Research Of Fault Tolerance And Stream Sharing Strategies In Clustered Video Server

With the advancement ofcomputer process capability, development of high-speed network technology and appearance of new multimedia device and compress technique, interactive video services, such as video-on-demand(VOD), get more and more notice.With the business of VOD fastly expanded,high performance of VOD system gets more and more important.As network bandwidth is not yet a bottle-neck,performance of VOD system mainly depends on performance of VOD server.According to the three level architecture of WanLan clustered video server,this paper proposes a three level fault tolerant scheme to get the high availability. A fault tolerant approach of cluster load-balance system named "mon+heartbeat+fake" is adopted,mon runs on front-end and backup node,monitor all the service nodes and service processes run on them;heartbeat processes exchange heartbeat info between front-end and backup node;fake process runs on backup node,while front-end crashed,fake process make backup node to automaticly take over the IP address of front-end.Fault-tolerance of data node is based on the checkpoint info packets sent form data-server to control-server during the playing time,the fault of data-server is detected and handled by it's control-server,this process is transparent to clients.Machine level fault-tolerance of control-server implements by the cluster load-balance system,RTSP-task level fault-tolerance implements by the cooperation of data-server,client and schedule system of front-end. This paper proposes a novel stream sharing strategy named TPG-Patching,which based on the stream creating algorithm of Grace-Patching,the regular stream management algorithm of PeriodPatch,and the stream schedule strategy of Patching First. The stream creating altorithm of Grace-Patching implements streams merging of requests of popular movies,which arrive within a short interval.The regular stream management algorithm of PeriodPatch makes the new regular streams more regular.Due to the fact that patching streams meet mostly client requests, schedule strategy of Patching First adopts MFPQ stream schedule algorithm to schedule patching streams first,that improves the stream schedule performance of WanLan system.In addtive ,this paper expend the normal RTSP protocol,and proposes new Multicast-RTSP protocol to support stream transport approaches of unicst,multicast and mixed mode. Based on the Linux platform with C/C++ language,the software implimentation of WanLan server fault tolerance and TPG-Patching stream sharing strategy are presented,the client design to support fault tolerance and stream sharing is also discussed.