Source code

001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.reef.task;
020
021import org.apache.reef.annotations.audience.EvaluatorSide;
022import org.apache.reef.annotations.audience.Public;
023import org.apache.reef.util.Optional;
024
025/**
026 * Message source for control flow messages from a task to the Driver.
027 * <p>
028 * The getMessage() method in an Implementation of this interface will be called by the Evaluator resourcemanager
029 * whenever it is about to communicate with the Driver anyway.
030 * Hence, this can be used for occasional status updates etc.
031 */
032@Public
033@EvaluatorSide
034public interface TaskMessageSource {
035
036  /**
037   * @return a message to be sent back to the Driver, or Optional.empty() if no message shall be sent at this time.
038   */
039  Optional<TaskMessage> getMessage();
040}