Previously, nodes would become voters immediately after joining, ensuring voter status was established before bootstrap completion. With the limited voters feature, voter assignment became deferred, creating a timing gap where nodes could finish bootstrapping without becoming voters.
This timing issue could lead to quorum loss scenarios, particularly observed in tests but theoretically possible in production environments.
This commit reorders voter assignment to occur before the `update_topology_state()` call, ensuring nodes achieve voter status before bootstrap operations are marked complete. This prevents the problematic timing gap while maintaining compatibility with limited voters functionality.
If voter assignment succeeds but topology state update fails, the operation will raise an exception and be retried by the topology coordinator, maintaining system consistency.
This commit also fixes issue where the `update_nodes` ignored leaving voters potentially exceeding the voter limit and having voters unaccounted for.
Fixes: scylladb/scylladb#24420
No backport: Fix of a theoretical bug + CI stability improvement (we can backport eventually later if we see hits in branches)
Closesscylladb/scylladb#24843
* https://github.com/scylladb/scylladb:
raft: fix voter assignment of transitioning nodes
raft: improve comments in group0 voter handler
145a38bc2e