Update documentation on long item usage;

README.md

@@ -376,12 +376,18 @@ To enable this option set the following configuration key.
 
 Do not forget to set this option back to `false` or to delte it after the transition period is over.
 
-## Restrictions
+## Restrictions && Limitations
 
-Key must be less than 250 characters and value must be less than 1MB of data.
+Key must be less than 250 characters and value must be less than the value `-I` configured during memcached instance start.
 
 The key length restriction can be lifted, see [Long keys support](#long-keys-support) section for the details.
 
+If the value is greater than the configured `-I` value the memcached client won't throw an exception - it simply won't store a key without any notification.
+Therefore, when trying to read such key - nothing will be returned.
+
+Also, please note that this library utilizes a memcached item `flags` to store item type information to simplify and make deserialization faster.
+This implies that one is not advised to use this library to read the data from memcached that you didn't put there using this library - it might be deserialized incorrectly or not deserialized at all.
+
 ## Additional configuration
 
 ### SASL

docker-compose.yaml

@@ -4,20 +4,23 @@ services:
     image: memcached:latest
     restart: always
     container_name: memcached-1
-    command: ["-m", "128"]  
-    ports:  
+    command: ["-m", "128", "-I", "1M"]
+    # command: ["-m", "128", "-I", "512k", "-o", "slab_chunk_max=524288"]
+    ports:
       - 11211:11211
   memcached-2:
     image: memcached:latest
     restart: always
     container_name: memcached-2
-    command: ["-m", "128"]  
-    ports:  
+    command: ["-m", "128", "-I", "1M"]
+    # command: ["-m", "128", "-I", "512k", "-o", "slab_chunk_max=524288"]
+    ports:
       - 11212:11211
   memcached-3:
     image: memcached:latest
     restart: always
     container_name: memcached-3
-    command: ["-m", "128"]  
-    ports:  
+    command: ["-m", "128", "-I", "1M"]
+    # command: ["-m", "128", "-I", "512k", "-o", "slab_chunk_max=524288"]
+    ports:
       - 11213:11211

src/Aer.Memcached.Client/Serializers/Binary/BinarySerializer.cs

@@ -13,7 +13,7 @@ public class BinarySerializer
     private const uint RawDataFlag = 0xfa52;
     private const uint TypeCodeSerializationMask = 0x0100;
     private const uint TypeCodeDeserializationMask = 0xff;
-
+    
     private readonly IObjectBinarySerializer _objectBinarySerializer;
 
     public BinarySerializer(IObjectBinarySerializerFactory objectBinarySerializerFactory)
@@ -119,6 +119,17 @@ internal DeserializationResult<T> Deserialize<T>(
         var typeCode = (TypeCode) (item.Flags & TypeCodeDeserializationMask);
         if (typeCode == TypeCode.Empty)
         {
+            // the flags value is set during item serialization
+            // it stores the cache item System.Runtime.TypeCode
+            // if it is not set -> Flags == 0 or Flags contain some unknown value 
+            // then the item is considered empty
+            // The Data property for such empty items though
+            // will contain ASCII bytes for "Not found" string
+            // 0x4E, 0x6F, 0x74, 0x20, 0x66, 0x6F, 0x75, 0x6E, 0x64
+            // we don't check them since typeCode absence already tells us that the item is empty
+            // it does, though impede using this library for reading existing
+            // memcached keys that were written not using this library
+            // since they may set Flags to some arbitrary value which we interpret 
             return DeserializationResult<T>.Empty;
         }
 

tests/Aer.Memcached.Tests/Aer.Memcached.Tests.csproj

@@ -5,6 +5,7 @@
         <ImplicitUsings>enable</ImplicitUsings>
 
         <IsPackable>false</IsPackable>
+        <LangVersion>latest</LangVersion>
     </PropertyGroup>
 
