Build Smarter Data Workflows with SeaTunnel’s New Event Listener Feature

In today's increasingly complex data integration tasks, the ability to track key events during job execution in real time—and trigger subsequent logic based on those events—has become an essential part of building modern data platforms. Since version 2.3.0, Apache SeaTunnel has introduced a brand-new Event Listener mechanism, offering a flexible hook system that empowers users to build smarter and more business-driven data integration workflows.

This article will dive into the powerful capabilities of this mechanism by exploring its overall architecture, core concepts, usage methods, and best practices.

What Is the Event Listener Mechanism?

The Event Listener mechanism in SeaTunnel is a pluggable hook system that allows users to capture and respond to critical events during job execution, such as:

• Before the job starts (JobStartEvent)
• After the job finishes successfully or fails (JobSuccessEvent / JobFailEvent)
• Task-level execution events (TaskStartEvent / TaskSuccessEvent/ TaskFailEvent)

Each type of event can be associated with corresponding listeners that perform various actions, such as sending alerts, logging audit data, or invoking external systems. This greatly enhances SeaTunnel's observability and extensibility.

Core Components

The Event Listener mechanism in SeaTunnel consists of three main components:

1. **Event \ Represents a certain behavior or state change within the system. Each event carries contextual information, such as job ID, task name, status, etc.
2. **Event Listener \ A pluggable component that receives events and executes the corresponding business logic.
3. **Event Dispatcher \ The event bus that dispatches events to the registered listeners.

Supported Event Types

These events allow users to insert control logic at different levels of granularity—for example, reporting metrics at the task level or sending alerts at the job level.

How to Use: Configuration Example

To enable the Event Listener mechanism, you need to add the event_listenersconfiguration in your SeaTunnel config file. For example:

env {
  execution.parallelism = 2
  job.name = "seatunnel-event-listener-demo"
  event_listeners = ["logging"]
}

This configuration enables an event listener named logging.

Note: event_listeners is an array of strings, and you can configure multiple listeners.

Built-in Listener Example

SeaTunnel currently includes a built-in logging listener, which prints event information to logs—useful for development and debugging.

• Example output:

[INFO] JobStartEvent triggered. Job Name: seatunnel-event-listener-demo  
[INFO] TaskStartEvent triggered. Task: mysql-source->hive-sink  
[INFO] TaskSuccessEvent triggered. Task: mysql-source->hive-sink  
[INFO] JobSuccessEvent triggered.  

Custom Event Listeners

SeaTunnel also supports custom event listeners, allowing users to extend event handling logic. The implementation steps are as follows:

1. Implement the Listener interface

public class MyCustomListener implements EventListener {
    @Override
    public void onEvent(Event event) {
        if (event instanceof JobStartEvent) {
            // Send DingTalk or Feishu notifications
        } else if (event instanceof TaskFailEvent) {
            // Write to failure audit table
        }
    }
}

2. Register with SPI
   Add the path to your implementation class in the fileMETA-INF/services/org.apache.seatunnel.api.event.EventListener:

com.example.MyCustomListener

3. Enable it in the configuration

env {
  event_listeners = ["my-custom"]
}

When SeaTunnel starts, it will automatically load and register your listener.

Example Use Cases

• Failure Alerts: Configure DingTalk or Feishu notification services to immediately push failure alerts to operations teams when a task fails.
• Audit Logging: Listen to job start and end events and write key information to an audit database for compliance and traceability.
• Trigger Downstream Jobs: Use HTTP notifications to trigger downstream systems once a job succeeds.
• Task Duration Monitoring: Capture timestamps in TaskStartEvent and TaskSuccessEvent to calculate and report task duration.

Notes

1. Multiple listeners can be active at the same time; SeaTunnel will trigger each one individually.
2. If a listener throws an exception, it won’t affect the execution of other listeners, but the error will be logged.
3. Custom listeners should be thread-safe and performant to avoid blocking the main execution flow.

Future Plans

The SeaTunnel community is planning to introduce more built-in event listener plugins—for DingTalk, WeCom (Enterprise WeChat), Feishu, Prometheus, etc.—and to support additional event types (such as data validation and metric reporting).

Community contributions are welcome! Feel free to submit a PR to help build a more powerful event listener ecosystem.

Summary

The Event Listener mechanism brings greater flexibility and extensibility to SeaTunnel. It fits well with various automation, monitoring, and business linkage scenarios. If you're using SeaTunnel for workflow orchestration or data integration, give this feature a try to level up your platform’s intelligence and observability.