Build an Event-Driven Integration

Time: Under 10 minutes | What you'll build: An event-driven integration that consumes messages from Orders queue in RabbitMQ broker and processes them.

Event integrations are designed for reactive workflows triggered by messages from a broker. This quick start demonstrates the complete flow: creating a RabbitMQ message listener, adding an event handler to process messages, and implementing the integration logic executed when a message is received.

Prerequisites

• WSO2 Integrator installed
• A running RabbitMQ instance (or use Docker: docker run -d -p 5672:5672 -p 15672:15672 rabbitmq:4.2-management)

Visual Designer

Step 1: Create the integration

1. Open WSO2 Integrator.
2. Select the Create New Integration card.
3. Set Integration Name to OrderProcessor.
4. Set Project Name to event-integration.
5. Select Create Integration.

Step 2: Add a RabbitMQ event listener

1. Select your integration from the project overview canvas.
2. Select + Add Artifact in the design canvas.
3. Select RabbitMQ under Event Integration.
4. Set Host to localhost and Port to 5672 (update these if your RabbitMQ instance runs elsewhere).
5. Set Queue Name to Orders.
6. Select Create.

Step 3: Add onMessage event handler

1. In the RabbitMQ service design view, select + Add Handler.
2. Select onMessage.
3. Select Save.

Step 4: Add message processing logic

1. Select + inside the resource flow.
2. Select Call Function.
3. Select printInfo under log.
4. Set Msg to Received order.
5. Select Save.

Step 5: Run and test the integration

1. Select Run.
2. The integration starts and listens for messages on the Orders queue.
3. Open the RabbitMQ Management UI at http://localhost:15672 (default credentials: guest/guest).
   • Go to Queues → Orders → Publish message, enter any text as the payload, and select Publish message.
   • Confirm the integration log displays Received order.

Ballerina Code

The following complete, runnable Ballerina program produces the same integration shown in the visual designer steps.

import ballerina/log;
import ballerinax/rabbitmq;

listener rabbitmq:Listener rabbitmqListener = new ("localhost", 5672);

service "Orders" on rabbitmqListener {
    remote function onMessage(rabbitmq:AnydataMessage message, rabbitmq:Caller caller) returns error? {
        do {
            log:printInfo("Received order");
        } on fail error err {
            // handle error
            return error("unhandled error", err);
        }
    }
}

Save this as main.bal, then run bal run from the project directory. Once running, open http://localhost:15672 (default credentials: guest/guest), navigate to Queues → Orders → Publish message, and publish any message. The terminal log should display Received order.

Supported event sources

Broker	Ballerina Package
Apache Kafka	ballerinax/kafka
RabbitMQ	ballerinax/rabbitmq
MQTT	ballerinax/mqtt
Azure Service Bus	ballerinax/azure.servicebus
Salesforce	ballerinax/salesforce
GitHub Webhooks	ballerinax/github

What's next

• Kafka — Consume and produce Kafka messages
• Azure Service Bus — Integrate with Azure Service Bus queues and topics
• RabbitMQ — Full RabbitMQ listener and publisher reference
• MQTT — Handle MQTT messages from IoT and messaging devices
• CDC for PostgreSQL — React to database changes with change data capture