     <ItemGroup>

tests/Aer.Memcached.Tests/TestClasses/MemcachedClientMethodsTestsBase.cs

@@ -114,7 +114,7 @@ public async Task Get_CheckAllTypes_DefaultValue()
             await StoreAndGet_CheckType<Dictionary<KeyObject, SimpleObject>>();
         }
     }
-    
+
     [DataTestMethod]
     [DataRow(true)]
     [DataRow(false)]
@@ -205,14 +205,14 @@ await Client.MultiStoreAsync(
         var getValue = await Client.MultiGetAsync<string>(new[] {key}, CancellationToken.None);
 
         getValue.Count.Should().Be(1);
-        
+
         await Task.Delay(TimeSpan.FromSeconds(CacheItemExpirationSeconds * 2));
 
-        getValue = await Client.MultiGetAsync<string>(new[]{key}, CancellationToken.None);
+        getValue = await Client.MultiGetAsync<string>(new[] {key}, CancellationToken.None);
 
         getValue.Count.Should().Be(0);
     }
-    
+
     [TestMethod]
     public async Task StoreAndGet_EmptyString()
     {
@@ -227,41 +227,47 @@ public async Task StoreAndGet_EmptyString()
         getValue.Success.Should().BeTrue();
         getValue.IsEmptyResult.Should().BeFalse();
     }
-    
+
     [TestMethod]
     public async Task MultiStoreAndGet_NullAsString()
     {
         var keyValues = new Dictionary<string, string>();
-    
+
         foreach (var _ in Enumerable.Range(0, 5))
         {
             keyValues[Guid.NewGuid().ToString()] = null;
         }
-
-        await Client.MultiStoreAsync(keyValues, TimeSpan.FromSeconds(CacheItemExpirationSeconds), CancellationToken.None);
-
+
+        await Client.MultiStoreAsync(
+            keyValues,
+            TimeSpan.FromSeconds(CacheItemExpirationSeconds),
+            CancellationToken.None);
+
         var getValues = await Client.MultiGetAsync<string>(keyValues.Keys, CancellationToken.None);
-    
+
         foreach (var keyValue in keyValues)
         {
             getValues[keyValue.Key].Should().Be(keyValues[keyValue.Key]);
         }
     }
-    
+
     [TestMethod]
     public async Task MultiStoreAndGet_EmptyString()
     {
         var keyValues = new Dictionary<string, string>();
-    
+
         foreach (var _ in Enumerable.Range(0, 5))
         {
             keyValues[Guid.NewGuid().ToString()] = string.Empty;
         }
-
-        await Client.MultiStoreAsync(keyValues, TimeSpan.FromSeconds(CacheItemExpirationSeconds), CancellationToken.None);
-
+
+        await Client.MultiStoreAsync(
+            keyValues,
+            TimeSpan.FromSeconds(CacheItemExpirationSeconds),
+            CancellationToken.None);
+
         var getValues = await Client.MultiGetAsync<string>(keyValues.Keys, CancellationToken.None);
-    
+
         foreach (var keyValue in keyValues)
         {
             getValues[keyValue.Key].Should().BeNull();
@@ -275,15 +281,15 @@ public async Task StoreAndGet_NullExpiration()
         var value = Fixture.Create<SimpleObject>();
 
         await Client.StoreAsync(
-            key, 
-            value, 
-            expirationTime: null, 
+            key,
+            value,
+            expirationTime: null,
             CancellationToken.None);
 
         var getValue = await Client.GetAsync<SimpleObject>(key, CancellationToken.None);
 
         getValue.Success.Should().BeTrue();
-        
+
         getValue.IsEmptyResult.Should().BeFalse();
         getValue.Result.Should().BeEquivalentTo(value);
     }
@@ -302,12 +308,12 @@ public async Task StoreAndGet_SimpleObject()
         getValue.Success.Should().BeTrue();
         getValue.IsEmptyResult.Should().BeFalse();
     }
-    
+
     [TestMethod]
     public async Task MultiStoreAndGet_SimpleObject()
     {
         var keyValues = new Dictionary<string, SimpleObject>();
-    
+
         foreach (var _ in Enumerable.Range(0, 5))
         {
             keyValues[Guid.NewGuid().ToString()] = Fixture.Create<SimpleObject>();
@@ -317,11 +323,14 @@ public async Task MultiStoreAndGet_SimpleObject()
 
