Implement minimal implementation of HybridCache #55147
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| // Licensed to the .NET Foundation under one or more agreements. | ||
| // The .NET Foundation licenses this file to you under the MIT license. | ||
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| namespace Microsoft.Extensions.Caching.Hybrid.Internal; | ||
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| partial class DefaultHybridCache | ||
| { | ||
| internal abstract class CacheItem<T> | ||
| { | ||
| public abstract T GetValue(); | ||
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| public abstract byte[]? TryGetBytes(out int length); | ||
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| } | ||
| } | ||
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| // Licensed to the .NET Foundation under one or more agreements. | ||
| // The .NET Foundation licenses this file to you under the MIT license. | ||
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| namespace Microsoft.Extensions.Caching.Hybrid.Internal; | ||
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| partial class DefaultHybridCache | ||
| { | ||
| private sealed class ImmutableCacheItem<T>(T value) : CacheItem<T> // used to hold types that do not require defensive copies | ||
| { | ||
| private static ImmutableCacheItem<T>? sharedDefault; | ||
| public static ImmutableCacheItem<T> Default => sharedDefault ??= new(default!); // this is only used when the underlying store is disabled | ||
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| public override T GetValue() => value; | ||
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| public override byte[]? TryGetBytes(out int length) | ||
| { | ||
| length = 0; | ||
| return null; | ||
| } | ||
| } | ||
| } |
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| using System; | ||
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| using System.Diagnostics; | ||
| using System.Runtime.CompilerServices; | ||
| using System.Threading; | ||
| using System.Threading.Tasks; | ||
| using Microsoft.Extensions.Caching.Distributed; | ||
| using Microsoft.Extensions.Caching.Memory; | ||
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| namespace Microsoft.Extensions.Caching.Hybrid.Internal; | ||
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| partial class DefaultHybridCache | ||
| { | ||
| internal ValueTask<ArraySegment<byte>> GetFromL2Async(string key, CancellationToken token) | ||
| { | ||
| switch (GetFeatures(CacheFeatures.BackendCache | CacheFeatures.BackendBuffers)) | ||
| { | ||
| case CacheFeatures.BackendCache: // legacy byte[]-based | ||
| var pendingLegacy = _backendCache!.GetAsync(key, token); | ||
| #if NETCOREAPP2_0_OR_GREATER || NETSTANDARD2_1_OR_GREATER | ||
| if (!pendingLegacy.IsCompletedSuccessfully) | ||
| #else | ||
| if (pendingLegacy.Status != TaskStatus.RanToCompletion) | ||
| #endif | ||
| { | ||
| return new(AwaitedLegacy(pendingLegacy, MaximumPayloadBytes)); | ||
| } | ||
| var bytes = pendingLegacy.Result; // already complete | ||
| if (bytes is not null) | ||
| { | ||
| if (bytes.Length > MaximumPayloadBytes) | ||
| { | ||
| ThrowQuota(); | ||
| } | ||
| return new(new ArraySegment<byte>(bytes)); | ||
| } | ||
| break; | ||
| case CacheFeatures.BackendCache | CacheFeatures.BackendBuffers: // IBufferWriter<byte>-based | ||
| var writer = RecyclableArrayBufferWriter<byte>.Create(MaximumPayloadBytes); | ||
| var cache = Unsafe.As<IBufferDistributedCache>(_backendCache!); // type-checked already | ||
| var pendingBuffers = cache.TryGetAsync(key, writer, token); | ||
| if (!pendingBuffers.IsCompletedSuccessfully) | ||
| { | ||
| return new(AwaitedBuffers(pendingBuffers, writer)); | ||
| } | ||
| ArraySegment<byte> result = pendingBuffers.GetAwaiter().GetResult() | ||
| ? new(writer.DetachCommitted(out var length), 0, length) | ||
|
There was a problem hiding this comment. Isn't this starving the array pool? The caller isn't returning the buffers to the pool. There was a problem hiding this comment. fair; fixed by adding a little extra (but necessary) complexity - we're now hooking the eviction notification on relevant cache entries, to add a "you don't need this buffer any more" signal; this has to be combined (interlocked) with people currently reading the buffer in-situ for defensive deserialize; long story short: this now works, including buffer-counting tests (256581b) |
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| : default; | ||
| writer.Dispose(); // it is not accidental that this isn't "using"; avoid recycling if not 100% sure what happened | ||
| return new(result); | ||
| } | ||
| return default; | ||
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| static async Task<ArraySegment<byte>> AwaitedLegacy(Task<byte[]?> pending, int maximumPayloadBytes) | ||
| { | ||
| var bytes = await pending.ConfigureAwait(false); | ||
| if (bytes is not null) | ||
| { | ||
| if (bytes.Length > maximumPayloadBytes) | ||
| { | ||
| ThrowQuota(); | ||
| } | ||
| return new(bytes); | ||
| } | ||
| return default; | ||
| } | ||
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| static async Task<ArraySegment<byte>> AwaitedBuffers(ValueTask<bool> pending, RecyclableArrayBufferWriter<byte> writer) | ||
| { | ||
| ArraySegment<byte> result = await pending.ConfigureAwait(false) | ||
