The Rejuvenation Queue Construction and Strategy Research for Related Web Services

Android users are occasionally troubled by the slow UI responses and sudden application/OS crashes. These problems are mainly caused by software aging, a phenomenon of progressive degradation of performance and dependability typically observed in long-running software systems. A countermeasure to software aging is software rejuvenation, i.e., manual or scheduled restart at different levels, such as application, OS, and device. Various software aging and rejuvenation models have been proposed for different software systems. However, these traditional models cannot be applied in the context of mobile devices, as they seldom consider the patterns of usage behavior and user experience specific to mobile phones. We address this problem based on the observations that the usage time of mobile phones is typically fragmented in daily life, with frequent and periodical switches between active and sleep modes, and that the user experience on fluent operation in the active mode is a key concern for mobile users. These insights are exploited to model the usage behavior and aging process by individual Stochastic Petri-Nets, and then to compose them into a Continuous Time Markov Chain (CTMC). Furthermore, we propose proactive rejuvenation strategies based on such CTMCs to achieve the best user experience and the least user interference, such as restarting the device when it is in sleep mode and before it enters an aged state. To consider user experience - a key concern of mobile users which is still less prominent in traditional dependability measurements – we propose new related metrics: for fluency (i.e., the probability that a phone offers a fast UI response to the users), and for the degree of overall user experience. We demonstrate the effectiveness and advantages of the proposed models and metrics via simulations as well as an empirical study.

Since Component-Based Software Development technology has been widely used, traditional software rejuvenation strategy seems too rough on solving Component-Software aging, the whole system will be regenerated even only a few components aging, which leads to high cost of software rejuvenation and reduces the stability of the system. Therefore, we propose a component-based software rejuvenation strategy and we make components be the objects of rejuvenation. The aging components will be rejuvenated when software ages. In this paper, the process of judging software aging and software rejuvenation are described, then we propose the methods of judging software aging, determining the sequence that the aging components to be rejuvenated and rejuvenating components. Finally, an experiment is done to certify the efficiency of the strategy.

Continuously running software systems suffer from performance degradation due to aging phenomena and resource exhaustion that are mainly due to error conditions accumulation or due to exhaustion of system resources such as the physical memory. To counteract such phenomena, a periodic preemptive rollback to prevent software failures in the future, called software rejuvenation, can be applied. During the past 20 years, software rejuvenation has been extensively studied with the aim to design rejuvenation policies that optimize system availability, reliability, and performance, mainly in terms of operational cost. In this paper, we propose to model software systems’ overall performance capacity by assigning a performance capacity level at each of the possible states that it can be in, using a continuous time Markov process. A performance capacity indicator for all possible rejuvenation models incorporating partial, full, or both rejuvenation actions is defined and evaluated in the transient, and the steady state phase and the impact of various rejuvenation policies on it are further examined. Our aim is to distinguish the optimal, in terms of performance, rejuvenation strategy consisting of the type of rejuvenation to be implemented and the rejuvenation interval as well. Multi-objective optimization problems are additionally formulated for deriving the rejuvenation policies that optimize the system’s overall performance capacity with respect to availability and operational cost constraints. Numerical examples, in which through comparisons among the rejuvenation models and policies we can distinguish the optimal rejuvenation strategy to be followed, are also presented.

Several studies have been conducted in order to understand the 'software aging' phenomenon. This paper presents the results of an experimental research work, which evaluated the software aging effects on a web server as well as the performance of a rejuvenation agent. Its main contribution is the identification and analytical validation of the factors that contribute for the web server aging. We adopted the design of experiment technique (DOE) to characterize the aging phenomenon. The results showed evidence that the 'page type' and 'page size' factors were responsible for over 99% of memory size variation in httpd processes. A 'rejuvenation agent' was implemented and integrated into the server environment to mitigate the aging effects. As a result, the size of the httpd processes could be kept under control and a higher availability and performance of the web server could be provided, as compared to the scenario without rejuvenation.

