def publish_message(producer_instance, topic_name, key, value):
    try:
        key_bytes = bytes(key, encoding='utf-8')
        value_bytes = bytes(value, encoding='utf-8')
        producer_instance.send(topic_name, key=key_bytes, value=value_bytes)
        producer_instance.flush()
        print('Message published successfully.')
    except Exception as ex:
        print('Exception in publishing message')
        print(str(ex))