AU6575600A - Mechanism controlling and ordering message propagation - Google Patents

Description

1 A MECHANISM FOR CONTROLLING AND SCHEDULING MESSAGE PROPAGATION The invention relates to handling the propagation of messages in an asynchronous system. In general, 5 efficient asynchronous communication between message supplier objects and message-consumer objects requires the presence of an intermediate object to decouple communication. Such an intermediate object possesses the capacity to store and transfer messages. It is referred 10 to as an asynchronous "broker". When messages are transmitted without taking into consideration the processing capacity of the destination, there is a danger of the destination becoming overloaded or of its performance becoming degraded. It is then 15 necessary to deliver messages as a function of the processing capacity of the message consumer. At present, the only known means consists in enabling the consumer to suspend receiving messages and to start receiving again once sufficient processing 20 capacity becomes available. That solution is not satisfactory since it requires the consumer to monitor instantaneous traffic continuously and that degrades performance. An alternative to that solution consists in monitoring periodically. However that inevitably leads 25 to traffic congestion in the consumer if traffic increases suddenly and unpredictably. Under such circumstances, the overloaded consumer is not even capable of reacting so as to cause the traffic to be interrupted. 30 The invention consists in a method of asynchronously communicating messages between a message-supplier object and a message-consumer object using at least asynchronous broker between said objects. The message-consumer object defines a set of rules concerning the rate at which 35 messages are to be received and it informs the asynchronous broker. The definition can be stationary or it can be redefined dynamically while communication is 2 on-going. For example, the rules can be redefined periodically. The rules can consist in defining an upper threshold for messages. 5 Advantageously, the asynchronous broker transmits information concerning message rate to the consumer object. Instead of overloading the consumer with the task of monitoring traffic, the invention puts the burden of 10 monitoring on the asynchronous broker, which from this point of view acts as a scheduler. The scheduler must then ensure that the scheduling time constraints that have been given to it by the consumer are indeed applied. When subscribing to the asynchronous broker, a 15 consumer informs the scheduler of scheduling rules that determine the rate at which the consumer desires to accept messages. The consumer adjusts traffic by requesting a change in the scheduling rules. If traffic drops, then the scheduler can end up doing no more than 20 forwarding messages directly from suppliers. If traffic increases, then the scheduler instructs the broker to store messages on behalf of the registered consumer. This ensures that the consumer receives at a constant rate. 25 It is possible to specify particular scheduling rules for each consumer. The main task of the scheduler consists in applying the scheduling rules provided by the consumer, its secondary task consists in measuring traffic state and in 30 supplying corresponding information. The invention is particularly well suited to a transaction context. In such a context, the accepting of messages in the broker is subordinate to validating the transaction that produced them. 35 In order to improve the reliability of the scheduler, each decision it takes concerning the transmission of messages to a consumer is made consistent 3 with the messages from the suppliers. Decisions taken by .the scheduler are stored in a secure-memory as part of the supplier's transaction. Thus, if the transaction fails, the decision is canceled. 5 The invention makes it possible to guarantee that message transmission between suppliers and consumers remains fluid. Consequently, the consumer is not subjected to sudden variations of traffic. The consumer no longer monitors traffic flow, but it does receive 10 accurate information about traffic, thereby enabling it to adjust the rate at which it receives messages. In addition, the conventional solution is contained within the invention. It is possible to suspend reception by defining a zero rate, and to restart reception by 15 changing said rate.