Random.java

/**
 *  Copyright 2007-2008 University Of Southern California
 *
 *  Licensed 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 edu.isi.pegasus.planner.selector.site;

import edu.isi.pegasus.planner.classes.Job;

import edu.isi.pegasus.planner.classes.PegasusBag;

import edu.isi.pegasus.common.logging.LogManager;


import java.util.List;

/**
 * A random site selector that maps to a job to a random pool, amongst the subset
 * of pools where that particular job can be executed.
 *
 * @author Karan Vahi
 * @version $Revision$
 */

public class Random extends AbstractPerJob {



    /**
     * The default constructor. Should not be called. Call the overloaded one.
     */
    public Random() {
    }


    /**
     * Initializes the site selector.
     *
     * @param bag   the bag of objects that is useful for initialization.
     *
     */
    public void initialize( PegasusBag bag ){
        super.initialize( bag );
    }

    /**
     * Maps a job in the workflow to an execution site.
     *
     * @param job    the job to be mapped.
     * @param sites  the list of <code>String</code> objects representing the
     *               execution sites that can be used.
     *
     */
    public void mapJob( Job job, List sites ){

        List rsites = mTCMapper.getSiteList( job.getTXNamespace(),job.getTXName(),
                                             job.getTXVersion(), sites );


        if( rsites == null || rsites.isEmpty() ){
            job.setSiteHandle( null );
        }
        else{
            job.setSiteHandle(selectRandomSite(rsites));
            StringBuffer message = new StringBuffer( );
            message.append( "[Random Selector] Mapped " ).append( job.getID() ).append( " to " ).append( job.getSiteHandle() );
            mLogger.log( message.toString(),
                         LogManager.DEBUG_MESSAGE_LEVEL );
        }
    }

    /**
     * Returns a brief description of the site selection technique being used.
     *
     * @return String
     */
    public String description() {
        String st = "Random Site Selection";
        return st;
    }

    /**
     * The random selection that selects randomly one of the records returned by
     * the transformation catalog.
     *
     * @param  sites  List of <code>String</code>objects.
     *
     * @return String
     */
    private String selectRandomSite(List sites) {
        double randNo;
        int noOfRecs = sites.size();

        //means we have to choose a random location between 0 and (noOfLocs -1)
        randNo = Math.random() * noOfRecs;
        int recSelected = new Double(randNo).intValue();
        /*
        String message = "Random Site selected is " + (recSelected + 1) +
            " amongst " + noOfRecs + " possible";
        mLogger.logMessage(message, 1, false);
        */
        return (String)sites.get(recSelected);
    }
}