@Override
  public boolean equals(Object obj) {
    if (this == obj)
      return true;
    if (obj == null)
      return false;
    if (!(obj instanceof CoordinatorStreamMessage))
      return false;
    CoordinatorStreamMessage other = (CoordinatorStreamMessage) obj;
    if (isDelete != other.isDelete)
      return false;
    if (!Arrays.equals(keyArray, other.keyArray))
      return false;
    if (messageMap == null) {
      if (other.messageMap != null)
        return false;
    } else if (getMessageValues() == null) {
      return other.getMessageValues() == null;
    } else if (!getMessageValues().equals(other.getMessageValues()))
      return false;
    return true;
  }
@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