Log a warning when instrumenting a cache that is not recording stats in CaffeineCacheMetrics

[izeye]

This PR changes to log a warning when instrumenting a cache that is not recording statistics in the CaffeineCacheMetrics.

See gh-5066

[izeye]

The Guava cache also has the same concept, but it doesn't seem to have an API corresponding to Policy.isRecordingStats() from the Caffeine cache.

[izeye]

In addition to logging the warning, we can try not to register meters that depend on the Caffeine.recordStats() call at all instead of registering zero-valued meters.

[shakuzen]

In addition to logging the warning, we can try not to register meters that depend on the Caffeine.recordStats() call at all instead of registering zero-valued meters.

That sounds like a good idea to me. It will be more clear we don't have metrics for those rather than saying the metrics for those are 0. Do you want to update this pull request with that or make a separate PR for it?

[izeye]

@shakuzen Thanks for the feedback!

Looking into its implementation details, it seems a bit tricky, so it would be better to be discussed in a separate issue. I can try another PR if it's proven to be okay in the issue.

[izeye]

Looking into its implementation details, it seems a bit tricky, so it would be better to be discussed in a separate issue.

I created #5408.

[izeye]

The Guava cache also has the same concept, but it doesn't seem to have an API corresponding to Policy.isRecordingStats() from the Caffeine cache.

I created google/guava#7381 to see if it could be improved.