@Override
  public int hashCode() {
    final int prime = 31;
    int result = Integer.hashCode(version);
    result = prime * result + (taskName != null ? taskName.hashCode() : 0);
    return result;
  }
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