From 61f78fffdddce086e95e6ec578dde352e8605342 Mon Sep 17 00:00:00 2001
From: Yagel <yagelba@payoneer.com>
Date: Sun, 25 Jul 2021 19:21:19 +0300
Subject: [PATCH] dispose of previous inner (in-memory) cache when calling
 ClearAll()

---
 Core.UnitTests/CacheInterfaceTests.cs         | 37 +++++++++++++++++++
 SystemRuntime.UnitTests/InMemoryCacheTests.cs |  1 +
 SystemRuntime/ObjectCache.cs                  | 17 +++++++--
 SystemRuntime/SystemRuntime.csproj            |  4 +-
 4 files changed, 54 insertions(+), 5 deletions(-)

diff --git a/Core.UnitTests/CacheInterfaceTests.cs b/Core.UnitTests/CacheInterfaceTests.cs
index a83f212..7f224b9 100644
--- a/Core.UnitTests/CacheInterfaceTests.cs
+++ b/Core.UnitTests/CacheInterfaceTests.cs
@@ -3,6 +3,7 @@
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
+using System.Threading;
 using System.Threading.Tasks;
 
 namespace PubComp.Caching.Core.UnitTests
@@ -214,6 +215,42 @@ public void TestCacheTimeToLive_Constant()
             Assert.AreNotEqual("1", result);
         }
 
+        [TestMethod]
+        [Ignore("Diagnose manually the memory consumption")]
+        public void LotsOfClearAll()
+        {
+            var cache = GetCache("cache1");
+            for (var i = 0; i < 5000; i++)
+            {
+                cache.ClearAll();
+            }
+            Thread.Sleep(1000);
+            GC.Collect();
+            Thread.Sleep(1000);
+            for (var i = 0; i < 5000; i++)
+            {
+                cache.ClearAll();
+            }
+        }
+
+        [TestMethod]
+        [Ignore("Diagnose manually the memory consumption")]
+        public async Task LotsOfClearAsyncAll()
+        {
+            var cache = GetCache("cache1");
+            for (var i = 0; i < 5000; i++)
+            {
+                await cache.ClearAllAsync().ConfigureAwait(false);
+            }
+            await Task.Delay(1000);
+            GC.Collect();
+            await Task.Delay(1000);
+            for (var i = 0; i < 5000; i++)
+            {
+                await cache.ClearAllAsync().ConfigureAwait(false);
+            }
+        }
+
         [TestMethod]
         public void TestCacheTryGet()
         {
diff --git a/SystemRuntime.UnitTests/InMemoryCacheTests.cs b/SystemRuntime.UnitTests/InMemoryCacheTests.cs
index bf03000..ce574f0 100644
--- a/SystemRuntime.UnitTests/InMemoryCacheTests.cs
+++ b/SystemRuntime.UnitTests/InMemoryCacheTests.cs
@@ -110,6 +110,7 @@ int Get()
         }
 
         [TestMethod]
+        [Ignore("only a one time test needed")]
         public void LoadTest_LockingStrategiesComparison()
         {
             const int numberOfThreads = 16;
diff --git a/SystemRuntime/ObjectCache.cs b/SystemRuntime/ObjectCache.cs
index 545fcf1..05374f9 100644
--- a/SystemRuntime/ObjectCache.cs
+++ b/SystemRuntime/ObjectCache.cs
@@ -220,13 +220,24 @@ public Task ClearAsync(string key)
 
         public void ClearAll()
         {
-            innerCache = new System.Runtime.Caching.MemoryCache(this.name);
+            var previousInnerCache = System.Threading.Interlocked.Exchange(ref innerCache,
+                new System.Runtime.Caching.MemoryCache(this.name));
+
+            if (previousInnerCache is IDisposable disposeMe)
+            {
+                // I had a concern that some classes will hold the reference of the previous cache
+                // and that the disposing will cause in certain edge race cases a serious exception (AlreadyDisposedException).
+                // But using the dispose cache object is ok, but does nothing and no exception as well.
+                // Set: will not set, as if the ClearAll was called a nanosecond after setting
+                // Get: will get nothing, as if the ClearAll was called a nanosecond before getting
+                disposeMe.Dispose();
+            }
         }
 
         public Task ClearAllAsync()
         {
-            innerCache = new System.Runtime.Caching.MemoryCache(this.name);
-            return Task.FromResult<object>(null);
+            ClearAll();
+            return Task.CompletedTask;
         }
 
         public object GetDetails() => new
diff --git a/SystemRuntime/SystemRuntime.csproj b/SystemRuntime/SystemRuntime.csproj
index be8b742..dfb599b 100644
--- a/SystemRuntime/SystemRuntime.csproj
+++ b/SystemRuntime/SystemRuntime.csproj
@@ -5,9 +5,9 @@
     <AssemblyName>PubComp.Caching.SystemRuntime</AssemblyName>
     <RootNamespace>PubComp.Caching.SystemRuntime</RootNamespace>
     <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
-    <Version>5.0.0</Version>
+    <Version>5.0.1</Version>
     <AssemblyVersion>5.0.0.0</AssemblyVersion>
-    <FileVersion>5.0.0.0</FileVersion>
+    <FileVersion>5.0.1.0</FileVersion>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|AnyCPU'">
     <NoWarn>1701;1702;1591</NoWarn>