Distributed subscriptions clustering with limited knowledge sharing for content-based publish/subscribe systems

One of the main issues in content-based publish/subscribe (CBPS) systems is how to dynamically determine groups of similar subscriptions to be adopted for exploiting efficient multicast techniques while guaranteeing at the same time the expressiveness of the subscription scheme. In this work, we propose a distributed mechanism which aims at satisfying important requirements of CBPS systems, that are: i) to guarantee the expressiveness of the subscription languages typical of the content-based paradigm, ii) to exploit efficient events dissemination, iii) to maintain the system scalability in terms of nodes and subscriptions, iv) to start an adaptive system reconfiguration despite new incoming subscriptions. One of the main feature of the proposed mechanism is the use of the system state knowledge sharing by system nodes, with the goal of limiting the system overhead in terms of computing, bandwidth and storage resources. Through a set of simulations we demonstrate the efficiency of the proposed solution

Distributed subscriptions clustering with limited knowledge sharing for content-based publish/subscribe systems

One of the main issues in content-based publish/subscribe (CBPS) systems is how to dynamically determine groups of similar subscriptions to be adopted for exploiting efficient multicast techniques while guaranteeing at the same time the expressiveness of the subscription scheme. In this work, we propose a distributed mechanism which aims at satisfying important requirements of CBPS systems, that are: i) to guarantee the expressiveness of the subscription languages typical of the content-based paradigm, ii) to exploit efficient events dissemination, iii) to maintain the system scalability in terms of nodes and subscriptions, iv) to start an adaptive system reconfiguration despite new incoming subscriptions. One of the main feature of the proposed mechanism is the use of the system state knowledge sharing by system nodes, with the goal of limiting the system overhead in terms of computing, bandwidth and storage resources. Through a set of simulations we demonstrate the efficiency of the proposed solution

Load Management for Publish/Subscribe Message Oriented Middleware

PhDTo provide time-critical early warnings in a Tsunami Warning System (TWS), the time delay for both the sensor data exchange process (upstream) and the warning message dissemination processes (downstream) should be minimal, maximising the time available for accurately analysing the situation and giving more time for people in the affected region to react to the warnings. Publish/Subscribe Message-oriented Middleware (PSMOM) in combination with a novel use of a federated broker (broker overlay) can be deployed in TWS to support both time-critical and resilient communication. PSMOM can better manage message bursts caused by a sudden increase in sensor data exchange frequency or by additional sensors coming online. PSMOM can better manage the decrease in available system resources (bottlenecks) caused by a disruption in the underlying network infrastructure (limited resource case). Otherwise, these burst and bottlenecks can cause some brokers to become overloaded, which may in turn degrade the overall system performance and delay decision-making. Existing PSMOM load management solutions have two key limitations when applied to TWS. First, existing work does not consider the message delay requirements for the redistribution and offloading phases of load management. Here, some data is only useful or valid for a short time-span (from tens of seconds to tens of minutes); hence, it needs to be exchanged within this maximum allowed end-to-end transmission delay. Time critical subscribers need to be de-prioritised from being offloaded, as the offloading processes take some time to complete, introducing unexpected delays to message exchange. Second, existing solutions assume that there are surplus system resources for offloading, i.e., less loaded brokers can accept loads from overloaded brokers. However, in a TWS, the underlying network infrastructure may be disrupted which in turn reduces the system capacity. It always takes time to recover from the limited resources situation and during that time, brokers may not have enough system resources to accept loads from overloaded brokers, which may result in total failure of the overloaded brokers. A novel load management framework called ePEER is proposed that extends an existing messaging system, Publish/Subscribe Efficient Event Routing (PEER), with the following main contributions. First, for the surplus resource case, the message delay requirements for different subscription services are considered in the load analysis process when offloading the load to different brokers. Second, for the limited resource case, a feedback driven congestion control mechanism can be used when the underlay network infrastructure is damaged, reducing the available bandwidth of PSMOM. This mechanism limits the publication rate of messages with less value, to better maintain the quality of experience (QoE) of subscribers for the more important messages ePEER is validated with emulation-based experiments. The results show that ePEER outperforms the state of the art load management solution used by PEER: through preventing unnecessary delays introduced to time critical services, and through ensuring important messages can be more efficiently exchanged to improve the QoE of subscribers

Management of Temporally and Spatially Correlated Failures in Federated Message Oriented Middleware for Resilient and QoS-Aware Messaging Services.

PhDMessage Oriented Middleware (MOM) is widely recognized as a promising solution for the communications between heterogeneous distributed systems. Because the resilience and quality-of-service of the messaging substrate plays a critical role in the overall system performance, the evolution of these distributed systems has introduced new requirements for MOM, such as inter domain federation, resilience and QoS support. This thesis focuses on a management frame work that enhances the Resilience and QoS-awareness of MOM, called RQMOM, for federated enterprise systems. A common hierarchical MOM architecture for the federated messaging service is assumed. Each bottom level local domain comprises a cluster of neighbouring brokers that carry a local messaging service, and inter domain messaging are routed through the gateway brokers of the different local domains over the top level federated overlay. Some challenges and solutions for the intra and inter domain messaging are researched. In local domain messaging the common cause of performance degradation is often the fluctuation of workloads which might result in surge of total workload on a broker and overload its processing capacity, since a local domain is often within a well connected network. Against performance degradation, a combination of novel proactive risk-aware workload allocation, which exploits the co-variation between workloads, in addition to existing reactive load balancing is designed and evaluated. In federated inter domain messaging an overlay network of federated gateway brokers distributed in separated geographical locations, on top of the heterogeneous physical network is considered. Geographical correlated failures are threats to cause major interruptions and damages to such systems. To mitigate this rarely addressed challenge, a novel geographical location aware route selection algorithm to support uninterrupted messaging is introduced. It is used with existing overlay routing mechanisms, to maintain routes and hence provide more resilient messaging against geographical correlated failures