         var tooLongKey = GetTooLongKey();
         keyValues[tooLongKey] = Fixture.Create<SimpleObject>();
-
-        await Client.MultiStoreAsync(keyValues, TimeSpan.FromSeconds(CacheItemExpirationSeconds), CancellationToken.None);
-
+
+        await Client.MultiStoreAsync(
+            keyValues,
+            TimeSpan.FromSeconds(CacheItemExpirationSeconds),
+            CancellationToken.None);
+
         var getValues = await Client.MultiGetAsync<SimpleObject>(keyValues.Keys, CancellationToken.None);
-    
+
         foreach (var keyValue in keyValues)
         {
             getValues[keyValue.Key].Should().BeEquivalentTo(keyValues[keyValue.Key]);
@@ -395,19 +404,19 @@ public async Task MultiStoreAndGet_ExpirationNowAndInThePast_NoKeysStored()
             CancellationToken.None);
 
         storeResult.Success.Should().BeFalse();
-        
+
         storeResult = await Client.MultiStoreAsync(
             keyValues,
             expirationTime: DateTimeOffset.Now,
             CancellationToken.None);
 
         storeResult.Success.Should().BeFalse();
 
-        var getValues = 
+        var getValues =
             await Client.MultiGetAsync<SimpleObject>(keyValues.Keys, CancellationToken.None);
 
         // no keys should be stored
-        
+
         getValues.Count.Should().Be(0);
     }
 
@@ -468,11 +477,64 @@ public async Task StoreAndGet_ObjectWithCollections()
 
         var getValue = await Client.GetAsync<ObjectWithCollections>(key, CancellationToken.None);
 
-        getValue.Result.Should().BeEquivalentTo(value);
         getValue.Success.Should().BeTrue();
+        getValue.Result.Should().BeEquivalentTo(value);
         getValue.IsEmptyResult.Should().BeFalse();
     }
 
+    [TestMethod]
+    public async Task StoreAndGet_VeryLargeObject()
+    {
+        var key = Guid.NewGuid().ToString();
+
+        // very large array 1_024_000 * 4 = 4MB
+        var value = new int[1_024_000];
+
+        // memcached, while restricting item to configured "-I" parameter, 
+        // returns success while trying to add a too large item to cache,
+        // it just does nothing - it does not throw anything but does not store the key either
+        var storeResult = await Client.StoreAsync(
+            key,
+            value,
+            TimeSpan.FromSeconds(CacheItemExpirationSeconds),
+            CancellationToken.None);
+
+        storeResult.Success.Should().BeTrue();
+
+        // when trying to read too large object
+        // memcached simply returns nothing since it was not set in the first place
+        var getValue = await Client.GetAsync<byte[]>(key, CancellationToken.None);
+
+        getValue.Success.Should().BeTrue();
+        getValue.IsEmptyResult.Should().BeTrue();
+    }
+
+    [TestMethod]
+    public async Task StoreAndMultiGet_VeryLargeObject()
+    {
+        var key = Guid.NewGuid().ToString();
+
+        // very large array 1_024_000 * 4 = 4MB
+        var value = new int[1_024_000];
+
+        // memcached, while restricting item to configured "-I" parameter, 
+        // returns success while trying to add a too large item to cache,
+        // it just does nothing - it does not throw anything but does not store the key either
+        var storeResult = await Client.StoreAsync(
+            key,
+            value,
+            TimeSpan.FromSeconds(CacheItemExpirationSeconds),
+            CancellationToken.None);
+
+        storeResult.Success.Should().BeTrue();
+
+        // when trying to read too large object
+        // memcached simply returns nothing since it was not set in the first place
+        var getValue = await Client.MultiGetAsync<byte[]>([key], CancellationToken.None);
+
+        getValue.ContainsKey(key).Should().BeFalse();
+    }
+
     [TestMethod]
     public async Task MultiStoreAndGet_ObjectWithCollections()
     {