Kafka Consumer is not reading the topic data through Java

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I am sending input JSON data to Kafka topic. I can see the same JSON data in kafka consumer by using below command.

.\bin\windows\kafka-console-consumer.bat --bootstrap-server localhost:9092 --topic mytopic --from-beginning

Case1: But when I am trying to read the records from kafka consumer (java) not getting any records in java console. I have tried the examples given in this link https://kafka.apache.org/090/javadoc/org/apache/kafka/clients/consumer/KafkaConsumer.html

Case2: If I send any message from the producer (command window) the same getting in the consumer(command window). and able to see the same records in the java console. This scenario is working.

If I submit the data to the topic through java program. Then the same JSON data appearing in consumer(command window). But not coming in java console.Case1 is not working. Case2 is working. Please let me know any configuration need to be done?

You need to make sure you are not sending empty lines at the end and only consuming the latest - use auto.offset.reset: 'earliest' like above, or properties.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");

And then, consumer.seekToBeginning(consumer.assignment()); to make sure.

Kafka consumer not able to start reading messages from the last , I have a 3-node Kafka cluster setup. I am using Apache spark (consumer) to read messages from Kafka broker. Each topic has 6 partitions. Kafka Consumers: Reading Data from Kafka. Applications that need to read data from Kafka use a KafkaConsumer to subscribe to Kafka topics and receive messages from these topics. Reading data from Kafka is a bit different than reading data from other messaging systems, and there are few unique concepts and ideas involved.

You need to set the ConsumerConfig.AUTO_OFFSET_RESET_CONFIG in order to read from the beginning.

kafkaConsumerProperties.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG,"earliest"); 

And also make sure that you are not running different-different consumer processes using the same consumer group ID, as the data from one partition might be read from one process and another will not see anything.

4. Kafka Consumers: Reading Data from Kafka, Kafka Consumers: Reading Data from Kafka Applications that need to read you need to specify classes that can take a byte array and turn it into a Java object. is not enough data flowing to the Kafka topic to satisfy the minimum amount of� Reading data in Consumer Group. The user can have more than one consumer reading data altogether. This can be done via a consumer group. In the consumer group, one or more consumers will be able to read the data from Kafka. If the user wants to read the messages from the beginning, either reset the group_id or change the group_id.

Documentation - Apache Kafka, 3.1 Broker Configs; 3.2 Topic Configs; 3.3 Producer Configs; 3.4 Consumer Configs We provide a Java client for Kafka, but clients are available in many It isn't enough to just read, write, and store streams of data, the purpose is to enable� A developer provides an in-depth tutorial on how to use both producers and consumers in the open source data framework, Kafka, while writing code in Java.

KafkaConsumer (clients 0.9.0.1 API), We provide a Java client for Kafka, but clients are available in many languages. the consumer is the only reader of that partition and consumes the data in order. over messages within a partition, not between different partitions in a topic. To test this example, you will need a Kafka broker running release 0.9.0.0 and a topic with some string data to consume. The easiest way to write a bunch of string data to a topic is to using the kafka-verifiable-producer.sh script. To make it interesting, we should also make sure the topic has more than one partition so that one member isn’t

KafkaConsumer (kafka 0.10.0.1 API), Unstable public class KafkaConsumer<K,V> extends java.lang. It automatically advances every time the consumer receives data calls This is achieved by balancing the partitions in the topic over the consumer processes in each group. The consumer application need not use Kafka's built-in offset storage, it can store� Kafka Tutorial: Writing a Kafka Consumer in Java. In this tutorial, you are going to create simple Kafka Consumer. This consumer consumes messages from the Kafka Producer you wrote in the last tutorial. This tutorial demonstrates how to process records from a Kafka topic with a Kafka Consumer.

KafkaConsumer (kafka 2.2.0 API), java.lang.Object. org.apache.kafka.clients.consumer.KafkaConsumer<K,V> So if there is a topic with four partitions, and a consumer group with two processes, a given topic without duplicating data (additional consumers are actually quite cheap). always be the offset of the next message that your application will read. Producer-Consumer: This contains a producer and consumer that use a Kafka topic named test. Streaming: This contains an application that uses the Kafka streaming API (in Kafka 0.10.0 or higher) that reads data from the test topic, splits the data into words, and writes a count of words into the wordcounts topic.

Comments
  • so you start consuming from java and then send new data to the topic and no messages appear (case 1)?
  • Are you running case2 using only one JVM?
  • How did you write your producer? Share us your code.
  • Start both console-consumer and custom-consumer. Then run your java producer. Also, make sure that your producer sends messages to Kafka. Do you see messages on both consumers ?