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fix(hooks): enforce plugin_timeout for synchronous native hooks - #424
gaodan-fang wants to merge 12 commits into
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The native adapter called a plugin's sync method inline inside the async dispatch. That blocked the event loop, so cpex's asyncio.wait_for timeout could not fire until the method returned, and the late result was then applied to the payload. Each native plugin now runs its sync methods on its own daemon worker thread, which no event loop owns, and the adapter awaits the result: - the timeout fires on time and follows on_error, as for async plugins; under the default "fail" it raises MemoryPolicyViolation; - a timed-out call is cancelled if it has not started; if it is running, its result is discarded and its per-call HookBackend view is revoked, so it cannot patch the store late; - calls to one plugin run one at a time, because detectors may share model objects that are not thread-safe; - while a timed-out call is still running, new calls to that plugin fail fast instead of queueing behind it; - contextvars are copied into each call, and a hook dispatched from a worker runs inline there, so it does not queue behind its own worker; - neither loop close nor interpreter exit waits for a stuck worker. Closes #422
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| Check name | Status | Explanation | Resolution |
|---|---|---|---|
| Linked Issues check |  |
Issue [#422] requires bounded outstanding native work and fast failure when the bound is full. _SyncHookRunner.run checks _abandoned before starting a daemon thread, but it admits every concurrent… |
Enforce an atomic bound on admitted native work, or use a dedicated bounded executor with explicit admission failure through the configured on_error path. Add a concurrent-admission test that proves the bound remains enforced when calls s… |
| Docstring Coverage | |
Docstring coverage is 17.76% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 107 functions across 3 files. | Write docstrings for the functions missing them to satisfy the coverage threshold. |
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Check name Status Explanation Description Check Check skipped - CodeRabbit’s high-level summary is enabled. Title check The title clearly and concisely describes the main change: enforcing plugin_timeout for synchronous native hooks. Out of Scope Changes check The changes remain within issue [ #422]. Per-call backend views and revocation protect against late effects from timed-out hooks. Fork handling, context propagation, documentation, and tests support th…Full details: Out of Scope Changes check
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Explanation
The changes remain within issue [
#422]. Per-call backend views and revocation protect against late effects from timed-out hooks. Fork handling, context propagation, documentation, and tests support the native-hook timeout fix. No unrelated change is established.
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Full details: Linked Issues check
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Explanation
Issue [
#422] requires bounded outstanding native work and fast failure when the bound is full._SyncHookRunner.runchecks_abandonedbefore starting a daemon thread, but it admits every concurrent call while those calls are still running. Several calls can then time out and remain active at the same time._MAX_ABANDONED = 1limits only later admissions after a timeout; it is not a bound on outstanding native work. The implementation otherwise covers off-loop execution, timeout behavior, late-result rejection, context propagation, and shutdown behavior. The tests cover concurrent execution, but they do not establish the required bound for concurrent admissions.Resolution
Enforce an atomic bound on admitted native work, or use a dedicated bounded executor with explicit admission failure through the configured
on_errorpath. Add a concurrent-admission test that proves the bound remains enforced when calls start before timeout cancellation.
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Independent review at 40e2d8d. I read #422/#420, every changed line, and the surrounding seam code (HookBackend, prepare_updates/collect_metadata_patches, dispatch_memory_post_read, _run_sync, cpex's _execute_with_timeout). I ran the new tests and wrote standalone probes, each run against base 2e32767 and this head.
Verdict: one blocking issue (fork safety), plus one should-fix where the headline "a late call cannot patch the store" guarantee doesn't hold. The core mechanism is sound, and it fixes #422. I'd approve once the first two items below are fixed and the three missing tests are added.
What I verified is correct
- #422 is fixed. A sync hook past
plugin_timeoutnow fails closed within the timeout, with and without a running loop, and the late result is discarded. - No lost wakeups. I set
_IDLE_SECONDS=0.0005and ran 900 calls from 6 threads, 3 runs. The worker restarted 74–86 times per run, with 0 errors and 0 calls slower than 0.5s._submitand the idle exit hold the same condition, so_thread = Noneis always visible to the next submit. - Exception semantics are unchanged. I ran a matrix of 5 modes (sequential/transform/fire_and_forget/concurrent/audit) × 3
on_errorvalues × 3 outcomes (HookPolicyViolationwith code/details,ValueError, transform), two calls each. The output is byte-identical between base and head.KeyboardInterrupt,SystemExitandCancelledErrorraised by the native method also behave as at base, and the next call recovers. plugin_timeout=0behaves the same at base and head. Both fail with "exceeded 0s timeout", so this is not a regression.- Dispatch from an
atexithandler still works, including after the worker has idled out. - Tests:
tests/unit/test_hooks*.pypassed 5 times out of 5 (127 passed, 3 skipped, no flakes).tests/unitpassed with 1476 passed, 4 skipped.ruff format --checkandruff checkare clean.mypyhas one error, a missinghypothesisstub in my shared venv, and it is the same at base.tests/e2e/test_processing_transactions.pyskips here because there is no PostgreSQL. - Merged onto current
origin/main(882e8c2): the merge is clean,tests/unitgives 1509 passed, and the fork repro below still reproduces. - Mutation testing: the suite kills my mutants for no fail-fast, no
_release, no revoked check, no_revoke, no worker flag, non-daemon worker and noctx.run. Three mutants survive; they are listed under item 3.
