Eggshell.java Source code

Introduction

Here is the source code for Eggshell.java

Source

/*
This file is part of Eggshell.
Copyright 2013 George Magiros
    
Eggshell is free software: you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation, either version 3 of the License, or (at
your option) any later version.
    
Eggshell is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
License for more details.
    
You should have received a copy of the GNU General Public License
along with Eggshell.  If not, see <http://www.gnu.org/licenses/>.
*/

import org.mozilla.javascript.*;

import java.util.Arrays;
import java.io.IOException;

// hadoop job
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

// hadoop file systems
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.fs.FileSystem;

// hadooop runner
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.conf.Configuration;

/** Class that processes the command-line options
 *  from Hadoop and submits the job.
 */
public class Eggshell extends Configured implements Tool {
    /* public static fields */

    /** The name of the file containing the Eggshell Javascript library */
    public static final String LIBRARY_FILE = "eggshell.js";
    /** HDFS temporary directory */
    public static final String SCRIPT_DIR = ".eggshell";
    /** The name of the file containing the serialized Javascript map function */
    public static final String MAP_FILE = "map.js";
    /** The name of the file containing the serialized Javascript reduce function */
    public static final String REDUCE_FILE = "reduce.js";
    /** The name of the file containing the serialized Javascript combine function */
    public static final String COMBINE_FILE = "combine.js";

    /* private fields */

    /** Holds the Javascript interpreter's state */
    private Script script;

    /* public methods */

    /** In charge of setting up and submitting the Hadoop job
     *  The method receives the remaining command-line arguments
     *  after first being processed by Hadoop.
     *
     * @param args        Hadoop processed command-line arguments
     * @return            Returns 0 for sucess
     */
    public int run(String[] args) throws Exception {
        String name = args[0];
        String[] params = Arrays.copyOfRange(args, 1, args.length);
        Object[] arguments = Arrays.copyOf(params, params.length, Object[].class);

        script = new Script(); // start the Javascript interpreter
        script.putProperty("arguments", script.newArray(arguments));

        EggGlobal.script = script;
        Egg.script = script;
        Egg.name = name;
        Egg.conf = getConf();

        Scriptable global = script.newObject("EggGlobal", null);
        script.setGlobalScope(global);

        script.evalLibrary(); // load the Eggshell Javascript library
        script.evalFile(name); // load the javascript job file

        /* create a temporary directory in hdfs to hold the seralized functions */
        FileSystem fs = FileSystem.get(getConf());
        Path dir = new Path(SCRIPT_DIR);
        if (fs.exists(dir))
            fs.delete(dir, true);
        fs.mkdirs(dir);

        /* call the 'eggshell' function */
        Object o = script.getProperty("eggshell");
        if (o instanceof Function) {
            Scriptable thisObj = script.newObject("Egg", null);
            Function f = (Function) o;
            o = script.callFunction(f, thisObj, params);
            script.exit();

            /* return the result of the 'eggshell' function */
            if (o instanceof NativeJavaObject)
                o = ((NativeJavaObject) o).unwrap();
            if (o instanceof Boolean)
                return (Boolean) o ? 0 : 1;
            if (o instanceof Integer)
                return (Integer) o;
            if (o instanceof Double)
                return ((Double) o).intValue();
        }
        return 0;
    }

    /** The static main method for the class
     *
     * @param args  The raw command-line
     */
    public static void main(String[] args) throws Exception {
        int ret = ToolRunner.run(new Eggshell(), args);
        System.exit(ret);
    }
}