v3.0.0 released

New features

• Added on disk state machine (statemachine.IOnDiskStateMachine) support. The on disk state machine is close to the concept described in the section 5.2 of Diego Ongaro's Raft thesis.
• Added new API for requesting a snapshot to be created or exported.
• Added the ability to use exported snapshot to repair permanently damaged cluster that no longer has majority quorum.
• Added new API for cleaning up data and release disk spaces after a node is removed from its Raft cluster.
• Added the ability to limit peak memory usage when disk or network is slow.
• Added Go module support. Go 1.12 is required.

Improvements

• Further improved self checking on configurations.
• Added snapshot binary format version 2 with block base checksum.
• Synchronous variants have been provided for all asynchronous user request APIs in NodeHost.

Breaking changes

• The Drummer package has been made invisible from user applications.
• The statemachine.IStateMachine interface has been upgraded to reflect the fact that not all state machine data is stored in memory (#46).