Findings
| # | Severity | Finding | Evidence (base → head) |
|---|---|---|---|
| 1 | Blocking | Not fork-safe. After os.fork() or a fork-context multiprocessing pool, _thread still points at the parent's thread, which doesn't exist in the child. So no worker ever starts, and every native hook call in the child times out, permanently. Under the default fail, every write and llm_pre_call raises. |
Parent dispatches once, then forks. Child: base 0.0s TAGGED ×3 → head 1.0s MemoryPolicyViolation … exceeded 1.0s timeout ×3 (with the default 30s timeout this would be 30s per call). A multiprocessing.get_context("fork").Pool gives the same result for 4 out of 4 tasks. |
| 2 | Should fix | The backend view is revoked only at _check. A timed-out call that already passed _check and is blocked in the backend read inside update_entity_metadata still appends to pending.patches. Under on_error="ignore"/"disable", that patch is committed. Revocation also doesn't reach nested views: a memory_post_read dispatched inline from the timed-out call gets a fresh, unrevoked HookBackend over the same pending patches. |
Pre-write plugin X (ignore) times out at 1.0s; its read returns at 1.5s; a second plugin Z runs until 1.8s. Head log: x timed out after 1s, then X appended patch at 1.51s, and the stored metadata is {'late': True}. The nested variant stores {'stamped_late': True} from a post_read plugin that ran after X's timeout. |
| 3 | Should fix (tests) | Three mutants survive the suite. Each is a real bug that my probes catch. (a) Removing self._thread = None on idle exit means every call after 30s idle times out forever. (b) Running jobs that were cancelled while queued makes the worker crash with InvalidStateError, and a call that timed out still runs. (c) Dropping _for_call() revokes the shared view, so the second native plugin in a chain gets The hook call that received this backend has finished. |
Probe with _IDLE_SECONDS=0.2: head ok → mutant 1.0s … exceeded 1s timeout. Two-reader chain: head r1 ok, r2 ok → mutant r2 refused. Queued-cancel probe: head runs 1 call → mutant runs 2 calls and raises InvalidStateError. |
| 4 | Medium (design) | Serializing each plugin, while queue time counts against plugin_timeout, turns concurrency into fail-closed errors. The PR body notes the trade-off, but its availability cost is large. #420 measured 7.5–13.6s per READI scan, so 3–4 concurrent requests are enough to exceed the default 30s. READI already serializes inference with its own inference_lock, so per-plugin serialization mostly matters for I/O-bound or GIL-releasing detectors. |
8 threads, a 0.2s detector, 1s timeout: base 8 ok in 0.21s → head 4 ok, 4 timeout in 1.01s. |
| 5 | Medium (docs) | A memory_post_read timeout now fails open. dispatch_memory_post_read swallows MemoryPolicyViolation, so a slow sync redactor returns unredacted results. This matches async plugins, but sync post_read plugins could not reach it before. The new docs line says a timeout under fail raises, which is not what a read caller sees. |
Slow redacting post_read plugin (1.5s, timeout 1s): base ['[REDACTED]'] → head ['alice@example.com'] plus a warning. |
| 6 | Low (docs) | "Calls to one plugin never overlap" is not true. A plugin reached through nested dispatch runs inline on the caller's worker, overlapping its own worker. That also bypasses its fail-fast state. | Post-read plugin Y with a concurrency counter: peak concurrency 2, on threads evolve-hook-x and evolve-hook-y. |
| 7 | Low | The idle worker's frame keeps the last job's fn/args/ctx/result alive for up to 30s, even after shutdown_hooks(). That holds the native plugin (and, for READI, its loaded model), the unredacted payload, and the HookBackend. Re-initialization leaves one live thread per plugin per cycle, for up to 30s. |
Native plugin weakref is still alive after shutdown_hooks(), and the worker frame's args holds messages=[{'content': 'ssn 123-45-6789'}]. 40 init cycles × 3 plugins leave 121 live threads (base: 1). |
| 8 | Low | A plugin that makes its context.backend callback from a helper thread (ThreadPoolExecutor doesn't copy contextvars) queues its own nested hook behind its busy worker. It waits the full timeout, then fails. |
Plugin on pre_write + pre_metadata_patch, patching from a pool thread: base 0.01s ok → head 2.0s MemoryPolicyViolation. |
Operational note (not a code defect): READI loads its weights lazily on the first detect, and may download them. That now happens inside a timed call, so a cold start longer than plugin_timeout fails the first write closed. Calls then fail fast until the load finishes. It may be worth warming the model in startup_validate, or documenting this.
