Fixing the bug with connections on database make restore fail (#473)

* closing the connections that don't need to be open and keeping track of the connections that should stay open

src/Microsoft.SqlTools.ServiceLayer/Connection/DatabaseLocksManager.cs

@@ -0,0 +1,113 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using Microsoft.SqlTools.ServiceLayer.LanguageServices;
+using System;
+using System.Collections.Generic;
+using System.Threading;
+
+namespace Microsoft.SqlTools.ServiceLayer.Connection
+{
+    public class DatabaseLocksManager: IDisposable
+    {
+        internal DatabaseLocksManager(int waitToGetFullAccess)
+        {
+            this.waitToGetFullAccess = waitToGetFullAccess;
+        }
+
+        private static DatabaseLocksManager instance = new DatabaseLocksManager(DefaultWaitToGetFullAccess);
+
+        public static DatabaseLocksManager Instance
+        {
+            get
+            {
+                return instance;
+            }
+        }
+
+        public ConnectionService ConnectionService { get; set; }
+
+        private Dictionary<string, ManualResetEvent> databaseAccessEvents = new Dictionary<string, ManualResetEvent>();
+        private object databaseAccessLock = new object();
+        public const int DefaultWaitToGetFullAccess = 60000;
+        public int waitToGetFullAccess = DefaultWaitToGetFullAccess;
+
+        private ManualResetEvent GetResetEvent(string serverName, string databaseName)
+        {
+            string key = GenerateKey(serverName, databaseName);
+            ManualResetEvent resetEvent = null;
+            lock (databaseAccessLock)
+            {
+                if (!databaseAccessEvents.TryGetValue(key, out resetEvent))
+                {
+                    resetEvent = new ManualResetEvent(true);
+                    databaseAccessEvents.Add(key, resetEvent);
+                }
+            }
+
+            return resetEvent;
+        }
+
+        public bool GainFullAccessToDatabase(string serverName, string databaseName)
+        {
+            /*
+            ManualResetEvent resetEvent = GetResetEvent(serverName, databaseName);
+            if (resetEvent.WaitOne(this.waitToGetFullAccess))
+            {
+                resetEvent.Reset();
+
+                foreach (IConnectedBindingQueue item in ConnectionService.ConnectedQueues)
+                {
+                    item.CloseConnections(serverName, databaseName);
+                }
+                return true;
+            }
+            else
+            {
+                throw new DatabaseFullAccessException($"Waited more than {waitToGetFullAccess} milli seconds for others to release the lock");
+            }
+            */
+            foreach (IConnectedBindingQueue item in ConnectionService.ConnectedQueues)
+            {
+                item.CloseConnections(serverName, databaseName);
+            }
+            return true;
+
+        }
+
+        public bool ReleaseAccess(string serverName, string databaseName)
+        {
+            /*
+            ManualResetEvent resetEvent = GetResetEvent(serverName, databaseName);
+
+            foreach (IConnectedBindingQueue item in ConnectionService.ConnectedQueues)
+            {
+                item.OpenConnections(serverName, databaseName);
+            }
+            
+            resetEvent.Set();
+            */
+            foreach (IConnectedBindingQueue item in ConnectionService.ConnectedQueues)
+            {
+                item.OpenConnections(serverName, databaseName);
+            }
+            return true;
+            
+        }
+
+        private string GenerateKey(string serverName, string databaseName)
+        {
+            return $"{serverName.ToLowerInvariant()}-{databaseName.ToLowerInvariant()}";
+        }
+
+        public void Dispose()
+        {
+            foreach (var resetEvent in databaseAccessEvents)
+            {
+                resetEvent.Value.Dispose();
+            }
+        }
+    }
+}