Spring Kafka Consumer Not Consuming Messages

The producer is working and I can consume the messages from the kafka broker but the messages also contain some header information like the following:. If you do not specify a value for bootstrap. This section gives a high-level overview of how the consumer works, an introduction to the configuration settings for tuning, and some examples from each client library. Before configuring Kafka to handle large messages, first consider the following options to reduce message size: The Kafka producer can compress messages. Records may be pruned on the basis of time and/or partition size. Added advertised. Kafka does not provide a feature to do this. This tutorial demonstrates how to send and receive messages from Spring Kafka. Normally in message queues, the messages are removed after subscribers have confirmed their receipt. It does the first of these with a partitioner, which typically selects a partition using a hash function. To avoid re-processing the last message read if a consumer is restarted, the committed offset should be the next message your application should consume, i. This post gives a step-by-step tutorial to enable messaging in a microservice using Kafka with Spring Cloud Stream. (Spring Cloud Stream consumer groups are similar to and inspired by Kafka consumer groups. Its because I was publishing event first and then starting a consumer. It basically says that we want to bind the output message channel to the Kafka timerTopic, and it says that we want to serialize the payload into JSON. The first challenge is how to collect large volume of data and the. In Kafka message can be subscribed by multi consumers, means, many consumer types not many instances of same one. So in the tutorial, JavaSampleApproach will show you how to start Spring Apache Kafka Application with SpringBoot. In Kafka, each topic is divided into set of partitions. group property to specify a group name. Spring Kafka - JSON Serializer Deserializer Example 6 minute read JSON (JavaScript Object Notation) is a lightweight data-interchange format that uses human-readable text to transmit data objects. Normally in message queues, the messages are removed after subscribers have confirmed their receipt. A TCP connection will be set up between the application and Apache Kafka. Then demonstrates Kafka consumer failover and Kafka broker failover. The host name and port number of the schema registry are passed as parameters to the deserializer through the Kafka consumer properties. It provides opinionated configuration of middleware from several vendors, introducing the concepts of persistent publish-subscribe semantics, consumer groups, and partitions. Spring-kafka, as most Spring-related libraries, likes annotations. Properties here supersede any properties set in boot and in the configuration property above. In addition to support known Kafka consumer properties, unknown consumer properties are allowed here as well. partitionKey, ItemDeleted(item))) In the previous post we showed how to subscribe to messages using that partition key:. In this tutorial, we'll look at how Kafka ensures exactly-once delivery between producer and consumer applications through the newly introduced Transactional API. Map with a key/value pair containing generic Kafka consumer properties. Producers write messages to the. Applications can directly use the Kafka Streams primitives and leverage. You are using schema that is supplied to both producer and consumer. In our example we'll create a producer that emits numbers from 1 to 1000 and send them to our Kafka broker. It subscribes to one or more topics in the Kafka cluster. Consuming messages. When getting the message key or value, a SerializationException may occur if the data is not well formed. 0 and CDH-5. Spring Boot with Spring. Kafka does not provide a feature to do this. Sometimes after a while the listener restarts and sometimes doesn't. After creating a Kafka Producer to send messages to Apache Kafka cluster. Spring Cloud Stream is a framework under the umbrella project Spring Cloud. Every deployment consists of. Kafka does not deletes consumed messages with its default settings. That's pretty much it, we now have successfully sent messages to an Apache Kafka topic using a Spring Boot application. We’ll send a Java Object as. If the message format version in a partition is before 0. We will also use Avro…. In this tutorial, we'll look at how Kafka ensures exactly-once delivery between producer and consumer applications through the newly introduced Transactional API. To enable SSL (between client on Node5 & Broker on Node4), Steps on Node 4 ->. Consumer - Kafka Consumers subscribes to a topic(s) and also reads and processes messages from the topic(s). : last_offset + 1. All network I/O happens in the thread of the application making the call. It does the first of these with a partitioner, which typically selects a partition using a hash function. Consumer Configuration. In Kafka message can be subscribed by multi consumers, means, many consumer types not many instances of same one. I am publishing to a Dockerized version of Kakfa using the official Confluent images. Hi, I have a session aware message listener inside a DMLC with 5 concurrent consumers consuming messages from a queue. Kafka is different from most other message queues in the way it maintains the concept of a "head" of