Sentinel improvements (#1431)

Add SentinelConnect and SentinelMasterConnect to ConnectionMultiplexer for working with sentinel setups (#1427)
Fix issue with duplicate endpoints being added in the UpdateSentinelAddressList method (#1430).

This change makes it a lot easier and more discoverable how to connect to a sentinel server while also allowing connecting with just a connection string change which allows existing libs that are using SE.Redis to be used in sentinel mode.

Adding a `serviceName` parameter to the connection string triggers sentinel mode. It will connect to the sentinel and discover the current master and return a managed connection that follows the master. 

```csharp
var conn = ConnectionMultiplexer.Connect("localhost,serviceName=mymaster");
var db = conn.GetDatabase();
db.StringSet("key", "value");
```

StackExchange.Redis.sln

@@ -23,6 +23,8 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "RedisConfigs", "RedisConfig
 		tests\RedisConfigs\cli-master.cmd = tests\RedisConfigs\cli-master.cmd
 		tests\RedisConfigs\cli-secure.cmd = tests\RedisConfigs\cli-secure.cmd
 		tests\RedisConfigs\cli-slave.cmd = tests\RedisConfigs\cli-slave.cmd
+		tests\RedisConfigs\docker-compose.yml = tests\RedisConfigs\docker-compose.yml
+		tests\RedisConfigs\Dockerfile = tests\RedisConfigs\Dockerfile
 		tests\RedisConfigs\start-all.cmd = tests\RedisConfigs\start-all.cmd
 		tests\RedisConfigs\start-all.sh = tests\RedisConfigs\start-all.sh
 		tests\RedisConfigs\start-basic.cmd = tests\RedisConfigs\start-basic.cmd
@@ -126,6 +128,12 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "TestConsoleBaseline", "toys
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = ".github", ".github\.github.csproj", "{8FB98E7D-DAE2-4465-BD9A-104000E0A2D4}"
 EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Docker", "Docker", "{A9F81DA3-DA82-423E-A5DD-B11C37548E06}"
+	ProjectSection(SolutionItems) = preProject
+		tests\RedisConfigs\Docker\docker-entrypoint.sh = tests\RedisConfigs\Docker\docker-entrypoint.sh
+		tests\RedisConfigs\Docker\supervisord.conf = tests\RedisConfigs\Docker\supervisord.conf
+	EndProjectSection
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -197,6 +205,7 @@ Global
 		{3DA1EEED-E9FE-43D9-B293-E000CFCCD91A} = {E25031D3-5C64-430D-B86F-697B66816FD8}
 		{153A10E4-E668-41AD-9E0F-6785CE7EED66} = {3AD17044-6BFF-4750-9AC2-2CA466375F2A}
 		{D58114AE-4998-4647-AFCA-9353D20495AE} = {E25031D3-5C64-430D-B86F-697B66816FD8}
+		{A9F81DA3-DA82-423E-A5DD-B11C37548E06} = {96E891CD-2ED7-4293-A7AB-4C6F5D8D2B05}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {193AA352-6748-47C1-A5FC-C9AA6B5F000B}

docs/Configuration.md

@@ -29,6 +29,14 @@ This will connect to a single server on the local machine using the default redi
 var conn = ConnectionMultiplexer.Connect("redis0:6380,redis1:6380,allowAdmin=true");
 ```
 
+If you specify a serviceName in the connection string, it will trigger sentinel mode. This example will connect to a sentinel server on the local machine
+using the default sentinel port (26379), discover the current master server for the `mymaster` service and return a managed connection
+pointing to that master server that will automatically be updated if the master changes:
+
+```csharp
+var conn = ConnectionMultiplexer.Connect("localhost,serviceName=mymaster");
+```
+
 An overview of mapping between the `string` and `ConfigurationOptions` representation is shown below, but you can switch between them trivially:
 
 ```csharp
@@ -79,7 +87,7 @@ The `ConfigurationOptions` object has a wide range of properties, all of which a
 | proxy={proxy type}     | `Proxy`                | `Proxy.None`                 | Type of proxy in use (if any); for example "twemproxy"                                                    |
 | resolveDns={bool}      | `ResolveDns`           | `false`                      | Specifies that DNS resolution should be explicit and eager, rather than implicit                          |
 | responseTimeout={int}  | `ResponseTimeout`      | `SyncTimeout`                | Time (ms) to decide whether the socket is unhealthy                                                       |
-| serviceName={string}   | `ServiceName`          | `null`                       | Not currently implemented (intended for use with sentinel)                                                |
+| serviceName={string}   | `ServiceName`          | `null`                       | Used for connecting to a sentinel master service                                                          |
 | ssl={bool}             | `Ssl`                  | `false`                      | Specifies that SSL encryption should be used                                                              |
 | sslHost={string}       | `SslHost`              | `null`                       | Enforces a particular SSL host identity on the server's certificate                                       |
 | sslProtocols={enum}    | `SslProtocols`         | `null`                       | Ssl/Tls versions supported when using an encrypted connection.  Use '\|' to provide multiple values.      |

