Keeps track of Pojo based object structure in RDBMS.
Schemafree is a key/value store based on Mysql. It directs to a specific Mysql shard by looking at the ID, it runs a mod function on the ID's hash. We support a special ObjectCollection case that can maintains id->id mappings, which once sent to SF through a put, "only additions", the diffs of ObjectCollection are inserted in the database. Normally key/value stores rewrite the whole list back increasing the changes of conflict. Sharding such special case collections are supported as well.
All interactions with database are accomplished through Database class. You can configure this interaction through a Configuration class; Size of connection pool, user, pass, etc can all be set through Configuration.
Schemafree supports Memcached out of the box. If you turn on caching, and supply list of memcached host name and port numbers through the Configuration class, and SF will integrate all its operations with Memcached servers. All gets will be looked up in the cache first.
We support fail-over by replicating to other shards; this feature is based on a "replication factor" parameter where a single shard's data is written to R other shards using r \elemof R, mod(mod(id, cluster-size) + r, cluster-size). When the failed db machine comes back up, it pulls newly added data from one of its replicates, bringing itself into sync.
