Yuanqiang Huang

Virtual machine mapping policy based on load balancing in private cloud environment

The virtual machine allocation problem is the key to build a private cloud environment. This paper presents a virtual machine mapping policy based on multi-resource load balancing. It uses the resource consumption of the running virtual machine and the self-adaptive weighted approach, which resolves the load balancing conflicts of each independent resource caused by different demand for resources of cloud applications. Meanwhile, it uses probability approach to ease the problem of load crowding in the concurrent users scene. The experiments and comparative analysis show that this policy achieves the better effect than existing approach.

Interconnect EGEE and CNGRID e-Infrastructures through Interoperability between gLite and GOS Middlewares

Interoperability between the grid middlewares gLite, used in European grid infrastructure EGEE, and GOS, used in the Chinese grid infrastructure CNGRID infrastructure, is one of the main activities of the EUChinaGRID project. The EUChinaGRID project is an initiative, funded by the European Commission, to extend the European GRID infrastructure for e-Science to China. The first aim of EUChinaGRID is to facilitate scientific data transfer and processing in a first sample of scientific communities that have already strong collaborations between Europe and China. The interoperability between gLite and GOS middlewares and, then, the interconnection between EGEE and CNGRID infrastructures, is fundamental to achieve this goal. This paper presents the interoperability solution adopted by the EUChinaGRID project, including job submission, data transfer, and information services. The implementation of a gateway for achieving interoperability is discussed and preliminary results are presented.

CDebugger: A scalable parallel debugger with dynamic communication topology configuration

With cloud computing to take off, the application range of cloud computing has been expanded significantly. Not limited to SOA applications, some high-performance parallel applications have been resident on cloud platform. Users can take advantages of large volume of resources and perform compute and data intensive parallel applications over clouds according to their applications demand without deploying actual physical infrastructure. In this context, tracing and debugging parallel applications become a pressing requirement in clouds. At present, there are still no widely adopted software tools to enable a robust parallel debugging environment for cloud computing. Considering the fact that the scale of parallel applications can be very large and a mass number of compute nodes are needed, we design a new parallel debugger named CDebugger with scalable communication and startup mechanism using the tree-based network in this paper. At the same time, a dynamic communication topology configuration algorithm is proposed to maximize debugging performance and reduce response time. The evaluation results reveal our parallel debugger with good scalability regarding to various application scales.

EOMT: A Master-Slave Task Scheduling Strategy for Grid Environment

Task scheduling has been a key issue to improve parallel execution in distributed systems. Master-slave task scheduling, as a technique of mapping and scheduling loads to heterogeneous platforms, has aroused interests of many researchers. Although minimizing the master-slave applications makespan (the overall completion time) in general case is a NP-complete problem, it is still meaningful in some special fields. In this paper, we aim at improving the performance of the master-slave pattern applications in the case with a large number of equal-sized and independent tasks and propose a new strategy EOMT (equilibrium overhead with multi-cycle tasking) for task scheduling in the grid environment. The EOMT strategy is designed for the grid environment with heterogeneous resources. The main concept of EOMT is to make the workload assigned to each slave node as even as possible to reduce applications makespan. A detailed analysis for master-slave task scheduling is given in this paper. Experiment results show that our strategy outperforms other traditional task scheduling strategies in different computation and network resource combinations in the grid environment.

Providing High Availability for Distributed Stream Processing Application with Replica Placement

With the popularity of cloud computing, high volume data needs to be processed in real-time. Therefore, many distributed stream processing systems have risen to deal with this requirement. One kind of distributed stream processing applications contains several PEs which are connected together to implement the application logic. As data is in the form of streams and it needs to be processed in real-time, high availability is important for the application. At the same time, the application requires a high performance, including a low resource cost. According to these features of the application, we propose a new replica placement method to guarantee the applications availability while controlling the resource cost under some constraint and trying to get the maximal resource usage. The result of our experiment shows that our placement method can acquire high availability and low resource cost comparing with other placement strategies.

