add memory cache options (#640)

* add memory cache options

* add a small test

Author: jennyf19

src/Microsoft.Identity.Web/Microsoft.Identity.Web.xml

@@ -74,7 +74,13 @@ protected override Task<byte[]> ReadCacheBytesAsync(string cacheKey)
         /// <returns>A <see cref="Task"/> that completes when a write operation has completed.</returns>
         protected override Task WriteCacheBytesAsync(string cacheKey, byte[] bytes)
         {
-            _memoryCache.Set(cacheKey, bytes, _cacheOptions.AbsoluteExpirationRelativeToNow);
+            MemoryCacheEntryOptions memoryCacheEntryOptions = new MemoryCacheEntryOptions()
+            {
+                AbsoluteExpirationRelativeToNow = _cacheOptions.AbsoluteExpirationRelativeToNow,
+                Size = bytes?.Length,
+            };
+
+            _memoryCache.Set(cacheKey, bytes, memoryCacheEntryOptions);
             return Task.CompletedTask;
         }
     }

src/Microsoft.Identity.Web/TokenCacheProviders/InMemory/MsalMemoryTokenCacheProvider.cs

@@ -5,6 +5,7 @@
 using System.Linq;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.Caching.Memory;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.DependencyInjection.Extensions;
@@ -32,16 +33,26 @@ internal MicrosoftIdentityAppCallsWebApiAuthenticationBuilder(
         /// Add in memory token caches.
         /// </summary>
         /// <param name="configureOptions"><see cref="MsalMemoryTokenCacheOptions"/> to configure.</param>
+        /// <param name="memoryCacheOptions"><see cref="MemoryCacheOptions"/> to configure.</param>
         /// <returns>the service collection.</returns>
         public MicrosoftIdentityAppCallsWebApiAuthenticationBuilder AddInMemoryTokenCaches(
-        Action<MsalMemoryTokenCacheOptions>? configureOptions = null)
+        Action<MsalMemoryTokenCacheOptions>? configureOptions = null,
+        Action<MemoryCacheOptions>? memoryCacheOptions = null)
         {
             if (configureOptions != null)
             {
                 Services.Configure(configureOptions);
             }
 
-            Services.AddMemoryCache();
+            if (memoryCacheOptions != null)
+            {
+                Services.AddMemoryCache(memoryCacheOptions);
+            }
+            else
+            {
+                Services.AddMemoryCache();
+            }
+
             Services.AddHttpContextAccessor();
             Services.AddSingleton<IMsalTokenCacheProvider, MsalMemoryTokenCacheProvider>();
             return this;

src/Microsoft.Identity.Web/WebAppExtensions/MicrosoftIdentityAppCallingWebApiAuthenticationBuilder.cs

@@ -388,10 +388,13 @@ public void AddMicrosoftIdentityWebApp_AddsInMemoryTokenCaches()
             services.AddAuthentication(OpenIdConnectDefaults.AuthenticationScheme)
                 .AddMicrosoftIdentityWebApp(_configureMsOptions)
                 .EnableTokenAcquisitionToCallDownstreamApi(_configureAppOptions)
-                .AddInMemoryTokenCaches(options => options.AbsoluteExpirationRelativeToNow = TimeSpan.FromHours(1));
+                .AddInMemoryTokenCaches(
+                    options => options.AbsoluteExpirationRelativeToNow = TimeSpan.FromHours(1),
+                    memoryCacheOptions: options => { options.SizeLimit = (long)1e9; });
 
             // Assert correct services added
             Assert.Contains(services, s => s.ServiceType == typeof(IConfigureOptions<MsalMemoryTokenCacheOptions>));
+            Assert.Contains(services, s => s.ServiceType == typeof(IConfigureOptions<MemoryCacheOptions>));
             Assert.Contains(services, s => s.ServiceType == typeof(IMemoryCache));
             Assert.Contains(services, s => s.ServiceType == typeof(IMsalTokenCacheProvider));
         }