Add override processor (#3773)

This plugin can perform the standard metric modifications using override semantics.

plugins/processors/override/override.go

@@ -0,0 +1,60 @@
+package override
+
+import (
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/plugins/processors"
+)
+
+var sampleConfig = `
+## NOTE This processor will override names, name prefixes, name suffixes and
+## values of tags, that are already present in the metric passed through this
+## filter.
+
+## All modifications on inputs and aggregators can be overridden:
+# name_override = "new name"
+#	name_prefix = "new name_prefix"
+#	name_suffix = "new name_suffix"
+
+## Tags to be added (all values must be strings)
+# [processors.overide.tags]
+#   additional_tag = "tag_value"
+`
+
+type Override struct {
+	NameOverride string
+	NamePrefix   string
+	NameSuffix   string
+	Tags         map[string]string
+}
+
+func (p *Override) SampleConfig() string {
+	return sampleConfig
+}
+
+func (p *Override) Description() string {
+	return "Add all configured tags to all metrics that pass through this filter."
+}
+
+func (p *Override) Apply(in ...telegraf.Metric) []telegraf.Metric {
+	for _, metric := range in {
+		if len(p.NameOverride) > 0 {
+			metric.SetName(p.NameOverride)
+		}
+		if len(p.NamePrefix) > 0 {
+			metric.SetPrefix(p.NamePrefix)
+		}
+		if len(p.NameSuffix) > 0 {
+			metric.SetSuffix(p.NameSuffix)
+		}
+		for key, value := range p.Tags {
+			metric.AddTag(key, value)
+		}
+	}
+	return in
+}
+
+func init() {
+	processors.Add("override", func() telegraf.Processor {
+		return &Override{}
+	})
+}