new feature: Add cache layer for opendal

[Xuanwo]

Provide high-quality built-in cache support in OpenDAL while ensuring users have the flexibility to implement their own caching logic.

[jorgehermo9]

Hi, I would like to work on this, can I? Or is anybody willing to work on this already?

I thought about using https://github.com/foyer-rs/foyer. I see It has been already discussed here.

[Xuanwo]

Hi, @jorgehermo9, that will be greatly appreciated. No one is currently working on this.

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Ideally, our cache layer should enable users to design and implement their own cache algorithms while seamlessly switching between different cache crates like Foyer or Moka. However, I believe we should integrate with Foyer first to clarify our direction moving forward.

Let's first build a FoyerLayer, and later, we can extract a CacheLayer from it.

[jorgehermo9]

I agree a lot with the plan!! Thanks @Xuanwo 😊

[jorgehermo9]

Just as an update about this, I have the initial implementation almost finished (for read and blocking_read operations for the moment) and will submit a PR in a few days/a week, as soon as I can 😄

[Xuanwo]

I have an idea that our future CacheLayer can accept an Operator instead. Take foyer as an example, we can implement a foyer service. And use it like:

let cache_op = Operator::from_config(FoyerConfig::default).finish()?;
let op = op.layer(CacheLayer::new(cache_op));

We will need a benchmark to evaluate their performance.