EDA - Event Driven Architecture demo

Three services that are composed together to simulate a really bad ticketing website. There are two modes that the demo can be run in:

1. a typical request/response system
2. an EDA configuration that uses either RabbitMQ or Azure ServiceBus Topics.

configuring Azure ServiceBus Topic

Note: there are opportunities for improvement here via automation

Using this demo solution with Azure requires that you have configured the appropriate resources.

1. you must have an Azure Subscription
2. create a Resource Group to contain the ServiceBus Namespace
3. create a Service Bus Namespace
   1. the Premium tier or higher is required
4. create a Topic within the namespace
5. create a Shared Access Policy (SAP) with the Send and Listen claims, at a minimum.
   1. you will need to supply one of the generated connection strings as shown below.
6. create three subscriptions against the topic. these subscriptions are named after the service that will make use of them.
   1. order-processor
   2. reservation-processor
   3. payment-processor

build and run the demo

the environment variable 'active_profile' needs to be set to either 'rabbitmq' to use RabbitMQ or 'azure-topic' for Azure ServiceBus Topic

the environment variable 'azure_topic_connectstring' should be set to one of the connection strings that were generated when you created the SAP above. I am using a single connection string for all the services for simplicity. a better practice would be for each service to have it's own access policy

mvn clean package
export active_profile=azure-topic
export azure_topic_connectstring=...
docker-compose build --no-cache
docker-compose up

sample requests

submit an order using the request/response sync configuration

POST http://localhost:8080/orders/sync
content-type: application/json
accept: application/json
{
  "showId":"456765",
  "status":"pending",
  "seats":["1A","1B","1C"]
}

retrieve the status of an order

GET http://localhost:8080/orders/00001
accept: application/json

submit an order using the event-driven configuration

POST http://localhost:8080/orders
content-type: application/json
accept: application/json

{
  "showId":"456765",
  "status":"pending",
  "seats":["1A","1B","1C"]
}

The above request will result in a 201 with the location header set to the URL of the order.

Simulating load

The included script run-gatling-container.sh will build and and launch a container with an instance of Gatling. There are two scripts. One will exercise the request/response path and the other will challenge the eventing path

on Windows

winpty bash ./run-gatling-container.sh

Embracing chaos

Netflix's Chaos Monkey has been integrated thanks to Chaos Monkey for Spring Book by CodeCentric. It can be activated by setting the environment variable chaos_monkey_enabled to true prior to spinning up the containers.

export chaos_monkey_enabled=true

cleanup

deleting the Azure Resource Group is a quick and easy way to release all of the resources that were created within Azure.

an easy way to remove all of the EDA images

 docker rmi $(docker images --filter=reference="eda*" -q)