Booking System POC

This application demonstrates an application architecture of a booking system. It served as only a prove of concept to implement an event sourced system with minimal flow of typical use case in cargo shipment business domain.

Overview of Booking Business Model

In a typical scenario, a customer requests to ship one or many cargos. A request causes a creation of booking request a long with the associated cargos requested. Knowing the origin location of the cargos and their final destinations, the system automatically obtains proper shipping port routing and detail routing legs for every cargo.

Other services in the system can react to actions in this booking service to create operation jobs to different stakeholders to perform tasks in order to fulfill the requested shipments.

Interactions with this booking service is also intended to serve different analytics data and lookup booking details and summaries using different search criteria.

The Architecture

Event based communication and sourcing is used in this architecture to handle interactions and cater various needed queryable data views. Separating system clients' commands from auto-generated data projections pattern of CQRS is found to be handy to achieve such goals.

The architecture consists of Spring-boot based microservics, mainly the command service and query service. events are in JSON format to easily serialize and deserialize between interested parties and even non-java based services.

External clients interact with the system via APIs, that in turns uses commands to perform actions on any of the entities via the "root" aggregate. Subsequently, domain events are published as a result of these interactions. Other services can listen to these domain events and project / aggregate needed data views.

Kafka messaging broker along with its KStream and KTable APIs are used in the POC. KStream listens to published domain events and keep any point-in-time snapshopt of the "root" aggregate in a KTable to source it by the command service.

Interaction with the service is happening through an API gateway that routes to appropriate underneath command or query service based on some routing rules. The service interacts with other services in the system via a message broker (Kafka in this case).

Project Modules

This repository consists of these modules

• poc-booking-common: Sharable domain, command and event models.
• poc-booking-service-cmd: The command service to interact with the system (write-only purpose).
• poc-booking-service-qry: The query service listens to command service's generated domain events to project data views and serve to query these views.
• poc-booking-gateway: API gateway serves as a proxy to the command and query services.

Run Kafka Locally

• Download kafka

• extract the downloaded file, and navigate to the kafka home directory

• run this command to bring up ZooKeeper

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

• run this command to bring up Kafka

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

Run the Project Locally

• Clone this project.

• Run the command below inside poc-booking-service-cmd, poc-booking-service-qry and poc-booking-service-gateway folders:

$ mvn spring-boot:run

Create Booking

To create a new booking, hit the url at (http://localhost:8081) with the JSON payload below.

{
   "cargoRequests": [
     {
       "requiredSize": "SIZE_20",
	   "nature": "DANGEROUS_CARGO",
	   "origin": {
		"opZone": "zone-1",
		"facility": "facility-1"
	   },
	   "destination": {
		"opZone": "zone-4",
		"facility": "facility-4"
	   },
       "cutOffDate": "2019-08-01 10:30:00"
     },
      {
       "requiredSize": "SIZE_40",
	   "nature": "GENERAL_CARGO",
	   "origin": {
		"opZone": "zone-5",
		"facility": "facility-5"
	   },
	   "destination": {
		"opZone": "zone-7",
		"facility": "facility-7"
	   },
       "cutOffDate": "2019-08-10 12:00:00"
     }
   ]
}

Common Cloud Services

Checkout out branch feature/common-cloud-services of this project

Clone these services from the other Github [repo] (https://github.com/Haybu/poc-cloud-common-service) and run both the config and Eureka servers.

Cloud config server is used to externalize services configurations.

Cloud Eureka is used for services registration and discovery.