the queue. In a previous tutorial we saw how to produce and consume messages using Spring Kafka. This is working fine, and consumer is able to consumer messages produced by the producer. Regarding data, we have two main challenges. The advantage of using Kafka is that, if our consumer breaks down, the new or fixed consumer will pick up reading where the previous one stopped. On this section, we will learn the internals that compose a Kafka consumer, responsible for reading messages from Kafka topics. After execution the test you should close the consumer with consumer. once stopped, after resuming & starting the container, it will not consume it again, but will process with the next incoming msg. ex : Micro-service - A has publish the kafka event with the request body. As with publish-subscribe, Kafka allows you to broadcast messages to multiple consumer groups. The binder implementation natively interacts with Kafka Streams "types" - KStream or KTable. By using the @Service annotation we make the Sender class eligible for the spring container to do auto discovery. xml for this component. This tutorial demonstrates how to process records from a Kafka topic with a Kafka Consumer. Nakul Mishra - Casumo. Over time we came to realize many of the limitations of these APIs. With Spring, develop application to interact with Apache Kafka is becoming easier. You can read my other article about Scaling using Kafka. The Kafka producer is conceptually much simpler than the consumer since it has no need for group coordination. Also, I went for "Spring for Apache Kafka" in hope of easier configuration. First of all, we need to set up a secure connection. We'll send a Java Object as. Let's say that you have 10000 people out and about all simultaneously collecting documents from other people. The Fulfillment service's Receiver class consumes the FulfillmentRequestEvent from the Kafka topic and instantiates a Fulfillment object, containing the data passed in the FulfillmentRequestEvent message payload. Map with a key/value pair containing generic Kafka consumer properties. Subject: Re: kafka consumer not consuming messages On extension to the same problem i am seeing this "INFO Closing socket connection to /127. Since version 0. Here's how you can avoid the pain!. Producers write messages to the. The underlying implementation is using the KafkaConsumer, see Kafka API for a description of consumer groups, offsets, and other details. Then a consumer will read the data from the broker and store them in a MongoDb collection. Hi, I have a session aware message listener inside a DMLC with 5 concurrent consumers consuming messages from a queue. Configure Kafka Producer. Few of the consumers are attached to the group but they do not consume any message. Kafka consumer internal structure is divided as we can see on the following diagram:. Receiving Messages Message Listeners Message Listener Containers @KafkaListener Annotation Container Thread Naming @KafkaListener on a class @KafkaListener Lifecycle Management. After execution the test you should close the consumer with consumer. Confluent Platform includes the Java consumer shipped with Apache Kafka®. if you're considering microservices, you have to give serious thought to how the different services will communicate. Then we could create an In-Memory cache by consuming Kafka messages. the messages do not have timestamps, null will be returned for that partition. I wanted to learn how to use Apache Kafka for publishing and consuming messages from Apache Kafka using Java client, so i followed these steps. For example, if the original message is a text-based format (such as XML), in most cases the compressed message will be sufficiently small. Now, we are creating a Kafka Consumer to consume messages from the Kafka cluster. Kafka is a highly scalable, highly available queuing system, which is built to handle huge message throughput at lightning-fast speeds. Hi, I have a session aware message listener inside a DMLC with 5 concurrent consumers consuming messages from a queue. As with the queue, the consumer group allows you to divide up processing over a collection of processes (the members of the consumer group). ; The auto-offset-reset property is set to earliest, which means that the consumers will start reading messages from the earliest one available when there is no existing offset for that consumer. In the next article, we will be discussing about consuming this log messages in logstash. Already noticed the difference between RabbitMQ and Kafka? The difference is, if a consumer is not connected to a fanout exchange in RabbitMQ when a message was published, it will be lost because other consumers have consumed the message, but this doesn't happen in Apache Kafka as any consumer can read any message as they maintain their own. Using the High Level Consumer Why use the High Level Consumer. The Kafka Consumer API allows applications to read streams of data from the cluster. The default behavior is to skip duplicates. Properties here supersede any properties set in boot and in the configuration property above. 