TaskActivity.java

// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License.
package io.dapr.durabletask;

/**
 * Common interface for task activity implementations.
 * <p>
 * Activities are the basic unit of work in a durable task orchestration. Activities are the tasks that are
 * orchestrated in the business process. For example, you might create an orchestrator to process an order. The tasks
 * ay involve checking the inventory, charging the customer, and creating a shipment. Each task would be a separate
 * activity. These activities may be executed serially, in parallel, or some combination of both.
 * <p>
 * Unlike task orchestrators, activities aren't restricted in the type of work you can do in them. Activity functions
 * are frequently used to make network calls or run CPU intensive operations. An activity can also return data back to
 * the orchestrator function. The Durable Task runtime guarantees that each called activity function will be executed
 * <strong>at least once</strong> during an orchestration's execution.
 * <p>
 * Because activities only guarantee at least once execution, it's recommended that activity logic be implemented as
 * idempotent whenever possible.
 * <p>
 * Activities are scheduled by orchestrators using one of the {@link TaskOrchestrationContext#callActivity} method
 * overloads.
 */
@FunctionalInterface
public interface TaskActivity {
    /**
     * Executes the activity logic and returns a value which will be serialized and returned to the calling orchestrator.
     *
     * @param ctx provides information about the current activity execution, like the activity's name and the input
     *            data provided to it by the orchestrator.
     * @return any serializable value to be returned to the calling orchestrator.
     */
    Object run(TaskActivityContext ctx);
}