Comments on the specific lines are inline. The probes are standalone scripts and I can share them on request.
| if self._abandoned is not None: | ||
| raise RuntimeError(f"Plugin {self._name} is still running a call that timed out; refusing new calls until it returns") | ||
| self._jobs.append((future, contextvars.copy_context(), fn, args)) | ||
| if self._thread is None: |
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Blocking: fork safety. After os.fork(), the child inherits self._thread (non-None), but that thread doesn't exist in the child. No worker is ever started, and each submitted job waits until cpex's timeout. This is permanent: the dead thread never runs the self._thread = None idle-exit line. The same goes for an inherited _abandoned, and for a _cond that the parent's worker held at fork time.
Repro: a native plugin dispatches once in the parent, then os.fork(), and the child dispatches 3 times. Base returns 0.0s TAGGED ×3. Head returns 1.0s MemoryPolicyViolation [PLUGIN_ERROR] Plugin tag exceeded 1.0s timeout ×3. A multiprocessing.get_context("fork").Pool(2) (the Linux default start method on 3.12/3.13) fails 4 out of 4 tasks the same way.
Suggested fix: store self._pid = os.getpid(). At the top of _submit, if os.getpid() != self._pid, rebuild _cond, clear _jobs, and reset _thread/_abandoned. Alternatively, call os.register_at_fork(after_in_child=...) over a module-level WeakSet of workers. Making the check self._thread is None or not self._thread.is_alive() would also guard against any future path that kills the thread without clearing _thread. Please add a fork test.
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Addressed in c5ca95a (and 8e0596a): the persistent worker is gone (8e0596a), so a child no longer inherits a _thread with nothing behind it. Your p1_fork now gives 0.0s TAGGED ×3 in the child, and p1b_mp_fork gives 4/4 TAGGED.
One fork hazard remained after that change: a child inherits the parent's set of abandoned calls, but none of their threads, so their done-callbacks never fire there. c5ca95a registers os.register_at_fork(after_in_child=...) over a WeakSet of runners. The hook clears the abandoned set and replaces the runner lock, in case another parent thread held it at fork time. backend.py's revocation lock gets the same reset. test_forked_child_is_not_blocked_by_the_parents_timed_out_call runs the parent with a stuck, timed-out call, then forks with both os.fork and a fork-context Pool(2). Without the reset, the child returns busy busy and the pool busy ×4; with it, all calls return TAGGED.
| self.__revoked = True | ||
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| def _check(self, namespace_id: str): | ||
| if self.__revoked: |
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Revocation is checked only here, at entry, so a call that has already passed _check is not stopped. In update_entity_metadata's pending path, the sequence is _check → _read (_check, then _search_entities_impl, which can be a slow DB round trip) → self.__pending.patches.append(...), and there's no check right before the append. Under on_error="ignore"/"disable", a patch that lands before prepare_updates deep-copies patches gets committed.
Repro: pre_write plugin X (ignore) patches an existing entity, and its read takes 1.5s. The timeout is 1s, and a second plugin Z takes 0.8s. Head logs Plugin x timed out after 1s, then X appended patch at 1.51s, and the stored metadata ends up {'late': True}.
Revocation also isn't transitive. If X's context.backend.search_entities(...) passed _read before the timeout, it dispatches memory_post_read inline, and _invoke builds a fresh HookBackend(raw_backend) that picks up the same _pending. A post_read plugin then patches through that unrevoked view. Repro: the stored metadata ends up {'stamped_late': True} after X's timeout. The non-pending path likewise runs self.__backend.update_entity_metadata to completion once its check has passed.
Suggestion: re-check revocation immediately before pending.patches.append (and before dispatching post_read in search_entities), and make _revoke and that check-and-append atomic with a small lock. For nested views, link a view created on a worker to the current call's view, for example through a contextvar set in _call_in_worker, so _check also fails once any ancestor is revoked. Or narrow the docs claim to "after its next backend call".
