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In several application contexts, Web Services adoption is limited due to performance issues. Design methods often propose the adoption of coarse-grained interfaces to reduce the number of interactions between clients and servers. This is an important design concern since marshaling and transferring small parts of complex business objects might enta...
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Citations
... One key feature of WS-Link is its transparency: developers do not have to change any line of code of the endpoints business logic, thanks to a dynamic proxing system we have extensively described in [33]. When offloading takes place, the framework adds specific meta-data to the header of the outgoing SOAP message concerning which attributes have not been sent yet, and how they can be retrieved. ...
Event-driven programming in large scale environments is becoming a common requirement of modern distributed applications. It introduces some beneficial effects such as real-time state updates and replications, which enable new kinds of applications and efficient architectural solutions. However, these benefits could be compromised if the adopted infrastructure is not designed to ensure efficient delivery of events and related data. This paper presents an architectural model, a middleware (WS-Link) and annotation-based mechanisms to ensure high performance in delivering events carrying large attachments. We transparently decouple event notification from related data to avoid useless data-transfers. This way, while event notifications are routed in a conventional manner through an event service, data are directly and transparently transferred from publishers to subscribers. The theoretical analysis shows that we can reduce the average event delivery time by half, compared to a conventional approach requiring the full mediation of the event service. The experimental analysis confirms that the proposed approach outperforms the conventional one (both for throughput and delivery time) even though the middleware overhead, introduced by the specific adopted model, slightly reduces the expected benefits.
... In the latter case, the attributes are made available from an OffloadingRepository. One key feature of the framework is its transparency: developers do not have to change any line of code of the endpoints business logic, thanks to a dynamic proxing system we extensively describe in [21]. When offloading takes place, the framework adds specific meta-data to the header of the outgoing SOAP message concerning which attributes have not been sent yet, and how they can be retrieved. ...
This paper presents a middleware that enables the efficient delivery of events carrying large attachments. We transparently decouple event-description from event-data, in order to avoid useless data-transfers and modifications to endpoints business logic. Our solution relieves the event-delivery system of large data transfers, by enabling direct, but transparent, publisher to subscriber data-exchange. The experiments show that we can reduce the average event delivery time by half, compared to a standard approach requiring the full mediation of the event-delivery system.
... However, exact prediction is not easy to achieve in general-purpose environments, and consequently lazy interactions are needed to transfer additional data when prediction fails [2]. To preserve the correct semantics, lazy accesses to the results of a Web service interaction need to work on dedicated copies of business object attributes that are stored on the server [3]. ...
... The LS also provides update operations, so that the remote endpoint may notify it about which attributes have been actually used and which have not. This information can be exploited to design a strategy that adapts itself to endpoints behaviour, as reported on in [3]. ...
... Once the list of the attributes to be offloaded has been obtained, the ORI serializes them to the OffloadingRepository (OR), which will make them available for lazy access (3,4). The request is then forwarded to the server (5) and handled by the IncomingRequestInterceptor (IRI), that is responsible of unwrapping it and hiding the applied loading strategy (6,7), by means of the ProxyManager (PM). ...
Improving performance of Web services interactions is an important factor to burst the adoption of SOAin mission-critical applications, especially when they deal with large business objects whose transfer time is not negligible. Designing messages dynamic granularity (offloading) is a key challenge for achieving good performances. This requires the server being able to predict the pieces of data actually used by clients in order to send only such data. However, exact prediction is not easy, and consequently lazy interactions are needed to transfer additional data whenever the prediction fails. To preserve semantics, lazy accesses to the results of a Web service interaction need to work on a dedicated copy of the business object stored as application state. Thus, dynamic offloading can experience an overhead due to a prediction failure, which is the sum of round-trip and storage access delays, which could compromise the benefits of the technique. This paper improves our previous work enabling dynamic offloading for both IN and OUT parameters, and analyses how attributes copies impact on the technique, by comparing the overheads introduced by different storage technologies in a real implementation of a Web services framework that extends CXF. More specifically, we quantitatively characterize the execution contexts that make dynamic offloading effective, and the expected accuracy of the predictive strategy to have a gain in term of response time compared to plain services invocations. Finally, the paper introduces the Attribute Loading Delegation technique that enables optimized data-transfers for those applications where data-intensive multiple-interactions take place.
... One key feature of WS-Link is its transparency: developers do not have to change any line of code of the endpoints business logic, thanks to a dynamic proxing system we have extensively described in [33]. When offloading takes place, the framework adds specific meta-data to the header of the outgoing SOAP message concerning which attributes have not been sent yet, and how they can be retrieved. ...
Modularity has been a key issue in the design and development of modern embedded Real-Time Software Systems (RTS) where modularity enables flexibility with respect to changes in platform, environment, and requirements, as well as reuse. In distributed RTS, similar ideas have led to the adoption of Commercial Off-The-Shelf (COTS) components integrated via Service-Oriented Architecture (SOA) principles and technologies that are already well-established in business-oriented information systems. However, current SOA technologies for orchestration, such as Enterprise Service Busses, do not meet strict time-dependent constraints on scalability and latency required by RTS. We present a novel approach to RTS development where the orchestration of real-time processes is decentralised among the services within a fully distributed rule-driven process framework. Our framework wraps around COTS components implementing individual processing steps in a decentralised real-time process. Our execution model incorporates real-time constraints and is configurable through message routing policies distributed as a knowledge base containing rule sets, and therefore dispenses with the need for a central orchestration component which could easily become a bottleneck. Deterministic behaviour can be achieved through the validation of the rule-sets and the use of Modular Performance Analysis (MPA). We analyse the performance of our architecture using the Real-Time Calculus and show by empirical evaluation that our method scales to a typical real-time process application found in a tactical naval combat system context.
