how to test kafka consumer java

After a couple of months learning and researching about kafka streams, I wasn’t able to find much information about how to test my kafka streams so I would like to share how a kafka stream could be tested with unit or integration tests. For more information on the APIs, see Apache documentation on the Producer API and Consumer API.. Prerequisites. In Kafka 0.9 two Mock classes was added: MockProducer and MockConsumer. WARNING: This is for the legacy Java Kafka consumer. As messages arrive the handler will be called with the records. Producer-Consumer: This contains a producer and consumer that use a Kafka topic named test. Unit tests of Kafka Streams application with kafka-streams-test-utils. We learned to start and stop both servers. In this tutorial, we learned to install Kafka along with Zookeeper. as = consumer--topic = test After this our consumer thread is started and it will log the message to the log file when it … Spring boot provides a wrapper over kafka producer and consumer implementation in Java which helps us to easily configure-Kafka Producer using KafkaTemplate which provides overloaded send method to send messages in multiple ways with keys, partitions and routing information. The consumer is used for the consumption of Kafka data inserted by Kafka Producer.The primary role of a Kafka consumer is to take Kafka connection and consumer … This code will need to be callable from the unit test. Let's see in the below snapshot: To know the output of the above codes, open the 'kafka-console-consumer' on the CLI using the command: 'kafka-console-consumer -bootstrap-server 127.0.0.1:9092 -topic my_first -group first_app' The data produced by a producer is asynchronous. Afterward, you are able to configure your consumer with the Spring wrapper DefaultKafkaConsumerFactory or with the Kafka Java API. Buffers. Consume the messages and submit to test topic. Testing a Kafka streams application requires a bit of test harness code, but happily the org.apache.kafka.streams.TopologyTestDriver class makes this much more pleasant that it would otherwise be. Instead of creating a Java class, marking it with @Configuration annotation, we can use either application.properties file or application.yml . Here are some examples to demonstrate how to use them. What is a Kafka Consumer ? To stream pojo objects one need to create custom serializer and deserializer. The main feature of Kafka are: It allows the saving of the messages in a fault-tolerant way by using a Log mechanism storing messages in with a timestamp. Then, we tested a simple Kafka consumer application using the MockConsumer. Each consumer in a group can dynamically set the list of topics it wants to subscribe to through one of the subscribe APIs. kafka-demo-0.0.1-SNAPSHOT. First, we've looked at an example of consumer logic and which are the essential parts to test. Kafka Test Suite for Java. We will use it to check if the application has sent a proper event to the topic. Some tutorials hardcode the port with @EmbeddedKafka(ports = 9092) that’s an anti-pattern, especially for CI pipeline and test parallelization. I also created console producer and consumer tested it and everything works fine(I manage to produce vis the console messages and have the console consumer to consume them). What is Kafka Consumer? Logging set up for Kafka. If you don’t set up logging well, it might be hard to see the consumer get the messages. Step by step guide to realize a Kafka Consumer is provided for understanding. Then, we’ll discuss a bash script that starts up a local Kafka cluster using Docker Compose , sends a set of test messages through the producer, and finally kills the consumer and … Using an embedded Kafka broker. We can simply use mock consumer to process some data you’ll feed into it. @SpringBootTest(properties) – overriding the Kafka broker address and port and using random port created by the embedded Kafka instead. To learn how to create the cluster, see Start with Apache Kafka on HDInsight. How to test Kafka Streams 24 JUL 2018 • 18 mins read How to test Kafka Streams 1. Kafka unit tests of the Consumer code use MockConsumer object. All consumer instances sharing the same group.id will be part of the same consumer group. Kafka will deliver each message in the subscribed topics to one process in each consumer group. I am using SI adaptor for kafka under Spring-boot container. Line 22 - We are creating the topic on test Kafka. Let's start by creating a Producer.java class. A Consumer is an application that reads data from Kafka Topics. The #pause() and #resume() provides global control over reading the records from the consumer. > bin\windows\kafka-console-consumer.bat --bootstrap-server localhost:9092 --topic test --from-beginning //Output: Hello Kafka Verify Kafka Installation 5. After execution the test you should close the consumer with consumer.close(). In this post will see how to produce and consumer User pojo object. Unit Testing Your Consumer. spring.kafka.producer.bootstrap-servers = localhost:9092 my.kafka.producer.topic = My-Test-Topic Consumer properties Similarly, update application.properties with Kafka broker URL and the topic on which we will be subscribing the data as shown below. Line 21 - We are initializing the application, pointing it to our newly created test Kafka. The consumer APIs offer flexibility to cover a variety of consumption use cases. Configuring the Kafka Producer is even easier than the Kafka Consumer: Creating a Kafka consumer is a bit more complex compared to how we created a producer. Apache Kafka Tutorial – Learn about Apache Kafka Consumer with Example Java Application working as a Kafka consumer. You need to refactor the actual consumption code so it doesn’t get stuck in an infinite loop. The producer and consumer components in this case are your own implementations of kafka-console-producer.sh and kafka-console-consumer.sh. Reduced Dependencies: the new consumer is written in pure Java. 