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Addressed in 7f31c1d (plus a test in c05a830). Revocation is now enforced where a patch is accepted, and it reaches nested views:
- Pending path. The patch is appended under the same lock
_revoke()takes, after a fresh_check, so nothing is accepted after the call times out. - Direct-write path. It now runs the template inline: patch hooks, then a
_check, then_update_entity_metadata_impl. A call revoked while its patch hooks ran is refused before the write starts. A write already under way when the timeout fires is not undone; the docs say so. search_entities. It re-checks after the read, before dispatchingmemory_post_read.- Nested views. The native call sets a
_calling_viewcontextvar to its own view. AnyHookBackendcreated under it (for example by a nested_invoke) records it as its parent, and_checkwalks the chain, so revoking a call revokes every view its hooks created.
Probe results:
p2_late_pending_patch:X refused: The hook call that received this backend has finished, stored{}(was{'late': True}).p2b_nested_view_not_revoked:X refused, stored{}(was{'stamped_late': True}).
New tests:
test_patch_from_a_call_that_timed_out_mid_read_is_refused[ignore|disable]test_revocation_reaches_views_created_by_nested_hooks, where the nested post_read starts before the outer timeout and patches after ittest_direct_write_is_refused_if_the_call_timed_out_during_the_patch_hooks
Each one fails with its piece removed: no re-check before the append, no parent walk, no _calling_view.set, no re-check before the direct write.
| if not self._jobs: | ||
| self._cond.wait(self._IDLE_SECONDS) | ||
| if not self._jobs: | ||
| self._thread = None |
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This idle-exit and restart path has no test. If I delete self._thread = None, all 18 new tests still pass. Yet with _IDLE_SECONDS=0.2, every call after the idle exit then times out: the result goes from 0.0s T to 1.0s … exceeded 1s timeout. Two other mutants also survive.
- In
_work, running a job whose future was cancelled while it was queued (set_running_or_notify_cancel()ignored) crashes the worker withInvalidStateErrorand runs a call that has already timed out. - Dropping
_for_call()on line 467 makes the first plugin's_revoke()revoke the shared view. The second native plugin in a chain then getsThe hook call that received this backend has finished.
Suggested tests: (1) monkeypatch _IDLE_SECONDS to something small, call, sleep past it, and call again; (2) two callers where the second times out while queued, then assert it never ran and that the worker still serves calls; (3) two native plugins in one pre_write chain that both use context.backend. Separately, wrapping the body of _work in try/finally that clears _thread (under the lock) would keep any unexpected worker death from wedging the plugin.
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Addressed in 8e0596a and 7f31c1d:
- (a) Idle exit and restart. That path no longer exists. 8e0596a replaced the per-plugin worker with one short-lived daemon thread per call, so there is no idle state to wedge.
p13(a) still gives0.0 Ton both calls. - (b) Call cancelled before it starts. The thread body checks
set_running_or_notify_cancel()before running anything.test_a_call_cancelled_before_it_starts_never_runsfails if that check is dropped. - (c) Each plugin's own view.
test_each_plugin_in_a_chain_gets_its_own_backend_view(7f31c1d) chains two native readers that both usecontext.backend. Dropping_for_call()fails it: r2 is refused.
I reran a 15-mutant set over the new code and all 15 are killed. The PR comment lists them with the tests that kill each one.
| if not self._jobs: | ||
| self._thread = None | ||
| return | ||
| future, ctx, fn, args = self._jobs.popleft() |
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Minor: after a job finishes, future, ctx, fn, args and result stay bound in this frame while the worker idles for up to _IDLE_SECONDS, including after shutdown_hooks(). That keeps the native plugin alive (for READI, its loaded model) along with the unredacted input payload, the HookContext, the HookBackend and the raw backend. Repro: a weakref to the native plugin is still alive after shutdown_hooks(), and the worker frame's args still holds messages=[{'content': 'ssn 123-45-6789'}]. Adding del future, ctx, fn, args (and result) at the end of each iteration fixes it.
Relatedly, re-initialization leaves one live thread per plugin per cycle for up to 30s: 40 cycles × 3 plugins left 121 threads, against 1 at base. It might be worth having shutdown_hooks() wake idle workers so they exit.
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Addressed in 8e0596a. Each call now has its own daemon thread, which exits as soon as the call returns. Nothing idles holding the frame, and threading.Thread drops its target and args on exit. p4_retention: the native plugin is not alive after shutdown_hooks(), and no evolve-hook threads remain (was: alive, plus a frame holding the ssn payload). p7_reinit_threads: 1 thread after 40 cycles × 3 plugins (was 121; base is 1). test_nothing_from_a_call_outlives_it covers both: a weakref to the plugin is dead after 5 init/shutdown cycles, and no evolve-hook threads remain.
| ) | ||
| try: | ||
| out = method(plain, hook_ctx) | ||
| if _in_sync_hook_worker.get(): |
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Running nested calls inline is the right call to avoid self-deadlock, but it means the "calls to one plugin never overlap" guarantee in the docstring and docs does not hold. Plugin Y reached through nested dispatch (X's pre_write → context.backend.search_entities → Y's post_read) runs on X's worker while Y's own worker serves another caller. My probe measured Y at peak concurrency 2, on evolve-hook-x and evolve-hook-y. It also skips Y's fail-fast state if Y has an abandoned call. I'd soften the wording to something like "calls dispatched from outside a hook never overlap".
