feat(raft): add membership proposals, snapshot checkpoints, and log compaction (B4+B5+B6)
- 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
This commit is contained in:
Joseph Doherty
253
tests/NATS.Server.Tests/Raft/RaftSnapshotCheckpointTests.cs
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253
tests/NATS.Server.Tests/Raft/RaftSnapshotCheckpointTests.cs
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using NATS.Server.Raft;
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namespace NATS.Server.Tests.Raft;
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/// <summary>
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/// Tests for B5: Snapshot Checkpoints and Log Compaction.
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/// Go reference: raft.go:3200-3400 (CreateSnapshotCheckpoint), raft.go:3500-3700 (installSnapshot).
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/// </summary>
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public class RaftSnapshotCheckpointTests
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{
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// -- Helpers --
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private static (RaftNode[] nodes, InMemoryRaftTransport transport) CreateCluster(int size)
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{
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var transport = new InMemoryRaftTransport();
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var nodes = Enumerable.Range(1, size)
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.Select(i => new RaftNode($"n{i}", transport))
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.ToArray();
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foreach (var node in nodes)
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{
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transport.Register(node);
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node.ConfigureCluster(nodes);
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}
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return (nodes, transport);
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}
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private static RaftNode ElectLeader(RaftNode[] nodes)
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{
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var candidate = nodes[0];
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candidate.StartElection(nodes.Length);
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foreach (var voter in nodes.Skip(1))
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candidate.ReceiveVote(voter.GrantVote(candidate.Term, candidate.Id), nodes.Length);
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return candidate;
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}
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// -- RaftSnapshotCheckpoint type tests --
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[Fact]
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public void Checkpoint_creation_with_data()
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{
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var checkpoint = new RaftSnapshotCheckpoint
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{
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SnapshotIndex = 10,
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SnapshotTerm = 2,
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Data = [1, 2, 3, 4, 5],
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};
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checkpoint.SnapshotIndex.ShouldBe(10);
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checkpoint.SnapshotTerm.ShouldBe(2);
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checkpoint.Data.Length.ShouldBe(5);
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checkpoint.IsComplete.ShouldBeFalse();
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}
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[Fact]
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public void Chunk_assembly_single_chunk()
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{
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var checkpoint = new RaftSnapshotCheckpoint
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{
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SnapshotIndex = 5,
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SnapshotTerm = 1,
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};
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checkpoint.AddChunk([10, 20, 30]);
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var result = checkpoint.Assemble();
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result.Length.ShouldBe(3);
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result[0].ShouldBe((byte)10);
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result[1].ShouldBe((byte)20);
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result[2].ShouldBe((byte)30);
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checkpoint.IsComplete.ShouldBeTrue();
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}
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[Fact]
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public void Chunk_assembly_multiple_chunks()
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{
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var checkpoint = new RaftSnapshotCheckpoint
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{
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SnapshotIndex = 5,
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SnapshotTerm = 1,
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};
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checkpoint.AddChunk([1, 2]);
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checkpoint.AddChunk([3, 4, 5]);
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checkpoint.AddChunk([6]);
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var result = checkpoint.Assemble();
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result.Length.ShouldBe(6);
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result.ShouldBe(new byte[] { 1, 2, 3, 4, 5, 6 });
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checkpoint.IsComplete.ShouldBeTrue();
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}
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[Fact]
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public void Chunk_assembly_empty_returns_data()
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{
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// When no chunks added, Assemble returns the initial Data property
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var checkpoint = new RaftSnapshotCheckpoint
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{
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SnapshotIndex = 5,
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SnapshotTerm = 1,
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Data = [99, 100],
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};
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var result = checkpoint.Assemble();
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result.ShouldBe(new byte[] { 99, 100 });
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checkpoint.IsComplete.ShouldBeFalse(); // no chunks to assemble
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}
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// -- RaftLog.Compact tests --
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[Fact]
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public void CompactLog_removes_old_entries()
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{
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// Go reference: raft.go WAL compact
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var log = new RaftLog();
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log.Append(1, "cmd-1");
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log.Append(1, "cmd-2");
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log.Append(1, "cmd-3");
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log.Append(2, "cmd-4");
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log.Entries.Count.ShouldBe(4);
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// Compact up to index 2 — entries 1 and 2 should be removed
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log.Compact(2);
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log.Entries.Count.ShouldBe(2);
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log.Entries[0].Index.ShouldBe(3);
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log.Entries[1].Index.ShouldBe(4);
