samza-api/src/main/java/org/apache/samza/scheduler/ScheduledCallback.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.samza.scheduler;

import org.apache.samza.task.MessageCollector;
import org.apache.samza.task.TaskCoordinator;


/**
 * The callback that is invoked when its corresponding schedule time registered via {@link CallbackScheduler} is
 * reached. The {@link CallbackScheduler} is available through
 * {@link org.apache.samza.context.TaskContext#getCallbackScheduler()}.
 * @param <K> type of the callback key
 */
public interface ScheduledCallback<K> {
  /**
   * Invoked when the corresponding schedule time is reached.
   * @param key key for callback
   * @param collector contains the means of sending message envelopes to the output stream.
   * @param coordinator manages execution of tasks.
   */
  void onCallback(K key, MessageCollector collector, TaskCoordinator coordinator);
}