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    import java.util.Map;
025    
026    import 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     */
048    public 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      }