Add topic tag options to kafka output

plugins/inputs/kafka_consumer/kafka_consumer.go

@@ -6,9 +6,11 @@ import (
 	"log"
 	"strings"
 	"sync"
+	"time"
 
 	"github.com/Shopify/sarama"
 	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/internal"
 	"github.com/influxdata/telegraf/internal/tls"
 	"github.com/influxdata/telegraf/plugins/common/kafka"
 	"github.com/influxdata/telegraf/plugins/inputs"
@@ -83,6 +85,7 @@ const (
 	defaultMaxUndeliveredMessages = 1000
 	defaultMaxMessageLen          = 1000000
 	defaultConsumerGroup          = "telegraf_metrics_consumers"
+	reconnectDelay                = 5 * time.Second
 )
 
 type empty struct{}
@@ -259,6 +262,7 @@ func (k *KafkaConsumer) Start(acc telegraf.Accumulator) error {
 			err := k.consumer.Consume(ctx, k.Topics, handler)
 			if err != nil {
 				acc.AddError(err)
+				internal.SleepContext(ctx, reconnectDelay)
 			}
 		}
 		err = k.consumer.Close()

plugins/outputs/kafka/README.md

@@ -10,6 +10,13 @@ This plugin writes to a [Kafka Broker](http://kafka.apache.org/07/quickstart.htm
   ## Kafka topic for producer messages
   topic = "telegraf"
 
+  ## The value of this tag will be used as the topic.  If not set the 'topic'
+  ## option is used.
+  # topic_tag = ""
+
+  ## If true, the 'topic_tag' will be removed from to the metric.
+  # exclude_topic_tag = false
+
   ## Optional Client id
   # client_id = "Telegraf"
 

plugins/outputs/kafka/kafka.go

@@ -26,16 +26,18 @@ var zeroTime = time.Unix(0, 0)
 
 type (
 	Kafka struct {
-		Brokers          []string
-		Topic            string
+		Brokers          []string    `toml:"brokers"`
+		Topic            string      `toml:"topic"`
+		TopicTag         string      `toml:"topic_tag"`
+		ExcludeTopicTag  bool        `toml:"exclude_topic_tag"`
 		ClientID         string      `toml:"client_id"`
 		TopicSuffix      TopicSuffix `toml:"topic_suffix"`
 		RoutingTag       string      `toml:"routing_tag"`
 		RoutingKey       string      `toml:"routing_key"`
-		CompressionCodec int
-		RequiredAcks     int
-		MaxRetry         int
-		MaxMessageBytes  int `toml:"max_message_bytes"`
+		CompressionCodec int         `toml:"compression_codec"`
+		RequiredAcks     int         `toml:"required_acks"`
+		MaxRetry         int         `toml:"max_retry"`
+		MaxMessageBytes  int         `toml:"max_message_bytes"`
 
 		Version string `toml:"version"`
 
@@ -57,7 +59,9 @@ type (
 		Log telegraf.Logger `toml:"-"`
 
 		tlsConfig tls.Config
-		producer  sarama.SyncProducer
+
+		producerFunc func(addrs []string, config *sarama.Config) (sarama.SyncProducer, error)
+		producer     sarama.SyncProducer
 
 		serializer serializers.Serializer
 	}
@@ -94,6 +98,13 @@ var sampleConfig = `
   ## Kafka topic for producer messages
   topic = "telegraf"
 
+  ## The value of this tag will be used as the topic.  If not set the 'topic'
+  ## option is used.
+  # topic_tag = ""
+
+  ## If true, the 'topic_tag' will be removed from to the metric.
+  # exclude_topic_tag = false
+
   ## Optional Client id
   # client_id = "Telegraf"
 
@@ -212,14 +223,29 @@ func ValidateTopicSuffixMethod(method string) error {
 	return fmt.Errorf("Unknown topic suffix method provided: %s", method)
 }
 
-func (k *Kafka) GetTopicName(metric telegraf.Metric) string {
+func (k *Kafka) GetTopicName(metric telegraf.Metric) (telegraf.Metric, string) {
+	topic := k.Topic
+	if k.TopicTag != "" {
+		if t, ok := metric.GetTag(k.TopicTag); ok {
+			topic = t
+
+			// If excluding the topic tag, a copy is required to avoid modifying
+			// the metric buffer.
+			if k.ExcludeTopicTag {
+				metric = metric.Copy()
+				metric.Accept()
+				metric.RemoveTag(k.TopicTag)
+			}
+		}
+	}
+
 	var topicName string
 	switch k.TopicSuffix.Method {
 	case "measurement":
-		topicName = k.Topic + k.TopicSuffix.Separator + metric.Name()
+		topicName = topic + k.TopicSuffix.Separator + metric.Name()
 	case "tags":
 		var topicNameComponents []string
-		topicNameComponents = append(topicNameComponents, k.Topic)
+		topicNameComponents = append(topicNameComponents, topic)
 		for _, tag := range k.TopicSuffix.Keys {
 			tagValue := metric.Tags()[tag]
 			if tagValue != "" {
@@ -228,9 +254,9 @@ func (k *Kafka) GetTopicName(metric telegraf.Metric) string {
 		}
 		topicName = strings.Join(topicNameComponents, k.TopicSuffix.Separator)
 	default:
-		topicName = k.Topic
+		topicName = topic
 	}
-	return topicName
+	return metric, topicName
 }
 
 func (k *Kafka) SetSerializer(serializer serializers.Serializer) {
@@ -306,7 +332,7 @@ func (k *Kafka) Connect() error {
 		config.Net.SASL.Version = version
 	}
 