The converse case: a plugin that makes its context.backend callback from a helper thread (ThreadPoolExecutor doesn't copy contextvars, so the worker flag is lost) queues its own nested hook behind its busy worker. It then waits the full timeout. Base returns 0.01s ok; head raises 2.0s MemoryPolicyViolation. That may be acceptable, but it's worth a sentence in the docs.
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Addressed in 8e0596a (code) and 3ba7109 (docs). With one thread per call there is no per-plugin queue, so the inline special case for nested dispatch is gone. A nested hook now runs on its own thread with its own timeout and fail-fast state, like any other call. The "never overlap" guarantee is also gone: calls from different threads overlap again, as they did at base. The docs now say native plugins must be thread-safe or lock internally. p3_nested_overlap gives peak 2, the same as base.
The helper-thread case is fixed by the same change, because nothing can queue behind a busy worker. p11_selfqueue gives 0.01 s ok (was 2.0 s MemoryPolicyViolation; base 0.01 s ok). It's covered by test_callback_from_a_plugin_helper_thread_does_not_wait_on_the_plugin.
| - **Execution modes and priorities.** Each plugin registers with a CPEX execution mode — `transform` (serial, chained, modifying, non-halting), `sequential` (may halt), `fire_and_forget` (side-effect only), `audit`, `concurrent`, `disabled` — a `priority` (lower runs earlier), and an `on_error` policy (`fail` / `ignore` / `disable`). | ||
| - **Fail-closed by default.** `on_error` defaults to `fail`: a plugin that crashes or times out halts the operation (a memory-write/`llm_pre_call` crash surfaces as `MemoryPolicyViolation`), rather than silently passing data through — the right default for a compliance plugin (e.g. PII redaction), but it trades availability for safety. A non-critical plugin (e.g. best-effort access auditing) can opt into `on_error="ignore"` so its failures don't block the operation. (A crash in a `memory_post_read` plugin never fails the read it rode in on — that hook is read-side transform-only and logs a warning instead.) | ||
| - **Sync bridge.** CPEX's `invoke_hook` is async-only; Evolve's call sites are sync. The seam uses `asyncio.run` when no event loop is running and a dedicated thread when one is. Fire-and-forget plugin tasks are awaited before the bridge returns so their side effects are never lost with the closing loop. | ||
| - **Timeouts for native plugins.** `plugin_timeout` applies to native (sync) plugins as it does to async ones. Each native plugin's methods run one call at a time on that plugin's own daemon worker thread, off the event loop, so the timeout can fire. Calls to one plugin never overlap, since detectors may share model objects that are not thread-safe. A call that times out is handled by `on_error` like any other timeout: under `fail` it raises `MemoryPolicyViolation`. Its late result is discarded and its `context.backend` is revoked. Python cannot stop a running thread, so the call keeps running until it returns. Until then, new calls to that plugin fail at once instead of queueing behind it. If you need hard cancellation, run the detector in a separate process. A C extension that holds the GIL for the whole call can still delay the timeout until it releases the GIL. |
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Three things this paragraph should say, since users will tune plugin_timeout from it:
- Queue time counts. Calls to one plugin are serialized and the wait counts against
plugin_timeout. Under concurrency that becomes fail-closed errors. 8 threads, a 0.2s detector and a 1s timeout give 8 ok in 0.21s at base, and 4 ok plus 4MemoryPolicyViolationat head. With Memory stress-test findings: corrections, redaction, timeouts and latency #420's 7.5–13.6s READI scans, 3–4 concurrent requests are enough to exceed the default 30s. Please consider whether serialization should be opt-out for plugins that declare themselves thread-safe (READI already has its owninference_lock). memory_post_readfails open on timeout.dispatch_memory_post_readswallows the violation and returns untransformed results. A slow sync redactor that returned['[REDACTED]']at base now returns['alice@example.com']. So "underfailit raisesMemoryPolicyViolation" isn't what a read caller sees.- Overlap. "Calls to one plugin never overlap" excludes nested dispatch from inside another plugin; see the comment on
manager.pyline 474.