src/StackExchange.Redis/EndPointCollection.cs

@@ -9,7 +9,7 @@ namespace StackExchange.Redis
     /// <summary>
     /// A list of endpoints
     /// </summary>
-    public sealed class EndPointCollection : Collection<EndPoint>, IEnumerable, IEnumerable<EndPoint>
+    public sealed class EndPointCollection : Collection<EndPoint>, IEnumerable<EndPoint>
     {
         /// <summary>
         /// Create a new EndPointCollection
@@ -59,6 +59,26 @@ public void Add(string hostAndPort)
         /// <param name="port">The port for <paramref name="host"/> to add.</param>
         public void Add(IPAddress host, int port) => Add(new IPEndPoint(host, port));
 
+        /// <summary>
+        /// Try adding a new endpoint to the list.
+        /// </summary>
+        /// <param name="endpoint">The endpoint to add.</param>
+        /// <returns>True if the endpoint was added or false if not.</returns>
+        public bool TryAdd(EndPoint endpoint)
+        {
+            if (endpoint == null) throw new ArgumentNullException(nameof(endpoint));
+
+            if (!Contains(endpoint))
+            {
+                base.InsertItem(Count, endpoint);
+                return true;
+            }
+            else
+            {
+                return false;
+            }
+        }
+
         /// <summary>
         /// See Collection&lt;T&gt;.InsertItem()
         /// </summary>

src/StackExchange.Redis/Interfaces/IServer.cs

@@ -792,7 +792,7 @@ public partial interface IServer : IRedis
         /// for the given service name.
         /// </summary>
         /// <param name="serviceName">the sentinel service name</param>
-        /// <param name="flags"></param>
+        /// <param name="flags">The command flags to use.</param>
         /// <returns>a list of the sentinel ips and ports</returns>
         EndPoint[] SentinelGetSentinelAddresses(string serviceName, CommandFlags flags = CommandFlags.None);
 
@@ -801,10 +801,28 @@ public partial interface IServer : IRedis
         /// for the given service name.
         /// </summary>
         /// <param name="serviceName">the sentinel service name</param>
-        /// <param name="flags"></param>
+        /// <param name="flags">The command flags to use.</param>
         /// <returns>a list of the sentinel ips and ports</returns>
         Task<EndPoint[]> SentinelGetSentinelAddressesAsync(string serviceName, CommandFlags flags = CommandFlags.None);
 
+        /// <summary>
+        /// Returns the ip and port numbers of all known Sentinel replicas
+        /// for the given service name.
+        /// </summary>
+        /// <param name="serviceName">the sentinel service name</param>
+        /// <param name="flags">The command flags to use.</param>
+        /// <returns>a list of the replica ips and ports</returns>
+        EndPoint[] SentinelGetReplicaAddresses(string serviceName, CommandFlags flags = CommandFlags.None);
+
+        /// <summary>
+        /// Returns the ip and port numbers of all known Sentinel replicas
+        /// for the given service name.
+        /// </summary>
+        /// <param name="serviceName">the sentinel service name</param>
+        /// <param name="flags">The command flags to use.</param>
+        /// <returns>a list of the replica ips and ports</returns>
+        Task<EndPoint[]> SentinelGetReplicaAddressesAsync(string serviceName, CommandFlags flags = CommandFlags.None);
+
         /// <summary>
         /// Show the state and info of the specified master.
         /// </summary>
@@ -1024,5 +1042,14 @@ internal static class IServerExtensions
         /// </summary>
         /// <param name="server">The server to simulate failure on.</param>
         public static void SimulateConnectionFailure(this IServer server) => (server as RedisServer)?.SimulateConnectionFailure();
+
+        public static string Role(this IServer server)
+        {
+            var result = (RedisResult[])server.Execute("ROLE");
+            if (result != null && result.Length > 0)
+                return result[0].ToString();
+
+            return null;
+        }
     }
 }

src/StackExchange.Redis/RedisLiterals.cs

@@ -119,12 +119,14 @@ public static readonly RedisValue
 
             // misc (config, etc)
             databases = "databases",
+            master = "master",
             no = "no",
             normal = "normal",
             pubsub = "pubsub",
             replica = "replica",
             replica_read_only = "replica-read-only",
             replication = "replication",
+            sentinel = "sentinel",
             server = "server",
             slave = "slave",
             slave_read_only = "slave-read-only",

src/StackExchange.Redis/RedisServer.cs

@@ -830,6 +830,18 @@ public Task<EndPoint[]> SentinelGetSentinelAddressesAsync(string serviceName, Co
             return ExecuteAsync(msg, ResultProcessor.SentinelAddressesEndPoints);
         }
 
