Modeling and Performance Analysis of Dispatching Policies in Dispatcher-Based Web Server Cluster

There are two kinds of dispatching policies in content-aware web server cluster; segregation dispatching policy and mixture dispatching policy. Traditional scheduling algorithms all adopt mixture dispatching policy. They do not consider that dynamic requests＇ serving has the tendency to slow down static requests＇ serving, and that different requests have different resource demands, so they can not use duster＇s resource reasonably and effectively. This paper uses stochastic reward net （SRN） to model and analyze the two dispatching policies, and uses stochastic Petri net package （SPNP） to simulate the models. The simulation results and practical tests both show that segregation dispatching policy is better than mixture dispatching policy. The principle of segregation dispatching policy can guide us to design efficient scheduling algorithm.

DYNAMIC REQUEST DISPATCHING ALGORITHM FOR WEB SERVER CLUSTER

Distributed architectures support increased load on popular web sites by dispatching client requests transparently among multiple servers in a cluster. Packet Single-Rewriting technology and client address hashing algorithm in ONE-IP technology which can ensure application-session-keep have been analyzed, an improved request dispatching algorithm which is simple, effective and supports dynamic load balance has been proposed. In this algorithm, dispatcher evaluates which server node will process request by applying a hash function to the client IP address and comparing the result with its assigned identifier subset; it adjusts the size of the subset according to the performance and current load of each server, so as to utilize all servers' resource effectively. Simulation shows that the improved algorithm has better performance than the original one.

Reliability analysis of web server cluster systems based on proportional hazards model

An approach for web server cluster(WSC)reliability and degradation process analysis is proposed.The reliability process is modeled as a non-homogeneous Markov process(NHMH)composed of several non-homogeneous Poisson processes(NHPPs).The arrival rate of each NHPP corresponds to the system software failure rate which is expressed using Cox s proportional hazards model(PHM)in terms of the cumulative and instantaneous load of the software.The cumulative load refers to software cumulative execution time,and the instantaneous load denotes the rate that the users requests arrive at a server.The result of reliability analysis is a time-varying reliability and degradation process over the WSC lifetime.Finally,the evaluation experiment shows the effectiveness of the proposed approach.

A Web Server Cluster Solution Based on Twitter Storm

Single Web server would become a bottleneck that influences the availability and stability of Web service. Ten years ago, what had been proposed is to add Web servers for resolving this problem—Web Server Cluster. In recent years, the concept of cloud computing has got rapid development, and is becoming the future development trend of the IT industry. One of the characteristics of cloud computing is putting lots of computing resources together to provide users with a unified service. In this paper, we have proposed a new Cloud-Based Web Server Cluster Solution, based on the existing cloud computing model—Twitter Storm. It involves a new way to handle the web request from client and some other new features compared to the traditional Web Server Cluster. Combining with cloud computing, it would be the new trend of Web Server Cluster, and its feasibility is described in the paper too.

HWM： a hybrid workload migration mechanism of metadata server cluster in data center

In data center, applications of big data analytics pose a big challenge to massive storage systems. It is signif- icant to achieve high availability, high performance and high scalability for PB-scale or EB-scale storage systems. Meta- data server （MDS） cluster architecture is one of the most effective solutions to meet the requirements of applications in data center. Workload migration can achieve load balance and energy saving of duster systems. In this paper, a hybrid workload migration mechanism of MDS cluster is proposed and named as HWM. In HWM, workload of MDS is classi- fied into two categories： metadata service and state service, and they can be migrated rapidly from a source MDS to a target MDS in different ways. Firstly, in metadata service migration, all the dirty metadata of one sub file system is flushed to a shared storage pool by the source MDS, and then is loaded by the target MDS. Secondly, in state service mi- gration, all the states of that sub file system are migrated from source MDS to target MDS through network at file granular- ity, and then all of the related structures of these states are reconstructed in target MDS. Thirdly, in the process of work- load migration, instead of blocking client requests, the source MDS can decide which MDS will respond to each request according to the operation type and the migration stage. The proposed mechanism is implemented in the Blue Whale MDS cluster. The performance measurements show that the HWM mechanism is efficient to migrate the workload of a MDS cluster system and provides low-latency access to metadata and states.

An Efficient Load Balancing Approach for N-Hierarchical Web Server Cluster

Aiming at the load imbalance and poor scalability in single-tier Web server clusters, an efficient load balancing ap- proach is proposed for constructing an N-hierarchical （multi-tier） Web server cluster. In each layer, multiple load balancers are set to receive the user requests simultaneously, and different load bal- ancing algorithms are used to construct the high-scalable Web cluster system. At the same time, an improved load balancing al- gorithm is proposed, which can dynamically calculate weights according to the utilization of the server resources, and reasonably distribute the loads for each server according to the load status of the servers. The experimental results show that the proposed ap- proach can greatly decrease the load imbalance among the Web servers and reduce the response time of the entire Web cluster system.