| ? new(writer.DetachCommitted(out var length), 0, length) | ||
| : default; | ||
| writer.Dispose(); // it is not accidental that this isn't "using"; avoid recycling if not 100% sure what happened | ||
| return result; | ||
| } | ||
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| static void ThrowQuota() => throw new InvalidOperationException("Maximum cache length exceeded"); | ||
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| } | ||
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| internal ValueTask SetL2Async(string key, byte[] value, int length, HybridCacheEntryOptions? options, CancellationToken token) | ||
| { | ||
| Debug.Assert(value.Length >= length); | ||
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| switch (GetFeatures(CacheFeatures.BackendCache | CacheFeatures.BackendBuffers)) | ||
| { | ||
| case CacheFeatures.BackendCache: // legacy byte[]-based | ||
| if (value.Length > length) | ||
| { | ||
| Array.Resize(ref value, length); | ||
| } | ||
| Debug.Assert(value.Length == length); | ||
| return new(_backendCache!.SetAsync(key, value, GetOptions(options), token)); | ||
| case CacheFeatures.BackendCache | CacheFeatures.BackendBuffers: // ReadOnlySequence<byte>-based | ||
| var cache = Unsafe.As<IBufferDistributedCache>(_backendCache!); // type-checked already | ||
| return cache.SetAsync(key, new(value, 0, length), GetOptions(options), token); | ||
| } | ||
| return default; | ||
| } | ||
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| private DistributedCacheEntryOptions GetOptions(HybridCacheEntryOptions? options) | ||
| { | ||
| DistributedCacheEntryOptions? result = null; | ||
| if (options is not null && options.Expiration.HasValue && options.Expiration.GetValueOrDefault() != _defaultExpiration) | ||
| { | ||
| result = options.ToDistributedCacheEntryOptions(); | ||
| } | ||
| return result ?? _defaultDistributedCacheExpiration; | ||
|
There was a problem hiding this comment. Super nit: I like the use of partial classes but perhaps defaults like these should be centralized into a constants class so it's easier to grok their values? There was a problem hiding this comment. which constant(s) do you mean? the only constant I can see there is |
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| } | ||
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| internal void SetL1<T>(string key, CacheItem<T> value, HybridCacheEntryOptions? options) | ||
| => _localCache.Set(key, value, options?.LocalCacheExpiration ?? _defaultLocalCacheExpiration); | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,40 @@ | ||
| // Licensed to the .NET Foundation under one or more agreements. | ||
| // The .NET Foundation licenses this file to you under the MIT license. | ||
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| using System.Buffers; | ||
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| namespace Microsoft.Extensions.Caching.Hybrid.Internal; | ||
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| partial class DefaultHybridCache | ||
| { | ||
| private sealed class MutableCacheItem<T> : CacheItem<T> // used to hold types that require defensive copies | ||
| { | ||
| public MutableCacheItem(byte[] bytes, int length, IHybridCacheSerializer<T> serializer) | ||
| { | ||
| _serializer = serializer; | ||
| _bytes = bytes; | ||
| _length = length; | ||
| } | ||
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| public MutableCacheItem(T value, IHybridCacheSerializer<T> serializer, int maxLength) | ||
| { | ||
| _serializer = serializer; | ||
| var writer = RecyclableArrayBufferWriter<byte>.Create(maxLength); | ||
| serializer.Serialize(value, writer); | ||
| _bytes = writer.DetachCommitted(out _length); | ||
|
There was a problem hiding this comment. More array pool starvation? |
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| writer.Dispose(); // only recycle on success | ||
| } | ||
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| private readonly IHybridCacheSerializer<T> _serializer; | ||
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| private readonly byte[] _bytes; | ||
| private readonly int _length; | ||
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| public override T GetValue() => _serializer.Deserialize(new ReadOnlySequence<byte>(_bytes, 0, _length)); | ||
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| public override byte[]? TryGetBytes(out int length) | ||
| { | ||
| length = _length; | ||
| return _bytes; | ||
| } | ||
| } | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,108 @@ | ||
| // Licensed to the .NET Foundation under one or more agreements. | ||
| // The .NET Foundation licenses this file to you under the MIT license. | ||
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| using System; | ||
| using System.Collections.Concurrent; | ||
| using System.ComponentModel; | ||
| using System.Linq; | ||
| using System.Reflection; | ||
| using System.Runtime.CompilerServices; | ||
| using System.Runtime.InteropServices; | ||
| using System.Runtime.Serialization; | ||
| using Microsoft.Extensions.DependencyInjection; | ||
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| namespace Microsoft.Extensions.Caching.Hybrid.Internal; | ||
| partial class DefaultHybridCache | ||
| { | ||
| private readonly ConcurrentDictionary<Type, object> _serializers = new(); // per instance cache of typed serializers | ||
|
