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  • 1.
    Adam, Constantin
    KTH, Skolan för elektro- och systemteknik (EES).
    A Middleware for Self-Managing Large-Scale Systems2006Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    This thesis investigates designs that enable individual components of a distributed system to work together and coordinate their actions towards a common goal. While the basic motivation for our research is to develop engineering principles for large-scale autonomous systems, we address the problem in the context of resource management in server clusters that provide web services.

    To this end, we have developed, implemented and evaluated a decentralized design for resource management that follows four principles. First, in order to facilitate scalability, each node has only partial knowledge of the system. Second, each node can adapt and change its role at runtime. Third, each node runs a number of local control mechanisms independently and asynchronously from its peers. Fourth, each node dynamically adapts its local configuration in order to optimize a global utility function.

    The design includes three fundamental building blocks: overlay construction, request routing and application placement. Overlay construction organizes the cluster nodes into a single dynamic overlay. Request routing directs service requests towards nodes with available resources. Application placement partitions the cluster resources between applications, and dynamically adjusts the allocation in response to changes in external load, node failures, etc.

    We have evaluated the design using complexity analysis, simulation and prototype implementation. Using complexity analysis and simulation, we have shown that the system is scalable, operates efficiently in steady state, quickly adapts to external events and allows for effective service differentiation by a system administrator. A prototype has been built using accepted technologies (Java, Tomcat) and evaluated using standard benchmarks (TPC-W and RUBiS). The evaluation results show that the behavior of the prototype matches closely that of the simulated design for key metrics related to adaptability and robustness, therefore validating our design and proving its feasibility.

  • 2.
    Adam, Constantin
    KTH, Skolan för elektro- och systemteknik (EES).
    Scalable Self-Organizing Server Clusters with Quality of Service Objectives2005Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Advanced architectures for cluster-based services that have been recently proposed allow for service differentiation, server overload control and high utilization of resources. These systems, however, rely on centralized functions, which limit their ability to scale and to tolerate faults. In addition, they do not have built-in architectural support for automatic reconfiguration in case of failures or addition/removal of system components.

    Recent research in peer-to-peer systems and distributed management has demonstrated the potential benefits of decentralized over centralized designs: a decentralized design can reduce the configuration complexity of a system and increase its scalability and fault tolerance.

    This research focuses on introducing self-management capabilities into the design of cluster-based services. Its intended benefits are to make service platforms dynamically adapt to the needs of customers and to environment changes, while giving the service providers the capability to adjust operational policies at run-time.

    We have developed a decentralized design that efficiently allocates resources among multiple services inside a server cluster. The design combines the advantages of both centralized and decentralized architectures. It allows associating a set of QoS objectives with each service. In case of overload or failures, the quality of service degrades in a controllable manner. We have evaluated the performance of our design through extensive simulations. The results have been compared with performance characteristics of ideal systems.

  • 3.
    Adam, Constantin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Stadler, Rolf
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    A Middleware Design for Large-scale Clusters offering Multiple Services2006Ingår i: IEEE Transactions on Network and Service Management, ISSN 1932-4537, E-ISSN 1932-4537, Vol. 3, nr 1, s. 1-12Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a decentralized design that dynamically allocates resources to multiple services inside a global server cluster. The design supports QoS objectives (maximum response time and maximum loss rate) for each service. A system administrator can modify policies that assign relative importance to services and, in this way, control the resource allocation process. Distinctive features of our design are the use of an epidemic protocol to disseminate state and control information, as well as the decentralized evaluation of utility functions to control resource partitioning among services. Simulation results show that the system operates both effectively and efficiently; it meets the QoS objectives and dynamically adapts to load changes and to failures. In case of overload, the service quality degrades gracefully, controlled by the cluster policies.

  • 4.
    Adam, Constantin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Stadler, Rolf
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Adaptable Server Clusters with QoS Objectives2005Ingår i: Integrated Network Management IX - MANAGING NEW NETWORKED WORLDS / [ed] Clemm A, Festor O, Pras A, New York: IEEE , 2005, s. 149-163Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present a decentralized design for a server cluster that supports a single service with response time guarantees. Three distributed mechanisms represent the key elements of our design. Topology construction maintains a dynamic overlay of cluster nodes. Request routing directs service requests towards available servers. Membership control allocates/releases servers to/from the cluster, in response to changes in the external load. We advocate a decentralized approach, because it is scalable, fault-tolerant, and has a lower configuration complexity than a centralized solution. We demonstrate through simulations that our system operates efficiently by comparing it to an ideal centralized system. In addition, we show that our system rapidly adapts to changing load. We found that the interaction of the various mechanisms in the system leads to desirable global properties. More precisely, for a fixed connectivity c (i.e., the number of neighbors of a node in the overlay), the average experienced delay in the cluster is independent of the external load. In addition, increasing c increases the average delay but decreases the system size for a given load. Consequently, the cluster administrator can use c as a management parameter that permits control of the tradeoff between a small system size and a small experienced delay for the service.