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Addressed in 3ba7109 (docs) and 8e0596a (design):
- Queue time. Removed at the source. Calls run concurrently again and there is no seam queue:
p6_concurrencygives 8 ok in 0.21s, the same as base.test_concurrent_callers_are_not_serializedfails if calls are serialized. The docs note that time a plugin spends waiting on its own lock still counts. READI'sinference_lockis an example. memory_post_read. The docs now say a timeout there fails open. The read returns untransformed results and logs a warning, as it does for a crash or for an async plugin, so a post_read plugin that might time out is not a reliable redactor. The same applies to the fail-fast refusals.- Overlap. The "never overlap" claim is removed. The bullet now covers concurrency and thread-safety, revocation (with the in-progress-write limit), stuck calls, the GIL limit, and READI's lazy model load inside a timed call (your operational note).
The per-plugin serial worker made callers on different threads queue behind each other, and the queue time counted against plugin_timeout. With 8 callers of a 0.2s detector and a 1s timeout, 3-4 failed closed, where they all passed when plugins ran inline. Each native call now runs on its own short-lived daemon thread, so concurrency matches the inline behaviour again and nothing queues. The bound on abandoned calls stays per plugin: while a timed-out call is still running, new calls fail fast. Because the thread exits when its call returns, no idle worker keeps the plugin, payload or backend alive, no threads pile up across re-initialization, and a plugin that calls back from its own helper thread no longer waits on itself. That also removes the idle-exit path and the need to run nested dispatch inline.
A forked child inherits the parent's record of timed-out calls, but none of their threads, so their done-callbacks never fire in the child. If the parent had one abandoned call at fork time, every call in the child failed fast for good. A lock held by another parent thread at fork time would also be stuck. An after-fork hook now clears each runner's abandoned calls and replaces its lock. Covered for os.fork and a fork-context multiprocessing pool.
Revocation was only checked when a HookBackend method was entered. A call that passed the check and then timed out while blocked in the backend read still appended its patch, and under on_error="ignore" or "disable" the patch was committed. Hooks dispatched from that call also built fresh, unrevoked views over the same pending patches. - Accepting a pending patch now re-checks revocation under the same lock that revokes, so no patch is accepted after the call times out. - Outside preparation, revocation is re-checked after the patch hooks, right before the write starts. - A view created by a hook that a native call dispatched records that call's view as its parent, and is revoked along with it. Also adds the test for each chained plugin getting its own view.
A memory_post_read timeout fails open: dispatch_memory_post_read returns untransformed results, as it does for a crash. Also describe the current concurrency model, which views are revoked, what fails fast while a call is stuck, and the GIL and lazy-model-load limits.
…h hooks Outside preparation, a stamp made just before the call's deadline is still in the memory_pre_metadata_patch hooks when the call times out. The write must be refused when they return.
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Review comments at @altk_evolve/hooks/manager.py:
- Around line 575-591: Update _Bounded call tracking in run so the limit is
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altk_evolve/hooks/backend.pyaltk_evolve/hooks/manager.pydocs/guides/memory-hooks.mdtests/unit/test_hooks_sync_timeout.py
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Second pass at c05a830. I read the 5 new commits line by line, re-ran all 15 of my earlier probes against origin/main (882e8c2) and this head, and wrote 11 new probes against the per-call-thread design.
Verdict: nothing blocks. Every finding from my first review is fixed or now documented, and I confirmed each fix by re-running its probe. I found four new issues, all non-blocking. I'd approve once item 1 is fixed or deliberately accepted and documented. Items 2–4 can be follow-ups.
First-review findings, re-run at this head
| # | Finding at 40e2d8d |
Status | Evidence (main → 40e2d8d → this head) |
|---|---|---|---|
| 1 | Fork safety (blocking) | Fixed | p1 child: 0.0s TAGGED → 1.0s timeout → 0.0s TAGGED ×3. p1b fork Pool: 4/4 ok → 4/4 timeout → 4/4 ok. New probe n4: forking while another thread holds both the revoke lock and a runner lock, with a native call in flight. The child dispatches, accepts a pending patch, and exits 0. |
| 2 | Late patch after the revocation check; nested views not revoked | Fixed (one gap: item 2 below) | p2: X refused, stored {}. p2b: stored {}. |
| 3 | Surviving mutants M6/M9/M10 | Fixed | M9's idle path is gone. M6 and M10 are now killed. |
| 4 | Serialization caused fail-closed errors under concurrency | Fixed | p6: 8 ok in 0.21s, the same as main. |
| 5 | post_read timeouts fail open | Documented | p12 is unchanged by design and the docs now say so. |
| 6 | "Never overlap" claim | Documented | The docs now state the thread-safety requirement instead. |
| 7 | Frame retention and thread build-up | Fixed | p4: the plugin is not alive after shutdown and no threads remain. p7: 1 thread (was 121). |
| 8 | Self-queue from a helper thread | Fixed | p11: 0.01 s ok. |
The remaining probes match main. p8 (45 combinations of mode × on_error × outcome) is identical to main. p9 (BaseException), p5 (plugin_timeout=0) and p15 (dispatch from atexit) also match.
