feat(localdb): SyncSession protocol state machine (handshake fail-closed, bidirectional delta pump)
This commit is contained in:
Joseph Doherty
@@ -0,0 +1,446 @@
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using System.Threading.Channels;
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using Microsoft.Extensions.Logging;
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using Microsoft.Extensions.Logging.Abstractions;
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using ZB.MOM.WW.LocalDb.Contracts;
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using ZB.MOM.WW.LocalDb.Internal;
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using ZB.MOM.WW.LocalDb.Replication;
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using ZB.MOM.WW.LocalDb.Replication.Internal;
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namespace ZB.MOM.WW.LocalDb.Tests;
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public sealed class SyncSessionTests : IDisposable
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{
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private const string OrdersSql = "CREATE TABLE orders (id INTEGER PRIMARY KEY, sku TEXT, qty INTEGER)";
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private static readonly TimeSpan RunTimeout = TimeSpan.FromSeconds(15);
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private readonly List<string> _paths = [];
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private readonly List<IDisposable> _disposables = [];
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public void Dispose()
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{
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foreach (var d in _disposables)
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d.Dispose();
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SqliteConnection_ClearAllPools();
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foreach (var p in _paths)
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{
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if (File.Exists(p)) File.Delete(p);
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if (File.Exists(p + "-wal")) File.Delete(p + "-wal");
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if (File.Exists(p + "-shm")) File.Delete(p + "-shm");
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}
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}
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private static void SqliteConnection_ClearAllPools() => Microsoft.Data.Sqlite.SqliteConnection.ClearAllPools();
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private sealed record Side(
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SqliteLocalDb Db, OplogStore Store, LwwApplier Applier, SyncSession Session);
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private async Task<Side> NewSideAsync(
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string createSql = OrdersSql,
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string table = "orders",
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ReplicationOptions? options = null,
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ILogger? logger = null,
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Func<DateTimeOffset>? utcNow = null)
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{
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var path = Path.Combine(Path.GetTempPath(), Guid.NewGuid() + ".db");
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_paths.Add(path);
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var db = new SqliteLocalDb(new LocalDbOptions { Path = path });
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_disposables.Add(db);
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await db.ExecuteAsync(createSql);
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db.RegisterReplicated(table);
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options ??= new ReplicationOptions { FlushInterval = TimeSpan.FromMilliseconds(20) };
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var store = new OplogStore(db, options, utcNow);
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var applier = new LwwApplier(db, utcNow);
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var session = new SyncSession(db, store, applier, options, logger ?? NullLogger.Instance, utcNow);
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return new Side(db, store, applier, session);
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}
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private static (SyncDuplex A, SyncDuplex B) DuplexPair()
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{
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var aToB = Channel.CreateUnbounded<SyncMessage>();
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var bToA = Channel.CreateUnbounded<SyncMessage>();
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var a = new SyncDuplex
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{
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Send = (m, ct) => aToB.Writer.WriteAsync(m, ct).AsTask(),
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Inbox = bToA.Reader,
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};
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var b = new SyncDuplex
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{
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Send = (m, ct) => bToA.Writer.WriteAsync(m, ct).AsTask(),
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Inbox = aToB.Reader,
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};
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return (a, b);
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}
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private static (SyncDuplex Duplex, ChannelWriter<SyncMessage> ToSession, ChannelReader<SyncMessage> FromSession) ScriptedPeer()
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{
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var toSession = Channel.CreateUnbounded<SyncMessage>();
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var fromSession = Channel.CreateUnbounded<SyncMessage>();
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var duplex = new SyncDuplex
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{
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Send = (m, ct) => fromSession.Writer.WriteAsync(m, ct).AsTask(),
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Inbox = toSession.Reader,
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};
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return (duplex, toSession.Writer, fromSession.Reader);
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}
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private static Handshake MatchingHandshake(SqliteLocalDb sessionDb, string peerNodeId, uint version = 1, long lastAppliedRemoteSeq = 0)
