Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Web/Hosting/CustomRuntimeManager.cs

@@ -0,0 +1,95 @@
+//------------------------------------------------------------------------------
+// <copyright file="CustomRuntimeSuspendManager.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>                                                                
+//------------------------------------------------------------------------------
+
+namespace System.Web.Hosting {
+    using System.Collections.Concurrent;
+    using System.Collections.Generic;
+    using System.Web.Util;
+
+    // Handles calling suspend and resume methods, including issues around
+    // synchronization and timeout handling.
+
+    internal sealed class CustomRuntimeManager : ICustomRuntimeManager {
+
+        private readonly ConcurrentDictionary<CustomRuntimeRegistration, object> _activeRegistrations = new ConcurrentDictionary<CustomRuntimeRegistration, object>();
+
+        private List<IProcessSuspendListener> GetAllSuspendListeners() {
+            List<IProcessSuspendListener> suspendListeners = new List<IProcessSuspendListener>();
+
+            foreach (var registration in _activeRegistrations.Keys) {
+                var suspendListener = registration.CustomRuntime as IProcessSuspendListener;
+                if (suspendListener != null) {
+                    suspendListeners.Add(suspendListener);
+                }
+            }
+
+            return suspendListeners;
+        }
+
+        public ICustomRuntimeRegistrationToken Register(ICustomRuntime customRuntime) {
+            CustomRuntimeRegistration registration = new CustomRuntimeRegistration(this, customRuntime);
+            _activeRegistrations[registration] = null;
+            return registration;
+        }
+
+        // Custom runtimes are expected to be well-behaved so will be suspended sequentially and aren't
+        // subject to the 5-second timeout that normal applications are subject to.
+        public Action SuspendAllCustomRuntimes() {
+            var suspendListeners = GetAllSuspendListeners();
+            if (suspendListeners == null || suspendListeners.Count == 0) {
+                return null;
+            }
+
+            List<IProcessResumeCallback> callbacks = new List<IProcessResumeCallback>(suspendListeners.Count);
+            foreach (var suspendListener in suspendListeners) {
+                IProcessResumeCallback callback = null;
+                try {
+                    callback = suspendListener.Suspend();
+                }
+                catch (AppDomainUnloadedException) {
+                    // There exists a race condition where a custom runtime could have been stopped (unloaded)
+                    // while a call to Suspend is in progress, so AD unloads may leak out. Don't treat this
+                    // as a failure; just move on.
+                }
+
+                if (callback != null) {
+                    callbacks.Add(callback);
+                }
+            }
+
+            return () => {
+                foreach (var callback in callbacks) {
+                    try {
+                        callback.Resume();
+                    }
+                    catch (AppDomainUnloadedException) {
+                        // There exists a race condition where a custom runtime could have been stopped (unloaded)
+                        // while a call to Suspend is in progress, so AD unloads may leak out. Don't treat this
+                        // as a failure; just move on.
+                    }
+                }
+            };
+        }
+
+        private sealed class CustomRuntimeRegistration : ICustomRuntimeRegistrationToken {
+            private readonly CustomRuntimeManager _customRuntimeManager;
+
+            public CustomRuntimeRegistration(CustomRuntimeManager customRuntimeManager, ICustomRuntime customRuntime) {
+                _customRuntimeManager = customRuntimeManager;
+                CustomRuntime = customRuntime;
+            }
+
+            public ICustomRuntime CustomRuntime { get; private set; }
+
+            public void Unregister() {
+                object dummy;
+                bool removed = _customRuntimeManager._activeRegistrations.TryRemove(this, out dummy);
+
+                Debug.Assert(removed, "Entry did not exist in the dictionary; was it removed twice?");
+            }
+        }
+    }
+}