ESO-PWN

Event Sourcing Order-Payment with NATS

Table of Contents

• Application Overview
• Development
• Integration Test
• Kubernetes

Application Overview

                                     ===============
                                     | event-store |
                                     ===============
                                      /          \
                                   grpc          grpc    
                                    /              \
   =============     -->     =========    --->    ===========
   | front-end |  GET, POST  | order |    nats    | payment |
   =============     <--     =========    <---    ===========

Application Flow

1. Order service acts as the main api gateway,
2. Front-end applications send POST request to / to create order.
3. Order service records the request in its own db and calls event-store's createEvent grpc method.
4. Event-store saves the create event request in the events table and then publishes order_created onto the nats-streaming network.
5. Payment service is subscribed to order_created event and processes the payment, and create events via call to event-store's createEvent grpc method.
6. Event-store publishes payment_confirmed if order description starts with test, payment_declined if order description starts with xxx, and a random pick between payment_confirmed & payment_declined if not matched.
7. Order service is subscribed to payment_confirmed & payment_declined event. Upon receiving either one of the event, it updates the order status to confirmed if payment_confirmed, cancelled if payment_declined and create events using event-store's createEvent grpc method.
8. Event-store publishes order_confirmed if payment was confirmed, and order_cancelled if payment was declined.
9. Order service is subscribed to order_confirmed and update the corresponding order status to delivered upon receiving such event.
10. Event-store publishes order_delivered event.

Development

Start docker services

docker-compose up -d 

Start applications From project root, open 4 terminals

Terminal 1:

cd order
npm run dev

Terminal 2:

cd event-store
npm run dev

Terminal 3:

cd payment
npm run dev

Sample create order request

/POST localhost:3000, with the following body:
{
	"amount": 207.00,
	"description": "test top up e wallet"
}

Sample create order response

{
	"id": "5e686586-5314-4f7d-bd0a-050cdca2d741"
}

Sample get order status request

/GET localhost:3000?id=5e686586-5314-4f7d-bd0a-050cdca2d741

Sample get order status response

{
    "id": "5e686586-5314-4f7d-bd0a-050cdca2d741",
    "amount": "207.00",
    "user_id": "4391424b-6cc6-4f1d-a011-2f82ff293126",
    "payee_id": "8c638d8e-f788-4111-9b05-7b49617015af",
    "description": "test top up e wallet",
    "status": "delivered",
    "created_at": "2020-06-07T04:43:12.134Z",
    "updated_at": "2020-06-07T04:43:12.234Z"
}

Integration Test

To run the integration test, ensure all the docker services have started and in proper order.

Then from project root, open 4 terminals (1-3 to start the services in development, and 4 to run the integeration test):

Terminal 1:

cd order
npm run dev

Terminal 2:

cd event-store
npm run dev

Terminal 3:

cd payment
npm run dev

Terminal 4

cd order
npm run test:integration

Kubernetes

This assumes that you have helm installed.

From the project root:

helm install <release-name> helm-charts

To interact with the order api, the ip of the order service can be obtained via:

kubectl get svc/order

Sample output

NAME    TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)    AGE
order   ClusterIP   10.43.219.72   <none>        3000/TCP   16s

Now can proceed to POST / GET to 10.43.219.72:3000 to create / get order.

To stop the stack:

helm uninstall <release-name>