There was a problem hiding this comment. Why There was a problem hiding this comment. the serializer API itself is typed, i.e. + public interface IHybridCacheSerializer {}
+ public interface IHybridCacheSerializer<T> : IHybridCacheSerializer
- public interface IHybridCacheSerializer<T>
{ ... }but... if that is only for this, it seems artificial; added 8c0e1b5 instead |
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| internal int MaximumPayloadBytes { get; } | ||
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| internal IHybridCacheSerializer<T> GetSerializer<T>() | ||
| { | ||
| return _serializers.TryGetValue(typeof(T), out var serializer) | ||
| ? Unsafe.As<IHybridCacheSerializer<T>>(serializer) : ResolveAndAddSerializer(this); | ||
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| static IHybridCacheSerializer<T> ResolveAndAddSerializer(DefaultHybridCache @this) | ||
| { | ||
| // it isn't critical that we get only one serializer instance during start-up; what matters | ||
| // is that we don't get a new serializer instance *every time* | ||
| var serializer = @this._services.GetService<IHybridCacheSerializer<T>>(); | ||
| if (serializer is null) | ||
| { | ||
| foreach (var factory in @this._serializerFactories) | ||
| { | ||
| if (factory.TryCreateSerializer<T>(out var current)) | ||
| { | ||
| serializer = current; | ||
| break; // we've already reversed the factories, so: the first hit is what we want | ||
| } | ||
| } | ||
| } | ||
| if (serializer is null) | ||
| { | ||
| throw new InvalidOperationException($"No {nameof(IHybridCacheSerializer<T>)} configured for type '{typeof(T).Name}'"); | ||
| } | ||
| // store the result so we don't repeat this in future | ||
| @this._serializers[typeof(T)] = serializer; | ||
| return serializer; | ||
| } | ||
| } | ||
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| internal static class ImmutableTypeCache<T> // lazy memoize; T doesn't change per cache instance | ||
| { | ||
| // note for blittable types: a pure struct will be a full copy every time - nothing shared to mutate | ||
| public static readonly bool IsImmutable = (typeof(T).IsValueType && IsBlittable<T>()) || IsImmutable(typeof(T)); | ||
| } | ||
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| private static bool IsBlittable<T>() // minimize the generic portion | ||
| { | ||
| #if NETCOREAPP2_0_OR_GREATER || NETSTANDARD2_1_OR_GREATER | ||
| return !RuntimeHelpers.IsReferenceOrContainsReferences<T>(); | ||
| #else | ||
| try // down-level: only blittable types can be pinned | ||
| { | ||
| // get a typed, zeroed, non-null boxed instance of the appropriate type | ||
| // (can't use (object)default(T), as that would box to null for nullable types) | ||
| var obj = FormatterServices.GetUninitializedObject(Nullable.GetUnderlyingType(typeof(T)) ?? typeof(T)); | ||
| GCHandle.Alloc(obj, GCHandleType.Pinned).Free(); | ||
| return true; | ||
| } | ||
| catch | ||
| { | ||
| return false; | ||
| } | ||
| #endif | ||
| } | ||
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| private static bool IsImmutable(Type type) | ||
| { | ||
| // check for known types | ||
| if (type == typeof(string)) | ||
| { | ||
| return true; | ||
| } | ||
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| if (type.IsValueType) | ||
| { | ||
| // switch from Foo? to Foo if necessary | ||
| if (Nullable.GetUnderlyingType(type) is { } nullable) | ||
| { | ||
| type = nullable; | ||
| } | ||
| } | ||
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| if (type.IsValueType || (type.IsClass & type.IsSealed)) | ||
| { | ||
| // check for [ImmutableObject(true)]; note we're looking at this as a statement about | ||
| // the overall nullability; for example, a type could contain a private int[] field, | ||
| // where the field is mutable and the list is mutable; but if the type is annotated: | ||
| // we're trusting that the API and use-case is such that the type is immutable | ||
| return type.GetCustomAttribute<ImmutableObjectAttribute>() is { Immutable: true }; | ||
| } | ||
| // don't trust interfaces and non-sealed types; we might have any concrete | ||
| // type that has different behaviour | ||
|
There was a problem hiding this comment. Gallingly, Microsoft's standard spelling doesn't include a 'u'. It doesn't matter in this private context, but I do it anyway to try to make it habitual. |
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| return false; | ||
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| } | ||
| } | ||
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Why? Technically API review needed.
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great question; this was mostly a reaction to comparisons to the related ones I found while working on this:
I assumed, therefore, that this was intentional and desirable; if I'm missing something, I'm all ears. It makes no difference to me whether we have this - I was simply trying to be consistent with convention
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@BrennanConroy disabled for now (d4133d1) - any opinions on whether we should implement this?
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I don't know what it adds. Like you pointed out we've done it in some places. But I wouldn't call it the convention, there are a lot more options objects without it. We should probably figure out what it does before adding it.