A Design of Cooperation Management System to Improve Reliability in Resource Sharing Computing Environment

Transcription

1 A Design of Cooperation Management System to Improve Reliability in Resource Sharing Computing Environment Ji Su Park, Kwang Sik Chung 1, Jin Gon Shon Dept. of Computer Science, Korea National Open University 169, Dongsung-dong, Jongro-ku, Seoul, Korea {bluejs77, kchung0825, Abstract. Resource sharing computing is a project that realizes high performance computing by utilizing the resources of peers that are connected to the Internet. Resource sharing computing provides a dynamic internet environment where peers can freely participate, but it raises questions on the reliability of operation processing. Existing resource sharing computing stores intermediate operation results in peers local disks. Thus, when faults happen on peers side, some peers need to wait for processing to reconnect with possibility of considerable delay. In case there is no reconnection, the intermediate operation results cannot be used. In addition, it is difficult to support cooperation due to incompatible modes of operation processing among heterogeneous systems. This thesis is to propose a cooperation management system, and define cooperation and cooperation groups necessary to improve the reliability in the resource sharing computing environment. Cooperation is a series of tasks that involve sorting tasks, processing tasks sequentially, and producing results. Cooperation group is a gathering of peers that can cooperate. Groups are created among different types of systems to enable cooperation among peers within the same group. Also, middle DB Server is proposed in a hierarchical structure to shorten delay and increase the reusability of intermediate operation results. As the intermediate operation results are stored in the middle DB Server in case there occurs a fault on peers side, waiting time for reconnection is reduced through cooperation, and the reusability of intermediate operation result is improved. In this paper, we propose a structure that can store intermediate operation result in middle DB Server to improve reliability in resource sharing computing environment, and suggest a design for cooperation group service, discovery service, and task management service of cooperation management system. Keywords: Resource Sharing Computing, Cooperation System. Reliability 1 Kwang Sik Chung is the corresponding author.

2 1 Introduction The advancement of the Internet has accelerated information sharing and distribution, and the existing client-server computing environment has turned into distributed multi-server environment. Furthermore, the source of information has extended from World Wide Web, Database and to personal computers. Due to such changes, users have begun to look for the other alternatives due to limitations in information search, the inaccuracy of search results, and various information search formats. As a result, P2P(Peer-to-Peer) computing where users themselves share computer resource and service via direct exchange has emerged[1,2]. Napster[3] and Soribada[4] that are examples of P2P systems are services to share MP3 music files. These services are gaining popularity in that they do not have files in the center server but just provide location information for personal computers to share files[1]. As P2P systems gained notice, P2P computing began to require more than just sharing files and thus distributed systems that utilize P2P technology were introduced. This is known as resource sharing computing. So far, studies on distributed systems focused on data processing by servers. However, SETI@HOME[5], through SETI@HOME project, has used the computing power of clients in order to gain huge computing power needed to analyze external radio signals, instead of composing distributed computing systems that required expensive servers. Similar movements are found in Korea. KOREA@HOME[6] project has started and some of its projects such as New Drug Candidate, Protein Folding analysis, Global Disk Management, etc. have been completed or are still under projects such as SETI@HOME, KOREA@HOME, etc. ensure that servers request clients to process data and the clients, in return, process data, which is opposite to how distributed systems process data. Since Internet-based distributed system allows individual peers to freely participate in operation or give up in the middle of operation, techniques to improve reliability in existing distributed computing cannot be directly applied to resource sharing computing [8]. In this paper, we attempt to design a cooperation management system that acts in the dynamic internet environment, in order to improve reliability in resource sharing computing environment. Cooperation enables one to carry on implementing halted operation after receiving the intermediate operation result from peers experiencing faults. Cooperation management system is composed of cooperation group service that creates and deletes groups among heterogeneous systems, of discovery service that analyzes peer information, searches for faulted peers, and explores peers available for cooperation from cooperation groups, and of task management service that distributes tasks to peers available for cooperation and requests intermediate operation results from faulted peers. Cooperation management system transmits or receives messages by XML for communication between these services.