A NEW DYNAMIC QUOTA-BASED ADMISSION CONTROL WITH SUB-NEGOTIATION FOR SOFTSWITCH-BASED CLUSTERED MEDIA SERVER

Based on the demand of the admission control of softswitch-based clustered media server, this pa- per proposed a new dynamic quota-based admission control algorithm that has a sub-negotiation process. The strongpoint of quota-based algorithm had been inherited in the algorithm and at the same time some new ideas had also been introduced into it. Simulations of the algorithm had been conducted on the Petri net model and the results show that this algorithm has excellent performance. In order to find the optimal resource quota set- ting in real time, the paper proposed two approximation analysis methods. It can be seen from analysis results that these two methods can be used to get sub-optimal quota values quickly and effectively. These two ap- proximation analysis methods will play important roles in implementation of the algorithm in system.

面向O-RAN的多级异构边缘资源分配与部署

为应对开放型无线接入网(Open Radio Access Network,O-RAN)中的数据传输成本过高及网络兼容不足等问题,研究了面向O-RAN的多级边缘服务资源分配与部署联合优化问题。首先,利用四层融合模型将多目标联合优化问题转化为异构边缘服务器数量选择及位置确定问题,并提出了一种负载约束和迭代优化的异构边缘服务器资源分配算法,解决了O-RAN网络中的异构资源分配与数据传输问题。然后,提出了一种能效驱动的异构节点部署优化算法,解决了多级异构资源最佳部署位置问题。最后,利用上海电信基站的真实数据集,验证了所提资源优化与部署算法的有效性,实验结果表明,所提算法较其它算法在部署成本上至少降低了22.5%,能效比值上至少提高了25.96%。

Block-based logical hierarchical cluster for distributed multimedia architecture on demand server

A structure of logical hierarchical cluster for the distributed multimedia on demand server is proposed. The architecture is mainly composed of the network topology and the resource management of all server nodes. Instead of the physical network hierarchy or the independent management hierarchy, the nodes are organized into a logically hieraxchical cluster according to the multimedia block they caches in the midderware layer. The process of a member joining/leaving or the structure adjustment cooperatively implemented by all members is concerned with decentralized maintenance of the logical cluster hierarchy. As the root of each logically hierarchical cluster is randomly mapped into the system, the logical structure of a multimedia block is dynamically expanded across some regions by the two replication policies in different load state respectively. The local load diversion is applied to fine-tune the load of nodes within a local region but belongs to different logical hierarchies. Guaranteed by the dynamic expansion of a logical structure and the load diversion of a local region, the users always select a closest idle node from the logical hierarchy under the condition of topology integration with resource management.

一种联合边缘服务器部署与服务放置的方法

边缘计算(EC)在靠近用户的网络边缘部署边缘服务器(ES),并将服务放置在ES上,从而可以满足用户的服务需求。独立研究ES部署和服务放置问题的成果已有很多,但两者存在高度耦合关系。考虑到EC系统的收益,有必要提供付费服务,使得EC系统处理用户服务请求时会获得相应收入。同时,EC系统处理用户服务请求时会产生时延和能耗成本,为了最大化EC系统的收益,在用户服务请求和服务价格不同的约束下,需要合适的服务放置方案来提高EC系统的收益。为此,在ES与基站之间的位置关系、ES部署和服务放置之间的耦合关系、服务副本数和服务价格等约束下,提出一种包括改进的k-means算法和多智能体强化学习算法的两步方法,使EC系统的收益最大化。首先,构建一个联合ES部署和服务放置模型,其中ES部署明确考虑了基站之间的位置关系,服务放置明确考虑了ES部署的位置,以及不同的服务请求和价格;然后,基于基站的位置关系和基站的服务请求负载,通过带约束的k-means算法,在不同约束条件下分别确定最佳的ES部署位置以及ES的协作域;最后,以最大化EC系统收益为目标,通过多智能体强化学习算法在ES上放置服务。实验结果表明,与对比方法相比,所提方法能够提高收益7%~23%。

可扩展并行Web Server集群技术

采用并行Ｗｅｂ Ｓｅｒｖｅｒ 集群技术实现高性能Ｗ ｅｂ Ｓｅｒｖｅｒ已经成为一种趋势． 该技术具有性能高、可扩展性好、可靠性高、成本低等优点． 本文介绍了我们研制的ＴＨＷｅｂ Ｃｌｕｓｔｅｒ的工作原理、组成结构和所采用的几种关键技术， 并与现有的技术和方法进行了比较． 本文还简要介绍了ＴＨＷｅｂ Ｃｌｕｓｔｅｒ 上开发的两个应用系统ＴＨＷｅｂ Ｄｉｇｇｅｒ（信息挖掘工具）和ＴＨＷ ｅｂ Ｓｅａｒｃｈ（搜索引擎）， 并以此说明Ｗ ｅｂ Ｓｅｒｖｅｒ

