Lifecycle callbacks

---

The section documents the lifecycle api and its behaviour.

Classes bound into an EventProcessor register for lifecycle callbacks with annotations on methods. A Lifecycle interface is implemented by the generated EventProcessor, lifecycle method calls are routed to annotated callback methods.

The source project for the examples can be found here

Lifecycle - init

EventProcessor#init Calls init on any node in the graph that has registered for an init callback. The init calls are invoked in topological order.

Lifecycle - teardown

EventProcessor#tearDown Calls tearDown on any node in the graph that has registered for an tearDown callback. The tearDown calls are invoked reverse topological order.

Lifecycle - start

EventProcessor#start Calls start on any node in the graph that has registered for an onStart callback. The start calls are invoked in topological order. Start must be called after init

Lifecycle - stop

EventProcessor#stop Calls stop on any node in the graph that has registered for an onStop callback. The stop calls are invoked reverse topological order.

Attaching a user node to lifecycle callback

User nodes that are added to the processing graph can attach to the lifecycle callbacks by annotating methods with the relevant annotations.

See sample - LifecycleCallback.java

public class LifecycleCallback {
    public static class MyNode {

        @Initialise
        public void myInitMethod() {
            System.out.println("Initialise");
        }

        @Start
        public void myStartMethod() {
            System.out.println("Start");
        }

        @Stop
        public void myStopMethod() {
            System.out.println("Stop");
        }

        @TearDown
        public void myTearDownMethod() {
            System.out.println("TearDown");
        }
    }

    public static void main(String[] args) {
        var processor = DataFlowBuilder
                .subscribeToNode(new MyNode())
                .build();

        //init is implicitly called
        processor.start();
        processor.stop();
        processor.tearDown();
    }
}

Output

Initialise
Start
Stop
TearDown