Add template processor (#6494)

plugins/processors/template/README.md

@@ -0,0 +1,26 @@
+# Template Processor
+
+The `template` processor applies a go template to tag, field, measurement and time values to create a new tag.
+
+Golang [Template Documentation]
+
+### Configuration
+
+```toml
+  # Concatenate two tags to create a new tag
+  [[processors.template]]
+     ## Tag to create
+     tag = "topic"
+     ## Template to create tag
+     # Note: Single quotes (') are used, so the double quotes (") don't need escaping (\")
+     template = '{{ .Tag "hostname" }}.{{ .Tag "level" }}'
+```
+
+### Example
+
+```diff
+- cpu,level=debug,hostname=localhost value=42i
++ cpu,level=debug,hostname=localhost,topic=localhost.debug value=42i
+```
+
+[Template Documentation]:https://golang.org/pkg/text/template/

plugins/processors/template/template.go

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+package template
+
+import (
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/plugins/processors"
+	"strings"
+	"text/template"
+)
+
+type TemplateProcessor struct {
+	Tag      string `toml:"tag"`
+	Template string `toml:"template"`
+	tmpl     *template.Template
+}
+
+const sampleConfig = `
+  ## Concatenate two tags to create a new tag
+  # [[processors.template]]
+  #   ## Tag to create
+  #   tag = "topic"
+  #   ## Template to create tag
+  # Note: Single quotes (') are used, so the double quotes (") don't need escaping (\")
+  #   template = '{{.Tag "hostname"}}.{{ .Tag "level" }}'
+`
+
+func (r *TemplateProcessor) SampleConfig() string {
+	return sampleConfig
+}
+
+func (r *TemplateProcessor) Description() string {
+	return "Uses a Go template to create a new tag"
+}
+
+func (r *TemplateProcessor) Apply(in ...telegraf.Metric) []telegraf.Metric {
+	// for each metric in "in" array
+	for _, metric := range in {
+		var b strings.Builder
+		newM := TemplateMetric{metric}
+
+		// supply TemplateMetric and Template from configuration to Template.Execute
+		err := r.tmpl.Execute(&b, &newM)
+		if err != nil {
+			panic(err)
+		}
+
+		metric.AddTag(r.Tag, b.String())
+	}
+	return in
+}
+
+func (r *TemplateProcessor) Init() error {
+	// create template
+	t, err := template.New("configured_template").Parse(r.Template)
+
+	r.tmpl = t
+	return err
+}
+
+func init() {
+	processors.Add("printer", func() telegraf.Processor {
+		return &TemplateProcessor{}
+	})
+}

plugins/processors/template/template_metric.go

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+package template
+
+import (
+	"github.com/influxdata/telegraf"
+	"time"
+)
+
+type TemplateMetric struct {
+	metric telegraf.Metric
+}
+
+func (m *TemplateMetric) Measurement() string {
+	return m.Measurement()
+}
+
+func (m *TemplateMetric) Tag(key string) string {
+	tagString, _ := m.metric.GetTag(key)
+	return tagString
+}
+
+func (m *TemplateMetric) Field(key string) interface{} {
+	field, _ := m.metric.GetField(key)
+	return field
+}
+
+func (m *TemplateMetric) Time() time.Time {
+	return m.metric.Time()
+}

plugins/processors/template/template_test.go

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+package template
+
+import (
+	"testing"
+	"time"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/testutil"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestTagTemplateConcatenate(t *testing.T) {
+	now := time.Now()
+
+	// Create Template processor
+	tmp := TemplateProcessor{Tag: "topic", Template: `{{.Tag "hostname"}}.{{ .Tag "level" }}`}
+	// manually init
+	err := tmp.Init()
+
+	if err != nil {
+		panic(err)
+	}
+
+	// create metric for testing
+	input := []telegraf.Metric{testutil.MustMetric("Tags", map[string]string{"hostname": "localhost", "level": "debug"}, nil, now)}
+
+	// act
+	actual := tmp.Apply(input[0])
+
+	// assert
+	expected := []telegraf.Metric{testutil.MustMetric("Tags", map[string]string{"hostname": "localhost", "level": "debug", "topic": "localhost.debug"}, nil, now)}
+	testutil.RequireMetricsEqual(t, expected, actual)
+}
+
+func TestMetricMissingTagsIsNotLost(t *testing.T) {
+	now := time.Now()
+
+	// Create Template processor
+	tmp := TemplateProcessor{Tag: "topic", Template: `{{.Tag "hostname"}}.{{ .Tag "level" }}`}
+	// manually init
+	err := tmp.Init()
+
+	if err != nil {
+		panic(err)
+	}
+
+	// create metrics for testing
+	m1 := testutil.MustMetric("Works", map[string]string{"hostname": "localhost", "level": "debug"}, nil, now)
+	m2 := testutil.MustMetric("Fails", map[string]string{"hostname": "localhost"}, nil, now)
+
+	// act
+	actual := tmp.Apply(m1, m2)
+
+	// assert
+	// make sure no metrics are lost when a template process fails
+	assert.Equal(t, 2, len(actual), "Number of metrics input should equal number of metrics output")
+}
+
+func TestTagAndFieldConcatenate(t *testing.T) {
+	now := time.Now()
+
+	// Create Template processor
+	tmp := TemplateProcessor{Tag: "LocalTemp", Template: `{{.Tag "location"}} is {{ .Field "temperature" }}`}
+	// manually init
+	err := tmp.Init()
+
+	if err != nil {
+		panic(err)
+	}
+
+	// create metric for testing
+	m1 := testutil.MustMetric("weather", map[string]string{"location": "us-midwest"}, map[string]interface{}{"temperature": "too warm"}, now)
+
+	// act
+	actual := tmp.Apply(m1)
+
+	// assert
+	expected := []telegraf.Metric{testutil.MustMetric("weather", map[string]string{"location": "us-midwest", "LocalTemp": "us-midwest is too warm"}, map[string]interface{}{"temperature": "too warm"}, now)}
+	testutil.RequireMetricsEqual(t, expected, actual)
+}