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{
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var h = new Handshake { NodeId = peerNodeId, LibSchemaVersion = version, LastAppliedRemoteSeq = lastAppliedRemoteSeq };
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foreach (var t in sessionDb.ReplicatedTables.Values.OrderBy(t => t.Name, StringComparer.Ordinal))
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h.Tables.Add(new TableDigest { TableName = t.Name, Digest = t.Digest });
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return h;
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}
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private static async Task<SyncMessage> NextAsync(ChannelReader<SyncMessage> reader, CancellationToken ct)
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{
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await reader.WaitToReadAsync(ct);
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reader.TryRead(out var msg);
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return msg!;
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}
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private static async Task SwallowAsync(Task task)
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{
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try { await task; }
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catch (OperationCanceledException) { }
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}
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private static async Task WaitForAsync(Func<Task<bool>> predicate, TimeSpan timeout)
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{
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var deadline = DateTime.UtcNow + timeout;
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while (DateTime.UtcNow < deadline)
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{
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if (await predicate()) return;
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await Task.Delay(20);
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}
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throw new TimeoutException("Condition not reached within " + timeout);
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}
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private static async Task<List<(long Id, string? Sku, long? Qty)>> ReadOrders(SqliteLocalDb db)
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{
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var rows = await db.QueryAsync(
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"SELECT id, sku, qty FROM orders ORDER BY id",
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x => (x.GetInt64(0), x.IsDBNull(1) ? null : x.GetString(1), (long?)(x.IsDBNull(2) ? null : x.GetInt64(2))));
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return rows.ToList();
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}
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private static async Task<long> OplogCount(SqliteLocalDb db)
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{
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var r = await db.QueryAsync("SELECT COUNT(*) FROM __localdb_oplog", x => x.GetInt64(0));
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return r[0];
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}
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private static async Task<long> LastAckedSeq(SqliteLocalDb db)
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{
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var r = await db.QueryAsync("SELECT last_acked_seq FROM __localdb_peer_state WHERE id = 1", x => x.GetInt64(0));
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return r[0];
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}
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[Fact]
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public async Task Handshake_Exchanged_BothProceed()
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{
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var a = await NewSideAsync();
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var b = await NewSideAsync();
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var (da, db) = DuplexPair();
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using var cts = new CancellationTokenSource(RunTimeout);
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var runA = a.Session.RunAsync(da, cts.Token);
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var runB = b.Session.RunAsync(db, cts.Token);
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await WaitForAsync(() => Task.FromResult(a.Session.PeerNodeId is not null && b.Session.PeerNodeId is not null), RunTimeout);
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Assert.Equal(b.Db.NodeId, a.Session.PeerNodeId);
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Assert.Equal(a.Db.NodeId, b.Session.PeerNodeId);
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cts.Cancel();
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await SwallowAsync(runA);
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await SwallowAsync(runB);
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}
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[Fact]
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public async Task Handshake_DigestMismatch_FailsClosed()
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{
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var a = await NewSideAsync();
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var b = await NewSideAsync("CREATE TABLE orders (id INTEGER PRIMARY KEY, sku TEXT, qty INTEGER, extra TEXT)");
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await a.Db.ExecuteAsync("INSERT INTO orders (id, sku, qty) VALUES (1, 'A', 5)");
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var (da, db) = DuplexPair();
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using var cts = new CancellationTokenSource(RunTimeout);
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var runA = a.Session.RunAsync(da, cts.Token);
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var runB = b.Session.RunAsync(db, cts.Token);
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var exA = await Assert.ThrowsAsync<LocalDbSchemaMismatchException>(() => runA);
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var exB = await Assert.ThrowsAsync<LocalDbSchemaMismatchException>(() => runB);
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Assert.Contains("orders", exA.Message);
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Assert.Contains("orders", exB.Message);
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// No delta crossed the handshake: B never received A's row.
