Adds BeginJointConsensus, CommitJointConsensus, and CalculateJointQuorum to
RaftNode per Raft paper Section 4. During a joint configuration transition
quorum requires majority from BOTH Cold and Cnew; CommitJointConsensus
finalizes Cnew as the sole active configuration. The existing single-phase
ProposeAddPeerAsync/ProposeRemovePeerAsync are unchanged. Includes 16 new
tests covering flag behaviour, quorum boundaries, idempotent commit, and
backward-compatibility with the existing membership API.
- SyncAsync: remove redundant FlushAsync, use single Flush(flushToDisk:true)
- ComputeCrc: use incremental Crc32.Append to avoid contiguous buffer heap allocation
- Load: cast pos+length to long to guard against int overflow in bounds check
- AppendAsync: delegate to WriteEntryTo (DRY — eliminates duplicated record-building logic)
- Load: extract ParseEntries static helper to eliminate goto pattern with early returns
- Entries: change return type from IEnumerable to IReadOnlyList for index access and Count property
- RaftNode.PersistAsync: remove redundant term.txt write (meta.json now owns term+votedFor)
- RaftWalTests: tighten ShouldBeGreaterThanOrEqualTo(1) -> ShouldBe(1) in truncation/CRC tests;
use .Count property directly on IReadOnlyList instead of .Count() LINQ extension
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
