feat(nsq_consumer): Add input plugin

to consume metrics from an nsqd topic

closes #1347
closes #1369

plugins/inputs/nsq_consumer/nsq_consumer.go

@@ -0,0 +1,99 @@
+package nsq_consumer
+
+import (
+	"log"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/plugins/inputs"
+	"github.com/influxdata/telegraf/plugins/parsers"
+	"github.com/nsqio/go-nsq"
+)
+
+//NSQConsumer represents the configuration of the plugin
+type NSQConsumer struct {
+	Server      string
+	Topic       string
+	Channel     string
+	MaxInFlight int
+	parser      parsers.Parser
+	consumer    *nsq.Consumer
+	acc         telegraf.Accumulator
+}
+
+var sampleConfig = `
+  ## An string representing the NSQD TCP Endpoint
+  server = "localhost:4150"
+  topic = "telegraf"
+  channel = "consumer"
+  max_in_flight = 100
+
+  ## Data format to consume.
+  ## Each data format has it's own unique set of configuration options, read
+  ## more about them here:
+  ## https://github.com/influxdata/telegraf/blob/master/docs/DATA_FORMATS_INPUT.md
+  data_format = "influx"
+`
+
+func init() {
+	inputs.Add("nsq_consumer", func() telegraf.Input {
+		return &NSQConsumer{}
+	})
+}
+
+// SetParser takes the data_format from the config and finds the right parser for that format
+func (n *NSQConsumer) SetParser(parser parsers.Parser) {
+	n.parser = parser
+}
+
+// SampleConfig returns config values for generating a sample configuration file
+func (n *NSQConsumer) SampleConfig() string {
+	return sampleConfig
+}
+
+// Description prints description string
+func (n *NSQConsumer) Description() string {
+	return "Read NSQ topic for metrics."
+}
+
+// Start pulls data from nsq
+func (n *NSQConsumer) Start(acc telegraf.Accumulator) error {
+	n.acc = acc
+	n.connect()
+	n.consumer.AddConcurrentHandlers(nsq.HandlerFunc(func(message *nsq.Message) error {
+		metrics, err := n.parser.Parse(message.Body)
+		if err != nil {
+			log.Printf("NSQConsumer Parse Error\nmessage:%s\nerror:%s", string(message.Body), err.Error())
+			return nil
+		}
+		for _, metric := range metrics {
+			n.acc.AddFields(metric.Name(), metric.Fields(), metric.Tags(), metric.Time())
+		}
+		message.Finish()
+		return nil
+	}), n.MaxInFlight)
+	n.consumer.ConnectToNSQD(n.Server)
+	return nil
+}
+
+// Stop processing messages
+func (n *NSQConsumer) Stop() {
+	n.consumer.Stop()
+}
+
+// Gather is a noop
+func (n *NSQConsumer) Gather(acc telegraf.Accumulator) error {
+	return nil
+}
+
+func (n *NSQConsumer) connect() error {
+	if n.consumer == nil {
+		config := nsq.NewConfig()
+		config.MaxInFlight = n.MaxInFlight
+		consumer, err := nsq.NewConsumer(n.Topic, n.Channel, config)
+		if err != nil {
+			return err
+		}
+		n.consumer = consumer
+	}
+	return nil
+}