Highly-available cluster configuration database

The cluster configuration database is a distributed configuration database wherein a consistent copy of the configuration database is maintained on each active node of the cluster. Each node in the cluster maintains its own copy of the configuration database and configuration database operations can be performed from any node. Configuration database updates are automatically propagated to each node in a lock-step manner. If any node experiences a failure, the configuration database uses a reconfiguration protocol to insure consistent data in each node of the cluster. The cluster configuration database uses a two-level consistency update framework to insure consistent data among the nodes. Each local configuration database uses a self-contained consistency record to uniquely identify and stamp each copy of the configuration database. The consistency of each individual copy of the configuration database can be verified from the consistency record. Additionally, the cluster configuration database uses a two-phase commit protocol to guarantee the copies of the configuration database are consistent among the nodes. Cluster operations may be performed from any node in the cluster. Cluster operations include restore, checkpoint, update, query, and consistency checking. Because each node maintains a local copy of the configuration database, configuration database queries are local operations and can be performed in parallel among the nodes. Update operations are global operations that involve each active node of the cluster. The cluster configuration database uses a global locking mechanism that implements single write/multiple reader semantics.