feat: add more functionality to template processor (#10316)

plugins/processors/template/README.md

@@ -23,9 +23,9 @@ Read the full [Go Template Documentation][].
   template = '{{ .Tag "hostname" }}.{{ .Tag "level" }}'
 ```
 
-## Example
+## Examples
 
-Combine multiple tags to create a single tag:
+### Combine multiple tags to create a single tag
 
 ```toml
 [[processors.template]]
@@ -38,7 +38,7 @@ Combine multiple tags to create a single tag:
 + cpu,level=debug,hostname=localhost,topic=localhost.debug time_idle=42
 ```
 
-Add measurement name as a tag:
+### Add measurement name as a tag
 
 ```toml
 [[processors.template]]
@@ -51,7 +51,7 @@ Add measurement name as a tag:
 + cpu,hostname=localhost,measurement=cpu time_idle=42
 ```
 
-Add the year as a tag, similar to the date processor:
+### Add the year as a tag, similar to the date processor
 
 ```toml
 [[processors.template]]
@@ -59,4 +59,48 @@ Add the year as a tag, similar to the date processor:
   template = '{{.Time.UTC.Year}}'
 ```
 
+### Add all fields as a tag
+
+Sometimes it is usefull to pass all fields with their values into a single message for sending it to a monitoring system (e.g. Syslog, GroundWork), then you can use `.FieldList` or `.TagList`:
+
+```toml
+[[processors.template]]
+  tag = "message"
+  template = 'Message about {{.Name}} fields: {{.FieldList}}'
+```
+
+```diff
+- cpu,hostname=localhost time_idle=42
++ cpu,hostname=localhost,message=Message\ about\ cpu\ fields:\ map[time_idle:42] time_idle=42
+```
+
+More advanced example, which might make more sense:
+
+```toml
+[[processors.template]]
+  tag = "message"
+  template = '''Message about {{.Name}} fields:
+{{ range $field, $value := .FieldList -}}
+{{$field}}:{{$value}}
+{{ end }}'''
+```
+
+```diff
+- cpu,hostname=localhost time_idle=42
++ cpu,hostname=localhost,message=Message\ about\ cpu\ fields:\ntime_idle:42\n time_idle=42
+```
+
+### Just add the current metric as a tag
+
+```toml
+[[processors.template]]
+  tag = "metric"
+  template = '{{.}}'
+```
+
+```diff
+- cpu,hostname=localhost time_idle=42
++ cpu,hostname=localhost,metric=cpu\ map[hostname:localhost]\ map[time_idle:42]\ 1257894000000000000 time_idle=42
+```
+
 [Go Template Documentation]: https://golang.org/pkg/text/template/

plugins/processors/template/template_metric.go

@@ -1,6 +1,7 @@
 package template
 
 import (
+	"fmt"
 	"time"
 
 	"github.com/influxdata/telegraf"
@@ -27,3 +28,15 @@ func (m *TemplateMetric) Field(key string) interface{} {
 func (m *TemplateMetric) Time() time.Time {
 	return m.metric.Time()
 }
+
+func (m *TemplateMetric) String() string {
+	return fmt.Sprint(m.metric)
+}
+
+func (m *TemplateMetric) TagList() map[string]string {
+	return m.metric.Tags()
+}
+
+func (m *TemplateMetric) FieldList() map[string]interface{} {
+	return m.metric.Fields()
+}

plugins/processors/template/template_test.go

@@ -115,3 +115,48 @@ func TestTagAndFieldConcatenate(t *testing.T) {
 	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)
 }
+
+func TestFieldList(t *testing.T) {
+	// Prepare
+	plugin := TemplateProcessor{Tag: "fields", Template: "{{.FieldList}}"}
+	require.NoError(t, plugin.Init())
+
+	// Run
+	m := testutil.TestMetric(1.23)
+	actual := plugin.Apply(m)
+
+	// Verify
+	expected := m.Copy()
+	expected.AddTag("fields", "map[value:1.23]")
+	testutil.RequireMetricsEqual(t, []telegraf.Metric{expected}, actual)
+}
+
+func TestTagList(t *testing.T) {
+	// Prepare
+	plugin := TemplateProcessor{Tag: "tags", Template: "{{.TagList}}"}
+	require.NoError(t, plugin.Init())
+
+	// Run
+	m := testutil.TestMetric(1.23)
+	actual := plugin.Apply(m)
+
+	// Verify
+	expected := m.Copy()
+	expected.AddTag("tags", "map[tag1:value1]")
+	testutil.RequireMetricsEqual(t, []telegraf.Metric{expected}, actual)
+}
+
+func TestDot(t *testing.T) {
+	// Prepare
+	plugin := TemplateProcessor{Tag: "metric", Template: "{{.}}"}
+	require.NoError(t, plugin.Init())
+
+	// Run
+	m := testutil.TestMetric(1.23)
+	actual := plugin.Apply(m)
+
+	// Verify
+	expected := m.Copy()
+	expected.AddTag("metric", "test1 map[tag1:value1] map[value:1.23] 1257894000000000000")
+	testutil.RequireMetricsEqual(t, []telegraf.Metric{expected}, actual)
+}