[Breaking change]: Extend MemoryCacheOptions with TrackLinkedCacheEntries

[maryamariyan]

Description

Background and Motivation

MemoryCache by default tracks linked cache entries to allow for propagating options.

In the following example, the expirationToken added for child is also applied to parent:

using (var parent = cache.CreateEntry(key))
{
    parent.SetValue(obj);

    using (var child = cache.CreateEntry(key1))
    {
        child.SetValue(obj);
        child.AddExpirationToken(expirationToken);
    }
}

Tracking internally uses AsyncLocal<T>, which is expensive and adds non-trivial overhead. The cost of using it has popped out in the performance reports that we have received from our customers (#45436).

Before this feature this behavior could not be disabled.

New API

Here we extend the existing MemoryCacheOptions with a flag that disables this behaviour.

namespace Microsoft.Extensions.Caching.Memory
{
    public class MemoryCacheOptions
    {
+        public bool TrackLinkedCacheEntries { get ; set; }
    }
}

Usage Examples

var options = new MemoryCacheOptions
{
    TrackLinkedCacheEntries = false
};

var cache = new MemoryCache(options);

Risks

We have changed the defaults, it's now disabled by default.

Version

.NET 7 Preview 1

Previous behavior

MemoryCache by default tracks linked cache entries to allow for propagating options.

New behavior

Using MemoryCacheOptions.TrackLinkedCacheEntries this behavior can be configured properly.

Type of breaking change

• Binary incompatible: Existing binaries may encounter a breaking change in behavior, such as failure to load/execute or different run-time behavior.
• Source incompatible: Source code may encounter a breaking change in behavior when targeting the new runtime/component/SDK, such as compile errors or different run-time behavior.

Reason for change

Performance improvement

Recommended action

Refer to usage sample.

Feature area

C#, Core .NET libraries, Extensions

Affected APIs

namespace Microsoft.Extensions.Caching.Memory
{
    partial class MemoryCacheOptions
    {
        public bool TrackLinkedCacheEntries { get ; set; } = false;
    }
}

[adamsitnik]

Introducing this API has no risks as long as we don't change the default settings (enabled by default).

We have changed the defaults, it's now disabled by default.

[maryamariyan]

Updated the description. Thanks @adamsitnik