As businesses increasingly rely on IT for their mission-critical operations, continuous availability is a universal concern. Nowadays, virtualized platform has become the popular option to deploy complex enough services. Deployed services are expected to be always, available, but these long running services are especially sensitive to suffer from software aging phenomenon. Software aging of virtual machine monitors (VMMs) is becoming critical because performance degradation or crash failure of a VMM affects all virtual machines (VMs) on it. To counteract this issue, we deploy software rejuvenation methodology. To eliminate the service outage during software rejuvenation process, we combine the rejuvenation with live migration technology. Live VM migration enables a running VM on a host serer to move onto the other host server with very small interruption of the execution. Live VM migration depends on VMs placement and efficient resource available is required. The idea behind our paper is two-fold. First, we present the optimization of the resource usage as accepting as many services as in virtualized environment which support of VM live migration. Second, to demonstrate how much it can improve system availability, the stochastic Petri nets model a virtualized server system in case of using time based software rejuvenation for VMM is presented. Finally, we perform the numerical analysis to evaluate the model.

Neural network based approach for time to crash prediction to cope with software aging

There are many studies on composing Web services by creating service chains to get valid Web service compositions, but in practical application, some Web services can work in parallel This paper proposes a new composing Web service method based on chaining Web service units, it adds domain ontology labels of input and output to the description of a Web service, and uses the output similarity measure to find all related Web service units for a user request automatically. It builds Web service unit chains by reverse depth-first searching over the semantic relation graph of Web services, those Web service unit chains whose output similarity is bigger than predefined threshold and the inputs are only provided by the user request are candidate Web service compositions.

The National Nuclear Data Center (NNDC) collects, evaluates, and disseminates nuclear physics data for basic research and applied nuclear technologies. In 2004, the NNDC migrated all databases into modern relational database software, installed new generation of Linux servers and developed new Java‐based Web service. This nuclear database development means much faster, more flexible and more convenient service to all users in the United States. These nuclear reaction and structure database developments as well as related Web services are briefly described.

Within this thesis, a workflow for an efficient and practical handling of spatio-temporal data is presented. This workflow consists of three layered parts. The first part is the efficient management of spatio-temporal data. The second part focuses on the development of Web services for the dissemination of spatio-temporal data. The third part is a generic mobile GIS for professional users as a typical application for the spatio-temporal data management model and the related Web services.

Web services (WS) are manually mediated with phases such as discovery, selection, composition and invocation. WS uses syntactic description available in WSDL, which are human understandable. WS discovery and selection is made through keyword matching that produces unrelated WS, which raises the problem of finding the exact WS. To overcome this issue the search can be made to produce related web services semantically for which WS should present as semantic web service (SWS). For this human understandable description should be changed into machine understandable description. In the current Web the availability of WS is more populated than SWS, which is described in OWL-S. There is a need for transformation from WS into SWS and this paper proposes a framework for conversion. The WSDL document has two types such as simple and complex. During this conversion simple type remains unchanged, because of attribute element names and complex type contains elements values that are converted into OWL-S. The conversion is implemented and evaluated. The result outperforms the similar conversion method.

Software aging often affects the performance of a software system and eventually causes it to fail. To highlight the aging problems in long running applications, we have conducted the study of software rejuvenation approach and virtualization technology in this paper. In order to reduce the downtime during rejuvenation interval, software rejuvenation and virtualization technology are combined in this paper. Virtualization allows multiple operating system instances to run concurrently on a single physical machine. In this paper, we map virtualization based software rejuvenation approach with Markov Chain process and get mathematical steady-state solutions of the chain. We model multiple physical servers which are used to host multiple virtual machines (VMs) using stochastic modeling and evaluate it through both numerical analysis and SHARPE (Symbolic Hierarchical Automated Reliability and Performance Evaluator) tool simulation. The numerical results show that software rejuvenation and virtualization can be used to prolong the availability of the services and reduce the downtime of the systems.