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Assert.Empty(await ReadOrders(b.Db));
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}
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[Fact]
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public async Task Handshake_SchemaVersionMismatch_FailsClosed()
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{
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var a = await NewSideAsync();
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var (duplex, toSession, _) = ScriptedPeer();
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using var cts = new CancellationTokenSource(RunTimeout);
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var run = a.Session.RunAsync(duplex, cts.Token);
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await toSession.WriteAsync(new SyncMessage { Handshake = MatchingHandshake(a.Db, "peer", version: 2) }, cts.Token);
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await Assert.ThrowsAsync<LocalDbSchemaMismatchException>(() => run);
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}
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[Fact]
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public async Task Deltas_FlowBothDirections_AcksAdvanceWatermarks()
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{
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var a = await NewSideAsync();
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var b = await NewSideAsync();
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await a.Db.ExecuteAsync("INSERT INTO orders (id, sku, qty) VALUES (1, 'FROM_A', 10)");
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await b.Db.ExecuteAsync("INSERT INTO orders (id, sku, qty) VALUES (2, 'FROM_B', 20)");
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var (da, db) = DuplexPair();
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using var cts = new CancellationTokenSource(RunTimeout);
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var runA = a.Session.RunAsync(da, cts.Token);
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var runB = b.Session.RunAsync(db, cts.Token);
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async Task<bool> Converged()
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{
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var ra = await ReadOrders(a.Db);
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var rb = await ReadOrders(b.Db);
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return ra.Count == 2 && rb.Count == 2
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&& await OplogCount(a.Db) == 0 && await OplogCount(b.Db) == 0;
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}
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await WaitForAsync(Converged, RunTimeout);
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var rowsA = await ReadOrders(a.Db);
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var rowsB = await ReadOrders(b.Db);
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Assert.Equal(rowsA, rowsB);
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Assert.Equal([(1L, "FROM_A", (long?)10), (2L, "FROM_B", (long?)20)], rowsA);
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Assert.True(await LastAckedSeq(a.Db) >= 1);
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Assert.True(await LastAckedSeq(b.Db) >= 1);
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cts.Cancel();
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await SwallowAsync(runA);
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await SwallowAsync(runB);
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}
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[Fact]
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public async Task Backlog_DrainsWithoutWaitingFlushInterval()
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{
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var options = new ReplicationOptions { MaxBatchSize = 5, FlushInterval = TimeSpan.FromSeconds(30) };
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var a = await NewSideAsync(options: options);
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var b = await NewSideAsync(options: options);
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const int rows = 15; // 3 x MaxBatchSize
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for (var i = 1; i <= rows; i++)
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await a.Db.ExecuteAsync("INSERT INTO orders (id, sku, qty) VALUES (@id, 'R', @id)", new { id = i });
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var (da, db) = DuplexPair();
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using var cts = new CancellationTokenSource(RunTimeout);
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var runA = a.Session.RunAsync(da, cts.Token);
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var runB = b.Session.RunAsync(db, cts.Token);
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// FlushInterval is 30 s: reaching convergence in a couple seconds proves the pump loops
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// immediately on backlog instead of waiting a flush tick between batches.
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var sw = System.Diagnostics.Stopwatch.StartNew();
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await WaitForAsync(async () => (await ReadOrders(b.Db)).Count == rows, TimeSpan.FromSeconds(5));
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sw.Stop();
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Assert.True(sw.Elapsed < TimeSpan.FromSeconds(5), $"drain took {sw.Elapsed}");
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cts.Cancel();
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await SwallowAsync(runA);
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await SwallowAsync(runB);
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}
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[Fact]
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public async Task HlcDriftAhead_Warns()
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{
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var logger = new ListLogger();
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var a = await NewSideAsync(
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options: new ReplicationOptions { FlushInterval = TimeSpan.FromMilliseconds(20), FailClosedOnDrift = false },
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logger: logger);
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var (duplex, toSession, fromSession) = ScriptedPeer();
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using var cts = new CancellationTokenSource(RunTimeout);
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var run = a.Session.RunAsync(duplex, cts.Token);
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await DriveHandshakeAsync(a.Db, toSession, fromSession, cts.Token);
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var aheadHlc = (DateTimeOffset.UtcNow.AddMinutes(10).ToUnixTimeMilliseconds() << 16);
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await toSession.WriteAsync(new SyncMessage
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{
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DeltaBatch = new DeltaBatch
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{
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Entries = { new OplogEntry
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{
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Seq = 1, TableName = "orders", PkJson = "{\"id\":1}",
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RowJson = "{\"id\":1,\"sku\":\"AHEAD\",\"qty\":9}", Hlc = aheadHlc, NodeId = "peer", IsTombstone = false,
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} },
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},
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}, cts.Token);
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// Drain the DeltaAck the session emits after applying.
