- move the "ignore handshake nodes" logic deeper into the client, so external callers can still fetch the value

- add new IgnoreFromClient internal member for ^^^, and use
- support "handshake" etc in the in-proc test server
- support "only initially connect to default node" in the in-proc test server
- add a unit test that handshake nodes are ignored

Author: mgravell

src/StackExchange.Redis/ClusterConfiguration.cs

@@ -181,11 +181,6 @@ internal ClusterConfiguration(ServerSelectionStrategy serverSelectionStrategy, s
                     if (node.IsNoAddr || node.IsFail || node.EndPoint == null)
                         continue;
 
-                    // Be resilient to "handshake" nodes, which are nodes that are in the process of joining the cluster and hence might not have all information available yet.
-                    // These nodes will be included in the configuration once they finish the handshake process and are fully part of the cluster, so we can safely ignore them for now.
-                    if (node.IsHandshake)
-                        continue;
-
                     // Override the origin value with the endpoint advertised with the target node to
                     // make sure that things like clusterConfiguration[clusterConfiguration.Origin]
                     // will work as expected.
@@ -431,6 +426,10 @@ public IList<ClusterNode> Children
         /// </summary>
         public IList<SlotRange> Slots { get; }
 
+        // Be resilient to "handshake" nodes, which are nodes that are in the process of joining the cluster and hence might not have all information available yet.
+        // These nodes will be included in the configuration once they finish the handshake process and are fully part of the cluster, so we can safely ignore them for now.
+        internal bool IgnoreFromClient => IsHandshake; // possibly also noaddr?
+
         /// <summary>
         /// Compares the current instance with another object of the same type and returns an integer that indicates
         /// whether the current instance precedes, follows, or occurs in the same position in the sort order as the other object.

src/StackExchange.Redis/ConnectionMultiplexer.cs

@@ -1760,7 +1760,7 @@ public EndPoint[] GetEndPoints(bool configuredOnly = false) =>
                 {
                     return null;
                 }
-                var clusterEndpoints = new EndPointCollection(clusterConfig.Nodes.Where(node => node.EndPoint is not null).Select(node => node.EndPoint!).ToList());
+                var clusterEndpoints = new EndPointCollection(clusterConfig.Nodes.Where(node => node.EndPoint is not null && !node.IgnoreFromClient).Select(node => node.EndPoint!).ToList());
                 // Loop through nodes in the cluster and update nodes relations to other nodes
                 ServerEndPoint? serverEndpoint = null;
                 foreach (EndPoint endpoint in clusterEndpoints)
@@ -1933,7 +1933,7 @@ internal void UpdateClusterRange(ClusterConfiguration configuration)
             }
             foreach (var node in configuration.Nodes)
             {
-                if (node.IsReplica || node.Slots.Count == 0) continue;
+                if (node.IgnoreFromClient || node.IsReplica || node.Slots.Count == 0) continue;
                 foreach (var slot in node.Slots)
                 {
                     if (GetServerEndPoint(node.EndPoint) is ServerEndPoint server)

src/StackExchange.Redis/ServerEndPoint.cs

@@ -324,6 +324,8 @@ public void UpdateNodeRelations(ClusterConfiguration configuration)
                 ServerEndPoint? primary = null;
                 foreach (var node in configuration.Nodes)
                 {
+                    if (node.IgnoreFromClient) continue;
+
                     if (node.NodeId == thisNode.ParentNodeId)
                     {
                         primary = Multiplexer.GetServerEndPoint(node.EndPoint);

tests/StackExchange.Redis.Tests/ClusterHandshakeNodesUnitTests.cs

@@ -0,0 +1,31 @@
+using System.Threading.Tasks;
+using Xunit;
+using Xunit.Sdk;
+
+namespace StackExchange.Redis.Tests;
+
+// context: https://github.com/StackExchange/StackExchange.Redis/pull/3043
+public class ClusterHandshakeNodesUnitTests(ITestOutputHelper log)
+{
+    [Fact]
+    public async Task ClusterHandshakeNodesAreIgnored()
+    {
+        using var server = new InProcessTestServer() { ServerType = ServerType.Cluster };
+        var a = server.DefaultEndPoint;
+        var b = server.AddEmptyNode();
+        var c = server.AddEmptyNode(Server.RedisServer.NodeFlags.Handshake);
+        using var conn = await server.ConnectAsync(defaultOnly: true); // defaultOnly: only connect to a initially
+
+        log.WriteLine($"a: {Format.ToString(a)}, b: {Format.ToString(b)}, c: {Format.ToString(c)}");
+        var ep = conn.GetEndPoints();
+        log.WriteLine("Endpoints:");
+        foreach (var e in ep)
+        {
+            log.WriteLine(Format.ToString(e));
+        }
+        Assert.Equal(2, ep.Length);
+        Assert.Contains(a, ep);
+        Assert.Contains(b, ep);
+        Assert.DoesNotContain(c, ep);
+    }
+}

tests/StackExchange.Redis.Tests/InProcessTestServer.cs

@@ -27,8 +27,8 @@ public InProcessTestServer(ITestOutputHelper? log = null, EndPoint? endpoint = n
         Tunnel = new InProcTunnel(this);
     }
 
