Add new basicstats aggregator (#2167)

plugins/aggregators/all/all.go

 package all
 
 import (
+	_ "github.com/influxdata/telegraf/plugins/aggregators/basicstats"
 	_ "github.com/influxdata/telegraf/plugins/aggregators/histogram"
 	_ "github.com/influxdata/telegraf/plugins/aggregators/minmax"
 )

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,
+emitting the aggregate every `period` seconds.
+
+### Configuration:
+
+```toml
+# Keep the aggregate basicstats of each metric passing through.
+[[aggregators.basicstats]]
+  ## General Aggregator Arguments:
+  ## The period on which to flush & clear the aggregator.
+  period = "30s"
+  ## If true, the original metric will be dropped by the
+  ## aggregator and will not get sent to the output plugins.
+  drop_original = false
+```
+
+### Measurements & Fields:
+
+- measurement1
+    - field1_count
+    - field1_max
+    - field1_min
+    - field1_mean
+    - field1_s2 (variance)
+    - field1_stdev (standard deviation)
+
+### Tags:
+
+No tags are applied by this aggregator.
+
+### Example Output:
+
+```
+$ 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=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
+```

plugins/aggregators/basicstats/basicstats.go

+package basicstats
+
+import (
+	"math"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/plugins/aggregators"
+)
+
+type BasicStats struct {
+	cache map[uint64]aggregate
+}
+
+func NewBasicStats() telegraf.Aggregator {
+	mm := &BasicStats{}
+	mm.Reset()
+	return mm
+}
+
+type aggregate struct {
+	fields map[string]basicstats
+	name   string
+	tags   map[string]string
+}
+
+type basicstats struct {
+	count float64
+	min   float64
+	max   float64
+	mean  float64
+	M2    float64 //intermedia value for variance/stdev
+}
+
+var sampleConfig = `
+  ## General Aggregator Arguments:
+  ## The period on which to flush & clear the aggregator.
+  period = "30s"
+  ## If true, the original metric will be dropped by the
+  ## aggregator and will not get sent to the output plugins.
+  drop_original = false
+`
+
+func (m *BasicStats) SampleConfig() string {
+	return sampleConfig
+}
+
+func (m *BasicStats) Description() string {
+	return "Keep the aggregate basicstats of each metric passing through."
+}
+
+func (m *BasicStats) Add(in telegraf.Metric) {
+	id := in.HashID()
+	if _, ok := m.cache[id]; !ok {
+		// hit an uncached metric, create caches for first time:
+		a := aggregate{
+			name:   in.Name(),
+			tags:   in.Tags(),
+			fields: make(map[string]basicstats),
+		}
+		for k, v := range in.Fields() {
+			if fv, ok := convert(v); ok {
+				a.fields[k] = basicstats{
+					count: 1,
+					min:   fv,
+					max:   fv,
+					mean:  fv,
+					M2:    0.0,
+				}
+			}
+		}
+		m.cache[id] = a
+	} else {
+		for k, v := range in.Fields() {
+			if fv, ok := convert(v); ok {
+				if _, ok := m.cache[id].fields[k]; !ok {
+					// hit an uncached field of a cached metric
+					m.cache[id].fields[k] = basicstats{
+						count: 1,
+						min:   fv,
+						max:   fv,
+						mean:  fv,
+						M2:    0.0,
+					}
+					continue
+				}
+
+				tmp := m.cache[id].fields[k]
+				//https://en.m.wikipedia.org/wiki/Algorithms_for_calculating_variance
+				//variable initialization
+				x := fv
+				mean := tmp.mean
+				M2 := tmp.M2
+				//counter compute
+				n := tmp.count + 1
+				tmp.count = n
+				//mean compute
+				delta := x - mean
+				mean = mean + delta/n
+				tmp.mean = mean
+				//variance/stdev compute
+				M2 = M2 + delta*(x-mean)
+				tmp.M2 = M2
+				//max/min compute
+				if fv < tmp.min {
+					tmp.min = fv
+				} else if fv > tmp.max {
+					tmp.max = fv
+				}
+				//store final data
+				m.cache[id].fields[k] = tmp
+			}
+		}
+	}
+}
+
+func (m *BasicStats) Push(acc telegraf.Accumulator) {
+	for _, aggregate := range m.cache {
+		fields := map[string]interface{}{}
+		for k, v := range aggregate.fields {
+			fields[k+"_count"] = v.count
+			fields[k+"_min"] = v.min
+			fields[k+"_max"] = v.max
+			fields[k+"_mean"] = v.mean
+			//v.count always >=1
+			if v.count > 1 {
+				variance := v.M2 / (v.count - 1)
+				fields[k+"_s2"] = variance
+				fields[k+"_stdev"] = math.Sqrt(variance)
+			}
+			//if count == 1 StdDev = infinite => so I won't send data
+		}
+		acc.AddFields(aggregate.name, fields, aggregate.tags)
+	}
+}
+
+func (m *BasicStats) Reset() {
+	m.cache = make(map[uint64]aggregate)
+}
+
+func convert(in interface{}) (float64, bool) {
+	switch v := in.(type) {
+	case float64:
+		return v, true
+	case int64:
+		return float64(v), true
+	default:
+		return 0, false
+	}
+}
+
+func init() {
+	aggregators.Add("basicstats", func() telegraf.Aggregator {
+		return NewBasicStats()
+	})
+}