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SyncMessage ack;
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do { ack = await NextAsync(fromSession, cts.Token); } while (ack.MsgCase != SyncMessage.MsgOneofCase.DeltaAck);
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Assert.Equal(1, ack.DeltaAck.AppliedThruSeq);
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Assert.Single(await ReadOrders(a.Db)); // applied despite drift
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Assert.Contains(logger.Entries, e => e.Level == LogLevel.Warning);
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cts.Cancel();
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await SwallowAsync(run);
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}
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[Fact]
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public async Task HlcDriftAhead_FailClosed_Throws()
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{
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var a = await NewSideAsync(
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options: new ReplicationOptions { FlushInterval = TimeSpan.FromMilliseconds(20), FailClosedOnDrift = true });
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var (duplex, toSession, fromSession) = ScriptedPeer();
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using var cts = new CancellationTokenSource(RunTimeout);
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var run = a.Session.RunAsync(duplex, cts.Token);
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await DriveHandshakeAsync(a.Db, toSession, fromSession, cts.Token);
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var aheadHlc = (DateTimeOffset.UtcNow.AddMinutes(10).ToUnixTimeMilliseconds() << 16);
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await toSession.WriteAsync(new SyncMessage
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{
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DeltaBatch = new DeltaBatch
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{
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Entries = { new OplogEntry
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{
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Seq = 1, TableName = "orders", PkJson = "{\"id\":1}",
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RowJson = "{\"id\":1,\"sku\":\"AHEAD\",\"qty\":9}", Hlc = aheadHlc, NodeId = "peer", IsTombstone = false,
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} },
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},
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}, cts.Token);
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await Assert.ThrowsAsync<InvalidOperationException>(() => run);
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Assert.Empty(await ReadOrders(a.Db)); // rejected, not applied
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}
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[Fact]
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public async Task PeerNeedsSnapshot_InvokesSnapshotHooks()
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{
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// (a) peer's HandshakeAck.snapshot_required = true -> our SnapshotSender fires.
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{
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var a = await NewSideAsync();
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var (duplex, toSession, fromSession) = ScriptedPeer();
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var sent = new TaskCompletionSource();
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a.Session.SnapshotSender = (_, _) => { sent.TrySetResult(); return Task.CompletedTask; };
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using var cts = new CancellationTokenSource(RunTimeout);
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var run = a.Session.RunAsync(duplex, cts.Token);
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await NextAsync(fromSession, cts.Token); // session Handshake
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await toSession.WriteAsync(new SyncMessage { Handshake = MatchingHandshake(a.Db, "peer") }, cts.Token);
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await NextAsync(fromSession, cts.Token); // session HandshakeAck
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await toSession.WriteAsync(new SyncMessage { HandshakeAck = new HandshakeAck { NodeId = "peer", SnapshotRequired = true } }, cts.Token);
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await sent.Task.WaitAsync(RunTimeout);
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cts.Cancel();
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await SwallowAsync(run);
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}
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// (b) inbound SnapshotBegin -> our SnapshotReceiver fires.
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{
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var a = await NewSideAsync();
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var (duplex, toSession, fromSession) = ScriptedPeer();
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var received = new TaskCompletionSource();
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a.Session.SnapshotReceiver = (_, _, _) => { received.TrySetResult(); return Task.CompletedTask; };
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using var cts = new CancellationTokenSource(RunTimeout);
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var run = a.Session.RunAsync(duplex, cts.Token);
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await DriveHandshakeAsync(a.Db, toSession, fromSession, cts.Token);
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await toSession.WriteAsync(new SyncMessage { SnapshotBegin = new SnapshotBegin { AsOfSeq = 0 } }, cts.Token);
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await received.Task.WaitAsync(RunTimeout);
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cts.Cancel();
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await SwallowAsync(run);
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}
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// (c) snapshot required but no sender hook -> NotSupportedException.
