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emitter.go
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emitter.go
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package kafka
import (
"encoding/json"
"log"
"os"
"strings"
"time"
"github.com/Shopify/sarama"
"github.com/martin-helmich/cloudnativego-backend/src/lib/helper/kafka"
"github.com/martin-helmich/cloudnativego-backend/src/lib/msgqueue"
)
type kafkaEventEmitter struct {
producer sarama.SyncProducer
}
type messageEnvelope struct {
EventName string `json:"eventName"`
Payload interface{} `json:"payload"`
}
func NewKafkaEventEmitterFromEnvironment() (msgqueue.EventEmitter, error) {
brokers := []string{"localhost:9092"}
if brokerList := os.Getenv("KAFKA_BROKERS"); brokerList != "" {
brokers = strings.Split(brokerList, ",")
}
client := <-kafka.RetryConnect(brokers, 5*time.Second)
return NewKafkaEventEmitter(client)
}
func NewKafkaEventEmitter(client sarama.Client) (msgqueue.EventEmitter, error) {
producer, err := sarama.NewSyncProducerFromClient(client)
if err != nil {
return nil, err
}
emitter := kafkaEventEmitter{
producer: producer,
}
return &emitter, nil
}
func (k *kafkaEventEmitter) Emit(evt msgqueue.Event) error {
jsonBody, err := json.Marshal(messageEnvelope{
evt.EventName(),
evt,
})
if err != nil {
return err
}
msg := &sarama.ProducerMessage{
Topic: "events",
Value: sarama.ByteEncoder(jsonBody),
}
log.Printf("published message with topic %s: %v", evt.EventName(), jsonBody)
_, _, err = k.producer.SendMessage(msg)
return err
}