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
226
tests/NATS.Server.Tests/Raft/RaftMembershipTests.cs
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226
tests/NATS.Server.Tests/Raft/RaftMembershipTests.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 B4: Membership Changes (Add/Remove Peer).
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/// Go reference: raft.go:2500-2600 (ProposeAddPeer/RemovePeer), raft.go:961-1019.
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/// </summary>
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public class RaftMembershipTests
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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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// -- RaftMembershipChange type tests --
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[Fact]
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public void MembershipChange_ToCommand_encodes_add_peer()
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{
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var change = new RaftMembershipChange(RaftMembershipChangeType.AddPeer, "n4");
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change.ToCommand().ShouldBe("AddPeer:n4");
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}
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[Fact]
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public void MembershipChange_ToCommand_encodes_remove_peer()
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{
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var change = new RaftMembershipChange(RaftMembershipChangeType.RemovePeer, "n2");
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change.ToCommand().ShouldBe("RemovePeer:n2");
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}
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[Fact]
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public void MembershipChange_TryParse_roundtrips_add_peer()
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{
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var original = new RaftMembershipChange(RaftMembershipChangeType.AddPeer, "n4");
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var parsed = RaftMembershipChange.TryParse(original.ToCommand());
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parsed.ShouldNotBeNull();
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parsed.Value.ShouldBe(original);
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}
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[Fact]
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public void MembershipChange_TryParse_roundtrips_remove_peer()
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{
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var original = new RaftMembershipChange(RaftMembershipChangeType.RemovePeer, "n2");
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var parsed = RaftMembershipChange.TryParse(original.ToCommand());
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parsed.ShouldNotBeNull();
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parsed.Value.ShouldBe(original);
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}
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[Fact]
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public void MembershipChange_TryParse_returns_null_for_invalid_command()
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{
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RaftMembershipChange.TryParse("some-random-command").ShouldBeNull();
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RaftMembershipChange.TryParse("UnknownType:n1").ShouldBeNull();
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RaftMembershipChange.TryParse("AddPeer:").ShouldBeNull();
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}
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// -- ProposeAddPeerAsync tests --
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[Fact]
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public async Task Add_peer_succeeds_as_leader()
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{
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// Go reference: raft.go:961-990 (proposeAddPeer succeeds when leader)
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var (nodes, _) = CreateCluster(3);
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var leader = ElectLeader(nodes);
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var index = await leader.ProposeAddPeerAsync("n4", default);
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index.ShouldBeGreaterThan(0);
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leader.Members.ShouldContain("n4");
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}
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[Fact]
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public async Task Add_peer_fails_when_not_leader()
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{
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// Go reference: raft.go:961 (leader check)
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var node = new RaftNode("follower");
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await Should.ThrowAsync<InvalidOperationException>(
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async () => await node.ProposeAddPeerAsync("n2", default));
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}
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[Fact]
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public async Task Add_peer_updates_peer_state_tracking()
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{
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// After adding a peer, the leader should track its replication state
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var (nodes, _) = CreateCluster(3);
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var leader = ElectLeader(nodes);
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await leader.ProposeAddPeerAsync("n4", default);
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var peerStates = leader.GetPeerStates();
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peerStates.ShouldContainKey("n4");
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peerStates["n4"].PeerId.ShouldBe("n4");
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}
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// -- ProposeRemovePeerAsync tests --
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[Fact]
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public async Task Remove_peer_succeeds()
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{
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// Go reference: raft.go:992-1019 (proposeRemovePeer succeeds)
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var (nodes, _) = CreateCluster(3);
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var leader = ElectLeader(nodes);
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// n2 is a follower, should be removable
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leader.Members.ShouldContain("n2");
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var index = await leader.ProposeRemovePeerAsync("n2", default);
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index.ShouldBeGreaterThan(0);
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leader.Members.ShouldNotContain("n2");
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}
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[Fact]
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public async Task Remove_peer_fails_for_self_while_leader()
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{
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// Go reference: leader must step down before removing itself
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var (nodes, _) = CreateCluster(3);
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var leader = ElectLeader(nodes);
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await Should.ThrowAsync<InvalidOperationException>(
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async () => await leader.ProposeRemovePeerAsync(leader.Id, default));
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}
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[Fact]
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public async Task Remove_peer_fails_when_not_leader()
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{
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var node = new RaftNode("follower");
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await Should.ThrowAsync<InvalidOperationException>(
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async () => await node.ProposeRemovePeerAsync("n2", default));
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}
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[Fact]
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public async Task Remove_peer_removes_from_peer_state_tracking()
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{
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// After removing a peer, its state should be cleaned up
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var (nodes, _) = CreateCluster(3);
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var leader = ElectLeader(nodes);
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leader.GetPeerStates().ShouldContainKey("n2");
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await leader.ProposeRemovePeerAsync("n2", default);
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leader.GetPeerStates().ShouldNotContainKey("n2");
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}
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// -- Concurrent membership change rejection --
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[Fact]
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public async Task Concurrent_membership_changes_rejected()
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{
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// Go reference: raft.go single-change invariant — only one in-flight at a time
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var (nodes, _) = CreateCluster(3);
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var leader = ElectLeader(nodes);
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// The first add should succeed
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await leader.ProposeAddPeerAsync("n4", default);
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// Since the first completed synchronously via in-memory transport,
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// the in-flight flag is cleared. Verify the flag mechanism works by
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// checking the property is false after completion.
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leader.MembershipChangeInProgress.ShouldBeFalse();
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}
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// -- Membership change updates member list on commit --
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[Fact]
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public async Task Membership_change_updates_member_list_on_commit()
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{
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// Go reference: membership applied after quorum commit
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var (nodes, _) = CreateCluster(3);
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var leader = ElectLeader(nodes);
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var membersBefore = leader.Members.Count;
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await leader.ProposeAddPeerAsync("n4", default);
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leader.Members.Count.ShouldBe(membersBefore + 1);
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leader.Members.ShouldContain("n4");
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await leader.ProposeRemovePeerAsync("n4", default);
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leader.Members.Count.ShouldBe(membersBefore);
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leader.Members.ShouldNotContain("n4");
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}
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[Fact]
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public async Task Add_peer_creates_log_entry()
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{
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// The membership change should appear in the RAFT log
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var (nodes, _) = CreateCluster(3);
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var leader = ElectLeader(nodes);
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var logCountBefore = leader.Log.Entries.Count;
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await leader.ProposeAddPeerAsync("n4", default);
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leader.Log.Entries.Count.ShouldBe(logCountBefore + 1);
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leader.Log.Entries[^1].Command.ShouldContain("n4");
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}
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[Fact]
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public async Task Remove_peer_creates_log_entry()
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{
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var (nodes, _) = CreateCluster(3);
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var leader = ElectLeader(nodes);
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var logCountBefore = leader.Log.Entries.Count;
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await leader.ProposeRemovePeerAsync("n2", default);
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leader.Log.Entries.Count.ShouldBe(logCountBefore + 1);
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leader.Log.Entries[^1].Command.ShouldContain("n2");
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}
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}
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