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Duchess-lab

The system components

Check the "Duchess Meetup at Trustly 2019.pdf" document in this folder for a faboulus diagram of our advanced system.

Producer

The jduchess-2019-producer repo (i.e. this one) contains a skeleton for sending messages to the Kafka topic "daily-quotes".

It is already configured to connect to a local Kafka instance at startup.

Consumer

The jduchess-2019-consumer repo (https://github.com/JavaJive/jduchess-2019-consumer) contains a skeleton for consuming messages from the Kafka topic"daily-quotes".

It is already configured to connect to a local Kafka instance at startup.

Kafka and Zookeeper

You will run Kafka and Zookeeper in Docker via the Docker Compose files in this repo, so no installation is required.

Tasks

  • Identify the class that sends messages to Kafka

  • Identify the class that receives messages from Kafka

  • Send a message to a specific partition

  • Send a message with a specific key

  • Add error handling when sending messages

  • Log the received message

  • Convert the received message to all upper case

  • Transform the received message mono to a flux that emits the words in the string one by one

How to send a message to Kafka

Make the producer send a message to Kafka by making a rest call to http://localhost:8081/publish. The easiest way to do this is to open your browser and navigate to the address.

Running Kafka and the producer and consumer services

Run Kafka, producer and consumer in the same Docker

Consumer workspace

From the top folder in the consumer workspace, build the project with Maven so you get a jar to place in the Docker image

mvn install

Build the docker image and name it "consumer"

docker build . -t consumer

Producer workspace

From the top folder in the producer workspace, build the project with Maven

mvn install

Build the docker image and name it "producer"

docker build . -t producer

Run docker compose

docker-compose up

Run Kafka in Docker, run producer and consumer separately

Producer workspace

Run docker compose and specify the compose file with only Kafka/Zookeeper defined

docker-compose -f docker-compose-kafka.yml up

Then start the services separately (in your IDEA, run a built jar etc)

Generic stuff regarding Docker

Stop Docker and clean up resources afterwards with docker-compose down Run this command from the same folder as you did the docker-compose up.

Check what images you have with docker images

Check running containers with docker ps

Check all containers, both running and inactive, with docker ps -a

Remove all unused containers, images, networks etc with docker system prune

Find more details regarding the Docker Compose cli here: https://docs.docker.com/compose/reference/overview/

Nice to have links

Reactive manifesto: https://www.reactivemanifesto.org/

How to read marble diagrams: https://medium.com/@jshvarts/read-marble-diagrams-like-a-pro-3d72934d3ef5

Project Reactor API: https://projectreactor.io/docs/core/release/api/index.html

Project Reactor, which operator to use: https://projectreactor.io/docs/core/release/reference/index.html#which-operator

ReactiveX: http://reactivex.io/

Reactive Streams: http://www.reactive-streams.org/