Copycat is a feature complete, fully asynchronous implementation of the Raft consensus algorithm in Java 8 built for Atomix and designed for use in any project. The implementation provides a fully featured client and server to operate on replicated state machines. The implementation includes:

• Pre-vote election protocol (§4.2.3)
• Session-based linearizable writes (§6.3)
• Lease-based fast linearizable reads from leaders (§6.4.1)
• Fast sequential reads from followers (§6.4.1)
• FIFO consistency for concurrent/asynchronous operations (§11.1.2)
• Session-based state machine events (§6.3)
• Membership changes (§4.3)
• Asynchronous gossip protocol
• Incremental log compaction (§5.3)
• Snapshots (§5.1)

Additionally, this implementation has undergone extensive Jepsen testing to verify it maintains linearizability in a number of different failure scenarios.

For more information on the Raft implementation itself, see Copycat architecture