Streaming Data Using Kafka Streams to Count Words

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Streaming Data Using Kafka Streams to Count Words

Kafka Streams is a library enabling you to perform per-event processing of records. You can use it to process data as soon as it arrives, versus having to wait for a batch to occur. In this hands-on lab, we use Kafka Streams to stream some input data as plain-text and process it in real-time. With this, we can count the number of words from our input stream.

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Lab Info

Level

Intermediate

Last updated

Sep 19, 2025

Duration

1h 0m

Challenge

Create the Input and Output Topic

Create the input topic named streams-plaintext-input.

bin/kafka-topics.sh --create --zookeeper localhost:2181 --replication-factor 1 --partitions 1 --topic streams-plaintext-input

Create the output topic named streams-wordcount-output.

bin/kafka-topics.sh --create --zookeeper localhost:2181 --replication-factor 1 --partitions 1 --topic streams-wordcount-output

Challenge

Open a Kafka Console Producer

Open a Kafka console producer.

bin/kafka-console-producer.sh --broker-list localhost:9092 --topic streams-plaintext-input

Type the three messages from the instructions.

>kafka streams is great
>kafka processes messages in real time
>kafka helps real information streams

Challenge

Open a Kafka Console Consumer

Open a Kafka console consumer using the default message formatter and the three properties given in the instructions.

bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 
--topic streams-wordcount-output 
--from-beginning 
--formatter kafka.tools.DefaultMessageFormatter 
--property print.key=true 
--property print.value=true 
--property key.deserializer=org.apache.kafka.common.serialization.StringDeserializer 
--property value.deserializer=org.apache.kafka.common.serialization.LongDeserializer

Challenge

Run the Kafka Streams Application
Use the kafka-run-class.sh command to run the WordCountDemo application.
```
bin/kafka-run-class.sh org.apache.kafka.streams.examples.wordcount.WordCountDemo
```

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