US Patent 9171019 Distributed lock service with external lock information database

A system that implements a distributed lock service may include a failure detector for servers and sessions, and may track the state of sessions on a per-client-connection basis. It may include an external lock information database that stores lock state information and that supports a higher write throughput rate than a distributed state manager. Each database record may store an identifier of a session during which a lock on a respective item was obtained (if any) and a staleness indicator. A distributed state manager may maintain a session identifier and a respective staleness indicator for each established session, and may push updates to this session information to interested client processes, which may cache the information. A client process wishing to lock an item may determine whether it can do so dependent on the information in a corresponding database record and on its own cached session information.