-    public Task<ConnectionMultiplexer> ConnectAsync(bool withPubSub = true /*, WriteMode writeMode = WriteMode.Default */, TextWriter? log = null)
-        => ConnectionMultiplexer.ConnectAsync(GetClientConfig(withPubSub /*, writeMode */), log);
+    public Task<ConnectionMultiplexer> ConnectAsync(bool withPubSub = true, bool defaultOnly = false /*, WriteMode writeMode = WriteMode.Default */, TextWriter? log = null)
+        => ConnectionMultiplexer.ConnectAsync(GetClientConfig(withPubSub, defaultOnly /*, writeMode */), log);
 
     // view request/response highlights in the log
     public override TypedRedisValue Execute(RedisClient client, in RedisRequest request)
@@ -60,7 +60,7 @@ public override TypedRedisValue Execute(RedisClient client, in RedisRequest requ
         return result;
     }
 
-    public ConfigurationOptions GetClientConfig(bool withPubSub = true /*, WriteMode writeMode = WriteMode.Default */)
+    public ConfigurationOptions GetClientConfig(bool withPubSub = true, bool defaultOnly = false /*, WriteMode writeMode = WriteMode.Default */)
     {
         var commands = GetCommands();
         if (!withPubSub)
@@ -106,9 +106,16 @@ public ConfigurationOptions GetClientConfig(bool withPubSub = true /*, WriteMode
 #endif
         */
 
-        foreach (var endpoint in GetEndPoints())
+        if (defaultOnly)
         {
-            config.EndPoints.Add(endpoint);
+            config.EndPoints.Add(DefaultEndPoint);
+        }
+        else
+        {
+            foreach (var endpoint in GetEndPoints())
+            {
+                config.EndPoints.Add(endpoint);
+            }
         }
         return config;
     }

toys/StackExchange.Redis.Server/RedisServer.cs

@@ -78,7 +78,19 @@ public bool Migrate(int hashSlot, EndPoint to)
         public bool Migrate(Span<byte> key, EndPoint to) => Migrate(ServerSelectionStrategy.GetClusterSlot(key), to);
         public bool Migrate(in RedisKey key, EndPoint to) => Migrate(GetHashSlot(key), to);
 
-        public EndPoint AddEmptyNode()
+        [Flags]
+        public enum NodeFlags
+        {
+            None = 0, // note: implicitly primary, since no replica flag
+            Replica = 1 << 0,
+            Handshake = 1 << 1,
+            Fail = 1 << 2,
+            PFail = 1 << 3,
+            NoAddress = 1 << 4,
+            NoFailover = 1 << 5,
+        }
+
+        public EndPoint AddEmptyNode(NodeFlags flags = NodeFlags.None)
         {
             EndPoint endpoint;
             Node node;
@@ -113,7 +125,7 @@ public EndPoint AddEmptyNode()
                         break;
                 }
 
-                node = new(this, endpoint);
+                node = new(this, endpoint, flags);
                 node.UpdateSlots([]); // explicit empty range (rather than implicit "all nodes")
             }
             // defensive loop for concurrency
@@ -124,7 +136,7 @@ public EndPoint AddEmptyNode()
         protected RedisServer(EndPoint endpoint = null, int databases = 16, TextWriter output = null) : base(output)
         {
             endpoint ??= new IPEndPoint(IPAddress.Loopback, 6379);
-            _nodes.TryAdd(endpoint, new Node(this, endpoint));
+            _nodes.TryAdd(endpoint, new Node(this, endpoint, NodeFlags.None));
             RedisVersion = s_DefaultServerVersion;
             if (databases < 1) throw new ArgumentOutOfRangeException(nameof(databases));
             Databases = databases;
@@ -487,7 +499,16 @@ protected virtual TypedRedisValue ClusterNodes(RedisClient client, in RedisReque
                 {
                     sb.Append("myself,");
                 }
-                sb.Append("master - 0 0 1 connected");
+                sb.Append((node.Flags & NodeFlags.Replica) == 0 ? "master" : "slave");
+                if ((node.Flags & NodeFlags.Handshake) != 0)
+                {
+                    sb.Append(",handshake");
+                }
+                if ((node.Flags & NodeFlags.Fail) != 0) sb.Append(",fail");
+                if ((node.Flags & NodeFlags.PFail) != 0) sb.Append(",fail?");
+                if ((node.Flags & NodeFlags.NoAddress) != 0) sb.Append(",noaddr");
+                if ((node.Flags & NodeFlags.NoFailover) != 0) sb.Append(",nofailover");
+                sb.Append(" - 0 0 1 connected");
                 foreach (var range in node.Slots)
                 {
                     sb.Append(" ").Append(range.ToString());
@@ -603,11 +624,13 @@ public override string ToString()
 
             private readonly RedisServer _server;
             public RedisServer Server => _server;
-            public Node(RedisServer server, EndPoint endpoint)
+            public NodeFlags Flags { get; }
+            public Node(RedisServer server, EndPoint endpoint, NodeFlags flags)
             {
                 Host = GetHost(endpoint, out var port);
                 Port = port;
                 _server = server;
+                Flags = flags;
             }
 
             public void UpdateSlots(SlotRange[] slots) => _slots = slots;