3 2 Related Works 2.1 P2P System P2P systems can be classified by system structures and objects for sharing. System structures include Hybrid P2P structure that puts a server in the middle for efficient communication and information flow among peers, Pure P2P structure that is consisted of only peers without central server, and Hierarchical P2P structure that utilizes the advantages of Hybrid P2P structure and Pure P2P structure by putting a middle server between servers and peers. In terms of objects for sharing, information sharing systems equals to data-oriented system that shares files and data, or exchanges messages, while resource sharing systems equals to distributed systems that borrowed P2P technology in order to share computer resources such as CPU, memory etc. Resource sharing system divides a big task - that cannot be processed by a single system - into small bits for distributed processing, and finally transmits operation results to a central server for combination. SETI@HOME, KOREA@HOME etc. are a few examples project related to such systems. SETI@HOME is a project led by Berkeley University, and it analyzes data sent by Arecibo - world s largest radio signal astronomical telescope - to find intelligent extraterrestrial life. SETI@HOME project involves installing Screen Saver on personal computers, and analyzing data when the computers are not in use. KOREA@HOME is a project to analyze huge of information such as New Drug Candidate, Protein Folding analysis, Global Disk Management, etc. KOREA@HOME system is composed of platform server, agent, and client, and it was developed with focus on detailed functions. Functions of platform server include resource-volunteers PC management, implementation and management of task management DB, Homepage operation and management, etc. Agent has basic functions of P2P, interacts with platform server, and carries out tasks. Client creates and submits application tasks, and implements distributed application programs, etc. [15]. 2.2 Reliability Problem Reliability issues remain with both SETI@HOME and KOREA@HOME. Though solutions have been presented, the reliability issues are still to be tackled. To solve reliability problems, SETI@HOME uses techniques to register intermediate operation result every 10 minutes just in case peers fault. It stores intermediate operation result in peers local disks and runs operation continuously once peer fault is solved. But, if peer fault is not solved, one needs to wait indefinitely until the peer restarts. This causes operation delay. Since intermediate operation result is stored in local disks, the result cannot be reused unless the peer restarts. There are no operation reliability techniques proposed by KOREA@HOME. It uses a method that reassigns the same operation to a new peer by canceling the operation in case peer fault happens. Projects such as Avaki, FightAIDS@HOME, and

4 Distributed.net etc. also have the reliability issues like and 3 The Design for Cooperation Management System 3.1 Definition of Cooperation and Cooperation Group Cooperation is a method that enables several peers to process a task through collaboration, just like many labors collaborate in production process. Cooperation can be classified by either synchronous or asynchronous cooperation. Synchronous cooperation means producing result by dividing a task for simultaneous processing, while asynchronous cooperation means tasks that involve sorting tasks, data processing tasks sequentially, and producing results [17]. In this paper, cooperation means asynchronous cooperation. That is, in case a peer cannot carry on a task allocated by a server due to faults, another peer that can solve these faults can take over the intermediate operation results and continue the remaining operation. Cooperation group is a peer set that can cooperate. In the existing resource sharing computing, peers from heterogeneous systems take part in operation. However, it is difficult to support cooperation among heterogeneous systems due to incompatible modes of processing. Thus, the solution is to create groups among heterogeneous systems so that peers within the same groups can cooperate. 3.2 Environment and Structure of Cooperation Management System Cooperation management system has a hierarchical structure that is compose of a central server, a high-capacity central DB server, a middle server, a middle DB server, and task nodes of peers. The hierarchical structure of cooperation management system can reduce the bottleneck by balancing the load that is normally centralized on a server in a centralized structure of resource sharing computing, and it ensures the network scalability. However, it is difficult to select a middle server and a middle DB server in a hierarchical structure. In this paper, we assume an environment where a central server, a high-capacity central DB server, a middle server and a middle DB server are already established, and we do not consider selecting a middle server and a middle DB server. A central server assigns tasks to a middle server, manages the middle server status (such as fault information, CPU, memory etc.) and peer status information, and processes the results received from the middle servers. A middle server observes the peer status, receives tasks from a central server, and allocates them to peers. It also receives operation results from peers, and transmits the result value to the central server after processing them. When a peer fails, the peer s intermediate operation results are stored not in a local disk but in the middle DB server, making it unnecessary to wait for the peer to restart the operation. Peers available for cooperation pick up the intermediate results

5 from the middle DB server and continue the operation, which shortens the delay time and ensures the reusability of intermediate operation results. Peers process the tasks allocated from the middle server and transmit their status information and the processed results. Figure 1 shows the relationship between a central server and a middle server, between a middle server and a peer, cooperation relationship among peers, and the flow of message transmission and reception in a resource sharing computing structure. The hierarchical system structure, even if the central server fails, enables independent operation on intermediate results that are stored in the middle server. When the middle server stops and fails, another middle server can pick up the task and continue the operation as long as the intermediate results are stored in a high-capacity central DB server. Fig. 1. Structure of System 3.3 System Design Service Structure Cooperation management system is composed of a cooperation group service, a discovery service, and a task management service. Figure 2 shows the service structure of cooperation management system. Application is a program that is applied to areas such as new drug candidate search, protein variation analysis, etc. in resource sharing computing, and its core layer represents a protocol for operating a task.

