[FEATURE] Metadata-less entries in distributed cache

[jarodriguez-itsoft]

Problem

I’m using this amazing library to manage both combined (in-memory and distributed) caches and distributed-only caches.

Some of these caches hold millions of entries, accessed concurrently by dozens of app nodes (following a producer/consumer pattern). Thanks to a new feature introduced in recent versions of the library, we can now use distributed-only caches, which has spared us from having nodes consume massive amounts of memory unnecessarily.

So far, so good, but KeyDB is also consuming a lot of memory, and we aim to reduce its usage as well.

The issue is that FusionCache stores a lot of metadata in Redis, which is essentially useless since Redis already handles expiration, and the in-memory part of the cache is disabled.

For example, to simply store the string value "var", we get something like this:

127.0.0.1:6379> HGETALL "v0:foo"

1. "absexp"
2. "638710876575684414"
3. "data"
4. "{"$id":"1","v":"bar","m":{"$id":"2","e":"2024-12-29T16:47:37.5660416+00:00"},"t":638684956575645632}"
5. "sldexp"
6. "-1"

That's quite too much memory overhead when the caches have millions of entries.

Solution

Add a cache-level (or entry-level option) to control, at the distributed level, if the value should be serialized/deserialized as usual or simply stored/retrieved in its raw form.

127.0.0.1:6379> GET "foo"
"bar"

[jodydonetti]

Hi @jarodriguez-itsoft ,
I'm doing some work on this in the new v2.

The idea is not to require a manual setting, but to make it automatic based on concrete usage: I'm already doing this for memory entries (eg: cache entries in L1, the memory level), whereby I only populate the metadata if it's needed, based on the features you are using like eager refresh & co.
This means that if you are not using any feature that requires metadata, metadata will not be there.

I've never done this for the L2 (distributed level) for... reasons 🤔 ... but I'm getting back to this again.

The short version is that in v2, metadata will be there only if needed.

Will update on this.

[jodydonetti]

I've never done this for the L2 (distributed level) for... reasons 🤔 ... but I'm getting back to this again.

I figured out why I did that: it was to make sure that when an entry comes in from L2 (distributed) to L1 (memory), the actual expiration woul be "aligned".

So anyway, now I'm trying to find a way to do the same while avoiding the metadata.

Will update.