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    /** Interface FlowStepListener provides hooks for receiving events on various stages of a {@link FlowStep} execution. */
024    public interface FlowStepListener
025      {
026      /**
027       * The onStarting event is fired when a  given {@link cascading.flow.FlowStep} job has been submitted i.e. to hadoop cluster
028       *
029       * @param flowStep
030       */
031      public void onStepStarting( FlowStep flowStep );
032    
033      /**
034       * The onStepStopping event is fired when a given {@link cascading.flow.FlowStep} job is stopped
035       *
036       * @param flowStep
037       */
038      public void onStepStopping( FlowStep flowStep );
039    
040      /**
041       * The onStepRunning event is fired when a given {@link cascading.flow.FlowStep} moves into the running state
042       *
043       * @param flowStep
044       */
045      public void onStepRunning( FlowStep flowStep );
046    
047      /**
048       * The onStepCompleted event is fired when a flowStepJob completed its work
049       *
050       * @param flowStep
051       */
052      public void onStepCompleted( FlowStep flowStep );
053    
054      /**
055       * The onStepThrowable event is fired if a given {@link cascading.flow.FlowStep} throws a Throwable type. This throwable is passed
056       * as an argument to the event. This event method should return true if the given throwable was handled and should
057       * not be rethrown from the {@link Flow#complete()} method.
058       *
059       * @param flowStep
060       * @param throwable
061       * @return returns true if this listener has handled the given throwable
062       */
063      public boolean onStepThrowable( FlowStep flowStep, Throwable throwable );
064      }