0 and CDH-5. I am publishing to a Dockerized version of Kakfa using the official Confluent images. Receiving Messages Message Listeners Message Listener Containers @KafkaListener Annotation Container Thread Naming @KafkaListener on a class @KafkaListener Lifecycle Management. The problem is that after a while (could be 30min or couple of hours), the consumer does not receive any messages from Kafka, while the data exist there (while the streaming of data to Kafka still running, so Kafka has inputs). Regarding data, we have two main challenges. In this tutorial, you are going to create simple Kafka Consumer. This has been covered at length in the proposal for an Idempotent Producer. Spring Kafka Tutorial - Getting Started with the Spring for Apache Kafka Apache Kafka, a distributed messaging system, is gaining very much attraction today. Nakul Mishra - Casumo. ; The auto-offset-reset property is set to earliest, which means that the consumers will start reading messages from the earliest one available when there is no existing offset for that consumer. reset=latest by default. 0 versions with Kafka version : 0. To enable SSL (between client on Node5 & Broker on Node4), Steps on Node 4 ->. It subscribes to one or more topics in the Kafka cluster. By using the @Service annotation we make the Sender class eligible for the spring container to do auto discovery. The following are code examples for showing how to use kafka. Then go to kafka directory by executing cd kafka_2. If you are just interested to consume the messages after running the consumer then you can just omit --from-beginning switch it and run. This is working fine, and consumer is able to consumer messages produced by the producer. When doing this, different instances of an application are placed in a competing consumer relationship, where only one of the instances is expected to handle a given message. It uses JSON for defining data types/protocols and serializes data in a compact binary format. Spring for Apache Kafka 1. The producer is happily producing messages. By default, consumer only consumes events published after it started because auto. Integration of Apache Kafka with Spring Boot Application. Kafka is an open-source distributed commit log addressing low latency, high throughput, scalability, fault-tolerance, and disk-based retention. Apache Kafka is an amazing tool for logging/streaming data at scale. The first because we are using group management to assign topic partitions to consumers so we need a group, the second to ensure the new consumer group will get the messages we just sent, because the container might start after the sends have completed. Go to Spring initializer. Consuming Kafka's internal consumer offsets topic Jul 5, 2016 #Kafka #Tips. In this tutorial we demonstrate how to add/read custom headers to/from a Kafka Message using Spring Kafka. If the message format version in a partition is before 0. Consuming Messages 5. Let's turn now turn to using Apache Kafka with Spring. consumer API in Java to fetch messages from kafka ( the same one which is stated in Kafka introduction example). In this article, let us explore setting up a test Kafka broker on a Windows machine, create a Kafka producer, and create a Kafka consumer using the. One strange thing I observed is when I am starting multiple Kafka consumers for multiple topics placed in a single group and on hitting. If the Commit message offset in Kafka property is selected, the consumer position in the log of messages for the topic is saved in Kafka as each message is processed; therefore, if the flow is stopped and then restarted, the input node starts consuming messages from the message position that had been reached when the flow was stopped. Consuming Kafka's internal consumer offsets topic Jul 5, 2016 #Kafka #Tips. As with the queue, the consumer group allows you to divide up processing over a collection of processes (the members of the consumer group). In several previous articles on Apache Kafka, Kafka Streams and Node. We will also use Avro…. xml for this component. And with that, let's get started! Table of contents. I can browse them using the web front end supplied with ActiveMQ. How to install Apache Kafka on Windows - Quick start on Windows Talk2 Amareswaran the topic and on another side consumer consume/read messages from this topic. For consuming messages, we need to configure a ConsumerFactory and a KafkaListenerContainerFactory. Kafka Tutorial: Writing a Kafka Consumer in Java. kafka spring-kafka 2. When getting the message key or value, a SerializationException may occur if the data is not well formed. If the group ID is not known by the broker, the consumer can be configured to ask the broker to point its corresponding pointer to the start of the journal (thereby consuming all messages since the broker accepted messages), or the end (consuming all messages starting from the next message to arrive). Kafka is an open-source distributed commit log addressing low latency, high throughput, scalability, fault-tolerance, and disk-based retention. Apache Kafka is a message bus and it can be very powerful when used as an integration bus. In this article, we'll cover Spring support for Kafka and the level of abstractions it provides over native Kafka Java client APIs. This is working fine, and consumer is able to consumer messages produced by the producer. (Spring Cloud Stream consumer groups are similar to and inspired by Kafka consumer groups. It uses JSON for defining data types/protocols and serializes data in a compact binary format. In several previous articles on Apache Kafka, Kafka Streams and Node. Kafka Consumer. Nakul Mishra - Casumo. group-id = test-group spring. On