SLA Detective Control Model for Workflow
Composition of Cloud Services
Yong Sun
1
, Wenan Tan
1 2*
, Ler Li
1
, Guangzhen Lu
1
, Anqiong Tang
2
1
School of Computer Science and Technology
Nanjing University of Aeronautics and Astronautics
Nanjing 210016, China
E-mail: syong@nuaa.edu.cn
2
School of Computer and Infomation
Shanghai Second Polytechnic University
Shanghai 210209, China
E-mail: wenantan@it.sspu.cn
Abstract—The disqualification of third-party cloud services has
caused great threat to large-scale Enterprise Systems (ESs).
Service Level Agreements (SLA) management is used to enhance
Quality of Service (QoS) in an effective way. Conventional service
exception handling is triggered to deal with functional failure.
However, in some critical business scenario, service failures and
performance violations need to be proactively prevented instead
of recovery triggered by the occurrence of those failures. In this
paper, a proactive detective control model is proposed to prevent
workflow SLA violation supported by the utilization of SLA
utility functions and control charts. Emulation case study
illustrates the proposed model, and simulation results show that
workflow SLA management can effectively avoid cloud services
composition failures.
Keywords- Service Level Agreements; Performance Monitor;
Quality of Service; Workflow Scheduling; Cloud Computing
I. INTRODUCTION
Cross-Organizational Enterprise Systems (ESs) are challenged
by their increasing complexity and dynamicity of large-scale
distributed applications to meet the business goals of
manufacturing and service industry [1]. For example, ESs are
extended and integrated with existing third-party infrastructure
for business goals. Cloud Computing and Service-Oriented
architecture (SOA) are promising techniques to aggregate and
share a large pool of services for supporting cooperative work
[2-6]. They are defined as a new style of adaptive
collaborative environment in which dynamically scalable and
virtualized resources are provided as a service over the
Internet [7-8]. Services composition has become a significant
and complex solution for ESs. ESs combined with cloud
computing and SOA enable the composition of cloud services
across organizational boundaries to meet enterprises
challenges. Such systems promote an effective way for
enterprises to adapt to ever changing workflow environments.
In the combining cloud computing and SOA environment,
enterprises rely heavily on workflow composition of multiple
cloud services supplied by the third-party services providers.
The existing cloud services are owned and operated by
geographically distributed heterogeneous organizations and
enterprises [12]. The inherent uncertainty and unreliability of
large-scale distributed systems have caused great threat to the
enterprise applications [13-15]. For example, cloud services
sometimes may be offline unpredictably due to malicious
behavior, changing environments, performance fluctuations
and hardware failures [16]. Although cloud computing allows
enterprises to achieve their business goals faster with less
manageability, performance fluctuations do occur because of
unpredictable quality issue of cloud service.
Organizations may have cooperative agreements to share
better quality services for their collaborators in cross-
organizational workflow composition systems. Service level
agreements, denoted as SLA, define a target of quality level
that the supplier should adhere to. SLA is usually adopted to
ensure the quality of service (QoS) which is a typical non-
functional performance of managing self-adaptive and
dependable cloud services [17]. Integrated third-party services
into workflow may be a challenge because the performance or
quality of the external service doesn’t always meet the quality
requirement. A disqualification service may cause
performance violation or failure of services workflow.
Therefore, SLA based QoS management need to be carried out
for the quality of services.
SLA management provides detailed performance statics to
support health assessment of cross-organizational ESs and
guarantee the consistency of workflow composition. It
involves gathering resource information, analyzing
performance of services workflow composition and managing
workflow life-cycle. Recently, autonomic computing has been
adopted in SLA management to anticipate workflow
performance and deal with problems with minimal
intervention. A good automated metrics serve to enhance and
complement SLA management of service composition due to
changes in functions and qualities of workflow, or failures in
service in workflow compositions [18-19]. An adaptable
service workflow system can maintain and optimize its
performance by monitoring and analyzing the significant
variables in SLA such as response time, throughput and
utilization.
SLA monitoring of service workflow composition can
improve the understanding the dynamically changing status of
workflow execution. Once service failing to delivery is
detected, conventional service exception handling such as
recovery is triggered to deal with functional failure. However,
in some critical businesses scenarios, service failures and
Proceedin
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