-	producer, err := sarama.NewSyncProducer(k.Brokers, config)
+	producer, err := k.producerFunc(k.Brokers, config)
 	if err != nil {
 		return err
 	}
@@ -348,14 +374,16 @@ func (k *Kafka) routingKey(metric telegraf.Metric) (string, error) {
 func (k *Kafka) Write(metrics []telegraf.Metric) error {
 	msgs := make([]*sarama.ProducerMessage, 0, len(metrics))
 	for _, metric := range metrics {
+		metric, topic := k.GetTopicName(metric)
+
 		buf, err := k.serializer.Serialize(metric)
 		if err != nil {
 			k.Log.Debugf("Could not serialize metric: %v", err)
 			continue
 		}
 
 		m := &sarama.ProducerMessage{
-			Topic: k.GetTopicName(metric),
+			Topic: topic,
 			Value: sarama.ByteEncoder(buf),
 		}
 
@@ -403,6 +431,7 @@ func init() {
 		return &Kafka{
 			MaxRetry:     3,
 			RequiredAcks: -1,
+			producerFunc: sarama.NewSyncProducer,
 		}
 	})
 }

plugins/outputs/kafka/kafka_test.go

@@ -4,6 +4,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/Shopify/sarama"
 	"github.com/influxdata/telegraf"
 	"github.com/influxdata/telegraf/metric"
 	"github.com/influxdata/telegraf/plugins/serializers"
@@ -81,7 +82,7 @@ func TestTopicSuffixes(t *testing.T) {
 			TopicSuffix: topicSuffix,
 		}
 
-		topic := k.GetTopicName(metric)
+		_, topic := k.GetTopicName(metric)
 		require.Equal(t, expectedTopic, topic)
 	}
 }
@@ -156,3 +157,146 @@ func TestRoutingKey(t *testing.T) {
 		})
 	}
 }
+
+type MockProducer struct {
+	sent []*sarama.ProducerMessage
+}
+
+func (p *MockProducer) SendMessage(msg *sarama.ProducerMessage) (partition int32, offset int64, err error) {
+	p.sent = append(p.sent, msg)
+	return 0, 0, nil
+}
+
+func (p *MockProducer) SendMessages(msgs []*sarama.ProducerMessage) error {
+	p.sent = append(p.sent, msgs...)
+	return nil
+}
+
+func (p *MockProducer) Close() error {
+	return nil
+}
+
+func NewMockProducer(addrs []string, config *sarama.Config) (sarama.SyncProducer, error) {
+	return &MockProducer{}, nil
+}
+
+func TestTopicTag(t *testing.T) {
+	tests := []struct {
+		name   string
+		plugin *Kafka
+		input  []telegraf.Metric
+		topic  string
+		value  string
+	}{
+		{
+			name: "static topic",
+			plugin: &Kafka{
+				Brokers:      []string{"127.0.0.1"},
+				Topic:        "telegraf",
+				producerFunc: NewMockProducer,
+			},
+			input: []telegraf.Metric{
+				testutil.MustMetric(
+					"cpu",
+					map[string]string{},
+					map[string]interface{}{
+						"time_idle": 42.0,
+					},
+					time.Unix(0, 0),
+				),
+			},
+			topic: "telegraf",
+			value: "cpu time_idle=42 0\n",
+		},
+		{
+			name: "topic tag overrides static topic",
+			plugin: &Kafka{
+				Brokers:      []string{"127.0.0.1"},
+				Topic:        "telegraf",
+				TopicTag:     "topic",
+				producerFunc: NewMockProducer,
+			},
+			input: []telegraf.Metric{
+				testutil.MustMetric(
+					"cpu",
+					map[string]string{
+						"topic": "xyzzy",
+					},
+					map[string]interface{}{
+						"time_idle": 42.0,
+					},
+					time.Unix(0, 0),
+				),
+			},
+			topic: "xyzzy",
+			value: "cpu,topic=xyzzy time_idle=42 0\n",
+		},
+		{
+			name: "missing topic tag falls back to  static topic",
+			plugin: &Kafka{
+				Brokers:      []string{"127.0.0.1"},
+				Topic:        "telegraf",
+				TopicTag:     "topic",
+				producerFunc: NewMockProducer,
+			},
+			input: []telegraf.Metric{
+				testutil.MustMetric(
+					"cpu",
+					map[string]string{},
+					map[string]interface{}{
+						"time_idle": 42.0,
+					},
+					time.Unix(0, 0),
+				),
+			},
+			topic: "telegraf",
+			value: "cpu time_idle=42 0\n",
+		},
+		{
+			name: "exclude topic tag removes tag",
+			plugin: &Kafka{
+				Brokers:         []string{"127.0.0.1"},
+				Topic:           "telegraf",
+				TopicTag:        "topic",
+				ExcludeTopicTag: true,
+				producerFunc:    NewMockProducer,
+			},
+			input: []telegraf.Metric{
+				testutil.MustMetric(
+					"cpu",
+					map[string]string{
+						"topic": "xyzzy",
+					},
+					map[string]interface{}{
+						"time_idle": 42.0,
+					},
+					time.Unix(0, 0),
+				),
+			},
+			topic: "xyzzy",
+			value: "cpu time_idle=42 0\n",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			s, err := serializers.NewInfluxSerializer()
+			require.NoError(t, err)
+			tt.plugin.SetSerializer(s)
+
+			err = tt.plugin.Connect()
+			require.NoError(t, err)
+
+			producer := &MockProducer{}
+			tt.plugin.producer = producer
+
+			err = tt.plugin.Write(tt.input)
+			require.NoError(t, err)
+
+			require.Equal(t, tt.topic, producer.sent[0].Topic)
+
+			encoded, err := producer.sent[0].Value.Encode()
+			require.NoError(t, err)
+			require.Equal(t, tt.value, string(encoded))
+		})
+	}
+}