spork-master/src/org/apache/pig/backend/executionengine/ExecJob.java
/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.pig.backend.executionengine;

import java.util.Iterator;
import java.util.Properties;
import java.io.OutputStream;

import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POStore;
import org.apache.pig.data.Tuple;
import org.apache.pig.tools.pigstats.PigStats;

/**
 * Abstraction on a job that the execution engine runs. It allows the front-end to
 * retrieve information on job status and manage a running job.
 *
 */

public interface ExecJob {

    public enum JOB_STATUS {
        FAILED,
        COMPLETED
    }

    public static final String PROGRESS_KEY = "job.progress";
    
    public JOB_STATUS getStatus();

    /**
     * true is the physical plan has executed successfully and results are ready
     * to be retrieved
     * 
     * @return true if execution has completed, false otherwise.
     * @throws ExecException
     */
    public boolean hasCompleted() throws ExecException;
    
    /**
     * if query has executed successfully we want to retrieve the results
     * via iterating over them. 
     * 
     * @return iterator for resulting tuples
     * @throws ExecException
     */
    public Iterator<Tuple> getResults() throws ExecException;

    /**
     * Returns the alias of relation generated by this job
     */
    public String getAlias() throws ExecException;
    
    /**
     * Get configuration information
     * 
     * @return configuration information for the execution engine
     */    
    public Properties getConfiguration();

    /**
     * Can be information about the state (not submitted, e.g. the execute method
     * has not been called yet; not running, e.g. execute has been issued, 
     * but job is waiting; running...; completed; aborted...; progress information
     * 
     * @return statistics relevant to the execution engine
     */
    public PigStats getStatistics();
    
    /**
     * 
     * @return {@link POStore} object associated with the store 
     */
    public POStore getPOStore();

    /**
     * hook for asynchronous notification of job completion pushed from the back-end
     */
    public void completionNotification(Object cookie);
    
    /**
     * Kills current job.
     * 
     * @throws ExecException
     */
    public void kill() throws ExecException;
    
    /**
     * Collecting various forms of outputs
     */
    public void getLogs(OutputStream log) throws ExecException;
    
    public void getSTDOut(OutputStream out) throws ExecException;
    
    public void getSTDError(OutputStream error) throws ExecException;

    /**
     * Get exceptions that happened during execution
     */
    public Exception getException();
}
