Canceled Context with go-redis results in ErrOnlyCachedRecords

[quoral]

Describe the bug
When calling sturdyc.GetOrFetchBatch with Distributed storage enabled, with a cancelled context, the behavior becomes quite unexpected. We have a minimally extended implementation on top of "github.com/redis/go-redis/v9" that we use.
The call ends up returning ErrOnlyCachedRecords, with an empty response. As we use the cache for now as a fallback instead of a real cache, we use the ErrOnlyCachedRecords as a signal that we can just re-use the value from the cache.

A context being done or cancelled in this case implies that we don't care about the response anyway, but due to this error in particular getting ignored by a

value, err := sturdyc.GetOrFetchBatch(ctx, client, keys, keyFunc, getConstantValue)
if errors.Is(err, sturdyc.ErrOnlyCachedRecords) {
	fmt.Println("Only cached records are available")
        return value, nil
}

We see unexpected error logs popping up in the errors logs (without user impact of course as the client is already gone with the context.Cancelled).

Expected behavior
Expected that the error should be one indicating that there was no response (ErrMissingRecord)? Or that the cache returns context.Cancelled.

To Reproduce
I creted a not-so-minally reproducing case for this issue
https://gist.github.com/quoral/dfdc44432aeea566255a5d2f27a80b56

Additional context
Potentially this does not belong in this repository, and should instead be a bug report towards go-redis. However, I lack knowledge of the innards of sturdyc, so wanted to ensure we track that part first.

[viccon]

Hi @quoral, and thank you so much for the gist. I don't believe there is an issue with go-redis. If you change your gist to do something like this (clear the in-memory cache) before you make the second call with the cancelled context, you'll get no data from the redis client:

	for _, id := range ids {
		cacheKey := keyFunc(id)
		client.Delete(cacheKey)
	}

I attempted to fix this issue in this PR: #40. I would really appreciate if you could install a version of sturdyc based on that branch, e.g:

go get github.com/viccon/sturdyc@additional-error-handling

and see if it behaves the way you'd expect.

[quoral]

Hi @viccon! I tested it locally, and it does indeed make it much clearer what's going on! Seeing a context.Cancelled error for these cases makes a lot of sense!