Task to ValueTask conversion in HybridCache - which way is better?

[edsdck]

Hey everyone,

I'm using HybridCache and ran into a small dilemma. My delegate returns a Task<TResponse> but the cache factory wants a ValueTask<T>.

Here's what I have:

public delegate Task<TResponse> RequestHandlerDelegate<TResponse>();

And HybridCache wants:

Func<CancellationToken, ValueTask<T>> factory

So I've got two ways to do this:

Option 1:

return await _cache.GetOrCreateAsync(
    request.Id.ToString(),
    _ => new ValueTask<TResponse>(next()),
    _cacheOptions);

Option 2:

return await _cache.GetOrCreateAsync(
    request.Id.ToString(),
    async _ => await next(),
    _cacheOptions);

I'm leaning towards option 1 because it seems like option 2 is just adding an extra async/await for no reason? But maybe I'm missing something.
Anyone know if there's a real difference here? Or if one is considered "the right way"?

[gfoidl]

Option 1.

It's as you said that the async-machinery can be avoided, as it doesn't add any benefit here (only more code and overhead here).

[edsdck]

Okay, thanks for a quick answer.

Any specific reason why HybridCache doesn't accept factory which returns Task instead? Like:

Func<CancellationToken, Task<T>> factory

[gfoidl]

Hybridcache has a multiple layers of underlying caches. A fast in-process L1 cache and a bigger out-of-process L2 cache.

When the L1 is hit, then there's no async operation involved, thus creating a Task<T> is overhead that can be avoided -- that's why ValueTask<T> came into play in .NET, as this will get allocation free.

The factory is part of GetOrCreateAsync, so there's a possibility that L1 can serve the "request", so be purely sync.

Doubling the APIs to also accept Task<T> is IMO not the way to go:

• lots of code that needs to be maintained
• which overload is picked (by the compiler)?
• the workaround is almost trivial (both option 1 and 2 are possible, but opt. 1 has less overhead)