sqlcache: also ignore integrity error integrity error can happens when multiple client tries to warm similar cache. Given we leave multiple hole in the cache that can be warmed by anyone, this is harder to avoid that we would like. We simply catch the error in this case. Someone will warm the missing entry later.

sqlcache: cache OperationError when saving This is a cache, so we should not crash when trying to operate on it. OperationError can happens when the database is seen as readonly or locked.

sqlcache: passe better connection option These new options should help with handling transaction consistency and database access on high load.

contrib: introduce a small script to stress tests obsolescence exchange Tester have been reporting some error that seems to originate from concurrent access/update to the cache. This script will be useful to reproduce these situations locally.