storage_service::replicate_to_all_cores has a sophisticated way
to mutate the token_metadata and effective_replication_map
on shard 0 and cloning those to all other shards, applying
the changes only mutate and clone succeeded on all shards
so we don't end up with only some of the shards with the mutated
copy if an error happend mid-way (and then we would need to
roll-back the change for exception safety).
shared_token_metadata::mutate_token_metadata is currently only called from
a unit test that needs to mutate the token metadata only on shard 0,
but a following patch will require doing that on all shards.
This change adds this capbility by enforcing the call to be
on shard 0m mutating the token_metdata into a temporary pending copy
and cloning it on all other shards. Only then, when all shard
succeeded, set the modified token_metadata on all shards.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
fd1a2591b5