Add stackdriver input plugin (#5406)

metric/series_grouper.go

@@ -0,0 +1,86 @@
+package metric
+
+import (
+	"hash/fnv"
+	"io"
+	"sort"
+	"strconv"
+	"time"
+
+	"github.com/influxdata/telegraf"
+)
+
+// NewSeriesGrouper returns a type that can be used to group fields by series
+// and time, so that fields which share these values will be combined into a
+// single telegraf.Metric.
+//
+// This is useful to build telegraf.Metric's when all fields for a series are
+// not available at once.
+//
+// ex:
+// - cpu,host=localhost usage_time=42
+// - cpu,host=localhost idle_time=42
+// + cpu,host=localhost idle_time=42,usage_time=42
+func NewSeriesGrouper() *SeriesGrouper {
+	return &SeriesGrouper{
+		metrics: make(map[uint64]telegraf.Metric),
+		ordered: []telegraf.Metric{},
+	}
+}
+
+type SeriesGrouper struct {
+	metrics map[uint64]telegraf.Metric
+	ordered []telegraf.Metric
+}
+
+// Add adds a field key and value to the series.
+func (g *SeriesGrouper) Add(
+	measurement string,
+	tags map[string]string,
+	tm time.Time,
+	field string,
+	fieldValue interface{},
+) error {
+	var err error
+	id := groupID(measurement, tags, tm)
+	metric := g.metrics[id]
+	if metric == nil {
+		metric, err = New(measurement, tags, map[string]interface{}{field: fieldValue}, tm)
+		if err != nil {
+			return err
+		}
+		g.metrics[id] = metric
+		g.ordered = append(g.ordered, metric)
+	} else {
+		metric.AddField(field, fieldValue)
+	}
+	return nil
+}
+
+// Metrics returns the metrics grouped by series and time.
+func (g *SeriesGrouper) Metrics() []telegraf.Metric {
+	return g.ordered
+}
+
+func groupID(measurement string, tags map[string]string, tm time.Time) uint64 {
+	h := fnv.New64a()
+	h.Write([]byte(measurement))
+	h.Write([]byte("\n"))
+
+	taglist := make([]*telegraf.Tag, 0, len(tags))
+	for k, v := range tags {
+		taglist = append(taglist,
+			&telegraf.Tag{Key: k, Value: v})
+	}
+	sort.Slice(taglist, func(i, j int) bool { return taglist[i].Key < taglist[j].Key })
+	for _, tag := range taglist {
+		h.Write([]byte(tag.Key))
+		h.Write([]byte("\n"))
+		h.Write([]byte(tag.Value))
+		h.Write([]byte("\n"))
+	}
+	h.Write([]byte("\n"))
+
+	io.WriteString(h, strconv.FormatInt(tm.UnixNano(), 10))
+	return h.Sum64()
+}