Provide API to see if a cache records statistics

[izeye]

API(s)

com.google.common.cache.Cache

How do you want it to be improved?

It would be nice to provide an API to see if recording statistics in a cache is activated similar to the Policy.isRecordingStats() from the Caffeine cache.

Why do we need it to be improved?

For libraries that collect metrics from a cache, it would be useful to warn a user that metrics won't be collected properly or not to register meters that produce only zero values by using the proposed API.

Example

if (!cache.isRecordingStats()) {
  // Warn a user that the cache doesn't provide statistics.
}

if (cache.isRecordingStats()) {
  // Register meters with its statistics.
}

Current Behavior

It's not possible to know if a cache records statistics.

Desired Behavior

It would be nice to know if a cache records statistics.

Concrete Use Cases

https://github.com/micrometer-metrics/micrometer/issues/5066 and https://github.com/micrometer-metrics/micrometer/pull/5402#issuecomment-2315785818 are examples that the proposed API is necessary.

Checklist

• [X] I agree to follow the code of conduct.

• [X] I have read and understood the contribution guidelines.

• [X] I have read and understood Guava's philosophy, and I strongly believe that this proposal aligns with it.

[hiddenHunter291]

Can you assign me this task

[lowasser]

It looks like you're aware of Caffeine's cache -- is there a particular reason you're not using it?

[izeye]

@lowasser As mentioned in the opening comment, I created this for libraries (ex. Micrometer), not for applications.

[PrimroseZhang]

Can you assign this to me?

[chaoren]

Does your library just accept an already-constructed Cache instance from your users? Could the library configure and construct the cache for the user instead? Then you can guarantee that the cache is recording stats.

[izeye]

Does your library just accept an already-constructed Cache instance from your users?

@chaoren Yes, it's accepting prebuilt caches for metrics as follows:

https://github.com/micrometer-metrics/micrometer/blob/4d9efae6b7f3635be5e99fa089eb2851f9d9ca78/micrometer-core/src/main/java/io/micrometer/core/instrument/binder/cache/GuavaCacheMetrics.java#L54-L57

Could the library configure and construct the cache for the user instead?

It's just a library for observability, so considering its nature, it doesn't seem to be an option.

[chaoren]

We're not planning to add more features to the caching library at this point. Perhaps your library could include a recommendation for your users to migrate to Caffeine for the desired feature.