/**
    * 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.hbase.mapreduce;
  
  import static org.junit.Assert.assertTrue;
  import static org.junit.Assert.fail;
  
  import java.io.File;
  import java.io.IOException;
  import java.util.Iterator;
  import java.util.Map;
  import java.util.NavigableMap;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.fs.FileUtil;
  import org.apache.hadoop.fs.Path;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.Cell;
  import org.apache.hadoop.hbase.CellUtil;
  import org.apache.hadoop.hbase.HBaseTestingUtility;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.TableName;
  import org.apache.hadoop.hbase.client.HTable;
  import org.apache.hadoop.hbase.client.Put;
  import org.apache.hadoop.hbase.client.Result;
  import org.apache.hadoop.hbase.client.ResultScanner;
  import org.apache.hadoop.hbase.client.Scan;
  import org.apache.hadoop.hbase.client.Table;
  import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
  import org.apache.hadoop.hbase.testclassification.LargeTests;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.mapreduce.Job;
  import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
  import org.junit.AfterClass;
  import org.junit.BeforeClass;
  import org.junit.Test;
  import org.junit.experimental.categories.Category;
  
  /**
   * Test Map/Reduce job over HBase tables. The map/reduce process we're testing
   * on our tables is simple - take every row in the table, reverse the value of
   * a particular cell, and write it back to the table.
   */
  @Category(LargeTests.class)
  public class TestMultithreadedTableMapper {
    private static final Log LOG = LogFactory.getLog(TestMultithreadedTableMapper.class);
    private static final HBaseTestingUtility UTIL =
        new HBaseTestingUtility();
    static final TableName MULTI_REGION_TABLE_NAME = TableName.valueOf("mrtest");
    static final byte[] INPUT_FAMILY = Bytes.toBytes("contents");
    static final byte[] OUTPUT_FAMILY = Bytes.toBytes("text");
    static final int    NUMBER_OF_THREADS = 10;
  
    @BeforeClass
    public static void beforeClass() throws Exception {
      // Up the handlers; this test needs more than usual.
      UTIL.getConfiguration().setInt(HConstants.REGION_SERVER_HIGH_PRIORITY_HANDLER_COUNT, 10);
      UTIL.setJobWithoutMRCluster();
      UTIL.startMiniCluster();
      HTable table =
          UTIL.createMultiRegionTable(MULTI_REGION_TABLE_NAME, new byte[][] { INPUT_FAMILY,
              OUTPUT_FAMILY });
      UTIL.loadTable(table, INPUT_FAMILY, false);
      UTIL.waitUntilAllRegionsAssigned(MULTI_REGION_TABLE_NAME);
    }
  
    @AfterClass
    public static void afterClass() throws Exception {
      UTIL.shutdownMiniCluster();
    }
  
    /**
     * Pass the given key and processed record reduce
     */
    public static class ProcessContentsMapper
    extends TableMapper<ImmutableBytesWritable, Put> {
  
      /**
       * Pass the key, and reversed value to reduce
       *
       * @param key
       * @param value
      * @param context
      * @throws IOException
      */
     @Override
     public void map(ImmutableBytesWritable key, Result value,
         Context context)
             throws IOException, InterruptedException {
       if (value.size() != 1) {
         throw new IOException("There should only be one input column");
       }
       Map<byte[], NavigableMap<byte[], NavigableMap<Long, byte[]>>>
       cf = value.getMap();
       if(!cf.containsKey(INPUT_FAMILY)) {
         throw new IOException("Wrong input columns. Missing: '" +
             Bytes.toString(INPUT_FAMILY) + "'.");
       }
       // Get the original value and reverse it
       String originalValue = Bytes.toString(value.getValue(INPUT_FAMILY, INPUT_FAMILY));
       StringBuilder newValue = new StringBuilder(originalValue);
       newValue.reverse();
       // Now set the value to be collected
       Put outval = new Put(key.get());
       outval.add(OUTPUT_FAMILY, null, Bytes.toBytes(newValue.toString()));
       context.write(key, outval);
     }
   }
 
