LevelDB Cache

This plugin caches terrain tiles, feature vectors, and other data to the local file system using the Google leveldb embedded key/value store library.

Example usage:

<map>
        <options>
        <cache driver      = "leveldb"
               path        = "c:/osgearth_cache"
               max_size_mb = "500" />
        </cache>
                    ...

The leveldb cache stores each class of data in its own bin. All bins are stored in the same directory, in the same database. We do this so we can impose a size limit on the entire database. Each record is timestamped; when the cache reaches the maximum size, it starts removing the oldest records first to make room.

Cache access is asynchronous and multi-threaded, but you may only access a cache from one process at a time.

The actual format of cached data files is “black box” and may change without notice. We do not intend for cached files to be used directly or for other purposes.

Properties:

path:Location of the root directory in which to store all cache bins and data.
max_size_mb:Maximum size of the cache in megabytes. The size is taken as a goal; there is no guarantee that the size of the cache will always be less than this value, but the driver will do its best to comply.