Make hit/miss ratio for EhCache look better.

[izeye]

EhCache's hit/miss ratio could be as follows:

  "cache.persons.hit.ratio" : 1.000019269809123,
  "cache.persons.miss.ratio" : -1.9269809123034776E-5,

We usually expect hit/miss ratio between 0 and 1 inclusive, not greater than 1 or negative.

You can reproduce it with ApplicationTests.test() in the following project:

https://github.com/izeye/samples-spring-boot-branches/tree/cache

[snicoll]

Meh, why would that value be higher than 1? @lorban

[chrisdennis]

The hitRatio is the ratio of two windowed rates that are calculated independently. They aren't updated or read transactionally, hence the ratio of the two can drift slightly from what might be expected. Does that make sense?

[snicoll]

Thanks for the answer. What do you suggest of the proposed PR?

[chrisdennis]

Assuming this is the best layer to sanitize things at (bearing in mind one potential sanitization layer is inside the users brain) then this looks fine. Personally I would have written:

//ratio is calculated 'racily' and can drift marginally above unity, so we cap it here
double hitRatio = Math.max(1.0, ehCacheStatistics.cacheHitRatio());

but that's obviously just personal preferences.

[snicoll]

well if you do that if the hitRatio is between 0 and 1, it become 1 :)