add support for streaming processors (#7634)

plugins/processors/registry.go

@@ -3,9 +3,24 @@ package processors
 import "github.com/influxdata/telegraf"
 
 type Creator func() telegraf.Processor
+type StreamingCreator func() telegraf.StreamingProcessor
 
-var Processors = map[string]Creator{}
+// all processors are streaming processors.
+// telegraf.Processor processors are upgraded to telegraf.StreamingProcessor
+var Processors = map[string]StreamingCreator{}
 
+// Add adds a telegraf.Processor processor
 func Add(name string, creator Creator) {
+	Processors[name] = upgradeToStreamingProcessor(creator)
+}
+
+// AddStreaming adds a telegraf.StreamingProcessor streaming processor
+func AddStreaming(name string, creator StreamingCreator) {
 	Processors[name] = creator
 }
+
+func upgradeToStreamingProcessor(oldCreator Creator) StreamingCreator {
+	return func() telegraf.StreamingProcessor {
+		return NewStreamingProcessorFromProcessor(oldCreator())
+	}
+}

plugins/processors/streamingprocessor.go

@@ -0,0 +1,49 @@
+package processors
+
+import (
+	"github.com/influxdata/telegraf"
+)
+
+// NewStreamingProcessorFromProcessor is a converter that turns a standard
+// processor into a streaming processor
+func NewStreamingProcessorFromProcessor(p telegraf.Processor) telegraf.StreamingProcessor {
+	sp := &streamingProcessor{
+		processor: p,
+	}
+	return sp
+}
+
+type streamingProcessor struct {
+	processor telegraf.Processor
+	acc       telegraf.Accumulator
+}
+
+func (sp *streamingProcessor) SampleConfig() string {
+	return sp.processor.SampleConfig()
+}
+
+func (sp *streamingProcessor) Description() string {
+	return sp.processor.Description()
+}
+
+func (sp *streamingProcessor) Start(acc telegraf.Accumulator) error {
+	sp.acc = acc
+	return nil
+}
+
+func (sp *streamingProcessor) Add(m telegraf.Metric, acc telegraf.Accumulator) {
+	for _, m := range sp.processor.Apply(m) {
+		acc.AddMetric(m)
+	}
+}
+
+func (sp *streamingProcessor) Stop() error {
+	return nil
+}
+
+// Unwrap lets you retrieve the original telegraf.Processor from the
+// StreamingProcessor. This is necessary because the toml Unmarshaller won't
+// look inside composed types.
+func (sp *streamingProcessor) Unwrap() telegraf.Processor {
+	return sp.processor
+}