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When we upgrade a cluster to use Raft, or perform manual Raft recovery procedure (which also creates a fresh group 0 cluster, using the same algorithm as during upgrade), we start with a non-empty group 0 state machine; in particular, the schema tables are non-empty. In this case we need to ensure that nodes which join group 0 receive the group 0 state. Right now this is not the case. In previous releases, where group 0 consisted only of schema, and schema pulls were also done outside Raft, those nodes received schema through this outside mechanism. In91f609d065we disabled schema pulls outside Raft; we're also extending group 0 with other things, like topology-specific state. To solve this, we force snapshot transfers by setting the initial snapshot index on the first group 0 server to `1` instead of `0`. During replication, Raft will see that the joining servers are behind, triggering snapshot transfer and forcing them to pull group 0 state. It's unnecessary to do this for cluster which bootstraps with Raft enabled right away but it also doesn't hurt, so we keep the logic simple and don't introduce branches based on that. Extend Raft upgrade tests with a node bootstrap step at the end to prevent regressions (without this patch, the step would hang - node would never join, waiting for schema). Fixes: #14066 Closes #14336 (cherry picked from commitff386e7a44) Backport note: contrary to the claims above, it turns out that it is actually necessary to create snapshots in clusters which bootstrap with Raft, because of tombstones in current schema state expire hence applying schema mutations from old Raft log entries is not really idempotent. Snapshot transfer, which transfers group 0 history and state_ids, prevents old entries from applying schema mutations over latest schema state. Ref: scylladb/scylladb#16683