| /* |
| * 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.operators.functions; |
| |
| import org.apache.samza.operators.Scheduler; |
| |
| import java.util.Collection; |
| |
| |
| /** |
| * Allows scheduling a callback for a specific epoch-time. |
| * Key must be a unique identifier for its corresponding logic to execute, and is provided in the callback when the |
| * corresponding schedule time occurs. |
| * |
| * <p> |
| * Example of a {@link FlatMapFunction} with {@link ScheduledFunction}: |
| * <pre>{@code |
| * public class ExampleScheduledFn implements FlatMapFunction<String, String>, ScheduledFunction<String, String> { |
| * // for recurring callbacks, keep track of the scheduler from "schedule" |
| * private Scheduler scheduler; |
| * |
| * public void schedule(Scheduler scheduler) { |
| * // save the scheduler for recurring callbacks |
| * this.scheduler = scheduler; |
| * long time = System.currentTimeMillis() + 5000; // fire after 5 sec |
| * scheduler.schedule("do-delayed-logic", time); |
| * } |
| * public Collection<String> apply(String s) { |
| * ... |
| * } |
| * public Collection<String> onCallback(String key, long timestamp) { |
| * // do some logic for key "do-delayed-logic" |
| * ... |
| * // for recurring callbacks, call the saved scheduler again |
| * this.scheduler.schedule("example-process", System.currentTimeMillis() + 5000); |
| * } |
| * } |
| * }</pre> |
| * @param <K> type of the key |
| * @param <OM> type of the output |
| */ |
| public interface ScheduledFunction<K, OM> { |
| /** |
| * Allows scheduling the initial callback(s) and saving the {@code scheduler} for later use for recurring callbacks. |
| * @param scheduler used to specify the schedule time(s) and key(s) |
| */ |
| void schedule(Scheduler<K> scheduler); |
| |
| /** |
| * Returns the output from the scheduling logic corresponding to the key that was triggered. |
| * @param key key corresponding to the callback that got invoked |
| * @param timestamp schedule time that was set for the callback for the key, in milliseconds since epoch |
| * @return {@link Collection} of output elements |
| */ |
| Collection<OM> onCallback(K key, long timestamp); |
| } |