Add support for setting kafka client id (#4418)

plugins/inputs/kafka_consumer/README.md

@@ -22,6 +22,9 @@ and use the old zookeeper connection method.
   ## Offset (must be either "oldest" or "newest")
   offset = "oldest"
 
+  ## Optional client id
+  # client_id = "my_client"
+
   ## Optional TLS Config
   # tls_ca = "/etc/telegraf/ca.pem"
   # tls_cert = "/etc/telegraf/cert.pem"

plugins/inputs/kafka_consumer/kafka_consumer.go

@@ -17,6 +17,7 @@ import (
 
 type Kafka struct {
 	ConsumerGroup string
+	ClientID      string `toml:"client_id"`
 	Topics        []string
 	Brokers       []string
 	MaxMessageLen int
@@ -59,6 +60,9 @@ var sampleConfig = `
   brokers = ["localhost:9092"]
   ## topic(s) to consume
   topics = ["telegraf"]
+  
+  ## Optional Client id
+  # client_id = "Telegraf"
 
   ## Optional TLS Config
   # tls_ca = "/etc/telegraf/ca.pem"
@@ -114,6 +118,12 @@ func (k *Kafka) Start(acc telegraf.Accumulator) error {
 		return err
 	}
 
+	if k.ClientID != "" {
+		config.ClientID = k.ClientID
+	} else {
+		config.ClientID = "Telegraf"
+	}
+
 	if tlsConfig != nil {
 		log.Printf("D! TLS Enabled")
 		config.Net.TLS.Config = tlsConfig