RandomWriter.java 文件源码

/**
 * Given an output filename, write a bunch of random records to it.
 */
public void map(WritableComparable key, 
                Writable value,
                Context context) throws IOException,InterruptedException {
  int itemCount = 0;
  while (numBytesToWrite > 0) {
    int keyLength = minKeySize + 
      (keySizeRange != 0 ? random.nextInt(keySizeRange) : 0);
    randomKey.setSize(keyLength);
    randomizeBytes(randomKey.getBytes(), 0, randomKey.getLength());
    int valueLength = minValueSize +
      (valueSizeRange != 0 ? random.nextInt(valueSizeRange) : 0);
    randomValue.setSize(valueLength);
    randomizeBytes(randomValue.getBytes(), 0, randomValue.getLength());
    context.write(randomKey, randomValue);
    numBytesToWrite -= keyLength + valueLength;
    context.getCounter(Counters.BYTES_WRITTEN).increment(keyLength + valueLength);
    context.getCounter(Counters.RECORDS_WRITTEN).increment(1);
    if (++itemCount % 200 == 0) {
      context.setStatus("wrote record " + itemCount + ". " + 
                         numBytesToWrite + " bytes left.");
    }
  }
  context.setStatus("done with " + itemCount + " records.");
}