    001    /*
    002     * Copyright (c) 2007-2014 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
    021    package cascading.flow;
    022
    023    import 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     */
    040    public interface FlowStepStrategy<Config>
    041      {
    042      void apply( Flow<Config> flow, List<FlowStep<Config>> predecessorSteps, FlowStep<Config> flowStep );
    043      }