* fix(skills): offload update_skill's blocking IO and share the config write lock
Re-applied on top of main rather than merged: update_skill has since gained
admin gating, user-scoped storage and a PUBLIC vs CUSTOM/LEGACY split, so the
offload is applied per path.
- PUBLIC: the extensions_config.json read-modify-write (path resolve, snapshot,
merge, write, reload) moves to a worker thread via asyncio.to_thread. The
payload is built from a snapshot so the cached singleton is never mutated in
place while the write is still in flight.
- CUSTOM/LEGACY: set_skill_enabled_state is offloaded; the non-user-scoped
fallback takes the same shared-file RMW path as PUBLIC.
- Both load_skills calls (and storage construction) are offloaded.
The RMW lock now lives next to reload_extensions_config as
get_extensions_config_write_lock() and is acquired by both the skills router and
the MCP router, which performs the same read-modify-write on the same file.
Previously each router held its own module-local lock, so once both sides
offloaded, a PUT /api/mcp/config could run inside a skill toggle's read->write
window and the later write would silently drop the other's change.
The lock is keyed by the running event loop rather than being a module-level
singleton: asyncio primitives bind to the first loop that awaits them, which
makes a plain module-level lock unusable in a process that runs more than one
loop.
Adds a cross-router regression anchor asserting a skill toggle and an MCP update
never overlap inside the RMW (max in-flight 1); it observes 2 when the routers
use separate locks.
* fix(config): own the extensions_config RMW lock from the worker thread
An asyncio.Lock held around `await asyncio.to_thread(...)` protects only the
awaiting task. If that task is cancelled the context manager releases the lock
immediately while Python keeps running the worker thread, so a second skills or
MCP writer could acquire it and operate on extensions_config.json concurrently
with the first worker — reopening the lost-update window this was meant to close.
The per-event-loop keying had a second hole: writers on different loops got
different locks and so did not exclude each other at all.
Replace it with a process-wide threading.Lock acquired *inside* the worker that
performs the RMW (`_write_extensions_skill_state` and `_apply_mcp_config_update`),
so ownership belongs to the thread doing the writing and is held until the write
and reload actually finish, regardless of what happens to the caller. A
threading.Lock also has no event-loop affinity.
Adds a cancellation regression: the skills worker is paused inside the lock, its
route task is cancelled, and the MCP writer is started — the MCP RMW must not
enter until the skills worker is released. Against the previous asyncio-lock
design this test fails with ['skills-enter', 'mcp-enter'].
The two existing serialization tests instrumented by replacing the worker
functions, which now bypasses the lock under test; they instead patch inside the
real workers (each module's reload_extensions_config, the last step under the
lock) so the production lock is exercised.
---------
Co-authored-by: ly-wang19 <ly-wang19@users.noreply.github.com>
Co-authored-by: Willem Jiang <willem.jiang@gmail.com>
* fix(mcp): offload blocking filesystem IO in MCP config update
update_mcp_configuration resolved the extensions config path, probed its
existence, read the raw JSON, wrote the merged config, and reloaded it — all
blocking filesystem IO on the event loop (PUT /api/mcp/config). The whole
read-modify-write after the async admin check has no interleaved awaits, so it
moves into one _apply_mcp_config_update helper dispatched via asyncio.to_thread;
the masked response is built on the loop. The secret-preserving merge, error
codes, and the stdio command allowlist are unchanged.
Found via `make detect-blocking-io`. Same class as #3457 / #3529 / #3551.
Add tests/blocking_io/test_mcp_router.py anchor, verified red->green under the
strict Blockbuster gate.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
* fix(mcp): serialize concurrent config updates with a write lock
Address review on #3552: offloading the read-modify-write to a worker thread
dropped the implicit serialization the single-threaded event loop provided, so
two concurrent PUT /api/mcp/config calls could interleave and clobber each
other. Guard the offloaded RMW with a module-level asyncio.Lock to restore
within-process atomicity (cross-process writers remain a separate, pre-existing
concern).
Add a serialization regression test (red->green: without the lock the tracked
max concurrency exceeds 1).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
* fix: address mcp config blocking io review
---------
Co-authored-by: ly-wang19 <ly-wang19@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-authored-by: Willem Jiang <willem.jiang@gmail.com>
