
+		"a_sum": float64(2),
+		"b_sum": float64(4),
+		"c_sum": float64(6),
+		"d_sum": float64(8),
+		"e_sum": float64(200),
+	}
+	expectedTags := map[string]string{
+		"foo": "bar",
+	}
+	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) {
 
@@ -328,6 +406,57 @@ func TestBasicStatsWithMinAndMax(t *testing.T) {
 	acc.AssertContainsTaggedFields(t, "m1", expectedFields, expectedTags)
 }
 
+// Test aggregating with all stats
+func TestBasicStatsWithAllStats(t *testing.T) {
+	acc := testutil.Accumulator{}
+	minmax := NewBasicStats()
+	minmax.Stats = []string{"count", "min", "max", "mean", "stdev", "s2", "sum"}
+
+	minmax.Add(m1)
+	minmax.Add(m2)
+	minmax.Push(&acc)
+
+	expectedFields := map[string]interface{}{
+		"a_count": float64(2), //a
+		"a_max":   float64(1),
+		"a_min":   float64(1),
+		"a_mean":  float64(1),
+		"a_stdev": float64(0),
+		"a_s2":    float64(0),
+		"a_sum":   float64(2),
+		"b_count": float64(2), //b
+		"b_max":   float64(3),
+		"b_min":   float64(1),
+		"b_mean":  float64(2),
+		"b_s2":    float64(2),
+		"b_sum":   float64(4),
+		"b_stdev": math.Sqrt(2),
+		"c_count": float64(2), //c
+		"c_max":   float64(4),
+		"c_min":   float64(2),
+		"c_mean":  float64(3),
+		"c_s2":    float64(2),
+		"c_stdev": math.Sqrt(2),
+		"c_sum":   float64(6),
+		"d_count": float64(2), //d
+		"d_max":   float64(6),
+		"d_min":   float64(2),
+		"d_mean":  float64(4),
+		"d_s2":    float64(8),
+		"d_stdev": math.Sqrt(8),
+		"d_sum":   float64(8),
+		"e_count": float64(1), //e
+		"e_max":   float64(200),
+		"e_min":   float64(200),
+		"e_mean":  float64(200),
+		"e_sum":   float64(200),
+	}
+	expectedTags := map[string]string{
+		"foo": "bar",
+	}
+	acc.AssertContainsTaggedFields(t, "m1", expectedFields, expectedTags)
+}
+
 // Test that if an empty array is passed, no points are pushed
 func TestBasicStatsWithNoStats(t *testing.T) {
 
@@ -357,3 +486,26 @@ func TestBasicStatsWithUnknownStat(t *testing.T) {
 
 	acc.AssertDoesNotContainMeasurement(t, "m1")
 }
+
+// Test that if Stats isn't supplied, then we only do count, min, max, mean,
+// stdev, and s2.  We purposely exclude sum for backwards compatability,
+// otherwise user's working systems will suddenly (and surprisingly) start
+// capturing sum without their input.
+func TestBasicStatsWithDefaultStats(t *testing.T) {
+
+	aggregator := NewBasicStats()
+
+	aggregator.Add(m1)
+	aggregator.Add(m2)
+
+	acc := testutil.Accumulator{}
+	aggregator.Push(&acc)
+
+	assert.True(t, acc.HasField("m1", "a_count"))
+	assert.True(t, acc.HasField("m1", "a_min"))
+	assert.True(t, acc.HasField("m1", "a_max"))
+	assert.True(t, acc.HasField("m1", "a_mean"))
+	assert.True(t, acc.HasField("m1", "a_stdev"))
+	assert.True(t, acc.HasField("m1", "a_s2"))
+	assert.False(t, acc.HasField("m1", "a_sum"))
+}