發(fā)布時(shí)間：2018-06-19 02:03

  本文選題：服務(wù)計(jì)算 + 服務(wù)組合��； 參考：《北京交通大學(xué)》2016年博士論文

【摘要】：服務(wù)計(jì)算模式允許組合各種Web服務(wù),獲得新的增值服務(wù),實(shí)現(xiàn)了服務(wù)的重用。然而,由于服務(wù)數(shù)量的快速增加,Web服務(wù)的質(zhì)量(Quality of Service, QoS)良莠不齊,在執(zhí)行組合應(yīng)用的過程中,可能由于某服務(wù)是惡意服務(wù)(攜帶病毒)或其QoS與服務(wù)提供商承諾的不一致而導(dǎo)致組合服務(wù)調(diào)用失敗,也可能因環(huán)境變化而導(dǎo)致服務(wù)執(zhí)行時(shí)所在的計(jì)算節(jié)點(diǎn)失效,導(dǎo)致組合Web服務(wù)應(yīng)用不可用。因此,如何在海量的Web服務(wù)中,根據(jù)用戶的服務(wù)請求,構(gòu)建滿足用戶QoS需求的服務(wù)組合及容錯(cuò)方法仍然存在諸多挑戰(zhàn),本文針對上述背景下的若干關(guān)鍵問題進(jìn)行了深入的研究,取得的主要成果如下：(1)研究基于QoS信任下的Web服務(wù)組合問題,提出了基于兩個(gè)階段的神經(jīng)網(wǎng)絡(luò)及QoS等級劃分的服務(wù)組合方法,該方法利用兩個(gè)階段的神經(jīng)網(wǎng)絡(luò)篩選QoS受信任的Web服務(wù),在保證全局約束條件及所有的組合成員服務(wù)都具有很好的QoS信任的條件下,建立等級劃分的服務(wù)組合模型。然后提出了基于等級劃分的服務(wù)組合算法,最大化組合后服務(wù)的效用值,進(jìn)而獲得QoS可信的近似最優(yōu)解。實(shí)驗(yàn)結(jié)果表明,非信任服務(wù)的識(shí)別率達(dá)到90%,明顯高于傳統(tǒng)的CorrelationLens識(shí)別方法。此外,與整型規(guī)劃方法相比,本文提出的基于QoS等級劃分的組合算法的求解速度提升了近3倍,且獲得的解已非常接近全局最優(yōu)解,更好地確保組合服務(wù)的QoS指標(biāo)受信任和最優(yōu)。(2)研究大規(guī)模備選服務(wù)下的服務(wù)組合效率問題,提出了一種以快速抽樣為核心的Web服務(wù)組合方法FAQS,該方法采用統(tǒng)計(jì)學(xué)抽樣理論對Web服務(wù)QoS數(shù)據(jù)庫進(jìn)行研究,并對每個(gè)效用值區(qū)間內(nèi)的服務(wù)進(jìn)行抽樣；其次,在樣本空間內(nèi),對于所抽取的典型Web服務(wù)進(jìn)行建模,即以Web服務(wù)效用值與Web服務(wù)使用頻率值為目標(biāo)參數(shù)建立服務(wù)選擇模型；最后,根據(jù)得到的樣本空間內(nèi)的服務(wù)組合結(jié)果,在完全空間中進(jìn)一步優(yōu)化,選出滿足全局QoS約束且保證QoS效用值與服務(wù)頻率值最大化的服務(wù)。實(shí)驗(yàn)結(jié)果表明,該方法可以在大規(guī)模備選服務(wù)中準(zhǔn)確、高效地獲取服務(wù)組合結(jié)果。(3)研究組合方案中成員服務(wù)失效的問題,提出了組合方案的可靠性模型FTDes,即決策模型與優(yōu)化模型,旨在提升Web服務(wù)組合方案的可靠性。在決策模型構(gòu)建過程中,通過選取決策參數(shù)、構(gòu)建決策矩陣、設(shè)計(jì)決策模型,為失效的成員服務(wù)找到可替代的備選Web服務(wù)集合；在優(yōu)化過程中,把策略優(yōu)化選擇問題歸結(jié)為0-1整型規(guī)劃問題,提出頂點(diǎn)凸殼的過濾方法并結(jié)合標(biāo)準(zhǔn)的整型規(guī)劃器CPLEX得到優(yōu)化的服務(wù)替換方案。實(shí)驗(yàn)結(jié)果表明,與傳統(tǒng)的決策方法(包括層次分析法APH、證據(jù)推理法ER、喜好值排序技術(shù)的決策模型TOPSIS、線性分配法LAM)相比,本文提出的方法從決策準(zhǔn)確度、響應(yīng)時(shí)間方面要優(yōu)于傳統(tǒng)方法,與此同時(shí),本文分析了優(yōu)化選擇過程、TopK算法以及不同參數(shù)對于決策結(jié)果的影響,更好地保證組合服務(wù)的整體QoS指標(biāo)得到進(jìn)一步維持與優(yōu)化,有效地提高了Web組合方案的可靠性。(4)研究組合Web服務(wù)應(yīng)用的節(jié)點(diǎn)失效問題,提出了環(huán)形心跳檢測機(jī)制與輕量級恢復(fù)機(jī)制,旨在提升組合Web應(yīng)用的可靠性。在環(huán)形心跳檢測機(jī)制中,為了減輕中心節(jié)點(diǎn)的壓力,基于環(huán)形拓?fù)涞臋z測方式設(shè)計(jì)了分布式的心跳算法,并在每個(gè)節(jié)點(diǎn)上部署該心跳算法；針對傳統(tǒng)恢復(fù)方法時(shí)間開銷過大的問題,提出了輕量級的恢復(fù)機(jī)制,設(shè)計(jì)了考慮負(fù)載重新分配的恢復(fù)算法,同時(shí)考慮集群負(fù)載超出閾值時(shí),在環(huán)形結(jié)構(gòu)中增加新的節(jié)點(diǎn),從而降低集群負(fù)載,避免因負(fù)載過高而引起節(jié)點(diǎn)失效。實(shí)驗(yàn)結(jié)果表明,與傳統(tǒng)的日志分析檢測方法和系統(tǒng)級恢復(fù)方法相比,該檢測與恢復(fù)機(jī)制的開銷小、延遲少,避免了服務(wù)器節(jié)點(diǎn)失效導(dǎo)致組合Web服務(wù)應(yīng)用的整體QoS降低,提升了組合Web服務(wù)應(yīng)用的可靠性。綜上所述,本文對QoS度量的Web服務(wù)組合中的組合方法與容錯(cuò)方法展開深入研究,提出了等級劃分與快速抽樣的Web服務(wù)組合方法,以及環(huán)形心跳檢測機(jī)制與輕量級恢復(fù)機(jī)制,提升了Web服務(wù)組合的效率、準(zhǔn)確性與可靠性,具有一定的理論意義及廣泛的應(yīng)用價(jià)值。
[Abstract]:The service computing mode allows the combination of various Web services to obtain new value-added services and achieve service reuse. However, because of the rapid increase in the number of services, the quality of the Web service (Quality of Service, QoS) is intermingled, and in the process of implementing the combined application, it may be from a service is a malicious service (carrying a virus) or its QoS and service. The inconsistent commitment of the supplier leads to the failure of the combined service call. It may also cause the failure of the computing node in the service execution due to the environment change, which leads to the unavailability of the combined Web service application. Therefore, how to build a service composition and fault tolerance method to meet the user's QoS requirements in the mass Web service There are many challenges in this paper. The main achievements of this paper are as follows: (1) research on Web service composition based on QoS trust, and propose a method of service combination based on two stages of neural network and QoS hierarchy. This method uses two stages of neural network. The collaterals selected QoS trusted Web services to establish a hierarchical service portfolio model under the condition of guaranteeing global constraints and all the combined member services having good QoS trust. Then, a hierarchy based service composition algorithm was proposed to maximize the utility value of the combined service, and then to obtain the approximate optimal QoS reliability. The experimental results show that the recognition rate of the untrusted service reaches 90%, which is obviously higher than the