src/main/java/org/apache/giraph/examples/SimpleVertexWithWorkerContext.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.giraph.examples;

import java.io.DataOutputStream;
import java.io.IOException;
import java.util.Iterator;

import org.apache.giraph.examples.SimpleSuperstepVertex.SimpleSuperstepVertexInputFormat;
import org.apache.giraph.graph.GiraphJob;
import org.apache.giraph.graph.EdgeListVertex;
import org.apache.giraph.graph.WorkerContext;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.DoubleWritable;
import org.apache.hadoop.io.FloatWritable;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.mapreduce.Mapper.Context;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

/**
 * Fully runnable example of how to
 * emit worker data to HDFS during a graph
 * computation.
 */
public class SimpleVertexWithWorkerContext extends
        EdgeListVertex<LongWritable, IntWritable, FloatWritable, DoubleWritable>
        implements Tool {

    public static final String OUTPUTDIR = "svwwc.outputdir";
    private static final int TESTLENGTH = 30;

    @Override
    public void compute(Iterator<DoubleWritable> msgIterator)
            throws IOException {

        long superstep = getSuperstep();

        if (superstep < TESTLENGTH) {
            EmitterWorkerContext emitter =
                    (EmitterWorkerContext) getWorkerContext();
            emitter.emit("vertexId=" + getVertexId() +
                         " superstep=" + superstep + "\n");
        } else {
            voteToHalt();
        }
    }

    @SuppressWarnings("rawtypes")
	public static class EmitterWorkerContext extends WorkerContext {

        private static final String FILENAME = "emitter_";
        private DataOutputStream out;

        @Override
        public void preApplication() {
            Context context = getContext();
            FileSystem fs;

            try {
                fs = FileSystem.get(context.getConfiguration());

                String p = context.getConfiguration()
                    .get(SimpleVertexWithWorkerContext.OUTPUTDIR);
                if (p == null) {
                    throw new IllegalArgumentException(
                        SimpleVertexWithWorkerContext.OUTPUTDIR +
                        " undefined!");
                }

                Path path = new Path(p);
                if (!fs.exists(path)) {
                    throw new IllegalArgumentException(path +
                            " doesn't exist");
                }

                Path outF = new Path(path, FILENAME +
                        context.getTaskAttemptID());
                if (fs.exists(outF)) {
                    throw new IllegalArgumentException(outF +
                            " aready exists");
                }

                out = fs.create(outF);
            } catch (IOException e) {
                throw new RuntimeException(
                        "can't initialize WorkerContext", e);
            }
        }

        @Override
        public void postApplication() {
            if (out != null) {
                try {
                    out.flush();
                    out.close();
                } catch (IOException e) {
                    throw new RuntimeException(
                            "can't finalize WorkerContext", e);
                }
                out = null;
            }
        }

        @Override
        public void preSuperstep() { }

        @Override
        public void postSuperstep() { }

        public void emit(String s) {
            try {
                out.writeUTF(s);
            } catch (IOException e) {
                throw new RuntimeException("can't emit", e);
            }
        }
    }

    @Override
    public int run(String[] args) throws Exception {
        if (args.length != 2) {
            throw new IllegalArgumentException(
                "run: Must have 2 arguments <output path> <# of workers>");
        }
        GiraphJob job = new GiraphJob(getConf(), getClass().getName());
        job.setVertexClass(getClass());
        job.setVertexInputFormatClass(
            SimpleSuperstepVertexInputFormat.class);
        job.setWorkerContextClass(EmitterWorkerContext.class);
        Configuration conf = job.getConfiguration();
        conf.set(SimpleVertexWithWorkerContext.OUTPUTDIR, args[0]);
        job.setWorkerConfiguration(Integer.parseInt(args[1]),
                                   Integer.parseInt(args[1]),
                                   100.0f);
        if (job.run(true) == true) {
            return 0;
        } else {
            return -1;
        }
    }

    public static void main(String[] args) throws Exception {
        System.exit(ToolRunner.run(new SimpleVertexWithWorkerContext(), args));
    }
}