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}
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[Fact]
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public void CompactLog_updates_base_index()
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{
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var log = new RaftLog();
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log.Append(1, "cmd-1");
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log.Append(1, "cmd-2");
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log.Append(1, "cmd-3");
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log.BaseIndex.ShouldBe(0);
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log.Compact(2);
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log.BaseIndex.ShouldBe(2);
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}
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[Fact]
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public void CompactLog_with_no_entries_is_noop()
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{
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var log = new RaftLog();
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log.Entries.Count.ShouldBe(0);
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log.BaseIndex.ShouldBe(0);
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// Should not throw or change anything
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log.Compact(5);
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log.Entries.Count.ShouldBe(0);
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log.BaseIndex.ShouldBe(0);
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}
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[Fact]
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public void CompactLog_preserves_append_indexing()
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{
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// After compaction, new appends should continue from the correct index
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var log = new RaftLog();
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log.Append(1, "cmd-1");
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log.Append(1, "cmd-2");
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log.Append(1, "cmd-3");
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log.Compact(2);
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log.BaseIndex.ShouldBe(2);
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// New entry should get index 4 (baseIndex 2 + 1 remaining entry + 1)
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var newEntry = log.Append(2, "cmd-4");
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newEntry.Index.ShouldBe(4);
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}
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// -- Streaming snapshot install on RaftNode --
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[Fact]
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public async Task Streaming_snapshot_install_from_chunks()
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{
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// Go reference: raft.go:3500-3700 (installSnapshot with chunked transfer)
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var node = new RaftNode("n1");
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node.Log.Append(1, "cmd-1");
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node.Log.Append(1, "cmd-2");
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node.Log.Append(1, "cmd-3");
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byte[][] chunks = [[1, 2, 3], [4, 5, 6]];
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await node.InstallSnapshotFromChunksAsync(chunks, snapshotIndex: 10, snapshotTerm: 3, default);
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// Log should be replaced (entries cleared, base index set to snapshot)
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node.Log.Entries.Count.ShouldBe(0);
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node.AppliedIndex.ShouldBe(10);
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node.CommitIndex.ShouldBe(10);
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}
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[Fact]
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public async Task Log_after_compaction_starts_at_correct_index()
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{
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// After snapshot + compaction, new entries should continue from the right index
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var (nodes, _) = CreateCluster(3);
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var leader = ElectLeader(nodes);
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await leader.ProposeAsync("cmd-1", default);
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await leader.ProposeAsync("cmd-2", default);
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await leader.ProposeAsync("cmd-3", default);
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leader.Log.Entries.Count.ShouldBe(3);
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// Create snapshot at current applied index and compact
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var snapshot = await leader.CreateSnapshotCheckpointAsync(default);
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snapshot.LastIncludedIndex.ShouldBe(leader.AppliedIndex);
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// Log should now be empty (all entries covered by snapshot)
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leader.Log.Entries.Count.ShouldBe(0);
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leader.Log.BaseIndex.ShouldBe(leader.AppliedIndex);
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// New entries should continue from the right index
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var index4 = await leader.ProposeAsync("cmd-4", default);
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index4.ShouldBe(leader.AppliedIndex); // should be appliedIndex after new propose
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leader.Log.Entries.Count.ShouldBe(1);
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}
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// -- CompactLogAsync on RaftNode --
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[Fact]
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public async Task CompactLogAsync_compacts_up_to_applied_index()
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{
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var (nodes, _) = CreateCluster(3);
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var leader = ElectLeader(nodes);
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await leader.ProposeAsync("cmd-1", default);
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await leader.ProposeAsync("cmd-2", default);
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await leader.ProposeAsync("cmd-3", default);
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leader.Log.Entries.Count.ShouldBe(3);
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var appliedIndex = leader.AppliedIndex;
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appliedIndex.ShouldBeGreaterThan(0);
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await leader.CompactLogAsync(default);
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// All entries up to applied index should be compacted
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leader.Log.BaseIndex.ShouldBe(appliedIndex);
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leader.Log.Entries.Count.ShouldBe(0);
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}
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[Fact]
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public async Task CompactLogAsync_noop_when_nothing_applied()
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{
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var node = new RaftNode("n1");
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node.AppliedIndex.ShouldBe(0);
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// Should be a no-op — nothing to compact
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await node.CompactLogAsync(default);
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node.Log.BaseIndex.ShouldBe(0);
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node.Log.Entries.Count.ShouldBe(0);
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}
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}
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