/**
 * 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.hadoop.mapred;

import java.io.IOException;

import junit.framework.TestCase;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.dfs.MiniDFSCluster;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.lib.IdentityMapper;
import org.apache.hadoop.mapred.lib.IdentityReducer;

/**
 * A JUnit test to test Map-Reduce empty jobs Mini-DFS.
 */
public class TestEmptyJobWithDFS extends TestCase {
  private static final Log LOG =
    LogFactory.getLog(TestEmptyJobWithDFS.class.getName());
  
  /**
   * Simple method running a MapReduce job with no input data. Used
   * to test that such a job is successful.
   * @param fileSys
   * @param jobTracker
   * @param conf
   * @param numMaps
   * @param numReduces
   * @return true if the MR job is successful, otherwise false
   * @throws IOException
   */
  public static boolean launchEmptyJob(String fileSys,
                                       String jobTracker,
                                       JobConf conf,
                                       int numMaps,
                                       int numReduces) throws IOException {
    // create an empty input dir
    final Path inDir = new Path("/testing/empty/input");
    final Path outDir = new Path("/testing/empty/output");
    FileSystem fs = FileSystem.getNamed(fileSys, conf);
    fs.delete(outDir, true);
    if (!fs.mkdirs(inDir)) {
      LOG.warn("Can't create " + inDir);
      return false;
    }

    // use WordCount example
    FileSystem.setDefaultUri(conf, fileSys);
    conf.set("mapred.job.tracker", jobTracker);
    conf.setJobName("empty");
    // use an InputFormat which returns no split
    conf.setInputFormat(EmptyInputFormat.class);
    conf.setOutputKeyClass(Text.class);
    conf.setOutputValueClass(IntWritable.class);
    conf.setMapperClass(IdentityMapper.class);        
    conf.setReducerClass(IdentityReducer.class);
    FileInputFormat.setInputPaths(conf, inDir);
    FileOutputFormat.setOutputPath(conf, outDir);
    conf.setNumMapTasks(numMaps);
    conf.setNumReduceTasks(numReduces);
      
    // run job and wait for completion
    JobClient jc = new JobClient(conf);
    RunningJob runningJob = jc.submitJob(conf);
    while (true) {
      try {
        Thread.sleep(1000);
      } catch (InterruptedException e) {}
      if (runningJob.isComplete()) {
        break;
      }
    }
      
    try {
      assertTrue(runningJob.isComplete());
      assertTrue(runningJob.isSuccessful());
    } catch (NullPointerException npe) {
      // This NPE should no more happens
      fail("A NPE should not have happened.");
    }
          
    // return job result
    LOG.info("job is complete: " + runningJob.isSuccessful());
    return (runningJob.isSuccessful());
  }
  
  /**
   * Test that a job with no input data (and thus with no input split and
   * no map task to execute) is successful.
   * @throws IOException
   */
  public void testEmptyJobWithDFS() throws IOException {
    String namenode = null;
    MiniDFSCluster dfs = null;
    MiniMRCluster mr = null;
    FileSystem fileSys = null;
    try {
      final int taskTrackers = 4;
      final int jobTrackerPort = 60050;
      Configuration conf = new Configuration();
      dfs = new MiniDFSCluster(conf, 1, true, null);
      fileSys = dfs.getFileSystem();
      namenode = fileSys.getName();
      mr = new MiniMRCluster(taskTrackers, namenode, 2);
      final String jobTrackerName = "localhost:" + mr.getJobTrackerPort();
      JobConf jobConf = new JobConf();
      boolean result;
      result = launchEmptyJob(namenode, jobTrackerName, jobConf, 
                              3, 1);
      assertTrue(result);
          
    } finally {
      if (fileSys != null) { fileSys.close(); }
      if (dfs != null) { dfs.shutdown(); }
      if (mr != null) { mr.shutdown(); }
    }
  }
  
}