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;
024import java.util.Map;
025
026import cascading.pipe.Pipe;
027
028/**
029 * Interface AssemblyPlanner is used to allow for lazy evaluation of a pipe assembly during planning of a {@link Flow}.
030 * <p/>
031 * This allows for new languages or frameworks that may require additional meta-data from the
032 * underlying platform or environment. Specifically field names and type information from incoming source
033 * and outgoing sink {@link cascading.tap.Tap}s.
034 * <p/>
035 * AssemblyPlanner implementations are handed to a {@link cascading.flow.planner.FlowPlanner}
036 * instance in the order they should be evaluated.
037 * Every instance has the opportunity to replace any prior tails with new branches and paths.
038 * <p/>
039 * Every instance of AssemblyPlanner evaluated is given the current {@link FlowDef} used on the current
040 * {@link FlowConnector}, the current Flow instance (only initialized with source and sink Taps provided by the
041 * FlowDef), and the tails provided by the FlowDef or those returned by prior AssemblyPlanner instances.
042 * <p/>
043 * An AssemblyPlanner cannot change or modify the Flow, or change out any Taps used as sources, sinks, traps, or
044 * checkpoints.
045 * <p/>
046 * This is an experimental API and subject to change without notice.
047 */
048public interface AssemblyPlanner
049  {
050  interface Context
051    {
052    FlowDef getFlowDef();
053
054    Flow getFlow();
055
056    List<Pipe> getTails();
057    }
058
059  /**
060   * Called when this AssemblyPlanner instance should return any additional tail Pipe instances for used
061   * when completing the Flow plan.
062   *
063   * @param context parameter object of the Context
064   * @return tail Pipe instances to replace the given tails
065   */
066  List<Pipe> resolveTails( Context context );
067
068  /**
069   * Returns a map of properties giving more details about the Flow object. This can be picked up by a Flow object and
070   * added to its internal FlowDescriptor.
071   *
072   * @return Map<String,String>
073   */
074  Map<String, String> getFlowDescriptor();
075  }