traditional CorrelationLens recognition method. In addition, compared with the integer programming method, the solution speed of the combined algorithm based on the QoS hierarchy is up to nearly 3 times, and the obtained solution is very close to the global optimal solution, and it is better to ensure the combination clothing. The QoS index of service is trusted and optimal. (2) to study the efficiency of service composition under large-scale alternative service, a Web service combination method, FAQS, which is based on rapid sampling, is proposed. The method uses statistical sampling theory to study Web service QoS database and sample each service value interval. Secondly, In the sample space, the typical Web service is modeled, that is, the service selection model is set up with the Web service utility value and the Web service use frequency value as the target parameter. Finally, according to the result of the service composition in the sample space, it is further optimized in the complete space, and the global QoS constraint is satisfied and the QoS utility value is guaranteed. The experimental results show that the method can accurately and efficiently obtain the service composition results in the large-scale alternative service. (3) the problem of member service failure in the combination scheme is studied, and the reliability model FTDes of the combination scheme, that is, the decision model and the optimization model, is designed to improve the Web service composition party. In the process of decision-making model construction, by selecting decision parameters, building decision matrix, designing decision model, finding alternative alternative Web service sets for invalid member service. In the process of optimization, the problem of strategy optimization is reduced to 0-1 integer rule problem, and the filtering method of vertex convex hull is proposed and combined with the standard. The experimental results show that the method proposed in this paper is superior to the traditional method in terms of decision accuracy and response time compared with traditional decision making methods (including analytic hierarchy process APH, evidence reasoning method ER, decision model TOPSIS of preference value sorting technique and linear allocation method LAM), and the experimental results show that the method proposed in this paper is superior to the traditional method in terms of decision accuracy and response time. At the same time, this paper analyzes the optimization selection process, the TopK algorithm and the influence of different parameters on the decision results, to better ensure the overall QoS index of the combination service to be further maintained and optimized, and effectively improve the reliability of the Web combination scheme. (4) study the node failure of the combination of Web service applications, and propose a ring heartbeat detection. The measurement mechanism and lightweight recovery mechanism are designed to improve the reliability of the combined Web application. In order to reduce the pressure of the central node in the ring heartbeat detection mechanism, a distributed heartbeat algorithm is designed based on the loop topology detection method, and the heartbeat method is deployed at the top of each node, and the time overhead of the traditional recovery method is too large. A lightweight recovery mechanism is proposed, and a recovery algorithm considering load redistribution is designed. At the same time, new nodes are added to the ring structure when the cluster load exceeds the threshold, thus reducing the load of the cluster and avoiding the node failure due to the high load. The experimental results show that the traditional log analysis method and system level are shown. Compared with the recovery method, the detection and recovery mechanism has less overhead and less delay, which avoids the failure of the server nodes to reduce the overall QoS of the combined Web service application and improves the reliability of the combined Web service application. The Web service combination method of level division and rapid sampling, as well as the ring heartbeat detection mechanism and lightweight recovery mechanism, improve the efficiency, accuracy and reliability of the Web service composition, and have a certain theoretical significance and wide application value.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：TP393.09

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