feat(processors.noop): Noop processor (#14297)

plugins/processors/all/noop.go

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+//go:build !custom || processors || processors.noop
+
+package all
+
+import _ "github.com/influxdata/telegraf/plugins/processors/noop" // register plugin

plugins/processors/noop/README.md

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+# Noop Processor Plugin
+
+The noop processor plugin does nothing to metrics. Instead it can be used to
+apply the global configuration options after other processing. Global config
+options like tagpass, fieldpass, and others are applied before a processor,
+aggregator, or output. As such a user might want to apply these after doing
+processing, but before an output or another processor.
+
+## Global configuration options <!-- @/docs/includes/plugin_config.md -->
+
+In addition to the plugin-specific configuration settings, plugins support
+additional global and plugin configuration settings. These settings are used to
+modify metrics, tags, and field or create aliases and configure ordering, etc.
+See the [CONFIGURATION.md][CONFIGURATION.md] for more details.
+
+[CONFIGURATION.md]: ../../../docs/CONFIGURATION.md#plugins
+
+## Configuration
+
+```toml @sample.conf
+# Do nothing processor
+[[processors.noop]]
+
+## Metric Filtering
+## The following options provide mechanisms to include or exclude entire
+## metrics. For specific details and examples see the metric filtering docs:
+## https://github.com/influxdata/telegraf/blob/master/docs/CONFIGURATION.md#metric-filtering
+
+## Metric Selectors - These will drop entire metrics
+## Filter on metric name or tag key + value
+# namepass = []
+# namedrop = []
+# tagpass = {}
+# tagdrop = {}
+
+## Filter on Common Expression Language (CEL) expression
+# metricpass = ""
+
+## Metric Modifiers - These will drop tags and fields from metrics
+## Filter on tag key or field key
+# taginclude = []
+# tagexclude = []
+# fieldpass = []
+# fielddrop = []
+```
+
+## Examples
+
+Consider a use-case where you have processed a metric based on a tag, but no
+longer need that tag for additional processing:
+
+```toml
+[[processors.ifname]]
+  order = 1
+  ...
+
+[[processors.noop]]
+  order = 2
+  tagexclude = ["useless_tag"]
+```

plugins/processors/noop/noop.go

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+//go:generate ../../../tools/readme_config_includer/generator
+package noop
+
+import (
+	_ "embed"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/plugins/processors"
+)
+
+//go:embed sample.conf
+var sampleConfig string
+
+type Noop struct{}
+
+func (*Noop) SampleConfig() string {
+	return sampleConfig
+}
+
+func (p *Noop) Apply(in ...telegraf.Metric) []telegraf.Metric {
+	return in
+}
+
+func init() {
+	processors.Add("noop", func() telegraf.Processor {
+		return &Noop{}
+	})
+}

plugins/processors/noop/noop_test.go

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+package noop
+
+import (
+	"testing"
+	"time"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/testutil"
+	"github.com/stretchr/testify/require"
+)
+
+func TestNoopNoMetric(t *testing.T) {
+	processor := Noop{}
+
+	m := []telegraf.Metric{}
+	actual := processor.Apply(m...)
+	require.Empty(t, actual)
+	testutil.RequireMetricsEqual(t, m, actual)
+}
+
+func TestNoopSingleMetric(t *testing.T) {
+	processor := Noop{}
+
+	m := []telegraf.Metric{
+		testutil.MustMetric(
+			"test",
+			map[string]string{
+				"tag": "tag_value",
+			},
+			map[string]interface{}{
+				"value": 42,
+			},
+			time.Now(),
+			telegraf.Gauge,
+		),
+	}
+	actual := processor.Apply(m...)
+	require.Len(t, actual, 1)
+	testutil.RequireMetricsEqual(t, m, actual)
+}
+
+func TestNoopMultipleMetrics(t *testing.T) {
+	processor := Noop{}
+
+	m := []telegraf.Metric{
+		testutil.MustMetric(
+			"test",
+			map[string]string{
+				"tag": "tag_value",
+			},
+			map[string]interface{}{
+				"value": 42,
+			},
+			time.Now(),
+			telegraf.Gauge,
+		),
+		testutil.MustMetric(
+			"test",
+			map[string]string{
+				"tag": "tag_value",
+			},
+			map[string]interface{}{
+				"value": 42,
+			},
+			time.Now(),
+			telegraf.Gauge,
+		),
+	}
+	actual := processor.Apply(m...)
+	require.Len(t, actual, 2)
+	testutil.RequireMetricsEqual(t, m, actual)
+}

plugins/processors/noop/sample.conf

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+# Do nothing processor
+[[processors.noop]]
+
+## Metric Filtering
+## The following options provide mechanisms to include or exclude entire
+## metrics. For specific details and examples see the metric filtering docs:
+## https://github.com/influxdata/telegraf/blob/master/docs/CONFIGURATION.md#metric-filtering
+
+## Metric Selectors - These will drop entire metrics
+## Filter on metric name or tag key + value
+# namepass = []
+# namedrop = []
+# tagpass = {}
+# tagdrop = {}
+
+## Filter on Common Expression Language (CEL) expression
+# metricpass = ""
+
+## Metric Modifiers - These will drop tags and fields from metrics
+## Filter on tag key or field key
+# taginclude = []
+# tagexclude = []
+# fieldpass = []
+# fielddrop = []