    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  }