   /**
    * Test multithreadedTableMappper map/reduce against a multi-region table
    * @throws IOException
    * @throws ClassNotFoundException
    * @throws InterruptedException
    */
   @Test
   public void testMultithreadedTableMapper()
       throws IOException, InterruptedException, ClassNotFoundException {
     runTestOnTable(new HTable(new Configuration(UTIL.getConfiguration()),
         MULTI_REGION_TABLE_NAME));
   }
 
   private void runTestOnTable(HTable table)
       throws IOException, InterruptedException, ClassNotFoundException {
     Job job = null;
     try {
       LOG.info("Before map/reduce startup");
       job = new Job(table.getConfiguration(), "process column contents");
       job.setNumReduceTasks(1);
       Scan scan = new Scan();
       scan.addFamily(INPUT_FAMILY);
       TableMapReduceUtil.initTableMapperJob(
           table.getTableName(), scan,
           MultithreadedTableMapper.class, ImmutableBytesWritable.class,
           Put.class, job);
       MultithreadedTableMapper.setMapperClass(job, ProcessContentsMapper.class);
       MultithreadedTableMapper.setNumberOfThreads(job, NUMBER_OF_THREADS);
       TableMapReduceUtil.initTableReducerJob(
           Bytes.toString(table.getTableName()),
           IdentityTableReducer.class, job);
       FileOutputFormat.setOutputPath(job, new Path("test"));
       LOG.info("Started " + table.getName().getNameAsString());
       assertTrue(job.waitForCompletion(true));
       LOG.info("After map/reduce completion");
       // verify map-reduce results
       verify(table.getName());
     } finally {
       table.close();
       if (job != null) {
         FileUtil.fullyDelete(
             new File(job.getConfiguration().get("hadoop.tmp.dir")));
       }
     }
   }
 
   private void verify(TableName tableName) throws IOException {
     Table table = new HTable(new Configuration(UTIL.getConfiguration()), tableName);
     boolean verified = false;
     long pause = UTIL.getConfiguration().getLong("hbase.client.pause", 5 * 1000);
     int numRetries = UTIL.getConfiguration().getInt(HConstants.HBASE_CLIENT_RETRIES_NUMBER, 5);
     for (int i = 0; i < numRetries; i++) {
       try {
         LOG.info("Verification attempt #" + i);
         verifyAttempt(table);
         verified = true;
         break;
       } catch (NullPointerException e) {
         // If here, a cell was empty.  Presume its because updates came in
         // after the scanner had been opened.  Wait a while and retry.
         LOG.debug("Verification attempt failed: " + e.getMessage());
       }
       try {
         Thread.sleep(pause);
       } catch (InterruptedException e) {
         // continue
       }
     }
     assertTrue(verified);
     table.close();
   }
 
   /**
    * Looks at every value of the mapreduce output and verifies that indeed
    * the values have been reversed.
    *
    * @param table Table to scan.
    * @throws IOException
    * @throws NullPointerException if we failed to find a cell value
    */
   private void verifyAttempt(final Table table)
       throws IOException, NullPointerException {
     Scan scan = new Scan();
     scan.addFamily(INPUT_FAMILY);
     scan.addFamily(OUTPUT_FAMILY);
     ResultScanner scanner = table.getScanner(scan);
     try {
       Iterator<Result> itr = scanner.iterator();
       assertTrue(itr.hasNext());
       while(itr.hasNext()) {
         Result r = itr.next();
         if (LOG.isDebugEnabled()) {
           if (r.size() > 2 ) {
             throw new IOException("Too many results, expected 2 got " +
                 r.size());
           }
         }
         byte[] firstValue = null;
         byte[] secondValue = null;
         int count = 0;
         for(Cell kv : r.listCells()) {
           if (count == 0) {
             firstValue = CellUtil.cloneValue(kv);
           }else if (count == 1) {
             secondValue = CellUtil.cloneValue(kv);
           }else if (count == 2) {
             break;
           }
           count++;
         }
         String first = "";
         if (firstValue == null) {
           throw new NullPointerException(Bytes.toString(r.getRow()) +
               ": first value is null");
         }
         first = Bytes.toString(firstValue);
         String second = "";
         if (secondValue == null) {
           throw new NullPointerException(Bytes.toString(r.getRow()) +
               ": second value is null");
         }
         byte[] secondReversed = new byte[secondValue.length];
         for (int i = 0, j = secondValue.length - 1; j >= 0; j--, i++) {
           secondReversed[i] = secondValue[j];
         }
         second = Bytes.toString(secondReversed);
         if (first.compareTo(second) != 0) {
           if (LOG.isDebugEnabled()) {
             LOG.debug("second key is not the reverse of first. row=" +
                 Bytes.toStringBinary(r.getRow()) + ", first value=" + first +
                 ", second value=" + second);
           }
           fail();
         }
       }
     } finally {
       scanner.close();
     }
   }
 
 }