Counters in Hadoop...

  1. Task Counters #248
    1. MAP_INPUT_RECORDS 
      1. No of records read by all Map Tasks
    2. MAP_OUTPUT_RECORDS
      1. No of records produced by all Map Tasks
    3. PHYSICAL_MEMORY_BYTES
      1. Amount of Physical memory used on a Particular Task attempt
  2. Filesystem counters
      1. BYTES_READ
        1. No of bytes read by the filesystem by map & reduce tasks
      2. BYTES_WRITTEN
        1. No of bytes written to filesystem by Map & Reduce tasks
  3. FileInputFormat Counters
    1. BYTES_READ
      1. No of bytes read by Map tasks via FileInputFormat
  4. FileOutputFormat Counters
    1. BYTES_WRITTEN
      1. No of bytes written by Map or Reduce task via the FileOutputFormat
  5. Job Counters
    1. Are maintained by a Application Master #250
    2. Maintains Job statistics
    3. TOTAL_LAUNCHED_MAPS
      1. No of Map tasks launched (Including the failed one and the one that started speculatively)