Mixing `threading.Thread + asyncio.run` workers with the long-lived
asyncio loop in gui/app.py is a real loop-affinity bug: the first worker
thread to call `asyncio.run` constructs a throwaway loop, which the
shared httpx clients then attach to, and the next call from the
persistent loop fails with "Event loop is closed" / "attached to a
different loop". This commit eliminates the pattern across the GUI and
adds the locking + cleanup that should have been there from the start.
Persistent loop accessor (core/concurrency.py — new)
- set_app_loop / get_app_loop / run_on_app_loop. BooruApp registers the
one persistent loop at startup; everything that wants to schedule
async work calls run_on_app_loop instead of spawning a thread that
builds its own loop. Three functions, ~30 lines, single source of
truth for "the loop".
Lazy-init lock + cleanup on shared httpx clients (core/api/base.py,
core/api/e621.py, core/cache.py)
- Each shared singleton (BooruClient._shared_client, E621Client._e621_client,
cache._shared_client) now uses fast-path / locked-slow-path lazy init.
Concurrent first-callers from the same loop can no longer both build
a client and leak one (verified: 10 racing callers => 1 httpx instance).
- Each module exposes an aclose helper that BooruApp.closeEvent runs via
run_coroutine_threadsafe(...).result(timeout=5) BEFORE stopping the
loop. The connection pool, keepalive sockets, and TLS state finally
release cleanly instead of being abandoned at process exit.
- E621Client tracks UA-change leftovers in _e621_to_close so the old
client doesn't leak when api_user changes — drained in aclose_shared.
GUI workers routed through the persistent loop (gui/sites.py,
gui/bookmarks.py)
- SiteDialog._on_detect / _on_test: replaced
`threading.Thread(target=lambda: asyncio.run(...))` with
run_on_app_loop. Results marshaled back through Qt Signals connected
with QueuedConnection. Added _closed flag + _inflight futures list:
closeEvent cancels pending coroutines and shorts out the result emit
if the user closes the dialog mid-detect (no use-after-free on
destroyed QObject).
- BookmarksView._load_thumb_async: same swap. The existing thumb_ready
signal already used QueuedConnection so the marshaling side was
already correct.
DB write serialization (core/db.py)
- Database._write_lock = threading.RLock() — RLock not Lock so a
writing method can call another writing method on the same thread
without self-deadlocking.
- New _write() context manager composes the lock + sqlite3's connection
context manager (the latter handles BEGIN / COMMIT / ROLLBACK
atomically). Every write method converted: add_site, update_site,
delete_site, add_bookmark, add_bookmarks_batch, remove_bookmark,
update_bookmark_cache_path, add_folder, remove_folder, rename_folder,
move_bookmark_to_folder, add/remove_blacklisted_tag,
add/remove_blacklisted_post, save_library_meta, remove_library_meta,
set_setting, add_search_history, clear_search_history,
remove_search_history, add_saved_search, remove_saved_search.
- _migrate keeps using the lock + raw _conn context manager because
it runs from inside the conn property's lazy init (where _write()
would re-enter conn).
- Reads stay lock-free and rely on WAL for reader concurrency. Verified
under contention: 5 threads × 50 add_bookmark calls => 250 rows,
zero corruption, zero "database is locked" errors.
Smoke-tested with seven scenarios: get_app_loop raises before set,
run_on_app_loop round-trips, lazy init creates exactly one client,
10 concurrent first-callers => 1 httpx, aclose_shared cleans up,
RLock allows nested re-acquire, multi-threaded write contention.
pax
eb58d76bc0