@Override
  public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = prime * result + (isDelete ? 1231 : 1237);
    result = prime * result + Arrays.hashCode(keyArray);
    result = prime * result + ((messageMap == null) ? 0 : getMessageValues() == null ? 0 : getMessageValues().hashCode());
    return result;
  }
@return The key for a message. The key's meaning is defined by the type of
        the message.
samza-core/src/main/java/org/apache/samza/coordinator/stream/messages/CoordinatorStreamMessage.java