New design: what I verified holds
- Fail-fast bookkeeping has no permanent wedge. n3 sent 480 calls from 8 threads that each finish within ±5ms of a 50ms timeout. Afterwards there were 0 abandoned records and 0 live hook threads. n2 sent 8 concurrent callers to a stuck plugin: it produced 8 stuck threads (the bound is on admission, so stuck threads scale with caller concurrency, not 1). The plugin fails fast while they run and recovers once they are released.
- No deadlocks.
_revoke_lockonly guards a flag write, and a check plus append in which nothing blocks. No other lock is taken while it is held, so there is no lock-ordering cycle. - Fork is handled for both the runner locks and the revoke lock (n4).
- Interpreter shutdown is clean. In n8, a timed-out daemon call wakes during finalization and uses logging, imports, a backend write and stdout. Across 10 runs with delays from 0.05s to 0.3s, every exit was rc=0 with no fatal error or traceback.
- The contextvar does not leak into the caller.
_calling_viewisNonein the caller after a call, both with and without a running loop (n5a). - Tests and lint.
- Hooks tests: 5 runs out of 5 passed (136 passed, 3 skipped).
tests/unit: 1485 passed.- Merged with current
origin/main(28fc0a5): 1525 passed. The 2 failures are the new secrets tests from #398, which also fail onorigin/mainalone in my unsynced venv (cpex-secrets-detection0.1.0 vs 0.3.11). ruffandmypyare clean.
- Mutation testing: 14 mutants, 11 killed. Killed: at-fork runner reset, re-check at patch acceptance, contextvar link, parent walk, fail-fast, release, re-check before direct write, daemon, cancelled-before-start, context copy, and revoke. The survivors:
- Revoke-lock reset after fork: my n4 probe deadlocks the child in this case. A test is worth adding.
- Re-check before post_read dispatch: it only matters on the helper-thread path in item 2.
_revokewithout the lock: the race window is too narrow to test deterministically, which is acceptable.
New findings
| # | Severity | Finding | Evidence (main → this head) |
|---|---|---|---|
| 1 | Medium, should fix | A non-timeout cancellation is recorded as an abandoned "timed-out" call. In concurrent mode, cpex cancels the other plugins' tasks when one plugin halts. The still-running native call is then marked abandoned, so the next dispatch fails closed with Plugin slow is still running a call that timed out (a plugin that never timed out) until that call returns. |
n9: plugin A halts once and B takes 0.5s, both in concurrent mode. Call 2 on main: 0.5s ok. On this head: 0.0s MemoryPolicyViolation … still running a call that timed out. |
| 2 | Low–medium | Transitive revocation goes through an ambient contextvar, so it follows the thread, not the capability. (a) It misses nested views created on a plugin's helper thread. That is the pattern test_callback_from_a_plugin_helper_thread… treats as supported. (b) It reaches work the call hands off with a copied context, after the call has finished normally. That work's later public-API writes then fail closed. |
n11: the same scenario as test_revocation_reaches_views_created_by_nested_hooks, with X's read on a pool thread. Same-thread: Y refused, stored {}. Pool thread: Y patched, stored {'stamped_late': True}. n5b: a plugin hands off follow-up work via copy_context().run, and its later client.update_entities(...): main ok → head MemoryPolicyViolation … The hook call that received this backend has finished. |
| 3 | Low | The per-call thread adds about 0.2 ms per native plugin per dispatch. The PR body's figure of about 0.05 ms is for a single plugin. | n1b on a noisy 56-CPU host (load ~48), best of 7 batches of 300, run 3 times. 5 sequential no-op plugins: main 0.40–0.86 ms → head 1.58–1.87 ms. 16 callers × 100 dispatches × 5 concurrent plugins: main 1.3–2.4s → head 4.9–5.6s. One plugin: within noise (main 0.29–0.58, head 0.50–0.57). |
| 4 | Low | HookBackend.update_entity_metadata's direct path now inlines BaseEntityBackend.update_entity_metadata and calls _update_entity_metadata_impl itself. A backend or "retry wrapper" that overrides the public template (base.py allows one to delegate to it) is bypassed for hook-originated writes. Nothing in-tree overrides it today. |
Code reading; grep finds no override. |
Also worth knowing (no action needed): when thread creation fails (can't start new thread), the call now fails closed where main ran it inline (n10). That's the right default.