the consuming side, the demarcator indicates that ConsumeKafka should produce a single flow file with the content containing all of the messages received from Kafka in a single poll, using the demarcator to separate them. The first because we are using group management to assign topic partitions to consumers so we need a group, the second to ensure the new consumer group will get the messages we just sent, because the container might start after the sends have completed. Questions: I have one project, and the workflow says; consume the request as an kafka-event from other micro-services, and publish that event again to the project and listen it to process that request. Consumers can "replay" these messages if they wish. Akka Event Bus offers us subscription by partition that we're missing in our Kafka High Level Consumer. Below are the stats of group command. Using Apache Kafka with Spring XD. MESSAGE_KEY but I am not getting back that either, wondering if there is away to accomplish this?. Let's turn now turn to using Apache Kafka with Spring. Part 2 of the Spring for Apache Kafka blog series provides an overview of Spring Cloud Stream and its programming model, Apache Kafka® integration in Spring Cloud Stream and stream processing using Kafka Streams and Spring Cloud Stream. Don't Use Apache Kafka Consumer Groups the Wrong Way! Apache Kafka is great — but if you're going to use it, you have to be very careful not to break things. The following are code examples for showing how to use kafka. However, it really comes into its own because it's fast enough and scalable enough that it can be used to route big-data through processing pipelines. In several previous articles on Apache Kafka, Kafka Streams and Node. Apache Kafka is a distributed publish-subscribe messaging system that is designed for high throughput (terabytes of data) and low latency (milliseconds). Spring Cloud Stream builds upon Spring Boot to create standalone, production-grade Spring applications, and uses Spring Integration to provide connectivity to message brokers. Even though you could run both the consumer and the producer on the same server, it is not as exciting. Run the spring boot application and ensure that it works fine. 72 version of Kafka on Windows. In this tutorial we will create a system written in Scala that uses Kafka to produce and consume messages. KafkaConsumer(). The recently released Spring Integration for Apache Kafka 1. This tutorial demonstrates how to send and receive messages from Spring Kafka. Spring Cloud Stream is a framework under the umbrella project Spring Cloud, which enables developers to build event-driven microservices with messaging systems like Kafka and RabbitMQ. Here's how you can avoid the pain!. We configure both with appropriate key/value serializers and deserializers. 推荐：分布式消息中间件（三）——Kafka生产者消费者模型. Spring Cloud Stream's Apache Kafka support also includes a binder implementation designed explicitly for Apache Kafka Streams binding. The producer is happily producing messages. If the Commit message offset in Kafka property is selected, the consumer position in the log of messages for the topic is saved in Kafka as each message is processed; therefore, if the flow is stopped and then restarted, the input node starts consuming messages from the message position that had been reached when the flow was stopped. From our Kafka Consumer we'll publish every message into the bus: itemDeletedBus. Spring Cloud Stream is a framework under the umbrella project Spring Cloud, which enables developers to build event-driven microservices with messaging systems like Kafka and RabbitMQ. Next we create a Spring Kafka Consumer which is able to listen to messages send to a Kafka topic. This wrapper of Spring Kafka facilitates the using of multi-threaded consumer model in Apache Kafka which improve the performance in message consumer. The producer only needs to send asynchronously, and does not do any processing when sending or consuming fails. Fortunately, docs include both approaches - plain Java code and annotations, so it's not that bad. We will also use Avro…. Watching this video is also recommended: Introducing exactly once semantics in Apache Kafka. consumer API in Java to fetch messages from kafka ( the same one which is stated in Kafka introduction example). Kafka has been widely used for event processing because it is not only Open Source but large active community. This demonstration explains how to craft classical (not reactive) consumer/producer componentS within you Spring apps. Observed client. They are extracted from open source Python projects. 