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README.md

Flowing Retail / Apache Kafka / Java

This folder contains services written in Java that connect to Apache Kafka as means of communication between the services.

Tech stack:

  • Java 8
  • Spring Boot 1.5.x
  • Spring Cloud Streams
  • Apache Kafka

For the workflow engine you can decide between:

  • Camunda (folder *-camunda)
  • Zeebe (folder *-zeebe)

Microservices

Run the application

You can either

  • Docker Compose with pre-built images from Docker Hub (simplest)
  • Build (Maven) and start via Docker Compose
  • Build (Maven) and start manually (including Zookeeper, Kafka)

The default is that Camunda is used in these settings. When you want to use Zeebe you have to manually build and run it.

Hint on using Camunda Enterprise Edition

For Camunda there is an enterprise edition available with [https://camunda.com/products/cockpit/#/features](additional features in Cockpit) (the monitoring tool). It is quite handy to use this when playing around with the example. You can easily switch to use enterprise edition:

Note that you do not need the enterprise edition to run the examples, the community edition will also do fine, you just cannot see and do that much in Camunda Cockpit.

Docker Compose with pre-build Docker images

cd docker-dist
  • Start using docker compose:
docker-compose up

If you like you can connect to Kafka from your local Docker host machine too. Because of so called advertised endpoints you have to map the Kafka container hostname to localhost. This is because the cluster manager of Kafka (Zookeeper) gives you his view of the Kafka cluster which containes of this hostname, even if you connected to localhost in the first place.

For example, on Windows append this entry to C:\Windows\System32\drivers\etc\hosts:

127.0.0.1 kafkaserver

On Linux edit the /etc/hosts accordingly.

Docker Compose with local build of Docker images

  • Download or clone the source code
  • Run a full maven build
mvn install
  • Build Docker images and start them up
docker-compose build
docker-compose up

If you like you can connect to Kafka from your local Docker host machine too. Because of so called advertised endpoints you have to map the Kafka container hostname to localhost. This is because the cluster manager of Kafka (Zookeeper) gives you his view of the Kafka cluster which containes of this hostname, even if you connected to localhost in the first place.

For example, on Windows append this entry to C:\Windows\System32\drivers\etc\hosts:

127.0.0.1 kafkaserver

On Linix edit the /etc/hosts accordingly.

Manual start (Kafka, mvn exec:java)

  • Download or clone the source code
  • Run a full maven build
mvn install
  • Install and start Kafka on the standard port
  • Create topic "flowing-retail"
kafka-topics.sh --create --zookeeper localhost:2181 --replication-factor 1 --partitions 1 --topic flowing-retail
  • You can check & query all topics by:
kafka-topics.sh --list --zookeeper localhost:2181
  • Start the different microservices components by Spring Boot one by one, e.g.
mvn -f checkout exec:java
mvn -f order-camunda exec:java
...

Here you could easily switch to use order-zeebe instead. In this case make sure that you startup your Zeebe broker and create the default-topic first as described in Install Zeebe.

You can also import the projects into your favorite IDE and start the following class yourself:

checkout/io.flowing.retail.java.CheckoutApplication
...