This application

1. Takes a comma delimited topic of userid,colour
2. Filters out bad data i.e. keep only colour of green,red and blue
3. Gets the running count of the favourite colour overall and output this to a topic

This is developed using java 8 and kafka stream 2.7.0

1. Setup kafka cluster on your local machine. Refer Kafka Cluster Setup section for help.

2. Create input and output compacted topics

   bin/kafka-topics.sh --create --zookeeper localhost:2181 --replication-factor 1 --partitions 1 --topic favourite-colour-input
   bin/kafka-topics.sh --create --zookeeper localhost:2181 --replication-factor 1 --partitions 1 --topic favourite-colour-output --config cleanup.policy=compact
   

3. Start this application

4. Produce message with key as userid and value as colour from kafka console producer

   bin/kafka-console-producer.sh --broker-list localhost:9092 --topic favourite-colour-input --property parse.key=true --property key.separator=,
   i.e.
   bin/kafka-console-producer.sh --broker-list localhost:9092 --topic favourite-colour-input --property parse.key=true --property key.separator=,
   >stephane,blue
   >john,green
   >stephane,red
   >alice,red
   

5. Consume messages from output topic

   bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 \
     --topic favourite-colour-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
   red	5
   red	5
   green	3
   red	4
   blue	2
   blue	3
   blue	2
   

• Download Kafka from https://kafka.apache.org/downloads

• Extract it somewhere by executing tar command on Terminal

  i.e. tar -xvf kafka_2.13-2.6.0.tgz

• Go to that extracted Kafka folder

  i.e. cd kafka_2.13-2.6.0/

• Start zookeeper

  bin/zookeeper-server-start.sh config/zookeeper.properties

  This will bring up zookeeper on default port 2181 configured in config/zookeeper.properties file

• Start first broker/node

  bin/kafka-server-start.sh config/server.properties

  This will start broker with below default broker id, log directory and port configured in config/server.properties

  broker.id=0  
  log.dirs=/tmp/kafka-logs  
  port=9092
  

• Create a copy of config/server.properties file for second broker/node

  i.e. cp config/server.properties config/server1.properties

• Change broker id, log directory and port in config/server1.properties file

  broker.id=1
  log.dirs=/tmp/kafka-logs-1
  port=9093
  

• Start second broker/node

  bin/kafka-server-start.sh config/server1.properties

• Create one more copy of config/server.properties file for third broker/node

  i.e. cp config/server.properties config/server2.properties

• Change broker id, log directory and port in config/server2.properties file

  broker.id=2
  log.dirs=/tmp/kafka-logs-2
  port=9094
  

• Start third broker/node

  bin/kafka-server-start.sh config/server2.properties

• Check what brokers are up and running

  bin/zookeeper-shell.sh localhost:2181 ls /brokers/ids

  will give you below output

  Connecting to localhost:2181
  
  WATCHER::
  
  WatchedEvent state:SyncConnected type:None path:null
  [0, 1, 2]