kafka-workshop

Exercise 03: Your First Kafka Producer

Duration: 30 mins

Procedure

1. Read the javadoc of KafkaProducer and ProducerConfig

2. Create a new Scala/sbt project in IntelliJ IDEA: kafka-101
   • Leave the sbt/Scala version defaults — latest is fine

3. Add the kafka-clients dependency to build.sbt, matching the broker version from 01_kafka_docker.md

    libraryDependencies += "org.apache.kafka" % "kafka-clients" % "4.3.1"
   

   Use mvnrepository to know the proper entry for kafka-clients dependency.

4. Write the code of a Kafka producer OrderProducerApp that:
   1. Lives in kafka101 package
   2. Creates a KafkaProducer[String, String]
   3. Starts with an empty Properties object and fill out the missing properties guided by exceptions at runtime
   4. Eventually, you should have a Properties object with bootstrap.servers, key.serializer and value.serializer — use the ProducerConfig constants, not raw string literals
   5. Sends 10 ProducerRecords to topic orders, with keys order-0 .. order-9 and a value of your choosing
   6. Calls close() on the producer at the end so buffered records are flushed before the JVM exits

5. Run it, then verify the records arrived with the console consumer from 02_topics_and_cli.md (recreate the orders topic first if you deleted it there)

6. Silence the slf4j “no logger attached” warnings
   1. Add slf4j-api and a binding (e.g. slf4j-simple) to build.sbt
   2. Drop a minimal config file in src/main/resources for whichever binding you picked
7. Discuss: what happens if you comment out close() (or replace it with System.exit(0) right after send)? Try it and watch the console consumer — do all 10 records still arrive?

Complete Code

OrderProducerApp

Complete producer code (spoiler — try it yourself first)

```scala package kafka101 import java.util.Properties import org.apache.kafka.clients.producer.{KafkaProducer, ProducerConfig, ProducerRecord} import org.apache.kafka.common.serialization.StringSerializer object OrderProducerApp { def main(args: Array[String]): Unit = { val props = new Properties() props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, ":9092") props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, classOf[StringSerializer].getName) props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, classOf[StringSerializer].getName) val producer = new KafkaProducer[String, String](props) try { for (i <- 0 until 10) { val key = s"order-$i" val value = s"""{"orderId":$i,"item":"widget","qty":${i + 1}}""" producer.send(new ProducerRecord[String, String]("orders", key, value)) } } finally { producer.close() } } } ```

build.sbt

Complete build definition (spoiler — try it yourself first)

```scala scalaVersion := "3.8.4" name := "kafka-101" libraryDependencies ++= Seq( "org.apache.kafka" % "kafka-clients" % "4.3.1", "org.slf4j" % "slf4j-api" % "2.0.18", "org.slf4j" % "slf4j-simple" % "2.0.18" ) ```

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