There are some schema modifications performed automatically (during
bootstrap, upgrade etc.) by Scylla that are announced by multiple calls
to `migration_manager::announce` even though they are logically one
change. Precisely, they appear in:
- `system_distributed_keyspace::start`,
- `redis:create_keyspace_if_not_exists_impl`,
- `table_helper::setup_keyspace` (for the `system_traces` keyspace).
All these places contain a FIXME telling us to `announce` only once.
There are a few reasons for this:
- calling `migration_manager::announce` with Raft is quite expensive --
taking a `read_barrier` is necessary, and that requires contacting a
leader, which then must contact a quorum,
- we must implement a retrying mechanism for every automatic `announce`
if `group0_concurrent_modification` occurs to enable support for
concurrent bootstrap in Raft-based topology. Doing it before the FIXMEs
mentioned above would be harder, and fixing the FIXMEs later would also
be harder.
This PR fixes the first two FIXMEs and improves the situation with the
last one by reducing the number of the `announce` calls to two.
Unfortunately, reducing this number to one requires a big refactor. We
can do it as a follow-up to a new, more specific issue. Also, we leave a
new FIXME.
Fixing the first two FIXMEs required enabling the announcement of a
keyspace together with its tables. Until now, the code responsible for
preparing mutations for a new table could assume the existence of the
keyspace. This assumption wasn't necessary, but removing it required
some refactoring.
Fixesscylladb/scylladb#15437Closesscylladb/scylladb#15897
* github.com:scylladb/scylladb:
table_helper: announce twice in setup_keyspace
table_helper: refactor setup_table
redis: create_keyspace_if_not_exists_impl: fix indentation
redis: announce once in create_keyspace_if_not_exists_impl
db: system_distributed_keyspace: fix indentation
db: system_distributed_keyspace: announce once in start
tablet_allocator: update on_before_create_column_family
migration_listener: add parameter to on_before_create_column_family
alternator: executor: use new prepare_new_column_family_announcement
alternator: executor: introduce create_keyspace_metadata
migration_manager: add new prepare_new_column_family_announcement
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