001    /*
002     * Copyright (c) 2007-2015 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      }