Gis Based On Reliable Group Communication Server Cluster

This dissertation introduced the background, evolution and challenges to current GIS applications. Then, it discussed the extension to Geographical Object Server (GOS) in distributed aspect, Based on which, the dissertation proposed a cluster of GOSs-GSC.Chapter 3 discussed the main concerns in GSC in detail. GSC has the feature of a single system image. It provides a single service entry through Workload Balancing Server(WBS) and balances workloads to GOS according to the running states of the GOS group. GOS caches some geographical data in distributed cache to avoid the efficiency bottleneck which is caused by accessing to databases. The distributed lock system is used to synchronize GOS steps when accessing data. The consistency of the distributed cache is guaranteed by updating strategies of write-through and write-invalidate. The dissertation analyzed message-transferring in GSC and message-passing based on TCP/IP. It provided a reliable multicast protocol based on IP multicast, which benefits from the hardware supporting of Ethernet.Chapter 4 introduced the design and implementing of GSC. GSC includes three components: GOSs group, WBS and the application programming circumstances. A GOS in GSC has many extensions to a GOS in GNet, which mainly in network communicating module and geographical objects management module. The WBS receives requests from users and transfers them to some GOS. WBS is divided to communicating layer, service-entry layer and service-scheduling layer. The application programming circumstances of GSC includes a series of API and a static lib.The dissertation finally summarized technical features in GSC and pointed out the future research direction of GSC.GIS; cluster; reliable multicast; workload-balancing; distributed cache...