Cesar-FD: An Effective Stateful Fault Detection Mechanism in Drug Discovery Grid

Workflow management system is widely accepted and used in the wide area network environment, especially in the e-Science application scenarios, to coordinate the operation of different functional components and to provide more powerful functions. The error-prone nature of the wide area network environment makes the fault-tolerance requirements of workflow management become more and more urgent. In this paper, we propose Cesar-FD, a stateful fault detection mechanism, which builds up states related to the runtime and external environments of workflow management system by aggregating multiple messages and provides more accurate notifications asynchronously. We demonstrate the use of this mechanism in the Drug Discovery Grid environment by two use cases. We also show that it can be used to detect faulty situations more accurately.

Reducing Communication Overhead in Threshold Monitoring with Arithmetic Aggregation

With increasing adoption of distributed systems, monitoring has become an important research topic in recent years. Monitoring itself introduces overhead to the system caused by communication for collecting measurement data between monitoring nodes and measuring nodes. Reducing communication frequency of monitoring is very significant, especially for threshold monitoring which only cares about whether some metric crosses certain threshold or not. Currently threshold monitoring only considers simple aggregation values such as sum or average of values of measurement data. However, in this paper, we take a further exploration to arithmetic aggregation which is more complicated arithmetic result of measurement data, not just the sum or average of them. We present an approach to solve the communication overhead problem of arithmetic aggregation in threshold monitoring, where corresponding algorithms are designed. In our approach, the global threshold can be split into many local thresholds which can be set remotely on distributed local monitoring nodes. Communication will only take place when the locally observed numerical value of measurement exceeds corresponding local thresholds. We argue that communications will be reduced significantly based on the assumption that numerical values of monitored measurements would not oscillate widely or rapidly all the time. By conducting experiments based on data from real scenes, we can demonstrate that our solutions outperform the traditional approaches.

Data Currency in Replicated Distributed Storage System

Application-level storage aggregation provides a massive storage capacity with high scalability and low cost. However, these systems usually only support their special sites, which ignores the legacy storage systems. So we developed a distributed storage system to aggregate these popular storages and provide a uniform access and management interface for these sites. To ensure high data availability, our distributed storage system utilizes a sophisticated way known as data replication. In this paper, we present the data currency scenario employed in our distributed storage system, which can be also used in other replicated distributed storage systems. We propose a Replica Access Service (RAS) to deal with data availability and efficient retrieval of current replicas based on version controlling, which can balance the data accessibility and replica consistency. We validate our solutions performance and scalability through simulation up to 10,000 distributed sites. The simulation results show that our algorithm used in RAS achieves major performance gains, in terms of response time, compared with a baseline algorithm.

A Two-Phase Log-Based Fault Recovery Mechanism in Master/Worker Based Computing Environment

The Master/worker pattern is widely used to construct the cross-domain, large scale computing infrastructure. The applications supported by this kind of infrastructure usually features long-running, speculative execution etc. Fault recovery mechanism is significant to them especially in the wide area network environment, which consists of error prone components. Inter-node cooperation is urgent to make the recovery process more efficient. The traditional log-based rollback recovery mechanism which features independent recovery cannot fulfill the global cooperation requirement due to the waste of bandwidth and slow application data transfer which is caused by the exchange of a large amount of logs. In this paper, we propose a two-phase log-based recovery mechanism which is of merits such as space saving and global optimization and can be used as a complement of the current log-based rollback recovery approach in some specific situations. We have demonstrated the use of this mechanism in the Drug Discovery Grid environment, which is supported by China National Grid. Experiment results have proved efficiency of this mechanism.

Design of a Sequential Tentative Hold Protocol for Efficient Coordination of Web Services Transaction

Web services technology enables integration of geographically distributed services and provides efficient and flexible coordination models for integration. The tentative hold protocol (THP) allows Web service transactions to reserve resources by applying tentative holds on them, which provides increased flexibility. However, the simple policy of THP is of shortage in maximizing resource utilization in transaction coordination. In this paper, we propose a sequential tentative hold protocol (S-THP) to overcome this shortage. It records the sequence of resource accessing when hold requests are submitted, and locks only indispensable resources instead of all resources during the transaction. By sequentially locking and accessing the resources, S-THP is able to achieve better resource utilization and efficiency. A detailed comparison is carried out to demonstrate the advantage of the proposed protocol. Finally, it can be concluded from the simulations that S-THP provides coordination with better efficiency and flexibility.