"me" sstable format includes an important feature of storing the
`host_id` of the local node when writing sstables. The is crucial
for validating the sstable's `replay_position` in stats metadata as
it is valid only on the originating node and shard (#10080), therefor
we would like to make the `me` format mandatory.
before making `me` mandatory, we need to stop handling `sstable_format`
option if it is "md".
in this change
- gms/feature_service: do not disable `ME_SSTABLE_FORMAT` even if
`sstable_format` is configured with "md". and in that case, instead,
a warning is printed in the logging message to note that
this setting is not valid anymore.
- docs/architecture/sstable: note that "me" is used by default now.
after this change, "sstable_format" will only accept "me" if it's
explicitly configured. and when a server with this change joins a
cluster, it uses "md" if the any of the node in the cluster still has
`sstable_format`. practically, this change makes "me" mandatory
in a 6.x cluster, assuming this change will be included in 6.x
releases.
Fixes#16551
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
