Fix #2173: Honor AbortOnConnectFail on sentinel path

src/StackExchange.Redis/ConnectionMultiplexer.Sentinel.cs

@@ -166,7 +166,8 @@ private static async Task<ConnectionMultiplexer> SentinelPrimaryConnectAsync(Con
     /// <param name="log">The writer to log to, if any.</param>
     public ConnectionMultiplexer GetSentinelMasterConnection(ConfigurationOptions config, TextWriter? log = null)
     {
-        if (ServerSelectionStrategy.ServerType != ServerType.Sentinel)
+        if (ServerSelectionStrategy.ServerType != ServerType.Sentinel
+            && (RawConfig.AbortOnConnectFail || IsConnected))
         {
             throw new RedisConnectionException(
                 ConnectionFailureType.UnableToConnect,
@@ -203,6 +204,18 @@ public ConnectionMultiplexer GetSentinelMasterConnection(ConfigurationOptions co
 
             if (newPrimaryEndPoint is null)
             {
+                if (!config.AbortOnConnectFail)
+                {
+                    connection = ConnectImpl(config, log, endpoints: config.EndPoints.Clone());
+                    connection.ConnectionRestored += OnManagedConnectionRestored;
+                    connection.ConnectionFailed += OnManagedConnectionFailed;
+                    lock (sentinelConnectionChildren)
+                    {
+                        sentinelConnectionChildren[serviceName] = connection;
+                    }
+                    return connection;
+                }
+
                 throw new RedisConnectionException(
                     ConnectionFailureType.UnableToConnect,
                     $"Sentinel: Failed connecting to configured primary for service: {config.ServiceName}");

tests/StackExchange.Redis.Tests/SentinelAbortOnConnectTests.cs

@@ -0,0 +1,41 @@
+using System.Threading.Tasks;
+using Xunit;
+
+namespace StackExchange.Redis.Tests;
+
+public class SentinelAbortOnConnectTests(ITestOutputHelper output) : TestBase(output)
+{
+    [Fact]
+    public void ConnectToUnreachableSentinelReturnsDisconnectedMultiplexer()
+    {
+        var config = ConfigurationOptions.Parse("nonexistent:26379,serviceName=mymaster");
+        config.AbortOnConnectFail = false;
+        config.ConnectTimeout = 1000;
+
+        using var mux = ConnectionMultiplexer.Connect(config);
+        Assert.NotNull(mux);
+        Assert.False(mux.IsConnected);
+    }
+
+    [Fact]
+    public async Task ConnectAsyncToUnreachableSentinelReturnsDisconnectedMultiplexer()
+    {
+        var config = ConfigurationOptions.Parse("nonexistent:26379,serviceName=mymaster");
+        config.AbortOnConnectFail = false;
+        config.ConnectTimeout = 1000;
+
+        await using var mux = await ConnectionMultiplexer.ConnectAsync(config);
+        Assert.NotNull(mux);
+        Assert.False(mux.IsConnected);
+    }
+
+    [Fact]
+    public void ConnectToUnreachableSentinelThrowsWhenAbortOnConnectFailIsTrue()
+    {
+        var config = ConfigurationOptions.Parse("nonexistent:26379,serviceName=mymaster");
+        config.AbortOnConnectFail = true;
+        config.ConnectTimeout = 1000;
+
+        Assert.Throws<RedisConnectionException>(() => ConnectionMultiplexer.Connect(config));
+    }
+}