Add new basicstats aggregator (#2167)

plugins/aggregators/basicstats/basicstats.go

@@ -0,0 +1,155 @@
+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()
+	})
+}