Backported PR #16822, commits f7e488dc9262685d6624755e0d3bb0a655863248,
67f17166bf2ba337dafb8e0ea8eea5f74a990767,
and f7ff898fd6c2d6dbb54278343073aa4fa5f46a03
Signed-off-by: Ivan Valdes <ivan@vald.es>
To avoid inconsistant behavior during cluster upgrade we are feature
gating persistance behind cluster version. This should ensure that
all cluster members are upgraded to v3.6 before changing behavior.
To allow backporting this fix to v3.5 we are also introducing flag
--experimental-enable-lease-checkpoint-persist that will allow for
smooth upgrade in v3.5 clusters with this feature enabled.
Current checkpointing mechanism is buggy. New checkpoints for any lease
are scheduled only until the first leader change. Added fix for that
and a test that will check it.
Thanks to this change:
- all the maps bucket -> buffer are indexed by int's instead of
string. No need to do: byte[] -> string -> hash conversion on each
access.
- buckets are strongly typed in backend/mvcc API.