2 thoughts on " Producing and Consuming Avro Messages with Kafka " Akshat August 10, 2017 at 6:28 am. The advantage of using Kafka is that, if our consumer breaks down, the new or fixed consumer will pick up reading where the previous one stopped. Before diving in, it is important to understand the general architecture of a Kafka deployment. When i am writing this article, there are two implementations of the Spring Cloud Stream. Properties here supersede any properties set in boot and in the configuration property above. When the property is left blank, PublishKafka will send the content of the flow file as s single message. Nakul Mishra - Casumo. Do you have any idea where might the problem be now? I can see number of sent messages in Cloudera Manager Chart "Total Messages Received Across Kafka Brokers". Spring for Apache Kafka brings the familiar Spring programming model to Kafka. group-id = test-group spring. Any pointers. He has been a committer on Spring Integration since 2010 and has led that project for several years, in addition to leading Spring for Apache Kafka and Spring AMQP (Spring for RabbitMQ). In our case, the currently logged in user is available through the Spring Security API, so ideally, we'd configure Spring Kafka to read the user from and write the user to the Spring Security SecurityContext with producing and consuming messages. In this post, we'll look at how to set up an Apache Kafka instance, create a user service to publish data to topics, and build a notification service to consume data from those topics. reset=latest by default. This wrapper of Spring Kafka facilitates the using of multi-threaded consumer model in Apache Kafka which improve the performance in message consumer. Here how to use it :. 2, kafka has had the ability to store consumer offsets in an internal compacted topic called __consumer_offsets. Only if the consumer needs to ignore the vast majority of messages (e. Then demonstrates Kafka consumer failover and Kafka broker failover. If you are interested in viewing the consumer offsets stored on the __consumer_offsets, you should do the following. Kafka provides at-least-once messaging guarantees. An alternative and more general. And while I do complain about EmbeddedKafka, setting up consumer and producer was fairly painless. /kafka-consumer-groups. We start by adding headers using either Message or ProducerRecord. 6) and Kafka (version 0. node-rdkafka (version 1. Kafka provides at-least-once messaging guarantees. In this tutorial, we'll look at how Kafka ensures exactly-once delivery between producer and consumer applications through the newly introduced Transactional API. It also provides support for Message-driven POJOs with @KafkaListener annotations and a "listener container". Consumers can "replay" these messages if they wish. Spring Cloud Stream's Apache Kafka support also includes a binder implementation designed explicitly for Apache Kafka Streams binding. Spring provides good support for Kafka and provides the abstraction layers to work with over the native Kafka Java clients. Afterward, you are able to configure your consumer with the Spring wrapper DefaultKafkaConsumerFactory or with the Kafka Java API. Hi, I have a session aware message listener inside a DMLC with 5 concurrent consumers consuming messages from a queue. So with the tutorial, JavaSampleApproach will show how to use Spring Kafka … Continue reading "How to use Spring Kafka JsonSerializer (JsonDeserializer) to produce/consume Java Object messages". But in most real-word applications, you won't be exchanging simple Strings between Kafka producers and consumers. Spring-kafka, as most Spring-related libraries, likes annotations. And if you're doing data processing, you really want Spring XD. As such, if you need to store offsets in anything other than Kafka, this API should not be used. Spring Kafka Consumer Producer Example 10 minute read In this post, you’re going to learn how to create a Spring Kafka Hello World example that uses Spring Boot and Maven. Its because I was publishing event first and then starting a consumer. Apache Kafka & Storm. (22 replies) Hi, Does Kafka offer a way to consume messages in batches, but "from the end"? This would be valuable to have in all systems where the most recent data is a lot more important than older data, such as performance metrics, and maybe even logsmaybe also trading/financial data, and such. I am wondering what is the right way to fetch data and keep track of offset in a partition. Normally in message queues, the messages are removed after subscribers have confirmed their receipt. kafka spring-kafka 2. Kafka Consumer. You can vote up the examples you like or vote down the ones you don't like. 0 versions with Kafka version : 0. The consumer does not have to be assigned the partitions. By default, consumer only consumes events published after it started because auto. In several previous articles on Apache Kafka, Kafka Streams and Node. As with publish-subscribe, Kafka allows you to broadcast messages to multiple consumer groups. 0 versions with Kafka version : 0. Consumer not able to consume messages from queue. I am publishing to a Dockerized version of Kakfa using the official Confluent images. Go to Spring initializer. ) Each consumer binding can use the spring. At this point, It will start producing messages into the Kafka topic without any issues. Below are the stats of group command. Kafka is an open-source distributed commit log addressing low latency, high throughput, scalability, fault-tolerance, and disk-based retention. Let's say that you have 10000 people out and about all simultaneously collecting documents from other people. On Node5, i've another Kafka instance, i start another console-consumer from Node5, for consuming the data from console-producer in node4. The Kafka consumer uses the poll method to get N Spring for Apache Kafka Milestone 1. For example, we had a “high-level” consumer API which supported consumer groups and handled failover, but didn’t support many of the more. Step by step guide to realize a Kafka Consumer is provided for understanding. Followed by reading the values inside the KafkaListener using @Header annotation