The cache does not check its own memory overhead, contained in the other SunCachedTile fields. Not much we can do about it, needs to be replaced with jai-ext own ConcurrentTileCache that has this issue fixed
The issue becomes visible when the tiles are really small, like less than 100-200 bytes worth of storage (which is the case of 10x10 tiles, being generated as the result of cutting larger images)
Resolved on master by using jai-ext own tile cache. We might want to backport too... I'm just being cautious and letting it be on master for a while
Backporting to 2.8.x since it has worked without causing known issues for a while in the dev series (and used in production under heavy load on the 2.8.x in a customer fork, too).
Mass closing all resolved issues not modified in the last 4 weeks