Message Queues Three Patterns for Asynchronous Information Exchange

Information exchange between concurrent processing elements like threads or tasks is one of the fundamental issues in information processing systems. In many cases, this information transfer needs to occur asynchronously, i.e. the `consumer´ must be enabled to receive the information at some later point in time than the `producer´ provides it. Of course, this may apply to data transfer within a sequential processing element as well. Messages and their in-termediate storage in queues are one of the most common solutions to this problem. This pa-per describes three patterns, addressing different combinations of requirements: the simple FIFO QUEUE, the SELECTABLE-MESSAGE QUEUE, and the SMART-MESSAGE QUEUE.