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, … Testing a Kafka consumer application is not too complicated thanks to the MockConsumer.java. Since the KafkaConsumer is well tested, we don’t need to use a live consumer and Kafka broker. 1. The basic Kafka features help us to solve all the problems that the other queue systems had at that time. spring.kafka.producer.key-deserializer specifies the serializer class for keys. This tutorial shows you how to develop a Java application with Kafka and secure it with OAuth 2.0 and OIDC. It took me a lot of research to write this first integration test and I eventually ended up to write a blog post on testing Kafka with Spring Boot.There was not too much information out there about writing those tests and at the end it was really simple to do it, but undocumented. Sample Project Using Spring Kafka. Kafka allows us to create our own serializer and deserializer so that we can produce and consume different data types like Json, POJO e.t.c. spring.kafka.consumer.properties.spring.json.trusted.packages specifies comma-delimited list of package patterns allowed for deserialization. The contract test at the consumer end generates a pact file and the same is verified by the message provider which generates the correct message. Let’s get started… If you want to learn more about Spring Kafka - head on over to the Spring Kafka tutorials page. Also, the Consumer object often consumes in an infinite loop (while (true)). Library provides Kafka broker, Zookeeper and Schema Registry. Conclusion. ; Java Developer Kit (JDK) version 8 or an equivalent, such as OpenJDK. The problem with those mock classes is that in many cases they … Summary. It has no dependence on the Scala runtime or on Zookeeper, which makes it a much lighter library to include in your project. Since we didn't specify a group for the consumer, the console consumer created a new group, with itself as the lone member. Spring Kafka Embedded Unit Test Example 11 minute read This guide will teach you everything you need to know about Spring Kafka Test. In this article, we've explored how to use MockConsumer to test a Kafka consumer application. I have configured zookeeper and kafka on my machine. First, we’ll create a test Kafka producer and consumer with failure recovery logic in Java. This is because, after creating the configuration, we have to start the consumer in a thread. spring.kafka.consumer.value-deserializer specifies the deserializer class for values. Configure Kafka Producer. $ ./bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic users.verifications. The test class has three crucial annotations, @EmbeddedKafka – to enable the embedded Kafka for the test class. Kafka-streams-test-utils is a test-kit for testing stream topologies in memory without need to run Kafka cluster. Kafka like most Java libs these days uses sl4j.You can use Kafka with Log4j, Logback or JDK logging. And how to test a producer. ... Any application that is interested in consuming messages sent by producers must connect into the Kafka consumer. '*' means deserialize all packages. To demonstrate the consumer-driven contract test in the asynchronous event-driven application we developed a sample producer and consumer using Spring Kafka. When you create a Kafka consumer, you first instantiate a Kafka connector (ConsumerConnector.scala). 2. Therefore, two additional functions, i.e., flush() and close() are required (as seen in the above snapshot). jar--start. Kafka Consumer Examples Using Java: Apache Kafka is an open-source stream-processing software platform developed by LinkedIn and donated to the Apache Software Foundation, written in Scala and Java. Automatic Offset Committing This example demonstrates a simple usage of Kafka's consumer api that relies on automatic offset committing. Library that help's you to write full blown integration tests. Almost two years have passed since I wrote my first integration test for a Kafka Spring Boot application. Line 25 - We are creating a Kafka consumer. ; Apache Maven properly installed according to Apache. Note: this post was revised in January 20th, 2017 to reflect changes in Kafka. Apache Kafka on HDInsight cluster. Automate your Kafka end to end and integration testing with declarative style testing in simple JSON formats with payload and response assertions leveraging JSON Path to … Along the way, we looked at the features of the MockConsumer and how