plugins/aggregators/basicstats/basicstats_test.go

+package basicstats
+
+import (
+	"math"
+	"testing"
+	"time"
+
+	"github.com/influxdata/telegraf/metric"
+	"github.com/influxdata/telegraf/testutil"
+)
+
+var m1, _ = metric.New("m1",
+	map[string]string{"foo": "bar"},
+	map[string]interface{}{
+		"a": int64(1),
+		"b": int64(1),
+		"c": float64(2),
+		"d": float64(2),
+	},
+	time.Now(),
+)
+var m2, _ = metric.New("m1",
+	map[string]string{"foo": "bar"},
+	map[string]interface{}{
+		"a":        int64(1),
+		"b":        int64(3),
+		"c":        float64(4),
+		"d":        float64(6),
+		"e":        float64(200),
+		"ignoreme": "string",
+		"andme":    true,
+	},
+	time.Now(),
+)
+
+func BenchmarkApply(b *testing.B) {
+	minmax := NewBasicStats()
+
+	for n := 0; n < b.N; n++ {
+		minmax.Add(m1)
+		minmax.Add(m2)
+	}
+}
+
+// Test two metrics getting added.
+func TestBasicStatsWithPeriod(t *testing.T) {
+	acc := testutil.Accumulator{}
+	minmax := NewBasicStats()
+
+	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),
+		"b_count": float64(2), //b
+		"b_max":   float64(3),
+		"b_min":   float64(1),
+		"b_mean":  float64(2),
+		"b_s2":    float64(2),
+		"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),
+		"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),
+		"e_count": float64(1), //e
+		"e_max":   float64(200),
+		"e_min":   float64(200),
+		"e_mean":  float64(200),
+	}
+	expectedTags := map[string]string{
+		"foo": "bar",
+	}
+	acc.AssertContainsTaggedFields(t, "m1", expectedFields, expectedTags)
+}
+
+// Test two metrics getting added with a push/reset in between (simulates
+// getting added in different periods.)
+func TestBasicStatsDifferentPeriods(t *testing.T) {
+	acc := testutil.Accumulator{}
+	minmax := NewBasicStats()
+
+	minmax.Add(m1)
+	minmax.Push(&acc)
+	expectedFields := map[string]interface{}{
+		"a_count": float64(1), //a
+		"a_max":   float64(1),
+		"a_min":   float64(1),
+		"a_mean":  float64(1),
+		"b_count": float64(1), //b
+		"b_max":   float64(1),
+		"b_min":   float64(1),
+		"b_mean":  float64(1),
+		"c_count": float64(1), //c
+		"c_max":   float64(2),
+		"c_min":   float64(2),
+		"c_mean":  float64(2),
+		"d_count": float64(1), //d
+		"d_max":   float64(2),
+		"d_min":   float64(2),
+		"d_mean":  float64(2),
+	}
+	expectedTags := map[string]string{
+		"foo": "bar",
+	}
+	acc.AssertContainsTaggedFields(t, "m1", expectedFields, expectedTags)
+
+	acc.ClearMetrics()
+	minmax.Reset()
+	minmax.Add(m2)
+	minmax.Push(&acc)
+	expectedFields = map[string]interface{}{
+		"a_count": float64(1), //a
+		"a_max":   float64(1),
+		"a_min":   float64(1),
+		"a_mean":  float64(1),
+		"b_count": float64(1), //b
+		"b_max":   float64(3),
+		"b_min":   float64(3),
+		"b_mean":  float64(3),
+		"c_count": float64(1), //c
+		"c_max":   float64(4),
+		"c_min":   float64(4),
+		"c_mean":  float64(4),
+		"d_count": float64(1), //d
+		"d_max":   float64(6),
+		"d_min":   float64(6),
+		"d_mean":  float64(6),
+		"e_count": float64(1), //e
+		"e_max":   float64(200),
+		"e_min":   float64(200),
+		"e_mean":  float64(200),
+	}
+	expectedTags = map[string]string{
+		"foo": "bar",
+	}
+	acc.AssertContainsTaggedFields(t, "m1", expectedFields, expectedTags)
+}