Move example Kafka implementation to a separate package

example/kafka/kafka.go

@@ -1,4 +1,4 @@
-package main
+package kafka
 
 import (
 	"encoding/json"
@@ -11,14 +11,14 @@ import (
 	"github.com/localhots/satan"
 )
 
-// KafkaConsumerState contains data that is required to create a Kafka consumer.
-type KafkaConsumerState struct {
+// ConsumerState contains data that is required to create a Kafka consumer.
+type ConsumerState struct {
 	Partition int32 `json:"partition"`
 	Offset    int64 `json:"offset"`
 }
 
-// KafkaStream is an implementation of satan.Stremer for Kafka messaging queue.
-type KafkaStream struct {
+// Stream is an implementation of satan.Stremer for Kafka messaging queue.
+type Stream struct {
 	messages chan []byte
 	shutdown chan struct{}
 }
@@ -30,10 +30,11 @@ const (
 var (
 	kafkaClient   sarama.Client
 	kafkaConsumer sarama.Consumer
-	consumers     = map[string]map[string]KafkaConsumerState{}
+	consumers     = map[string]map[string]ConsumerState{}
 )
 
-func initKafka(brokers []string) {
+// Initialize sets up the kafka package.
+func Initialize(brokers []string) {
 	conf := sarama.NewConfig()
 	conf.ClientID = "Satan Example"
 
@@ -44,9 +45,12 @@ func initKafka(brokers []string) {
 	if kafkaConsumer, err = sarama.NewConsumerFromClient(kafkaClient); err != nil {
 		panic(err)
 	}
+
+	loadConsumerConfig()
 }
 
-func shutdownKafka() {
+// Shutdown shuts down the kafka package.
+func Shutdown() {
 	if err := kafkaConsumer.Close(); err != nil {
 		panic(err)
 	}
@@ -55,7 +59,8 @@ func shutdownKafka() {
 	}
 }
 
-func makeStream(consumer, topic string) satan.Streamer {
+// MakeStream creates a satan.Streamer implementation for Kafka messaging queue.
+func MakeStream(consumer, topic string) satan.Streamer {
 	c, ok := consumers[consumer]
 	if !ok {
 		panic(fmt.Errorf("Consumer %q has no config", consumer))
@@ -70,7 +75,7 @@ func makeStream(consumer, topic string) satan.Streamer {
 		panic(err)
 	}
 
-	stream := &KafkaStream{
+	stream := &Stream{
 		messages: make(chan []byte),
 		shutdown: make(chan struct{}),
 	}
@@ -91,6 +96,16 @@ func makeStream(consumer, topic string) satan.Streamer {
 	return stream
 }
 
+// Messages returns a channel that stream messages.
+func (s *Stream) Messages() <-chan []byte {
+	return s.messages
+}
+
+// Close stops Kafka partition consumer.
+func (s *Stream) Close() {
+	close(s.shutdown)
+}
+
 func loadConsumerConfig() {
 	if b, err := ioutil.ReadFile(consumerStateFile); err != nil {
 		fmt.Println(`Kafka consumers state file was not found at ` + consumerStateFile + `
@@ -111,13 +126,3 @@ Config file contents should look like this:
 		}
 	}
 }
-
-// Messages returns a channel that stream messages.
-func (s *KafkaStream) Messages() <-chan []byte {
-	return s.messages
-}
-
-// Close stops Kafka partition consumer.
-func (s *KafkaStream) Close() {
-	close(s.shutdown)
-}

example/main.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/localhots/satan"
 	"github.com/localhots/satan/example/daemons"
+	"github.com/localhots/satan/example/kafka"
 )
 
 func main() {
@@ -17,7 +18,7 @@ func main() {
 	var brokers string
 
 	flag.BoolVar(&debug, "v", false, "Verbose mode")
-	flag.StringVar(&brokers, "brokers", "127.0.0.1:9092", "Kafka broker addresses (separated by space)")
+	flag.StringVar(&brokers, "brokers", "127.0.0.1:9092", "Kafka broker addresses separated by space")
 	flag.Parse()
 
 	log.SetOutput(ioutil.Discard)
@@ -25,12 +26,11 @@ func main() {
 		log.SetOutput(os.Stderr)
 	}
 
-	loadConsumerConfig()
-	initKafka(strings.Split(brokers, " "))
-	defer shutdownKafka()
+	kafka.Initialize(strings.Split(brokers, " "))
+	defer kafka.Shutdown()
 
 	s := satan.Summon()
-	s.SubscribeFunc = makeStream
+	s.SubscribeFunc = kafka.MakeStream
 	s.AddDaemon(&daemons.NumberPrinter{})
 	s.AddDaemon(&daemons.PriceConsumer{})