and MessageHeaders class. Spring Cloud Stream's Apache Kafka support also includes a binder implementation designed explicitly for Apache Kafka Streams binding. Key/Value map of arbitrary Kafka client consumer properties. You have successfully created a Kafka producer, sent some messages to Kafka, and read those messages by creating a Kafka consumer. The consumer fires the ready event The consumer does NOT receive. Once these beans are available in the Spring bean factory, POJO based consumers can be configured using @KafkaListener annotation. The following tutorial demonstrates how to send and receive a Java Object as a JSON byte[] to and from Apache Kafka using Spring Kafka, Spring Boot and Maven. In this tutorial, we'll look at how Kafka ensures exactly-once delivery between producer and consumer applications through the newly introduced Transactional API. publish(MsgEnvelope(item. While in the development, POJO (Plain Old Java Object) are often used to construct messages. Spring Cloud Stream models this behavior through the concept of a consumer group. Maven users will need to add the following dependency to their pom. Consumers, on the other hand, store no message. node-rdkafka (version 1. This can be achieved by an end-to-end reconciliation strategy - Producer-Consumer Reconciliation. Spring for Apache Kafka 1. Path to properties file where you can set the Consumer — similar to what you provide to Kafka command line tools. That is not a big deal: consuming messages from Kafka is very cheap, so even if a consumer ends up ignoring half of the events, the cost of this overconsumption is probably not significant. How Kafka consumer can start reading messages from a different offset and get back to the start. When doing this, different instances of an application are placed in a competing consumer relationship, where only one of the instances is expected to handle a given message. A consumer subscribes to Kafka topics and passes the messages into an Akka Stream. We start by adding headers using either Message or ProducerRecord. At this point, It will start producing messages into the Kafka topic without any issues. We will be configuring apache kafka and zookeeper in our local machine and create a test topic with multiple partitions in a kafka broker. When consuming messages from Kafka you can use your own offset management and not delegate this management to Kafka. Additionally, we'll use this API to implement transactional. 72 version of Kafka on Windows. Afterward, you are able to configure your consumer with the Spring wrapper DefaultKafkaConsumerFactory or with the Kafka Java API. This wrapper of Spring Kafka facilitates the using of multi-threaded consumer model in Apache Kafka which improve the performance in message consumer. Now, we are creating a Kafka Consumer to consume messages from the Kafka cluster. Processor)" in my log continuously. Apache Kafka is a distributed publish-subscribe messaging system that is designed for high throughput (terabytes of data) and low latency (milliseconds). consumerProperties. In this article, we'll cover Spring support for Kafka and the level of abstractions it provides over native Kafka Java client APIs. We will implement a simple example to send a message to Apache Kafka using Spring Boot Spring Boot + Apache Kafka Hello World Example In this post we will integrate Spring Boot and Apache Kafka instance. The producer is happily producing messages. It basically says that we want to bind the output message channel to the Kafka timerTopic, and it says that we want to serialize the payload into JSON. Spring Cloud Stream models this behavior through the concept of a consumer group. The advantage of using Kafka is that, if our consumer breaks down, the new or fixed consumer will pick up reading where the previous one stopped. Kafka Consumer. A broker is a kafka server which stores/keeps/maintains incoming messages in files with offsets. id = console-producer for producer. 6) and Kafka (version 0. Then demonstrates Kafka consumer failover and Kafka broker failover. Consumer architecture. Watching this video is also recommended: Introducing exactly once semantics in Apache Kafka. It basically says that we want to bind the output message channel to the Kafka timerTopic, and it says that we want to serialize the payload into JSON. Writing a Kafka Consumer in Java You created a Kafka Consumer that uses the topic to receive messages. publish(MsgEnvelope(item. Consumer: Consumers read messages from Kafka topics by subscribing to topic partitions. The host name and port number of the schema registry are passed as parameters to the deserializer through the Kafka consumer properties. consumerProperties. In this article, let us explore setting up a test Kafka broker on a Windows machine, create a Kafka producer, and create a Kafka consumer using the. Manage transactions to make sure a message is processed once and only once; Downsides of using SimpleConsumer. If you do not specify a value for bootstrap. Kafka does not deletes consumed messages with its default settings. For other CDH-5. In traditional message brokers, consumers acknowledge the messages they have processed and the broker deletes them so that all that rem. Receiving Messages Message Listeners Message Listener Containers @KafkaListener Annotation Container Thread Naming @KafkaListener on a class @KafkaListener Lifecycle Management.