When a node shuts down, do_drain() calls stop_transport() which tears
down the messaging service. After this point, MUTATION_DONE responses
from replicas can no longer reach the coordinator, so any in-flight
write_response_handlers will never complete naturally. These handlers
hold ERMs referencing stale token_metadata versions.
If the topology coordinator calls barrier_and_drain (either on itself
or via RPC), it blocks in stale_versions_in_use() waiting for these
stale versions to be released. This causes:
- On the coordinator node: do_drain -> wait_for_group0_stop deadlock
(the topology coordinator fiber is stuck in barrier_and_drain).
- On non-coordinator nodes: ss::stop -> uninit_messaging_service
deadlock (the barrier_and_drain RPC handler holds the gate open).
Fix: cancel all write response handlers on all shards right after
stop_transport() in do_drain(). This releases their ERMs and the
associated stale token_metadata versions, unblocking
stale_versions_in_use().
Heap-allocate _write_handlers_gate and add an allow_new parameter to
cancel_all_write_response_handlers(). When allow_new=true (used by
do_drain), the gate is closed and swapped with a fresh one — existing
handlers are waited on while new handlers can still be created. This
avoids blocking internal writes (paxos learn, compaction history
updates) that still need to create handlers during the remainder of
the drain sequence. When allow_new=false (used by drain_on_shutdown),
the gate is closed permanently — no new handlers can be created after
final shutdown.
Update test_lwt_shutdown to wait for 'Stop transport: done' instead
of 'Shutting down storage proxy RPC verbs'. The latter message is
now only logged after do_drain() completes, but do_drain() blocks
in cancel_all_write_response_handlers() waiting for the background
paxos learn handler — which is exactly what the test needs to release
before shutdown can proceed.
Fixes: SCYLLADB-2163
Refs: scylladb/scylladb#23665
(cherry picked from commit 2927f0dd21)
a2b2a42936