dojo-quarkus-mp-messaging

A Quarkus dojo to experiment MicroProfile reactive messaging with Kafka

First, start the Kafka broker using the provided docker compose:

docker-compose up

Then, you will develop an application with three components:

• order-api: A REST API to manage orders, each time an order is created it will send a Kafka message with the new order.
• order-enhancer: A messaging component that listens to order messages and enhance them with user information.
• search-api: A REST API to search for enhanced orders. It listens to enhanced order messages.

Before going to the various steps of the dojo, please take some time to read the following documentations:

• Smallrye Reactive Messaging
• Smallrye Reactive Messaging - Concepts

You can refer to the Quarkus USING APACHE KAFKA WITH REACTIVE MESSAGING guide at any time.

Step 1

For this step, you can refer to the Sending / Receiving messages from non-reactive code documentation.

• Go to the order-api and open the fr.loicmathieu.dojo.quarkus.messaging.order.api.OrderResource REST endpoint.
• Define an Emitter<Order> configured with the orders. This channel is already configured in the application.properties.
• Update the create(Order order) method to use this emitter to send the Order to the broker.

Start the application with mvn quarkus:dev.

You can send orders to the endpoint with this curl:

curl -XPOST -d '{"nbItem":2, "totalPrice": 200, "userId": "user1", "shippingAddress": "1 rue du Paradis à Lille"}' \
    -H "Content-Type: application/json" \
    http://localhost:8080

NOTE: The user service of the order-enhancer is able to handle the users with id "user1", "user2" and "user3".

Step 2

• Go to the order-enhancer and open the fr.loicmathieu.dojo.quarkus.messaging.order.enhancer.MessageManager.
• Create a method that takes an Order as parameter and return the EnhancedOrder enhanced with the User information recovered from the UserService.
• Annotate this method so it listens to the orders channel and send the enhanced order to the enhanced-orders channel. These channels are already configured in the application.properties. You can read the section The price converter of the Quarkus Kafka guide for an exemple.
• Add some logging to see if the message arrives.

Start the application with mvn quarkus:dev and create orders on the order API.

Step 3

It’s not rare to have to test your application but deploying the infrastructure can be cumbersome. While Docker or Test Containers have improved the testing experience, you may want to mock this infrastructure.

• Open the test class fr.loicmathieu.dojo.quarkus.messaging.order.enhancer.MessageManagerTest, run it, it should fail.
• Open the class fr.loicmathieu.dojo.quarkus.messaging.order.enhancer.InMemoryChannelTestResource and mock the channels. Check the SmallRye Reactive Messaging Testing section for an example.

Step 4

• Go to the search-api and open the fr.loicmathieu.dojo.quarkus.messaging.search.MessageManager.
• Create a method that takes an EnhancedOrder as parameter and save it via the EnhancedOrderService.add() method.
• Annotate this method so it listens to the enhanced-orders channel. This channel is already configured in the application.properties.

Start the application with ̀mvn quarkus:dev.

After creating a new order via the order API, you should have this order enhanced, then available via the search API.

You can test the search endpoint via:

curl http://localhost:8081