6 Fig. 2. Service structure of cooperation management system Cooperation group service is a service that creates and deletes groups that have the same CPU, OS etc. among heterogeneous systems. Cooperation group service mainly creates a cooperation group for peers available for cooperation, adds peers to the group, and deletes faulted peers and groups. Discovery service is a service that searches for peer information to find failing peers, and discovers peers available for cooperation in a cooperation group. Discovery service mainly observes the peer status by constantly examining the peer information received from a cooperation group. And, according to the peer status, it sends the peer information to a task management service and a cooperation group service so that they can carry out tasks, respectively. Task management service mainly allocates tasks to new peers, assigns tasks to peers available for cooperation, and returns the intermediate operation results produced by faulted peers Message flow in Cooperation Management System Cooperation management system transmits and receives messages for communications among services, and the messages are expressed in XML. In this paper, we refer to the messages as the peer information. Figure 3 shows a message flow in cooperation management system. A peer, when registering, transmits its information to a cooperation group service, while the cooperation group transmits the peer group information to a discovery service. A discovery service grasps the peer status and transmits the information to a task management service and a cooperation group service. The peer information includes the information on the peer, the peer group, and the peer status. A peer, when registering in the cooperation group service, records its basic information such as CPU, OS, memory capacity, hard disk capacity, location, IP address, etc. The cooperation group service receives the peer information, creates a group, and adds the group information to the peer information with the group name. It also transmits the peer information to the discovery service. The discovery service receives the peer information and records the peer status

7 information after analyzing the status of new peers and the exiting peers in the cooperation group. The peer status information is transmitted to the task management service and the cooperation group service. Fig. 3. Message flow in cooperation management system Cooperation Management Service The main job of the cooperation group service is to create and delete cooperation groups. Fig. 4. Flowchart of creating a cooperation group Figure 4 shows the flow of creating a cooperation group. When registration is requested from a peer, the cooperation group service receives and analyzes the peer information. After analyzing the peer information, it checks whether there is any group that corresponds to the peer s system, and adds the peer to an existing group or to a new group. Once the peer is added to either a new group or an existing one, the

8 cooperation service group transmits the peer information to the discovery service after adding or modifying the group name information to the peer information. Figure 5 shows the flow of deleting a cooperation group. When receiving information from the discovery service about a peer that failed, it searches for the group the peer belongs to, and deletes the peer. If the deleted peer is the last one in the group, the service deletes the whole group. Fig. 5. Flowchart of deleting a cooperation group Table 1 shows the functions of a cooperation group service. Table 1. Function of a cooperation group service Method addpeerinfo() isexistgroup() gengroup() delgroup() addpeergroup() delpeergroup() searchgrouppeer() sendgroupmsg() Function add Peer information confirms exist group create group delete group add peer of group delete peer from group search peer from group transmit peer group information Discovery Service Discovery service receives, from the cooperation group service, the peer information to which group information is added, analyzes whether the peer is available for a task or for cooperation, and then transmits the peer information to the task management service. It continues broadcasting the peer information to see if there is any changes in the peer status, and when the status changes, it sends the peer information to the task management service and cooperation group service. It also analyzes the peer information periodically, and makes sure that the intermediate operation results are saved. Updated peer information is stored in the middle DB server and high-capacity DB server so that the latest information is kept. Figure 6 shows the flow of a discovery service.

9 Fig. 6. Flowchart of discovery service Table 2 shows the functions of a discovery service. Table 2. Method acceptpeerinfo() sendpeerinfo() querypeerinfo() ispeerstate() broaddiscovery() savepeerinfo() Function of a discovery service Function receive peer information transmit peer information request peer information analyze peer state continue search and request store peer information Task Management Service A task management service receives the peer status information from a discovery service. If the peer status indicates that the peer is available for a task, the discovery service requests the intermediate operation results and if there is any, it allocates the results to the peer. If there is nothing, it assigns a new task to the peer. If the peer is unable to carry out a task, it requests the interim result to be stored. But, the results cannot be stored if there is no connection due to a peer fault. So, it modifies the peer information, transmits the peer information to a discovery service and continues analyzing the peer status. Figure 7 shows the flow of a task management service.

