refactor API and improve eventing

Author: mgravell

src/StackExchange.Redis/ConfigurationOptions.cs

@@ -117,8 +117,7 @@ internal const string
                 Tunnel = "tunnel",
                 SetClientLibrary = "setlib",
                 Protocol = "protocol",
-                HighIntegrity = "highIntegrity",
-                Weight = "weight";
+                HighIntegrity = "highIntegrity";
 
             private static readonly Dictionary<string, string> normalizedOptions = new[]
             {
@@ -150,7 +149,6 @@ internal const string
                 CheckCertificateRevocation,
                 Protocol,
                 HighIntegrity,
-                Weight,
             }.ToDictionary(x => x, StringComparer.OrdinalIgnoreCase);
 
             public static string TryNormalize(string value)
@@ -851,7 +849,6 @@ public static ConfigurationOptions Parse(string configuration, bool ignoreUnknow
             heartbeatInterval = heartbeatInterval,
             heartbeatConsistencyChecks = heartbeatConsistencyChecks,
             highIntegrity = highIntegrity,
-            Weight = Weight,
         };
 
         /// <summary>
@@ -934,11 +931,6 @@ public string ToString(bool includePassword)
             Append(sb, OptionKeys.SetClientLibrary, setClientLibrary);
             Append(sb, OptionKeys.HighIntegrity, highIntegrity);
             Append(sb, OptionKeys.Protocol, FormatProtocol(Protocol));
-            var weight = Weight;
-            if (!float.IsNaN(weight))
-            {
-                Append(sb, OptionKeys.Weight, weight);
-            }
             if (Tunnel is { IsInbuilt: true } tunnel)
             {
                 Append(sb, OptionKeys.Tunnel, tunnel.ToString());
@@ -995,7 +987,6 @@ private void Clear()
             ChannelPrefix = default;
             SocketManager = null;
             Tunnel = null;
-            Weight = float.NaN;
         }
 
         object ICloneable.Clone() => Clone();
@@ -1107,9 +1098,6 @@ private ConfigurationOptions DoParse(string configuration, bool ignoreUnknown)
                         case OptionKeys.HighIntegrity:
                             HighIntegrity = OptionKeys.ParseBoolean(key, value);
                             break;
-                        case OptionKeys.Weight:
-                            Weight = OptionKeys.ParseSingle(key, value);
-                            break;
                         case OptionKeys.Tunnel:
                             if (value.IsNullOrWhiteSpace())
                             {
@@ -1186,11 +1174,6 @@ private ConfigurationOptions DoParse(string configuration, bool ignoreUnknown)
         /// </summary>
         public RedisProtocol? Protocol { get; set; }
 
-        /// <summary>
-        /// Specify the preference of this connection group relative to others.
-        /// </summary>
-        public float Weight { get; set; } = float.NaN;
-
         internal bool TryResp3()
         {
             // note: deliberately leaving the IsAvailable duplicated to use short-circuit

src/StackExchange.Redis/Interfaces/IConnectionGroup.cs

@@ -0,0 +1,106 @@
+using System;
+using System.IO;
+using System.Text;
+using System.Threading.Tasks;
+
+// ReSharper disable once CheckNamespace
+namespace StackExchange.Redis;
+
+/// <summary>
+/// A group of connections to redis servers, that manages connections to multiple
+/// servers, routing traffic based on the availability of the servers and their
+/// relative <see cref="ConnectionGroupMember.Weight"/>.
+/// </summary>
+public interface IConnectionGroup : IConnectionMultiplexer
+{
+    /// <summary>
+    /// A change occured to one of the connection groups.
+    /// </summary>
+    event EventHandler<GroupConnectionChangedEventArgs>? ConnectionChanged;
+
+    /// <summary>
+    /// Adds a new member to the group.
+    /// </summary>
+    Task AddAsync(ConnectionGroupMember group, TextWriter? log = null);
+
+    /// <summary>
+    /// Removes a member from the group.
+    /// </summary>
+    bool Remove(ConnectionGroupMember group);
+
+    /// <summary>
+    /// Get the members of the group.
+    /// </summary>
+    ReadOnlySpan<ConnectionGroupMember> GetMembers();
+}
+
+/// <summary>
+/// Represents a change to a connection group.
+/// </summary>
+public class GroupConnectionChangedEventArgs(GroupConnectionChangedEventArgs.ChangeType type, ConnectionGroupMember group, ConnectionGroupMember? previousGroup = null) : EventArgs, ICompletable
+{
+    /// <summary>
+    /// The group relating to the change. For <see cref="ChangeType.ActiveChanged"/>, this is the new group.
+    /// </summary>
+    public ConnectionGroupMember Group => group;
+
+    /// <summary>
+    /// The previous group relating to the change, if applicable.
+    /// </summary>
+    public ConnectionGroupMember? PreviousGroup => previousGroup;
+
+    /// <summary>
+    /// The type of change that occurred.
+    /// </summary>
+    public ChangeType Type => type;
+
+    private EventHandler<GroupConnectionChangedEventArgs>? _handler;
+    private object? _sender;
+
+    /// <summary>
+    /// The type of change that occurred.
+    /// </summary>
+    public enum ChangeType
+    {
+        /// <summary>
+        /// Unused.
+        /// </summary>
+        Unknown = 0,
+
+        /// <summary>
+        /// A new connection group was added.
+        /// </summary>
+        Added = 1,
+
+        /// <summary>
+        /// A connection group was removed.
+        /// </summary>
+        Removed = 2,
+
+        /// <summary>
+        /// A connection group became disconnected.
+        /// </summary>
+        Disconnected = 3,
+
+        /// <summary>
+        /// A connection group became reconnected.
+        /// </summary>
+        Reconnected = 4,
+
+        /// <summary>
+        /// The active connection group changed, changing how traffic is routed.
+        /// </summary>
+        ActiveChanged = 5,
+    }
+
+    internal void CompleteAsWorker(EventHandler<GroupConnectionChangedEventArgs> handler, object sender)
+    {
+        _handler = handler;
+        _sender = sender;
+        ConnectionMultiplexer.CompleteAsWorker(this);
+    }
+
+    void ICompletable.AppendStormLog(StringBuilder sb) { }
+
+    bool ICompletable.TryComplete(bool isAsync) => ConnectionMultiplexer.TryCompleteHandler(_handler, _sender!, this, isAsync);
+}