  • 5.
    Adam, Constantin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Stadler, Rolf
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Externally Controllable, Self-Oganizing Server Clusters2005Ingår i: Designing a Scalable, Self-organizing Middleware for Server Clusters (NGNM05): in the scope of Networking 2005, 2005, s. 1-12Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 6.
    Adam, Constantin
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Stadler, Rolf
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Implementation and evaluation of a middleware for self-organizing decentralized web services2006Ingår i: Integrated Network Management IX: MANAGING NEW NETWORKED WORLDS, 2006, Vol. 3996, s. 1-14Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present the implementation of Chameleon, a peer-to-peer middleware for self-organizing web services, and we provide evaluation results from a test bed. The novel aspect of Chameleon is that key functions, including resource allocation, are decentralized, which facilitates scalability and robustness of the overall system. Chameleon is implemented in Java on the Tomcat web server environment. The implementation is non-intrusive in the sense that it does not require code modifications in Tomcat or in the underlying operating system. We evaluate the system by running the TPC-W benchmark. We show that the middleware dynamically and effectively reconfigures in response to changes in load patterns and server failures, while enforcing operating policies, namely, QoS objectives and service differentiation under overload.

  • 7.
    Adam, Constantin
    et al.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Stadler, Rolf
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Patterns for Routing and Self-Stabilization2004Ingår i: NOMS 2004: IEEE/IFIP NETWORK OPERATIONS AND MANAGMENT SYMPOSIUM - MANAGING NEXT GENERATION CONVERGENCE NETWORKS AND SERVICES, New York: IEEE , 2004, s. 61-74Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper contributes towards engineering self-stabilizing networks and Services. We propose the use of navigation patterns, which define how information for state updates is disseminated in the system, as fundamental building blocks for self-stabilizing systems. We present two navigation patterns for self-stabilization: the progaressive wave pattern and the stationary wave pattern. The progressive wave pattern defines the update dissemination in Internet routing systems running the DUAL and OSPF protocols. Similarly, the stationary wave pattern defines the interactions of peer nodes in structured-peer-to-peer systems, including Chord, Pastry, Tapestry, and CAN. It turns out that both patterns are related. They both disseminate information in form of waves, i.e, sets of messages that originate from single events. Patterns can be instrumented to obtain wave statistics, which enables monitoring the process of self-stabilization in a system. We focus on Internet routing and peer-to-peer systems in this work, since we believe that studying these (existing) systems can lead to engineering principles for self-stabilizing system in various application areas.

  • 8.
    Adam, Constantin
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Stadler, Rolf
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Service middleware for self-managing large-scale systems2007Ingår i: IEEE Transactions on Network and Service Management, ISSN 1932-4537, E-ISSN 1932-4537, Vol. 4, nr 3, s. 50-64Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Resource management poses particular challenges in large-scale systems, such as server clusters that simultaneously process requests from a large number of clients. A resource management scheme for such systems must scale both in the in the number of cluster nodes and the number of applications the cluster supports. Current solutions do not exhibit both of these properties at the same time. Many are centralized, which limits their scalability in terms of the number of nodes, or they are decentralized but rely on replicated directories, which also reduces their ability to scale. In this paper, we propose novel solutions to request routing and application placementtwo key mechanisms in a scalable resource management scheme. Our solution to request routing is based on selective update propagation, which ensures that the control load on a cluster node is independent of the system size. Application placement is approached in a decentralized manner, by using a distributed algorithm that maximizes resource utilization and allows for service differentiation under overload. The paper demonstrates how the above solutions can be integrated into an overall design for a peer-to-peer management middleware that exhibits properties of self-organization. Through complexity analysis and simulation, we show to which extent the system design is scalable. We have built a prototype using accepted technologies and have evaluated it using a standard benchmark. The testbed measurements show that the implementation, within the parameter range tested, operates efficiently, quickly adapts to a changing environment and allows for effective service differentiation by a system administrator.

  • 9.
    Adam, Constantin
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Stadler, Rolf
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Tang, Chunqiang
    Steinder, Malgorzata
    Spreitzer, Michael
    A service middleware that scales in system size and applications2007Ingår i: 2007 10TH IFIP/IEEE INTERNATIONAL SYMPOSIUM ON INTEGRATED NETWORK MANAGEMENT (IM 2009): VOLS 1 AND 2, NEW YORK: IEEE , 2007, s. 70-79Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present a peer-to-peer service management middleware that dynamically allocates system resources to a large set of applications. The system achieves scalability in number of nodes (1000s or more) through three decentralized mechanisms that run on different time scales. First, overlay construction interconnects all nodes in the system for exchanging control and state information. Second, request routing directs requests to nodes that offer the corresponding applications. Third, application placement controls the set of offered applications on each node, in order to achieve efficient operation and service differentiation. The design supports a large number of applications (100s or more) through selective propagation of configuration information needed for request routing. The control load on a node increases linearly with the number of applications in the system. Service differentiation is achieved through assigning a utility to each application which influences the application placement process. Simulation studies show that the system operates efficiently for different sizes, adapts fast to load changes and failures and effectively differentiates between different applications under overload.

  • 10.
    Johansson, Björn
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Adam, Constantin
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Stadler, Rolf
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Distributed resource allocation strategies for achieving quality of service in server clusters2006Ingår i: PROCEEDINGS OF THE 45TH IEEE CONFERENCE ON DECISION AND CONTROL, 2006, s. 1990-1995Konferensbidrag (Refereegranskat)
    Abstract [en]

    We investigate the resource allocation problem for large-scale server clusters with quality-of-service objectives, where key functions are decentralized. Specifically, the optimal service selection is posed as a discrete utility maximization problem that reflects management objectives and resource constraints. We develop an efficient centralized algorithm that solves this problem, and we propose three suboptimal schemes that operate with local information. The performance of the suboptimal schemes is evaluated in simulations, both under idealized conditions and in a full-scale system simulator.

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