fix(processors.template): Handle tracking metrics correctly (#13947)

metric.go

@@ -126,7 +126,7 @@ type Metric interface {
 
 // TemplateMetric is an interface to use in templates (e.g text/template)
 // to generate complex strings from metric properties
-// e.g. '{{.Neasurement}}-{{.Tag "foo"}}-{{.Field "bar"}}'
+// e.g. '{{.Name}}-{{.Tag "foo"}}-{{.Field "bar"}}'
 type TemplateMetric interface {
 	Name() string
 	Field(key string) interface{}
@@ -136,3 +136,9 @@ type TemplateMetric interface {
 	Time() time.Time
 	String() string
 }
+
+type UnwrappableMetric interface {
+	// Unwrap allows to access the underlying raw metric if an implementation
+	// wraps it in the first place.
+	Unwrap() Metric
+}

plugins/processors/lookup/lookup.go

@@ -17,8 +17,6 @@ import (
 	"github.com/influxdata/telegraf/plugins/processors"
 )
 
-type unwrappableMetric interface{ Unwrap() telegraf.Metric }
-
 //go:embed sample.conf
 var sampleConfig string
 
@@ -68,7 +66,7 @@ func (p *Processor) Apply(in ...telegraf.Metric) []telegraf.Metric {
 	out := make([]telegraf.Metric, 0, len(in))
 	for _, raw := range in {
 		m := raw
-		if wm, ok := raw.(unwrappableMetric); ok {
+		if wm, ok := raw.(telegraf.UnwrappableMetric); ok {
 			m = wm.Unwrap()
 		}
 

plugins/processors/template/template.go

@@ -29,13 +29,17 @@ func (*TemplateProcessor) SampleConfig() string {
 
 func (r *TemplateProcessor) Apply(in ...telegraf.Metric) []telegraf.Metric {
 	// for each metric in "in" array
-	for _, metric := range in {
+	for _, raw := range in {
-		m, ok := metric.(telegraf.TemplateMetric)
+		m := raw
+		if wm, ok := raw.(telegraf.UnwrappableMetric); ok {
+			m = wm.Unwrap()
+		}
+		tm, ok := m.(telegraf.TemplateMetric)
 		if !ok {
-			r.Log.Errorf("metric of type %T is not a template metric", metric)
+			r.Log.Errorf("metric of type %T is not a template metric", raw)
 			continue
 		}
-		newM := TemplateMetric{m}
+		newM := TemplateMetric{tm}
 
 		var b strings.Builder
 		if err := r.tmplTag.Execute(&b, &newM); err != nil {
@@ -51,8 +55,9 @@ func (r *TemplateProcessor) Apply(in ...telegraf.Metric) []telegraf.Metric {
 		}
 		value := b.String()
 
-		metric.AddTag(tag, value)
+		raw.AddTag(tag, value)
 	}
+
 	return in
 }
 

plugins/processors/template/template_test.go

@@ -1,12 +1,14 @@
 package template
 
 import (
+	"sync"
 	"testing"
 	"time"
 
 	"github.com/stretchr/testify/require"
 
 	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/metric"
 	"github.com/influxdata/telegraf/testutil"
 )
 
@@ -263,3 +265,39 @@ func TestDot(t *testing.T) {
 	expected.AddTag("metric", "test1 map[tag1:value1] map[value:1.23] 1257894000000000000")
 	testutil.RequireMetricsEqual(t, []telegraf.Metric{expected}, actual)
 }
+
+func TestTracking(t *testing.T) {
+	// Create a tracking metric and tap the delivery information
+	var mu sync.Mutex
+	delivered := make([]telegraf.DeliveryInfo, 0, 1)
+	notify := func(di telegraf.DeliveryInfo) {
+		mu.Lock()
+		defer mu.Unlock()
+		delivered = append(delivered, di)
+	}
+	m := testutil.TestMetric(1.23)
+	input, _ := metric.WithTracking(m, notify)
+
+	// Create an expectation
+	e := m.Copy()
+	e.AddTag("metric", "test1 map[tag1:value1] map[value:1.23] 1257894000000000000")
+	expected := []telegraf.Metric{e}
+
+	// Configure the plugin
+	plugin := TemplateProcessor{Tag: "metric", Template: "{{.}}"}
+	require.NoError(t, plugin.Init())
+
+	// Process expected metrics and compare with resulting metrics
+	actual := plugin.Apply(input)
+	testutil.RequireMetricsEqual(t, expected, actual)
+
+	// Simulate output acknowledging delivery
+	input.Accept()
+
+	// Check delivery
+	require.Eventuallyf(t, func() bool {
+		mu.Lock()
+		defer mu.Unlock()
+		return len(delivered) > 0
+	}, time.Second, 100*time.Millisecond, "%d delivered but 1 expected", len(delivered))
+}