Clustering Algorithms for Scale-free Networks and Applications to Cloud Resource Management

In this paper we introduce algorithms for the construction of scale-free networks and for clustering around the nerve centers, nodes with a high connectivity in a scale-free networks. We argue that such overlay networks could support self-organization in a complex system like a cloud computing infrastructure and allow the implementation of optimal resource management policies.Comment: 14 pages, 8 Figurs, Journa

A survey on online monitoring approaches of computer-based systems

This report surveys forms of online data collection that are in current use (as well as being the subject of research to adapt them to changing technology and demands), and can be used as inputs to assessment of dependability and resilience, although they are not primarily meant for this use

Load Index Metrics for an Optimized Management of Web Services: A Systematic Evaluation

The lack of precision to predict service performance through load indices may lead to wrong decisions regarding the use of web services, compromising service performance and raising platform cost unnecessarily. This paper presents experimental studies to qualify the behaviour of load indices in the web service context. The experiments consider three services that generate controlled and significant server demands, four levels of workload for each service and six distinct execution scenarios. The evaluation considers three relevant perspectives: the capability for representing recent workloads, the capability for predicting near-future performance and finally stability. Eight different load indices were analysed, including the JMX Average Time index (proposed in this paper) specifically designed to address the limitations of the other indices. A systematic approach is applied to evaluate the different load indices, considering a multiple linear regression model based on the stepwise-AIC method. The results show that the load indices studied represent the workload to some extent; however, in contrast to expectations, most of them do not exhibit a coherent correlation with service performance and this can result in stability problems. The JMX Average Time index is an exception, showing a stable behaviour which is tightly-coupled to the service runtime for all executions. Load indices are used to predict the service runtime and therefore their inappropriate use can lead to decisions that will impact negatively on both service performance and execution cost

IDEA: An Infrastructure for Detection-based Adaptive Consistency Control in Replicated Services

In Internet-scale distributed systems, replication-based scheme has been widely deployed to increase the availability and efficiency of services. Hence, consistency maintenance among replicas becomes an important research issue because poor consistency results in poor QoS or even monetary loss. Recent research in this area focuses on enforcing a certain consistency level, instead of perfect consistency, to strike a balance between consistency guarantee and system’s scalability. In this paper, we argue that, besides balancing consistency and scalability, it is equally, if not more, important to achieve adaptability of consistency maintenance. I.e., the system adjusts its consistency level on the fly to suit applications’ ongoing need. This paper then presents the design, implementation, and evaluation of IDEA (an Infrastructure for DEtection-based Adaptive consistency control), which adaptively controls consistency in replicated services by utilizing an inconsistency detection framework that detects inconsistency among nodes in a timely manner. Besides, IDEA achieves high performance of inconsistency resolution in terms of resolution delay. Through two emulated distribution application on Planet-Lab, IDEA is evaluated from two aspects: its adaptive interface and its performance of inconsistency resolution. According the experimentation, IDEA achieves adaptability by adjusting the consistency level according to users’ preference on-demand. As for performance, IDEA achieves low inconsistency resolution delay and communication cost

Monitoring Scheduling for Home Gateways

International audienceIn simple and monolithic systems such as our current home gateways, monitoring is often overlooked: the home user can only reboot the gateway when there is a problem. In next-generation home gateways, more services will be available (pay-per-view TV, games. . . ) and different actors will provide them. When one service fails, it will be impossible to reboot the gateway without disturbing the other services. We propose a management framework that monitors remote gateways. The framework tests response times for various management activities on the gateway, and provides reference time/performance ratios. The values can be used to establish a management schedule that balances the rate at which queries can be performed with the resulting load that the query will induce locally on the gateway. This allows the manager to tune the ratio between the reactivity of monitoring and its intrusiveness on performance

Kajian Web Load Balancing Berbasis Round Robin dan IP Hash untuk Peningkatan Kinerja Layanan Server = Study Of Web Load Balancing Based On Round Robin And IP Hash For Improving Server Service Performance

Saat ini penggunaan akses terhadap layanan yang ada di Internet sangatlah penting. Salah satu dari layanan tersebut adalah layanan sistem informasi berupa web. Jika layanan tersebut tidak dapat diakses maka informasi yang dibutuhkan seseorang tidak akan didapatkan. Oleh karena itu server yang digunakan untuk aplikasi tersebut harus tetap nyala. Namun, dalam prakteknya sering terjadi kegagalan layanan tersebut karena server bermasalah, dalam proses perbaikan, maupun mendapatkan beban berlebih. Salah satu cara untuk mengatasinya adalah memasukkan aplikasi ke dalam beberapa server sekaligus, sehingga bila salah satu server bermasalah maka masih dapat dilayani oleh server lain. Digunakannya beberapa server juga membuat beban server menjadi ringan karena permintaan akses ke server dibagi ke beberapa server sekaligus. Hal tersebut biasanya disebut dengan penyeimbang beban web server. Di dalam penyeimbang beban web server juga terdapat metode-metode untuk menyeimbangkan beban server. Dalam penelitian ini dibuat manajemen sistem berupa penyeimbang beban web server untuk meningkatkan ketersediaan yang tinggi. Cara yang digunakan adalah dengan menggunakan beberapa server untuk melayani layanan web yang didapatkan dan membagi beban ke beberapa server tersebut. Dalam penelitian ini juga didapatkan metode penyeimbang beban web server terbaik pada kondisi tertentu. Seperti pada kondisi spesifikasi server upstream yang sama didapatkan metode round robin mempunyai kesuksesan terbaik yaitu sebesar 99.905 persen. Sedangkan pada kondisi spesifikasi server yang berbeda didapatkan prosentase kesuksesan terbaik ada pada metode IP Hash yaitu sebesar 99,95 persen. =========================================================================================================== Nowadays, the access to Internet services is very important. One of these internet services is web service information system. If the service is inaccessible, then the required information will not be obtained. Therefore, the server for that application must remain on. However, in practice there is often a failure of the service because the server is in trouble, in the process of repair, or get excessive load. One way to overcome this, is to make the web application run in multiple servers at once, if one of the server is get problem then it can still be running in another server. The use of several servers also makes the server load becomes light because access to the server is divided into several servers at once. This is usually called a web server load balancer. In the web server load balancer there are also methods to balance the server load. In this research is made management system based on web server load balancing to increase the high availability. The way it is used is to use multiple servers to serve web service request and share the load to those servers. In this study also found the best method to balance the web server load under certain conditions. As in the condition with same upstream server spesification, we obtained round robin method has the best success reply that is 99.905 percent. While in different server spesification condition, we obtained the best percentage of success is on the IP Hash metho that is 99.95 percent

Utility-based placement of dynamic Web applications with fairness goals

Abstract—We study the problem of dynamic resource allo-cation to clustered Web applications. We extend application server middleware with the ability to automatically decide the size of application clusters and their placement on physical machines. Unlike existing solutions, which focus on maximizing resource utilization and may unfairly treat some applications, the approach introduced in this paper considers the satisfaction of each application with a particular resource allocation and attempts to at least equally satisfy all applications. We model satisfaction using utility functions, mapping CPU resource al-location to the performance of an application relative to its objective. The demonstrated online placement technique aims at equalizing the utility value across all applications while also satisfying operational constraints, preventing the over-allocation of memory, and minimizing the number of placement changes. We have implemented our technique in a leading commercial middleware product. Using this real-life testbed and a simulation we demonstrate the benefit of the utility-driven technique as compared to other state-of-the-art techniques. I