Apprehensive QoS monitoring of Service choreographies

Abstract

Service choreographies specify the intended interaction protocol among a set of cooperating services at the business application level. For end-users the non-functional properties exposed by a choreographed service composition can be as important as its functional behaviour, if not even more. Therefore, in any choreography development process, the capability of specifying and assessing the established Service Level Agreements (SLAs) becomes a crucial requisite. However, by their very nature, choreography requirements can be quite abstract and may on purpose avoid formalizing non-functional properties for every step of each individual service, nonetheless the overall QoS choreography will be affected by them. In this paper, we propose a monitor enhanced with the capability to detect potential deviations from a choreography-prescribed QoS level, based on the observed non-functional behaviour of the contributing services. Such an apprehensive monitor, as we call it, can thus contribute to predict SLA violations in due time for taking useful counter-measures, and not only detect them after they have occurred. We illustrate the feasibility of the approach on a use-case from the European Project CHOReOS.

A Requirements-Led Approach for Specifying QoS-Aware Service Choreographies: An Experience Report

“…In addition, the specification of such Q4BPMN properties of the choreography activities enables the definition of software modules monitoring the fulfillment of QoS constraints directly traced from the requirements [9].…”

Extending WS-Agreement to Support Automated Conformity Check on Transport and Logistics Service Agreements

“…Bartoline et al [2] proposed to monitor the QoS attributes of service choreographies to detect violations on the choreography SLA. The authors present a new approach to annotate the BPMN Choreography Diagram with functional and non-functional constraints that need to be fulfilled by a service entering the choreography.…”

“…Conformity checks in SLAs of computational services, like Cloud services and SBAs (Service Based Applications), have been extensively proposed. Two main groups of proposals can be found: One group aims at checking whether the execution of a service conforms with the SLOs on the SLA document [2]. The other group focuses on supporting consistent SLA definition, avoiding errors or inconsistent terms between documents [10,4].…”

Adequate monitoring of service compositions

“…The approach in [14] focuses on cumulative QoS metrics and estimates the allowed QoS values for the remainder of the execution of the orchestration, starting from those cumulated QoS values. In [4], a monitoring approach is proposed for choreographies that calculates statically implicit QoS constraints and issues a warning when these are violated at runtime: as for an adequate monitor warning, a violation of an implicit QoS constraint could likely, but not necessarily, lead to the failure of a contractual constraint.…”