Restaurant Showcase

This project showcases a good and a bad example of how to use Camunda 8 orchestrating microservices. In the example the restaurants customer orders food via a web interface. The basic process involves a waiter, a kitchen and a payment service.

The kitchen and payment service are closed external services and a waiter team in part of the restaurant organisation, which is responsible to implement the workflow.

1. Bad Example

In a first approach the waiter team designed a bpmn process and uses Camunda 8 Rest Connectors to call the services.

1.1 Run

Follow these steps to run the example:

1. Start the docker services:

   docker-compose -f stack/docker-compose.yml up -d
   

2. Start the applications: waiter-plain, payment, kitchen and satisfaction-miranum.

The running frontend can be found at:

• waiter-plain: http://localhost:8081

The other running services can be found at:

• kitchen: http://localhost:8881
• payment: http://localhost:8882
• satisfaction-miranum: http://localhost:8080

1.2 Problems

In production the waiter team is facing the following issues:

• Having technical aspects in the bpmn process model, like HTTP Method, URL, Body, etc. a new version of the model needs to be deployed, if the endpoint changes. (separation of concerns)
• Calling the external services directly, the model is dependent on those. Switching to another provider is not possible without updating the model.
• The connectors drive the need for a larger dataset flowing in the scope of the process. They are parameterized in such a way that all information used by the connectors needs to be in the process.

2. Good Example

Together with the Miragon consultants, the waiter team designed a new bpmn process, to address those issues. The new architecture is based on the following principles:

• Avoid technical aspects in bmpn models by using External Tasks.
• Usage of Domain Driven Design and a Hexagonal Architecture to implement adapters for external services. That makes it easy to switch from one provider to another without changing th domain.
• Avoid boilerplate code by using Miranum Connect to communicate with Camunda.

2.1 Run

Just shutdown the waiter-plain and start the waiter-miranum instead.

2.2 Further Improvements

After the refactoring, the restaurant was so successful, that they had more resources. They decided to set up a new team, which is now responsible for the customer satisfaction. Using a message broker like kafka allows both teams to work independently and communicate over Domain Events.