Maintenance events: add NodeMaintenanceScaleComplete (#1902)

Recognize the upcoming `NodeMaintenanceScaleComplete` event to handle Redis cluster scaling (either direction).

Author: NickCraver

docs/ReleaseNotes.md

@@ -1,6 +1,7 @@
 # Release Notes
 
 ## Unreleased
+- Add support for NodeMaintenanceScaleComplete event (handles Redis cluster scaling) (#1902 via NickCraver)
 
 ## 2.2.79
 

src/StackExchange.Redis/Maintenance/AzureMaintenanceEvent.cs

@@ -138,6 +138,7 @@ await sub.SubscribeAsync(PubSubChannelName, async (channel, message) =>
                     {
                         case AzureNotificationType.NodeMaintenanceEnded:
                         case AzureNotificationType.NodeMaintenanceFailoverComplete:
+                        case AzureNotificationType.NodeMaintenanceScaleComplete:
                             await multiplexer.ReconfigureAsync(first: false, reconfigureAll: true, log: logProxy, blame: null, cause: $"Azure Event: {newMessage.NotificationType}").ForAwait();
                             break;
                     }
@@ -188,6 +189,7 @@ await sub.SubscribeAsync(PubSubChannelName, async (channel, message) =>
             // This is temporary until server changes go into effect - to be removed in later versions
             "NodeMaintenanceFailover" => AzureNotificationType.NodeMaintenanceFailoverComplete,
             "NodeMaintenanceFailoverComplete" => AzureNotificationType.NodeMaintenanceFailoverComplete,
+            "NodeMaintenanceScaleComplete" => AzureNotificationType.NodeMaintenanceScaleComplete,
             _ => AzureNotificationType.Unknown,
         };
     }

src/StackExchange.Redis/Maintenance/AzureNotificationType.cs

@@ -34,5 +34,10 @@ public enum AzureNotificationType
         /// Indicates that a replica has been promoted to primary.
         /// </summary>
         NodeMaintenanceFailoverComplete,
+
+        /// <summary>
+        /// Indicates that a scale event (adding or removing nodes) has completed for a cluster.
+        /// </summary>
+        NodeMaintenanceScaleComplete,
     }
 }

tests/StackExchange.Redis.Tests/AzureMaintenanceEventTests.cs

@@ -20,6 +20,7 @@ public AzureMaintenanceEventTests(ITestOutputHelper output) : base(output)
         [InlineData("NotificationType|NodeMaintenanceStarting|StartTimeInUTC|2021-03-02T23:26:57|IsReplica|j|IPAddress||SSLPort|char|NonSSLPort|char", AzureNotificationType.NodeMaintenanceStarting, "2021-03-02T23:26:57", false, null, 0, 0)]
         [InlineData("NotificationType|NodeMaintenanceStarting|somejunkkey|somejunkvalue|StartTimeInUTC|2021-03-02T23:26:57|IsReplica|False|IPAddress||SSLPort|15999|NonSSLPort|139991", AzureNotificationType.NodeMaintenanceStarting, "2021-03-02T23:26:57", false, null, 15999, 139991)]
         [InlineData("NotificationType|NodeMaintenanceStarting|somejunkkey|somejunkvalue|StartTimeInUTC|2021-03-02T23:26:57|IsReplica|False|IPAddress|127.0.0.1|SSLPort|15999|NonSSLPort|139991", AzureNotificationType.NodeMaintenanceStarting, "2021-03-02T23:26:57", false, "127.0.0.1", 15999, 139991)]
+        [InlineData("NotificationType|NodeMaintenanceScaleComplete|somejunkkey|somejunkvalue|StartTimeInUTC|2021-03-02T23:26:57|IsReplica|False|IPAddress|127.0.0.1|SSLPort|15999|NonSSLPort|139991", AzureNotificationType.NodeMaintenanceScaleComplete, "2021-03-02T23:26:57", false, "127.0.0.1", 15999, 139991)]
         [InlineData("NotificationTypeNodeMaintenanceStartingsomejunkkeysomejunkvalueStartTimeInUTC2021-03-02T23:26:57IsReplicaFalseIPAddress127.0.0.1SSLPort15999NonSSLPort139991", AzureNotificationType.Unknown, null, false, null, 0, 0)]
         [InlineData("NotificationType|", AzureNotificationType.Unknown, null, false, null, 0, 0)]
         [InlineData("NotificationType|NodeMaintenanceStarting1", AzureNotificationType.Unknown, null, false, null, 0, 0)]