Implements a binary write-ahead log (RaftWal) for durable RAFT entry
storage, replacing in-memory-only semantics. The WAL uses a magic header
("NWAL" + version), length-prefixed records with per-record CRC32
integrity checking, and CompactAsync with atomic temp-file rename.
Load() tolerates truncated or corrupt tail records for crash safety.
Also fixes RaftNode to persist and reload TermState.VotedFor via a
meta.json file alongside term.txt, ensuring vote durability across
restarts. Falls back gracefully to legacy term.txt when meta.json is
absent.
6 new tests in RaftWalTests: persist/recover, compact, truncation
tolerance, VotedFor round-trip, empty WAL, and CRC corruption.
All 458 Raft tests pass.
- ProposeAddPeerAsync/ProposeRemovePeerAsync: single-change-at-a-time membership
changes through RAFT consensus (Go ref: raft.go:961-1019)
- RaftLog.Compact: removes entries up to given index for log compaction
- CreateSnapshotCheckpointAsync: creates snapshot and compacts log in one operation
- DrainAndReplaySnapshotAsync: drains commit queue, installs snapshot, resets indices
- Pre-vote protocol skipped (Go NATS doesn't implement it either)
- 23 new tests in RaftMembershipAndSnapshotTests
- CommitQueue<T>: channel-based queue for committed entries awaiting state machine application
- RaftPeerState: tracks replication and health state (nextIndex, matchIndex, lastContact)
- RaftNode: CommitIndex/ProcessedIndex tracking, election timer with randomized 150-300ms interval,
peer state integration with heartbeat and replication updates
- 52 new tests across RaftApplyQueueTests, RaftElectionTimerTests, RaftHealthTests
Implements RaftSubjects static class with Go's $NRG.* subject constants
and NatsRaftTransport which routes RAFT RPCs over those subjects using
RaftAppendEntryWire / RaftVoteRequestWire encoding. 43 tests cover all
subject patterns, wire encoding fidelity, and transport construction.
