`check_and_repair_cdc_streams` is an existing API which you can use when the
current CDC generation is suboptimal, e.g. after you decommissioned a node the
current generation has more stream IDs than you need. In that case you can do
`nodetool checkAndRepairCdcStreams` to create a new generation with fewer
streams.
It also works when you change number of shards on some node. We don't
automatically introduce a new generation in that case but you can use
`checkAndRepairCdcStreams` to create a new generation with restored
shard-colocation.
This PR implements the API on top of raft topology, it was originally
implemented using gossiper. It uses the `commit_cdc_generation` topology
transition state and a new `publish_cdc_generation` state to create new CDC
generations in a cluster without any nodes changing their `node_state`s in the
process.
Closes#13683
* github.com:scylladb/scylladb:
docs: update topology-over-raft.md
test: topology_experimental_raft: test `check_and_repair_cdc` API
raft topology: implement `check_and_repair_cdc_streams` API
raft topology: implement global request handling
raft topology: introduce `prepare_new_cdc_generation_data`
raft_topology: `get_node_to_work_on_opt`: return guard if no node found
raft topology: remove `node_to_work_on` from `commit_cdc_generation` transition
raft topology: separate `publish_cdc_generation` state
raft topology: non-node-specific `exec_global_command`
raft topology: introduce `start_operation()`
raft topology: non-node-specific `topology_mutation_builder`
topology_state_machine: introduce `global_topology_request`
topology_state_machine: use `uint16_t` for `enum_class`es
raft topology: make `new_cdc_generation_data_uuid` topology-global
9d4bca26cc