CODEWITHSUNDEEP
apache-kafkakafka-consumer-api
DaliMidou
DaliMidou

Reputation: 121

The KafkaConsumer does not read from the offset 0

I want to test a Kafka example. I am using Kafka 0.10.0.1 The producer:

object ProducerApp extends App {

val topic = "topicTest"
val  props = new Properties()
props.put("bootstrap.servers", "localhost:9092")
props.put(ConsumerConfig.GROUP_ID_CONFIG, "consumer")
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)
for(i <- 0 to 20)
{    
val record = new ProducerRecord(topic, "key "+i," value "+i)    
producer.send(record)    
Thread.sleep(100)    
}
}

The consumer (the topic "topicTest" is created with 1 partition):

object ConsumerApp extends App {
val topic = "topicTest"  
val properties = new Properties
properties.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092")
properties.put(ConsumerConfig.GROUP_ID_CONFIG, "consumer")  
properties.put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, "false")  
properties.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest")
properties.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer")
properties.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer")
val consumer = new KafkaConsumer[String, String](properties)  
consumer.subscribe(scala.List(topic).asJava)    
while (true) {
consumer.seekToBeginning(consumer.assignment())
val records:ConsumerRecords[String,String] = consumer.poll(20000)
println("records size "+records.count())
records.asScala.foreach(rec => println("offset "+rec.offset()))    
}  
}

the problem is that the consumer does not read from the offset 0 at the first iteration but at the other oiterations it does. I want to know the reason and how can I make the consumer reads from the offset 0 at all the iterations. The expected result is:

records size 6
offset 0
offset 1
offset 2
offset 3
offset 4
offset 5
records size 6
offset 0
offset 1
offset 2
offset 3
offset 4
offset 5
...

but the obtained result is:

records size 4
offset 2
offset 3
offset 4
offset 5
records size 6
offset 0
offset 1
offset 2
offset 3
offset 4
offset 5
...

Upvotes: 0

Views: 2489

Answers (1)

shakeel
shakeel

Reputation: 901

I am unable to figure out what is exact mistake, I have written same code as yours. but for me it is working fine. if you want you can use below snippet.

import java.util
import org.apache.kafka.clients.consumer.ConsumerRebalanceListener;
import org.apache.kafka.clients.consumer.KafkaConsumer
import org.apache.kafka.common.TopicPartition
import org.apache.kafka.common.serialization.LongDeserializer;
import scala.collection.JavaConverters._
import java.util.Properties

object ConsumerExample extends App {

  val TOPIC = "test-stack"

  val props = new Properties()

  props.put("bootstrap.servers", "localhost:9092")


  props.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer")
  props.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer")
  props.put("group.id", "testinf")
  props.put("auto.offset.reset", "earliest")
  props.put("auto.offset.reset.config", "false")

  var listener = new ConsumerRebalanceListener() {
    override def onPartitionsAssigned(partitions: util.Collection[TopicPartition]): Unit = {
      println("Assignment : " + partitions)

    }
    override def onPartitionsRevoked(partitions: util.Collection[TopicPartition]): Unit = {
      // do nothing
    }

  }

  val consumer = new KafkaConsumer[String, String](props)

  consumer.subscribe(util.Collections.singletonList(TOPIC), listener)

  while (true) {


    consumer.seekToBeginning(consumer.assignment())
    val records = consumer.poll(20000)
    // for (record <- records.asScala) {
    //   println(record)
    // }
    println("records size "+records.count())
    records.asScala.foreach(rec => println("offset "+rec.offset()))  
  }

}

Try it out and let me know. if you have any issues.

Upvotes: 1

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