A tutorial on reliability in publish/subscribe services

Publish/subscribe services are required in several long-term on-going industrial projects that envision a radical rethinking of software systems by integrating existing legacy systems in large-scale federating architectures. In fact, such systems are made of a constellation of systems that cooperate with each other by means of the event notiffcation provided by publish/subscribe services over wide-area networks. Such services have met an enthusiastic success in implementing these large-scale federations thanks to their intrinsic decoupling properties that improve the offered scalability guarantees. However, a very important requirement of such federations is the capability of the adopted publish/subscribe service to tolerate faults occurring in the network and/or computing nodes composing the federation, without negatively affecting the provided event notiffcation. Therefore, it is crucial that publish/subscribe services are equipped with proper methods to support reliable event notiffcation. In this paper, we present this topic of reliable event notiffcation by introducing its definition, a model of the faults that have to be tolerated, the available methods to recover from such faults and how current publish/subscribe products deal with reliability. Copyright © 2012 ACM.