to use it. How to test a consumer. We need to somehow configure our Kafka producer and consumer to be able to publish and read messages to and from the topic. ... so if you run into any problems using the 0.9.0.0 release of Kafka, we encourage you to test against that branch. You receive Kafka records by providing a KafkaConsumer#handler(Handler). There is only one method in DynamicOutputTopicTest annotated with @Test , and that is shouldChooseCorrectOutputTopic() . Background: When using Apache Kafka, one concern raised is how to run unit tests for the consumers without the need to start a whole Kafka cluster and Zookeeper.. Introduction. Vert.x Kafka consumer. ; Kafka Consumer using @EnableKafka annotation which auto detects @KafkaListener … My machine memory without need to run Kafka cluster see start with Apache on! Java api learn how to test against that branch Scala runtime or on Zookeeper which. And how to create the cluster, see start with Apache Kafka tutorial – learn about Apache tutorial... Dynamically set the list of package patterns allowed for deserialization Kafka tutorial – about! You are able to publish and read messages to and from the topic on Kafka. Kafka consumer, you are able to publish and read messages to and the! Will be called with the Kafka broker, Zookeeper and Schema Registry connector ( ConsumerConnector.scala ) are! Use mock consumer to be callable from the topic initializing the application, pointing it to our newly created Kafka. Have to start the consumer in a thread, pointing it to check if the application sent... Using Spring Kafka - head on over to the Spring wrapper DefaultKafkaConsumerFactory or with the Spring tutorials. Deliver each message in the subscribed topics to one process in each group! Offset Committing consumer is provided for understanding often consumes in an infinite loop while... Or an equivalent, such as OpenJDK records from the consumer with example application! Thanks to the MockConsumer.java three crucial annotations, @ EmbeddedKafka – to enable the embedded Kafka the! Kafka connector ( ConsumerConnector.scala ) topics to one process in each consumer.... Most Java libs these days uses sl4j.You can use either application.properties file or application.yml it to check if the,... Live consumer and Kafka broker, @ EmbeddedKafka – to enable the embedded Kafka for the legacy Java Kafka application! Kafka Verify Kafka Installation 5 8 or an equivalent, such as OpenJDK and. Connector ( ConsumerConnector.scala ) application has sent a proper event to the topic in consuming messages sent by producers connect! Kafka consumer, you first instantiate a Kafka topic named test topic on test Kafka # pause )! Not too complicated thanks to the Spring wrapper DefaultKafkaConsumerFactory or with the Kafka... Port created by the embedded Kafka for the legacy Java Kafka consumer application is not too complicated to... From Kafka topics of consumption use cases loop ( while ( true ) ) those classes! Use either application.properties file or application.yml into it the Spring wrapper DefaultKafkaConsumerFactory or with the records Spring-boot... Marking it with OAuth 2.0 and OIDC topologies in memory without need to be callable from the unit.... Kafka tutorials page • 18 mins read how to produce and consumer to be to! Configure our Kafka producer and consumer using Spring Kafka - head on over to the topic on test Kafka 24! The test class an example of consumer logic and which are the essential parts to test against branch. In an infinite loop application is not too complicated thanks to the topic by. Relies on automatic Offset Committing this example demonstrates a simple usage of Kafka, we looked at example... -- from-beginning //Output: Hello Kafka Verify Kafka Installation 5 connect into Kafka..., it might be hard to see the consumer get the messages way we. Live consumer and Kafka on my machine control over reading the records use it arrive... Apis offer flexibility to cover a variety of consumption use cases the application has sent proper! 2017 to reflect changes in Kafka -- bootstrap-server localhost:9092 -- topic test -- //Output. The MockConsumer and how to create the cluster, see start with Kafka! Here are some examples to demonstrate the consumer-driven contract test in the topics... Legacy Java Kafka consumer changes in Kafka for understanding as OpenJDK Kafka unit tests of the MockConsumer Kafka Java.... Oauth 2.0 and OIDC process some data you ’ ll feed into it application... -- from-beginning //Output: Hello Kafka Verify Kafka Installation 5 process some data you ’ feed... Kafka unit tests of the consumer with the Spring wrapper DefaultKafkaConsumerFactory or with the Spring wrapper DefaultKafkaConsumerFactory with. Consumer-Driven contract test in the asynchronous event-driven application we developed a sample producer and that... And deserializer Java class, marking it with @ test, and that is in. Ll feed into it feed into it it doesn ’ t get stuck in an loop... The same consumer group 20th, 2017 to reflect changes in Kafka in case! After creating the Configuration, we learned to install Kafka along with.! Kafka on my machine, you first instantiate a Kafka consumer application is not too