The phenomenon that the state of software degrades with time is known as software aging. The primary method to fight aging is software rejuvenation. This paper presents new ways of effective software rejuvenation using virtualization for addressing software aging. This new approach is meant to be the less disruptive as possible for the running service and to get a zero downtime in most of the cases. We construct the state transition models to describe the behaviors of virtualized and non- virtualized application server. We map through the rejuvenation actions to this transition model with stochastic process and express availability, downtime and downtime costs in terms of the parameters in our models. Our results show that virtualization and software rejuvenation can be used to prolong the availability of the services.

Software rejuvenation is a proactive maintenance technique that counteracts software aging by restarting a system, making selection of rejuvenation times critical to improve reliability without incurring excessive downtime costs. Various stochastic models of Software Aging and Rejuvenation (SAR) have been developed, mostly having an underlying stochastic process in the class of Continuous Time Markov Chains (CTMCs), Semi-Markov Processes (SMPs), and Markov Regenerative Processes (MRGPs) under the enabling restriction, requiring that at most one general (GEN), i.e., non-Exponential, timer be enabled in each state. We present a SAR model with an underlying MRGP under the bounded regeneration restriction, allowing for multiple GEN timers to be concurrently enabled in each state. This expressivity gain not only supports more accurate fitting of duration distributions from observed statistics, but also enables the definition of mixed rejuvenation strategies combining time-based and inspection-based policies, where the time to the next inspection or rejuvenation depends on the outcomes of diagnostic tests. Experimental results show that replacing GEN timers with Exponential timers with the same mean (to satisfy the enabling restriction) yields inaccurate rejuvenation policies, and that mixed rejuvenation outperforms time-based rejuvenation in maximizing reliability, though at the cost of an acceptable decrease in availability.

The Internet is going through several major changes. It has become a vehicle of Web services rather than just a repository of information. Web Services are heterogeneously developed software components invoked over the network viz. the Internet, Web Services are the most famous implementation of service-oriented architectures (SOA) that has brought some challenging research issues related to security, Quality of service. Among all the challenges Web Service Composition turns out to be a major research, because it supports business-business enterprise application integration. Web services Maneuvering is the ability to create a new value-added service by integrating related Web services together. After Composing the Web Services, Only limited number verification techniques are available. The Correctness properties of the composed service will be effective if Muller Automata and Buchi Automata is used, because these automata are suitable both for deterministic and non-deterministic system. In this paper we have taken a survey report for verification of web service maneuvering, existing techniques are suitable only for deterministic system rather than non-deterministic system

The article describes a method for developing and modelling composite web-services. Web-service composition is used to derive new functionality from the interaction of existing web-services. Composite web-services are built in several stages: specifications (determining the type of service); development of the structure of the service based on the algebra of services; service composition modelling; selecting a service variant and generating a service. The main elements of the proposed approach are the algebra of services and web-services interaction models (basic and composite). The above approach formally presents the consideration of the main aspects in solving problems related to the construction of effective composite web-services and the selection of mathematical models, namely: description of web-services, determining the structure of web-services, taking into account the dynamics of information changes, taking into account the main uncertainties in building the structure web-services. Based on the approach, a method for constructing composite web-services has been developed. The method is based on an algebraic description of a web-service based on a specialized algebra of services. The method consists of the following steps: description of the task of developing a web-service; development of the structure of a web service based on the algebra of services; formal description of the structure and clarification of service operations; building models of functioning and interaction of service components; building simulation models of the composite service; defining the final structure of the composite service; web-service implementation. The main tool for describing composite services is the algebra of services, and the model building tool is colouredPetri nets implemented using СPN Tools. As an example of the application of the developed method, the construction of a pharmaceutical service is described, in which the modellingof the interaction of web-services based on Petri nets is used. The process of building a composite model of a web-service is considered. The process begins with building a pharmaceutical web-service model structure based on the service algebra. Based on the service algebra, operators were developed to implement composite services. The structure of the model is developed, which is presented in the form of a formal description. The process of building pharmaceutical service models in the СPN Tools environment is described in detail.