基于VMware Server的课程群实验平台的应用

先对传统数据库课程群实验中出现的问题进行阐述,接着介绍VMware Server体系结构,并提出了采用VMware Serv-er软件虚拟数据库课程群实验平台,最后给出该课程群实验平台的优势。实践证明,VMware Server对提升实验室管理与维护,提高服务器硬件使用效率,加强学生动手能力,有着非常积极的意义。

融合注意力机制的BiLSTM集群负载预测模型

服务器集群的负载预测有助于集群资源的优化配置,以提升集群资源的利用率。针对传统负载预测算法存在预测精度低的问题,本文在双向长短期记忆网络模型的基础上,提出一种融合注意力机制的负载预测模型(Att-BiLSTM)。该模型充分考虑到服务器CPU、内存、磁盘和网络等因素,利用双向长短期记忆网络前后传递信息的特点,并使用注意力机制关注负载时间序列中的重要信息,从而提高了预测精度。实验结果表明,相对于目前已经提出的负载预测模型ARIMA、CNN-LSTM和BiLSTM、Att-BiLSTM模型具有更好的预测性能。

基于OpenResty的一种自定义负载均衡算法

为了解决服务器集群中负载调度不均衡导致高并发情况下服务器响应时间过长以及实际并发数过低的问题,提出一种基于加权轮询算法以及层次分析法(Analystic Hierarchy Process,AHP)的自定义请求类型负载均衡算法。首先收集服务器集群的负载信息,其次定时与负载均衡服务器通信,同步集群节点的负载情况,最后根据请求类型使用对应的权重。实验结果表明,文章提出的算法能够有效应对高并发情形。

Performance Modeling and Approximate Analysis of Multiserver Multiqueue Systems with Poisson and Self-similar Arrivals

The problem of state space explosion is still ran outstanding challenge in Markovian performance analysis for multiserver multiqueue (MSMQ) systems. The system behavior of a MSMQ system is described using stochastic high-level Petri net (SHLPN) models, and an approximate performance analysis technique is proposed based on decomposition and refinement methods as well as iteration technique. A real MSMQ system, Web-server cluster, is investigated. The performance of an integrated scheme of request dispatching and scheduling is analyzed with both Poisson and self-similar request arrivals. The study shows that the approximate analysis technique significantly reduces the complexity of the model solution and is also efficient for accuracy of numerical results.

Web Server集群在校园网开放实验中应用研究

高校校园网上依托Web技术开设实验课程,达到开放实验目的。这使得Web服务器不仅要提供更多的应用服务,而且要对不同的请求做出快速响应。因此,加重了Web服务器负荷,导致其性能下降。为了解决这个问题,研究了采用WebServer集群技术的具体解决方案。

基于SQL Server的OLAM的研究及应用

OLAM(On-line Analytical Mining)是当前的热点技术,是融合了联机分析处理(OLAP)和数据挖掘(Data Mining)的一种新的数据挖掘技术。本文主要研究数据仓库中OLAP,On-line Analytical Processing和数据挖掘技术,这两个技术是商业智能中的核心技术和主要内容,在两者的基础上引入OLAM的概念,并阐述其基本原理和核心技术。基于微软的SQL Server平台,为一个商业案例建立数据仓库,利用Analysis Services服务,建立销售分析的多维数据集,利用OLAM的基本模型实现OLAP和聚类挖掘技术的结合,借助两者的各自优势,得到很好的客户聚类分析结果。

PVM用于Client/Server方式的网络编程

PVM是一个针对网络并行计算而发展起来的软件包,主要用于科学计算领域。但实际上,借助于PVM内部的共享信息库机制,可以很方便地进行网络Olient/Server模式的编程。本文在讨论了Socket网络编程界面的复杂性以后,详细探讨了如何用PVM来进行Client/Server模式的网络编程方法。

基于Zabbix集群系统的SQL Server数据库监控方式

随着气象信息技术发展,人们对数据的时效性、精细化以及可用性监控要求越来越高,而如何对承载数据的数据库系统进行监控显得尤为重要。笔者通过搭建Zabbix集群监控平台,提供几种对SQLServer数据库数据获取和监控的方法,在具体应用过程中取得了非常好的效果,使数据监控精准,数据服务更加精细。

基于SQL SERVER 2000的数据挖掘方案研究

微软SQLSERVER2000第一次包含了数据挖掘功能,微软的数据挖掘解决方案是基于一个称为OLEDBforDataMining规范的工业标准,它是由微软提出并且由众多数据挖掘公司支持的工业标准。这个规范展示了一个新的类似于SQL语言的数据挖掘语言,数据库开发者们可以利用它去建设数据挖掘应用。本文提出了如何利用SQLSERV-ER2000去建设数据挖掘应用的方案。