Previously, only nodes in the 'normal' state and decommissioning nodes
were included in the set of nodes participating in barrier and
barrier_and_drain commands. Joining nodes are not included because they
don't coordinate requests, given their cql port is closed.
However, joining nodes may receive mutations from other nodes, for which
they may generate and coordinate materialized view updates. If their
group0 state is not synchronized it could cause lost view updates.
For example:
1. On the topology coordinator, the join completes and the joining node
becomes normal, but the joining node's state lags behind. Since it's
not synchronized by the barrier, it could be in an old state such as
`write_both_read_old`.
2. A normal node coordinates a write and sends it to the new node as the
new replica.
3. The new node applies the base mutation but doesn't generate a view
update for it, because it calculates the base-view pairing according
to its own state and replication map, and determines that it doesn't
participate in the base-view pairing.
Therefore, since the joining node participates as a coordinator for view
updates, it should be included in these barriers as well. This ensures
that before the join completes, the joining node's state is
`write_both_read_new`, where it does generate view updates.
Fixes https://github.com/scylladb/scylladb/issues/26976
backport to previous versions since it fixes a bug in MV with vnodes
Closesscylladb/scylladb#27008
* github.com:scylladb/scylladb:
test: add mv write during node join test
topology_coordinator: include joining node in barrier
2ccc94c496