simple-rabbitmq

A simple RabbitMQ sample with Java to implement the Stock Trading API.

This project uses RabbitMQ as:

1. A RPC system: the method of communication between services (APIService and StockService).
2. A Pub/sub system: send order update messages to all subcribers.
3. A task queue: Limit update DB request/second with queue.

1. Use RabbitMQ to build an RPC system.

In this project, we use RabbitMQ to set up RPC as a method of communication between APIService and StockService.

Our RPC will work like this:

1. We will setup a new DirectExchange
2. The APIService will leverage the convertSendAndReceive method, passing the exchange name, the routingKey, and the message.
3. The request is sent to an Request Queue.
4. The StockService is waiting for requests on that queue. When a request appears, it performs the task and sends a message with the result back to the APIService, using the queue from the replyTo field.
5. The APIService waits for data on the Callback Queue. When a message appears, it checks the correlationId property. If it matches the value from the request it returns the response to the application.

2. Use RabbitMQ to build Publish/Subscribe system.

In this project, we use RabbitMQ to set up Pub/Sub system to broadcast all order updates to all clients.

Once any Order updated, StockService send message to an exchange. An exchange is a very simple thing. On one side it receives messages from producers and the other side it pushes them to queues.

3. Use RabbitMQ to build a Task Queue.

The main idea behind Task Queue is to avoid doing a resource-intensive task immediately and having to wait for it to complete. Instead we schedule the task to be done later. We encapsulate a task as a message and send it to a queue. A worker process running in the background will pop the tasks and eventually execute the job.

In this project, assuming our DB only suffered around 200 request at the same time, that means if more than 200 request at the same time, our DB will die.

4. Run project

4.1. Setup RabbitMQ

Official RabbitMQ docker image at https://hub.docker.com/_/rabbitmq

$ cd ./rabbitmq && docker-compose up -d

RabbitMQ Server listens on port 5672 as default.

Below are mutual properties between APIService and StockService:

mq.rabbitmq.queue=stocktrading.queue
mq.rabbitmq.exchange=stocktrading.exchange
mq.rabbitmq.routingkey=stocktrading.routing
mq.rabbitmq.queue.json=stocktrading.queue.json
mq.rabbitmq.routingkey.json=stocktrading.routing.json
mq.rabbitmq.db.task.queue=db.task.queue
mq.rabbitmq.pubsub.queue=pubsub.queue
mq.rabbitmq.pubsub.exchange=fanout.exchange

spring.rabbitmq.host=localhost
spring.rabbitmq.port=5672
spring.rabbitmq.username=user
spring.rabbitmq.password=passw0rd

4.2. Utils

Project dir: ./Utils. Run $ mvn install to build project.

4.3. StockService

$ mvn spring-boot:run

4.4. APIService

$ mvn spring-boot:run

RESTful server listens on port 8081 (see application.properties -> server.port for more detail).

Available apis:

curl --request POST \
  --url http://localhost:8081/api/enterOrder \
  --header 'Content-Type: application/json' \
  --data '{
	"clientID": "C123456",
	"stockID": "AAPL",
	"marketID": "NASDAQ",
	"price": "100.4",
	"qty": "10000"
}'

curl --request POST \
  --url http://localhost:8081/api/orderEnquiry \
  --header 'Content-Type: application/json' \
  --data '{
	"clientID": "C123456"
}'

curl --request POST \
  --url http://localhost:8081/api/cancelOrder \
  --header 'Content-Type: application/json' \
  --data '{
	"clientID": "C123456",
	"orders": [
		{
			"orderID": "1"
		},
		{
			"orderID": "2"
		}
	]
}'