Merge pull request #3433 from heejaechang/implicitcache2

fix flaky unit test

src/EditorFeatures/Core/Implementation/Workspaces/ProjectCacheServiceFactory.ProjectCacheService.cs

@@ -54,11 +54,11 @@ public void ClearImplicitCache()
                 }
             }
 
-            public void ClearExpiredImplicitCache(int expirationTimeInMS)
+            public void ClearExpiredImplicitCache(DateTime expirationTime)
             {
                 lock (_gate)
                 {
-                    _implicitCache.ClearExpiredItems(expirationTimeInMS);
+                    _implicitCache.ClearExpiredItems(expirationTime);
                 }
             }
 
@@ -89,8 +89,8 @@ public IDisposable EnableCaching(ProjectId key)
                     }
                     else if (!PartOfP2PReferences(key))
                     {
-                        _implicitCacheMonitor?.Touch();
                         _implicitCache.Touch(instance);
+                        _implicitCacheMonitor?.Touch();
                     }
 
                     return instance;

src/EditorFeatures/Core/Implementation/Workspaces/ProjectCacheServiceFactory.SimpleMRUCache.cs

@@ -40,32 +40,32 @@ public bool Empty
                 public void Touch(object instance)
                 {
                     var oldIndex = -1;
-                    var oldTime = Environment.TickCount;
+                    var oldTime = DateTime.UtcNow;
 
                     for (var i = 0; i < nodes.Length; i++)
                     {
                         if (instance == nodes[i].Data)
                         {
-                            nodes[i].LastTouchedInMS = Environment.TickCount;
+                            nodes[i].LastTouched = DateTime.UtcNow;
                             return;
                         }
 
-                        if (oldTime >= nodes[i].LastTouchedInMS)
+                        if (oldTime >= nodes[i].LastTouched)
                         {
-                            oldTime = nodes[i].LastTouchedInMS;
+                            oldTime = nodes[i].LastTouched;
                             oldIndex = i;
                         }
                     }
 
                     Contract.Requires(oldIndex >= 0);
-                    nodes[oldIndex] = new Node(instance, Environment.TickCount);
+                    nodes[oldIndex] = new Node(instance, DateTime.UtcNow);
                 }
 
-                public void ClearExpiredItems(int expirationTimeInMS)
+                public void ClearExpiredItems(DateTime expirationTime)
                 {
                     for (var i = 0; i < nodes.Length; i++)
                     {
-                        if (nodes[i].Data != null && nodes[i].LastTouchedInMS < expirationTimeInMS)
+                        if (nodes[i].Data != null && nodes[i].LastTouched < expirationTime)
                         {
                             nodes[i] = default(Node);
                         }
@@ -80,12 +80,12 @@ public void Clear()
                 private struct Node
                 {
                     public readonly object Data;
-                    public int LastTouchedInMS;
+                    public DateTime LastTouched;
 
-                    public Node(object data, int lastTouchedInMS)
+                    public Node(object data, DateTime lastTouched)
                     {
                         Data = data;
-                        LastTouchedInMS = lastTouchedInMS;
+                        LastTouched = lastTouched;
                     }
                 }
             }
@@ -108,7 +108,7 @@ private class ImplicitCacheMonitor : IdleProcessor
 
                 protected override Task ExecuteAsync()
                 {
-                    _owner.ClearExpiredImplicitCache(Environment.TickCount - BackOffTimeSpanInMS);
+                    _owner.ClearExpiredImplicitCache(DateTime.UtcNow - TimeSpan.FromMilliseconds(BackOffTimeSpanInMS));
 
                     return SpecializedTasks.EmptyTask;
                 }

src/EditorFeatures/Test/Workspaces/ProjectCacheHostServiceFactoryTests.cs

@@ -120,14 +120,35 @@ public void TestImplicitCacheKeepsObjectAlive1()
         public void TestImplicitCacheMonitoring()
         {
             var cacheService = new ProjectCacheHostServiceFactory.ProjectCacheService(null, 10, forceCleanup: true);
+            var weak = PutObjectInImplicitCache(cacheService);
+
+            var timeout = TimeSpan.FromSeconds(10);
+            var current = DateTime.UtcNow;
+            do
+            {
+                Thread.Sleep(100);
+                CollectGarbage();
+
+                if (DateTime.UtcNow - current > timeout)
+                {
+                    break;
+                }
+            }
+            while (weak.IsAlive);
+
+            Assert.False(weak.IsAlive);
+            GC.KeepAlive(cacheService);
+        }
+
+        private static WeakReference PutObjectInImplicitCache(ProjectCacheHostServiceFactory.ProjectCacheService cacheService)
+        {
             var instance = new object();
             var weak = new WeakReference(instance);
+
             cacheService.CacheObjectIfCachingEnabledForKey(ProjectId.CreateNewId(), (object)null, instance);
             instance = null;
-            Thread.Sleep(100);
-            CollectGarbage();
-            Assert.False(weak.IsAlive);
-            GC.KeepAlive(cacheService);
+
+            return weak;
         }
 
         [Fact]
@@ -224,9 +245,12 @@ private class Owner : ICachedObjectOwner
 
         private static void CollectGarbage()
         {
-            GC.Collect();
-            GC.WaitForPendingFinalizers();
-            GC.Collect();
+            for (var i = 0; i < 10; i++)
+            {
+                GC.Collect();
+                GC.WaitForPendingFinalizers();
+                GC.Collect();
+            }
         }
     }
 }