Problems with the expiration about ristretto

[martinmr]

Question 1:

Yes, it is possible to skip some buckets if the values for how big a bucket is and how often the cleanup is run were set up incorrectly. But the cleanup ticker is set to run twice for every bucket (if the bucket size is 10sec, cleanup runs every 5s). This gives us enough confidence that cleanup will have a chance to clean every bucket. It's still possible that a bucket could be skipped but the get checks the actual expiration time so skipping a bucket won't lead to invalid values being returned by gets.

Question 2:

cleanup always tries to cleanup a bucket that has only expired items. The check inside the for loop is there just as a safeguard.
Gets don't delete expired entries to make them as fast as possible. In general, most of the design decisions in Ristretto are geared towards doing work outside of the critical path. In the case of cleanup, it means expired entries will remain in the map until the cleanup routine runs in the background.

Question 3:

This is not how the cleanup works. The bucket is based on the expiration time, not the insertion time. So if there's an entry that expires in a day, it won't be processed by cleanup until roughly a day from now. An item that expires in 5 sec and another one that expires in one day will not share a bucket.

Feel free to reopen if you still have questions.