Active Grid Node Metadata Directory Service Synchronization Mechanism: Take the Case of the China Geological Survey Information Grid Platform

With the wide application of spatial information grid, how to solve the data synchronization has become a current research focus in spatial information grid. Because of the confidentiality and specificity of spatial data, it needs each grid node can only have their own data. When one grid node wants to use the data in another one, it must obey the principle of using the data without owning the data. Therefore, the establishment of the grid node metadata directory is an effective way to realize the spatial data's integration and sharing. There are two main technical difficulties in grid data synchronization currently. The one is poor data security and the other is not able to implement real-time synchronization. Aiming at the two problems, after studied the current mainstream data synchronization techniques, we proposed an active grid node metadata directory service synchronization mechanism. The mechanism releases all kinds of allowed sharing data in the source nodes through the form of metadata directory and uses services to implement the metadata's transformation and synchronization among different grid nodes. Each node in the grid environment uses the message queue mechanism to monitor the spatial data changes themselves, and uploads these changes to metadata directory to implement the active synchronous updates with the metadata upload tool. In this mechanism, each grid node cannot only be the source data nodes providing synchronous metadata, but also be the target data nodes accepting the synchronous updates. It allows multiple source data nodes and a number of target data nodes existence at the same time. Therefore, the synchronization mechanism can implement double-ways metadata real-time synchronization among grid nodes. This synchronization mechanism has been successfully applied to the China geological survey information grid platform and achieved very good actual operation results.