+        public EndPoint[] SentinelGetReplicaAddresses(string serviceName, CommandFlags flags = CommandFlags.None)
+        {
+            var msg = Message.Create(-1, flags, RedisCommand.SENTINEL, RedisLiterals.SLAVES, (RedisValue)serviceName);
+            return ExecuteSync(msg, ResultProcessor.SentinelAddressesEndPoints);
+        }
+
+        public Task<EndPoint[]> SentinelGetReplicaAddressesAsync(string serviceName, CommandFlags flags = CommandFlags.None)
+        {
+            var msg = Message.Create(-1, flags, RedisCommand.SENTINEL, RedisLiterals.SLAVES, (RedisValue)serviceName);
+            return ExecuteAsync(msg, ResultProcessor.SentinelAddressesEndPoints);
+        }
+
         public KeyValuePair<string, string>[] SentinelMaster(string serviceName, CommandFlags flags = CommandFlags.None)
         {
             var msg = Message.Create(-1, flags, RedisCommand.SENTINEL, RedisLiterals.MASTER, (RedisValue)serviceName);
@@ -866,6 +878,7 @@ public Task<KeyValuePair<string, string>[][]> SentinelMastersAsync(CommandFlags
             return ExecuteAsync(msg, ResultProcessor.SentinelArrayOfArrays);
         }
 
+        // For previous compat only
         KeyValuePair<string, string>[][] IServer.SentinelSlaves(string serviceName, CommandFlags flags)
             => SentinelReplicas(serviceName, flags);
 
@@ -876,6 +889,7 @@ public KeyValuePair<string, string>[][] SentinelReplicas(string serviceName, Com
             return ExecuteSync(msg, ResultProcessor.SentinelArrayOfArrays);
         }
 
+        // For previous compat only
         Task<KeyValuePair<string, string>[][]> IServer.SentinelSlavesAsync(string serviceName, CommandFlags flags)
             => SentinelReplicasAsync(serviceName, flags);
 

src/StackExchange.Redis/ResultProcessor.cs

@@ -126,7 +126,10 @@ public static readonly ResultProcessor<EndPoint>
             SentinelMasterEndpoint = new SentinelGetMasterAddressByNameProcessor();
 
         public static readonly ResultProcessor<EndPoint[]>
-            SentinelAddressesEndPoints = new SentinelGetSentinelAddresses();
+            SentinelAddressesEndPoints = new SentinelGetSentinelAddressesProcessor();
+
+        public static readonly ResultProcessor<EndPoint[]>
+            SentinelReplicaEndPoints = new SentinelGetReplicaAddressesProcessor();
 
         public static readonly ResultProcessor<KeyValuePair<string, string>[][]>
             SentinelArrayOfArrays = new SentinelArrayOfArraysProcessor();
@@ -2036,7 +2039,62 @@ protected override bool SetResultCore(PhysicalConnection connection, Message mes
             }
         }
 
-        private sealed class SentinelGetSentinelAddresses : ResultProcessor<EndPoint[]>
+        private sealed class SentinelGetSentinelAddressesProcessor : ResultProcessor<EndPoint[]>
+        {
+            protected override bool SetResultCore(PhysicalConnection connection, Message message, in RawResult result)
+            {
+                List<EndPoint> endPoints = new List<EndPoint>();
+
+                switch (result.Type)
+                {
+                    case ResultType.MultiBulk:
+                        foreach (RawResult item in result.GetItems())
+                        {
+                            var arr = item.GetItemsAsValues();
+                            string ip = null;
+                            string portStr = null;
+
+                            for (int i = 0; i < arr.Length && (ip == null || portStr == null); i += 2)
+                            {
+                                string name = arr[i];
+                                string value = arr[i + 1];
+
+                                switch (name)
+                                {
+                                    case "ip":
+                                        ip = value;
+                                        break;
+                                    case "port":
+                                        portStr = value;
+                                        break;
+                                }
+                            }
+
+                            if (ip != null && portStr != null && int.TryParse(portStr, out int port))
+                            {
+                                endPoints.Add(Format.ParseEndPoint(ip, port));
+                            }
+                        }
+                        break;
+
+                    case ResultType.SimpleString:
+                        //We don't want to blow up if the master is not found
+                        if (result.IsNull)
+                            return true;
+                        break;
+                }
+
+                if (endPoints.Count > 0)
+                {
+                    SetResult(message, endPoints.ToArray());
+                    return true;
+                }
+
+                return false;
+            }
+        }
+
+        private sealed class SentinelGetReplicaAddressesProcessor : ResultProcessor<EndPoint[]>
         {
             protected override bool SetResultCore(PhysicalConnection connection, Message message, in RawResult result)
             {

tests/RedisConfigs/Docker/docker-entrypoint.sh

@@ -4,7 +4,7 @@ if [ "$#" -ne 0 ]; then
     exec "$@"
 else
     mkdir -p /var/log/supervisor
-    mkdir Temp/
+    mkdir -p Temp/
 
     supervisord -c /etc/supervisord.conf
     sleep 3