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{
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var a = await NewSideAsync();
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var (duplex, toSession, fromSession) = ScriptedPeer();
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using var cts = new CancellationTokenSource(RunTimeout);
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var run = a.Session.RunAsync(duplex, cts.Token);
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await NextAsync(fromSession, cts.Token);
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await toSession.WriteAsync(new SyncMessage { Handshake = MatchingHandshake(a.Db, "peer") }, cts.Token);
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await NextAsync(fromSession, cts.Token);
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await toSession.WriteAsync(new SyncMessage { HandshakeAck = new HandshakeAck { NodeId = "peer", SnapshotRequired = true } }, cts.Token);
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await Assert.ThrowsAsync<NotSupportedException>(() => run);
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}
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// (d) inbound SnapshotBegin but no receiver hook -> NotSupportedException.
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{
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var a = await NewSideAsync();
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var (duplex, toSession, fromSession) = ScriptedPeer();
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using var cts = new CancellationTokenSource(RunTimeout);
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var run = a.Session.RunAsync(duplex, cts.Token);
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await DriveHandshakeAsync(a.Db, toSession, fromSession, cts.Token);
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await toSession.WriteAsync(new SyncMessage { SnapshotBegin = new SnapshotBegin { AsOfSeq = 0 } }, cts.Token);
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await Assert.ThrowsAsync<NotSupportedException>(() => run);
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}
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}
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[Fact]
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public async Task SecondHandshake_MidStream_IsProtocolError()
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{
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var a = await NewSideAsync();
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var (duplex, toSession, fromSession) = ScriptedPeer();
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using var cts = new CancellationTokenSource(RunTimeout);
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var run = a.Session.RunAsync(duplex, cts.Token);
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await DriveHandshakeAsync(a.Db, toSession, fromSession, cts.Token);
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await toSession.WriteAsync(new SyncMessage { Handshake = MatchingHandshake(a.Db, "peer") }, cts.Token);
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await Assert.ThrowsAsync<InvalidOperationException>(() => run);
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}
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// Completes the two-phase handshake against a real session: consumes its Handshake + HandshakeAck
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// and replies with a matching Handshake + a no-snapshot HandshakeAck, leaving the session in steady state.
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private static async Task DriveHandshakeAsync(
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SqliteLocalDb sessionDb, ChannelWriter<SyncMessage> toSession, ChannelReader<SyncMessage> fromSession, CancellationToken ct)
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{
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var hs = await NextAsync(fromSession, ct);
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Assert.Equal(SyncMessage.MsgOneofCase.Handshake, hs.MsgCase);
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await toSession.WriteAsync(new SyncMessage { Handshake = MatchingHandshake(sessionDb, "peer") }, ct);
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var ack = await NextAsync(fromSession, ct);
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Assert.Equal(SyncMessage.MsgOneofCase.HandshakeAck, ack.MsgCase);
|
||||
await toSession.WriteAsync(new SyncMessage { HandshakeAck = new HandshakeAck { NodeId = "peer", SnapshotRequired = false } }, ct);
|
||||
}
|
||||
|
||||
private sealed class ListLogger : ILogger
|
||||
{
|
||||
public List<(LogLevel Level, string Message)> Entries { get; } = [];
|
||||
|
||||
public IDisposable BeginScope<TState>(TState state) where TState : notnull => NullScope.Instance;
|
||||
public bool IsEnabled(LogLevel logLevel) => true;
|
||||
|
||||
public void Log<TState>(
|
||||
LogLevel logLevel, EventId eventId, TState state, Exception? exception, Func<TState, Exception?, string> formatter)
|
||||
{
|
||||
lock (Entries)
|
||||
Entries.Add((logLevel, formatter(state, exception)));
|
||||
}
|
||||
|
||||
private sealed class NullScope : IDisposable
|
||||
{
|
||||
public static readonly NullScope Instance = new();
|
||||
public void Dispose() { }
|
||||
}
|
||||
}
|
||||
}
|
||||
Reference in New Issue
Block a user