001/*
002 * Copyright (c) 2007-2016 Concurrent, Inc. All Rights Reserved.
003 *
004 * Project and contact information: http://www.cascading.org/
005 *
006 * This file is part of the Cascading project.
007 *
008 * Licensed under the Apache License, Version 2.0 (the "License");
009 * you may not use this file except in compliance with the License.
010 * You may obtain a copy of the License at
011 *
012 *     http://www.apache.org/licenses/LICENSE-2.0
013 *
014 * Unless required by applicable law or agreed to in writing, software
015 * distributed under the License is distributed on an "AS IS" BASIS,
016 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
017 * See the License for the specific language governing permissions and
018 * limitations under the License.
019 */
020
021package cascading.flow;
022
023import java.util.List;
024
025/**
026 * The FlowStepStrategy interface allows for on the fly customization of {@link cascading.flow.FlowStep} configuration values
027 * before they are submitted to the underlying platform.
028 * <p/>
029 * Use a strategy instance to change the display name for a job, or in the case of Hadoop, the number of
030 * mapper or reducer instances.
031 * <p/>
032 * Note, to change the configuration information, {@link cascading.flow.FlowStep#getConfig()} must be
033 * called to get access to the current configuration.
034 * <p/>
035 * If any, the completed predecessor steps are provided so that the predecessors can be inspected via the
036 * {@link cascading.stats.FlowStepStats} interface for any information that may influence the current job.
037 * <p/>
038 * It is also possible to block submission of the job by blocking in this method.
039 */
040public interface FlowStepStrategy<Config>
041  {
042  void apply( Flow<Config> flow, List<FlowStep<Config>> predecessorSteps, FlowStep<Config> flowStep );
043  }