Why a successful migration is showing (0 created, 0 updated, 0 failed, 0 ignored)?
Got answer!!

I missed the following code from the abstract class MigrateDestination:

/**
 * Maintain stats on the number of destination objects created or updated.
 *
 * @var int
 */
protected $numCreated = 0;
public function getCreated() {
  return $this-&gt;numCreated;
}
protected $numUpdated = 0;
public function getUpdated() {
  return $this-&gt;numUpdated;
}


These variables need to be updated during the import process and need to be defined/updated in class that is extending the MigrateDestination.