Can anyone share a Flink Kafka example in Scala?

Question

Can anyone share a working example of Flink Kafka (mainly receiving messages from Kafka) in Scala? I know there is a KafkaWordCount example in Spark. I just need to print out Kafka message in Flink. It would be really helpful.

Answer 1

The following code shows how to read from a Kafka topic using Flink's Scala DataStream API:

import org.apache.flink.streaming.api.scala._
import org.apache.flink.streaming.connectors.kafka.FlinkKafkaConsumer082
import org.apache.flink.streaming.util.serialization.SimpleStringSchema


object Main {
  def main(args: Array[String]) {
    val env = StreamExecutionEnvironment.getExecutionEnvironment
    val properties = new Properties()
    properties.setProperty("bootstrap.servers", "localhost:9092")
    properties.setProperty("zookeeper.connect", "localhost:2181")
    properties.setProperty("group.id", "test")
    val stream = env
      .addSource(new FlinkKafkaConsumer082[String]("topic", new SimpleStringSchema(), properties))
      .print

    env.execute("Flink Kafka Example")
  }
}

Answer 2

In contrast to what Robert added, below is a piece of application code for sending messages to the Kafka topic.

import org.apache.kafka.clients.producer.{KafkaProducer, ProducerRecord}

object KafkaProducer {

  def main(args: Array[String]): Unit = {
    KafkaProducer.sendMessageToKafkaTopic("localhost:9092", "topic_name")
  }    

  def sendMessageToKafkaTopic(server: String, topic:String): Unit = {
    val props = new Properties()
    props.put("bootstrap.servers", servers)
    props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer")
    props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer")
    val producer = new KafkaProducer[String,String](props)
    val record = new ProducerRecord[String,String](topic, "HELLO WORLD!")
    producer.send(record)
    producer.close()
  }
}