10 Fig. 7. Flowchart of a task management service Table 3 shows the function of a task management service. Table 3. Function of a task management service Method assignwork() savework() sendpeerstateinfo() acceptpeerstateinfo() workcooperation() ispeerstate() Function allocate task store task transmit peer state information receive peer state information task cooperation analyze peer state 3.5 Comparison with other System The most well-known resource sharing computing systems are SETI@HOME in the U.S. and KOREA@HOME in Korea. As mentioned in 2.2, SETI@HOME and KOREA@HOME do not ensure operation reliability. Table 4 shows the comparison with other systems.

11 Table 4. Other system and comparison System trait Proposed system intermediate operation results Store a place intermediate operation results reusability Local disk No store Local disk middle DB server Limitation to peer self Restart Limitation to peer self Peer in cooperation group Support of cooperation No No No Yes Group service no Yes no structure server /client server /client server /client Support of cooperation group Hierarchical Since SETI@HOME and FightAIDS@HOME store the intermediate operation results in a local disk, the reuse of the operation results is limited to the peer itself. In addition, there is no cooperation between peers and message transmission and reception is conducted only between a server and a peer with no group supporting it. KOREA@HOME does not use the intermediate results, but restarts a task from the beginning when defects happen. But, it assigns several tasks within the same group so that other peers can pick up the task in case one peer fails and is unable to perform the task. The cooperation management system we proposed has a middle DB server so that the interim results are stored in the middle DB server. As it searches a peer from a cooperation group that is available for cooperation, it has higher reusability of the interim results than other systems, and reduces time spent on waiting for the defected peer to reconnect. Though its hierarchical structure makes it difficult to selection the middle server, network bottleneck is less seen compared with a server/client structure, and its scalability improves the reliability of resource sharing computing. 4 Conclusion In this paper, we have designed a cooperation management system that supports cooperation to improve the reliability in resource sharing computing environment. The system we have designed is composed of a cooperation group service, a discovery service, and a task management service. For communications between services, the cooperation management system transmits or receives messages which we defined as peer information expressed in XML. A cooperation group service is a service that creates and deletes groups among heterogeneous systems. A discovery service searches for peer information, discovers faulted peers, and look for peers available for cooperation from cooperation groups. A task management service assigns tasks to new peers, allocates tasks to peers available for cooperation, and returns the intermediate operation results of faulted peers. Due to incompatible modes of processing, cooperation is hard to attain among heterogeneous systems. In order to solve the issue, one can create a cooperation group and let peers within the same

12 group cooperate. A hierarchical structure and a middle DB server are suggested for the cooperation management system so that the interim operation results are stored to the middle DB server. Therefore, the reusability of intermediate operation results is improved and the delay time to wait for a peer to reconnect is reduced. It is suggested that further researches be conducted on how to select a middle server and how to search peers in a cooperation group. References 1. Andy Oram, "Peer-To-Peer", O'reilly, March D. Barkai, "An Introduction to Peer-to-Peer Computing", Intel Developer update magazine, February MaengSoon Baik, SungJin Choi, JunWon Yoon, HongSu Kim, ChongSun Hwang and HyunChang Yoo, Study on Improvement of Reliability for Distributed Computing in P2P Architecture, korea university, December, JaeGyu Lee, Force of keyword P2P of network new generation, Micro software, October, HeeKwan Koo, Design and Implementation of a Cooperation System Based on JXTA Platform in P2P File sharing Environment, kwangwoon university, thesis of M.S., GiChul Yoon, P2P model hierarchical for CPU public sharing, Proceedings of Korea Information Science Society Conference, K. Aberer, M. Punceva, M. Hauswirth, R. Schmidt, Improving Data Access in P2P Systems" IEEE Internet Computing, 6(1):58-67, January-February, Peer-to-Peer-Enabled Distributed Computering, Intel White Paper 14. "JXTA 2001", A. Paul, "DNS and BIND", O'Reilly, May JangHo Lee, A Software Architecture for Supporting Dynamic Cooperation Environment on the Internet, Journal of Korea Information Science Societ, vol. 2, no. 9, April, InGu Kang, A Structural Comparison of Cooperative Learning and Collaborative Learning, Journal of The Institute for Educational Research, Vol. 18, pp , HyunJin Jo, GuSu Kim, Young Ik Eom Design of Mobile Agent Based Cooperation Group Management Scheme for Dynamic Scalability, Proceedings of Korea Information Science Society Conference, May Ji Su Park, KwangSik Chung, JinGon Shon, A Design of Cooperation Management System for Improving Reliability in Resource Sharing on Base Internet, Proceedings of Korea Information Science Society Conference, Vol. 12, No. 2, pp , May 2005