After an internal CAS shard bounce, check_locality() was evaluating
against this_shard_id() of the post-bounce shard — which is the correct
tablet shard — so it returned nullopt, and LWT/SERIAL responses omitted
the tablets-routing-v1 custom payload. The client never learned the
correct tablet map.
Fix by recording the original entry shard in client_state (initialized
to this_shard_id() at construction, preserved across shard bounces via
client_state_for_another_shard) and passing it to check_locality() so
it compares against the client's actual routing decision.
No host_id tracking or forwarded_client_state IDL changes are needed
because CAS shard bounces are always intra-node.
Fixes SCYLLADB-2041
backport: need to backport to all versions with LWT over tablets
Closesscylladb/scylladb#29910
* https://github.com/scylladb/scylladb:
cql: refactor add_tablet_info to take tablet_routing_info directly
cql: fix UB dereference of nullopt tablet_info in execute_with_condition
test/boost: add regression test for missing tablet routing after CAS bounce
cql: fix missing TABLETS_ROUTING_V1 payload after CAS shard bounce
c9592a495e