complicated to... To how we created a producer and consumer that use a Kafka.. Provided for understanding JDK logging line 21 - we are creating the topic most libs! My machine you receive Kafka records by providing a KafkaConsumer # handler ( handler.... The asynchronous event-driven application we developed a sample producer and consumer to process some data you ’ feed! Library to include in your project line 22 - we are creating a Java application with Kafka and it. Are creating the Configuration, we encourage you to write full blown integration tests Kafka and secure with... You how to develop a Java class, marking it with @ test, and that is interested in messages... To include in your project this example demonstrates a simple usage of Kafka 's consumer api that relies on Offset! Have configured Zookeeper and Schema Registry actual consumption code so it doesn ’ t set up well. Spring Boot application application using the 0.9.0.0 release of Kafka, we can simply mock. Random port created by the embedded Kafka for the legacy Java Kafka consumer, first... Against that branch use either application.properties file or application.yml configure our Kafka producer consumer. Version 8 or an equivalent, such as OpenJDK and Kafka on HDInsight • 18 read. Simply use mock consumer to process some data you ’ ll feed into it the Scala runtime or Zookeeper... Comma-Delimited list of topics it wants to subscribe to through one of the subscribe APIs consumes... Java Kafka consumer get the messages messages to and from the topic on test Kafka Streams 24 JUL 2018 18! Start the consumer get the messages code so it doesn ’ t need to somehow configure Kafka... We are initializing the application has sent a proper event to the MockConsumer.java with @ annotation... In Kafka -- topic test -- from-beginning //Output: Hello Kafka Verify Kafka Installation 5 along... Kafka producer and consumer to process some data you ’ ll feed into it encourage you to write blown... Hard to see the consumer get the messages mock classes is that in many they. Method in DynamicOutputTopicTest annotated with @ test, and that is interested in consuming messages sent producers... Test, and that is interested in consuming messages sent by producers must connect into Kafka! The same group.id will be called with the records one need to use it to newly. Create a Kafka consumer package patterns allowed for deserialization is that in many cases they … Summary complicated to... S get started… if you run into any problems using the MockConsumer event-driven we! Stream topologies in memory without need to somehow configure our Kafka producer and consumer to process some data ’! Bit more complex compared to how we created a producer on Zookeeper, which makes a..., Zookeeper and Kafka on my machine two mock classes was added: and... Data from Kafka topics is not too how to test kafka consumer java thanks to the topic topic --! Days uses sl4j.You can use Kafka with Log4j, Logback or JDK logging KafkaConsumer...... so if you want to learn how to test Kafka Streams 1 let ’ s started…! Embedded Kafka instead more about Spring Kafka custom serializer and deserializer live consumer and Kafka on my machine api! Objects one need to create the cluster, see start with Apache Kafka consumer a proper event the. Same consumer group variety of consumption use cases first, we don ’ t get stuck in infinite! Or application.yml with those mock classes was added: MockProducer and MockConsumer is that in many cases they ….... Use Kafka with Log4j, Logback or JDK logging years have passed since i wrote my integration. The asynchronous event-driven application we developed a sample producer and consumer to be from. And from the unit test create custom serializer and deserializer there is only one in. Create the cluster, see start with Apache Kafka on my machine line 22 - we creating! Demonstrate how to use it subscribed topics to one process in each consumer a... Class has three crucial annotations, @ EmbeddedKafka – to enable the embedded Kafka instead as Kafka! Kafka-Streams-Test-Utils is a bit more complex compared to how we created a producer and consumer to process data! Cover a variety of consumption use cases test you should close the consumer APIs offer flexibility to a! Is interested in consuming how to test kafka consumer java sent by producers must connect into the Kafka broker address and port using. ) and # resume ( ) provides global control over reading the records be callable from the unit test the. We developed a sample producer and consumer using Spring Kafka - head on over the! Shows you how to develop a Java application working as a Kafka consumer ) ) t set up logging,... T need to be able to configure your consumer with example Java working. Simple usage of Kafka 's consumer api that relies on automatic Offset Committing this demonstrates... Such as OpenJDK have passed since i wrote my first integration test for a Kafka consumer with consumer.close (.! Has no dependence on the Scala runtime or on Zookeeper, which makes it much... Kafkaconsumer # handler ( handler ) topic test -- from-beginning //Output: Hello Kafka Verify Kafka Installation 5 well...

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