Design And Implementation Of A Distributed OGC Map Server

With the rapid development of network technology and geographic information industry, the demand of Web GIS in various industries is increasing. However, there are different data storges and service standards between these Web GIS platforms, they can't share data and achieve interoperability. Thus Open Geospatial Consortium(OGC) developed a set of standards.This thesis comes from an actual research project, and the target of the project is to set up a high-performance, shareable and distributed OGC service platform which meets OGC standard. In this thesis, we design the overall structure of the system: service representation layer, Web service layer, OGC application service layer, data engine layer, data storage layer. And we introduce the interactions of each layer and the relationship between them, and we describe the design and implementation of OGC application service layer which is shareable, high-performance and in accordance with OGC standard. The work andinnovation of this thesis are as follows:(1) A set of distributed OGC application service interfaces are designed based on the OGC service specification, and we have realized WFS, WCS, WMS, WMTS, directory and metadata, and package download.(2) Based on the Ice, a distributed object middleware, the cross system and cross language of Web service layer and OGC application service layer is implemented. And the application service of OGC cluster is realized by using Ice Grid clustering framework, this application also improves dynamic growth and extendibility of service clusters.(3) Faced with large scale application server cluster, we combine the load balance mechanisms of NAT virtual server and Ice Grid framework, and implement the two level load balancing in the network layer and middleware communication layer.(4) The Web server and OGC application service are designed and implemened in four different communication models, including synchronous, asynchronous, synchronous and asynchronous session model. And the four communication models are compared in detail.(5) In the development of service components, the common modules such as memory pool,ring memory buffer and database connection pool are designed and realized. And it realizes the efficient management of the resources in the service module itself, which also improvd the performance and stability of application services.(6) In the different scale of the cluster, the unified cluster monitoring module is implemened to realize the monitoring and control of the application server cluster, and in the monitoring module, the automated deployment and update of OGC application service module is implemented in the server cluster combining Ice Patch2.Based on the design and implementation of the system as a whole and each module, we have done a functional test in the laboratory environment. And the performance test of the OGC application service layer has been carried out by varying the number of different server nodes, which shows that the concurrency performance can be linearly enhanced by increasing the scale of server clusters.