[outputs/stackdriver] Allow to group metrics to bypass MetricDescriptor quota (500)

plugins/outputs/stackdriver/README.md

@@ -24,6 +24,9 @@ Additional resource labels can be configured by `resource_labels`. By default th
   ## Custom resource type
   # resource_type = "generic_node"
 
+  ## Compact by type
+  # group_metrics = false
+
   ## Additonal resource labels
   # [outputs.stackdriver.resource_labels]
   #   node_id = "$HOSTNAME"

plugins/outputs/stackdriver/stackdriver.go

@@ -1,6 +1,7 @@
 package stackdriver
 
 import (
+	"bytes"
 	"context"
 	"fmt"
 	"hash/fnv"
@@ -22,6 +23,7 @@ import (
 type Stackdriver struct {
 	Project        string
 	Namespace      string
+	GroupMetrics   bool              `toml:"group_metrics"`
 	ResourceType   string            `toml:"resource_type"`
 	ResourceLabels map[string]string `toml:"resource_labels"`
 
@@ -59,6 +61,9 @@ var sampleConfig = `
   ## Custom resource type
   # resource_type = "generic_node"
 
+  ## Compact by type
+  # GroupMetrics = false
+
   ## Additonal resource labels
   # [outputs.stackdriver.resource_labels]
   #   node_id = "$HOSTNAME"
@@ -169,10 +174,20 @@ func (s *Stackdriver) Write(metrics []telegraf.Metric) error {
 				Value:    value,
 			}
 
+			metricType := path.Join("custom.googleapis.com", s.Namespace, m.Name(), f.Key)
+			if s.GroupMetrics {
+				var buffer bytes.Buffer
+				buffer.WriteString(m.Name())
+				buffer.WriteString("-")
+				buffer.WriteString(f.Key)
+				m.AddTag("name", buffer.String())
+				metricType = path.Join("custom.googleapis.com", s.Namespace, getStackdriverMetricGroupName(m.Type(), f.Value))
+			}
+
 			// Prepare time series.
 			timeSeries := &monitoringpb.TimeSeries{
 				Metric: &metricpb.Metric{
-					Type:   path.Join("custom.googleapis.com", s.Namespace, m.Name(), f.Key),
+					Type:   metricType,
 					Labels: getStackdriverLabels(m.TagList()),
 				},
 				MetricKind: metricKind,
@@ -265,6 +280,28 @@ func getStackdriverTimeInterval(
 	}
 }
 
+func getStackdriverMetricGroupName(vt telegraf.ValueType, value interface{}) string {
+	switch vt {
+	case telegraf.Untyped:
+		switch value.(type) {
+		case uint64:
+			return "counter"
+		case int64:
+			return "counter"
+		case float64:
+			return "gauge"
+		default:
+			return "untag"
+		}
+	case telegraf.Gauge:
+		return "gauge"
+	case telegraf.Counter:
+		return "derive"
+	default:
+		return "unspecified"
+	}
+}
+
 func getStackdriverMetricKind(vt telegraf.ValueType) (metricpb.MetricDescriptor_MetricKind, error) {
 	switch vt {
 	case telegraf.Untyped: