Metrics for hit/miss ratio in cache?

[raycheung]

Thanks for having this amazing project. I'm trying to understand the Prometheus metrics available in the run-time, while I found a lot of go / the api-endpoint related metrics (unfortunately I don't care much about those), I want to get some insight about the effectiveness of the cache, i.e. the hit/miss ratio.

Frankly, I think it'd be far more effective and useful if there is metrics about cache ratio, dns resolution time, etc. performance related ones.

Would that be available please?