Add compression/acks/retry conf to Kafka output plugin

The following configuration is now possible

	## CompressionCodec represents the various compression codecs
recognized by Kafka in messages.
	##  "none" : No compression
	##  "gzip" : Gzip compression
	##  "snappy" : Snappy compression
	# compression_codec = "none"

	##  RequiredAcks is used in Produce Requests to tell the broker how
many replica acknowledgements it must see before responding
	##  "none" : the producer never waits for an acknowledgement from the
broker. This option provides the lowest latency but the weakest
durability guarantees (some data will be lost when a server fails).
	##  "leader" : the producer gets an acknowledgement after the leader
replica has received the data. This option provides better durability
as the client waits until the server acknowledges the request as
successful (only messages that were written to the now-dead leader but
not yet replicated will be lost).
	##  "leader_and_replicas" : the producer gets an acknowledgement after
all in-sync replicas have received the data. This option provides the
best durability, we guarantee that no messages will be lost as long as
at least one in sync replica remains.
	# required_acks = "leader_and_replicas"

	##  The total number of times to retry sending a message
	# max_retry = "3"

plugins/outputs/kafka/kafka.go

@@ -3,6 +3,8 @@ package kafka
 import (
 	"crypto/tls"
 	"fmt"
+	"strconv"
+	"strings"
 
 	"github.com/influxdata/telegraf"
 	"github.com/influxdata/telegraf/internal"
@@ -19,6 +21,12 @@ type Kafka struct {
 	Topic string
 	// Routing Key Tag
 	RoutingTag string `toml:"routing_tag"`
+	// Compression Codec Tag
+	CompressionCodec string
+	// RequiredAcks Tag
+	RequiredAcks string
+	// MaxRetry Tag
+	MaxRetry string
 
 	// Legacy SSL config options
 	// TLS client certificate
@@ -53,6 +61,21 @@ var sampleConfig = `
   ##  ie, if this tag exists, it's value will be used as the routing key
   routing_tag = "host"
 
+	## CompressionCodec represents the various compression codecs recognized by Kafka in messages.
+	##  "none" : No compression
+	##  "gzip" : Gzip compression
+	##  "snappy" : Snappy compression
+	# compression_codec = "none"
+
+	##  RequiredAcks is used in Produce Requests to tell the broker how many replica acknowledgements it must see before responding
+	##  "none" : the producer never waits for an acknowledgement from the broker. This option provides the lowest latency but the weakest durability guarantees (some data will be lost when a server fails).
+	##  "leader" : the producer gets an acknowledgement after the leader replica has received the data. This option provides better durability as the client waits until the server acknowledges the request as successful (only messages that were written to the now-dead leader but not yet replicated will be lost).
+	##  "leader_and_replicas" : the producer gets an acknowledgement after all in-sync replicas have received the data. This option provides the best durability, we guarantee that no messages will be lost as long as at least one in sync replica remains.
+	# required_acks = "leader_and_replicas"
+
+	##  The total number of times to retry sending a message
+	# max_retry = "3"
+
   ## Optional SSL Config
   # ssl_ca = "/etc/telegraf/ca.pem"
   # ssl_cert = "/etc/telegraf/cert.pem"
@@ -71,12 +94,66 @@ func (k *Kafka) SetSerializer(serializer serializers.Serializer) {
 	k.serializer = serializer
 }
 
+func requiredAcks(value string) (sarama.RequiredAcks, error) {
+	switch strings.ToLower(value) {
+	case "none":
+		return sarama.NoResponse, nil
+	case "leader":
+		return sarama.WaitForLocal, nil
+	case "", "leader_and_replicas":
+		return sarama.WaitForAll, nil
+	default:
+		return 0, fmt.Errorf("Failed to recognize required_acks: %s", value)
+	}
+}
+
+func compressionCodec(value string) (sarama.CompressionCodec, error) {
+	switch strings.ToLower(value) {
+	case "gzip":
+		return sarama.CompressionGZIP, nil
+	case "snappy":
+		return sarama.CompressionSnappy, nil
+	case "", "none":
+		return sarama.CompressionNone, nil
+	default:
+		return 0, fmt.Errorf("Failed to recognize compression_codec: %s", value)
+	}
+}
+
+func maxRetry(value string) (int, error) {
+	if value == "" {
+		return 3, nil
+	}
+	maxRetry, err := strconv.Atoi(value)
+	if err != nil {
+		return -1, fmt.Errorf("Failed to parse max_retry: %s", value)
+	}
+	if maxRetry < 0 {
+		return -1, fmt.Errorf("max_retry is %s but it should not be negative", value)
+	}
+	return maxRetry, nil
+}
+
 func (k *Kafka) Connect() error {
 	config := sarama.NewConfig()
-	// Wait for all in-sync replicas to ack the message
-	config.Producer.RequiredAcks = sarama.WaitForAll
-	// Retry up to 10 times to produce the message
-	config.Producer.Retry.Max = 10
+
+	requiredAcks, err := requiredAcks(k.RequiredAcks)
+	if err != nil {
+		return err
+	}
+	config.Producer.RequiredAcks = requiredAcks
+
+	compressionCodec, err := compressionCodec(k.CompressionCodec)
+	if err != nil {
+		return err
+	}
+	config.Producer.Compression = compressionCodec
+
+	maxRetry, err := maxRetry(k.MaxRetry)
+	if err != nil {
+		return err
+	}
+	config.Producer.Retry.Max = maxRetry
 
 	// Legacy support ssl config
 	if k.Certificate != "" {