@Override
  public boolean equals(Object obj) {
    if (this == obj)
      return true;
    if (obj == null)
      return false;
    if (getClass() != obj.getClass())
      return false;

    final ControlMessage other = (ControlMessage) obj;
    if (version != other.version) {
      return false;
    }

    if (taskName != null
        ? !taskName.equals(other.getTaskName())
        : other.taskName != null) {
      return false;
    }

    return true;
  }
The abstract class of all control messages, containing
the task that produces the control message, the total number of producer tasks,
and a version number.
samza-api/src/main/java/org/apache/samza/system/ControlMessage.java