Inline comments follow. All probes are standalone scripts, and I can share them.
| if future.cancel(): # not started yet: it will never run | ||
| return | ||
| with self._lock: | ||
| self._abandoned.add(future) |
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This branch also runs for cancellations that aren't the timeout. In concurrent mode, cpex cancels the remaining plugins when one halts: the log line is Pipeline halted by CONCURRENT plugin … cancelling N pending task(s). The native call that's still running lands here and is recorded as abandoned, so the next dispatch to this plugin raises Plugin slow is still running a call that timed out until that call returns. The plugin never timed out.
Repro (n9): plugin A halts on its first call (HookPolicyViolation) and B sleeps 0.5s, both in concurrent mode. On main, call 2 returns 0.5s ok. On this head, call 2 raises 0.0s MemoryPolicyViolation [PLUGIN_ERROR] RuntimeError('Plugin slow is still running a call that timed out…') under the default fail. With a multi-second detector, every request in the few seconds after a policy block fails closed.
Options: (a) record the call only if it has run for at least the executor's timeout (pass pm.executor.timeout to the runner, or time the call from the start of run); (b) don't refuse new calls because of a cancelled call, and only bound genuinely timed-out ones; or (c) at minimum, reword the message to "timed out or was cancelled" and document the concurrent-mode interaction.
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Addressed in 4959877. I took option (b), implemented via (a). The runner now records a cancelled call as abandoned only if it had used up plugin_timeout, timed from the start of _run with 5% slack, since cpex's clock starts slightly earlier.
A call cancelled early (a halting sibling in concurrent mode) doesn't make the plugin refuse new calls, because the plugin isn't stuck. Its result is still discarded and its backend view is still revoked by _run's finally. Its thread is bounded by the caller that admitted it, as for any running call.
n9 now gives call 2 0.5 ok, the same as main. test_a_call_cancelled_by_a_halting_sibling_does_not_refuse_new_calls fails without the fix, with still running a call that timed out. A mutant that treats every cancellation as a timeout is killed by that test. One that treats none as a timeout is killed by the fail-fast and fork tests.
| if view is not None: | ||
| from altk_evolve.hooks.backend import _calling_view | ||
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| _calling_view.set(view) |
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Linking through an ambient contextvar ties revocation to the thread rather than the capability. That fails in two directions:
- It misses helper threads.
ThreadPoolExecutordoesn't copy contextvars, so a view created by a hook dispatched from a plugin's pool thread has no parent. n11 is thetest_revocation_reaches_views_created_by_nested_hooksscenario with X'scontext.backend.search_entitiesmade on a pool thread. Same-thread:Y refused, stored{}. Pool thread:Y patched, stored{'stamped_late': True}. The PR treats this helper-thread pattern as supported (test_callback_from_a_plugin_helper_thread_does_not_wait_on_the_plugin). - It reaches past the call. Work the call hands off with a copied context (
copy_context().run,asyncio.to_thread, or OTel-wrapped executors) inherits the link after the call returns normally. That work's later public-API write then gets a view whose parent is revoked. n5b: mainok→ headMemoryPolicyViolation … The hook call that received this backend has finishedfor an unrelatedclient.update_entities(...).
Suggestion: set the link inside HookBackend instead of here. Each HookBackend method that dispatches (search_entities, both update_entity_metadata paths) could run token = _calling_view.set(self) / reset(token) around its nested dispatch. The link then follows the capability onto whatever thread uses it, and work outside a context.backend call isn't linked at all. A test with a pool-thread read would pin it.
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Addressed in 1d7e006, as you suggested. _calling_view is now set only inside the HookBackend methods that dispatch (search_entities, and both update_entity_metadata paths), through a small _dispatching() context manager, and reset afterwards. The native-call wrapper is gone.
Results:
- n11 pool:
Y refused, stored{}(wasY patched,{'stamped_late': True}). - n5b: the follow-up write is
ok(wasMemoryPolicyViolation). - n5a: the caller still sees
None.
New tests, both of which fail at c05a830:
test_revocation_reaches_views_created_from_a_plugin_helper_threadtest_work_handed_off_by_a_finished_call_is_not_revoked
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| def _reset_revoke_lock_after_fork() -> None: | ||
| global _revoke_lock | ||
| _revoke_lock = threading.Lock() |
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This reset is untested. With it reduced to pass, all 136 hooks tests still pass. In my n4 probe, though (another thread holds _revoke_lock at fork time), the forked child then deadlocks at its first view._revoke()/patch acceptance, and the probe timed out at 30s. The existing fork test could hold _revoke_lock from a helper thread across the fork to cover it.
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Addressed in cf63d88. test_forked_child_can_revoke_while_a_parent_thread_held_the_revoke_lock holds _revoke_lock on a parent thread across os.fork. The child calls HookBackend(None)._revoke(), and the parent polls waitpid with a 5s deadline. With the reset reduced to pass, the test fails with child hung. n4 still exits 0 at the new head.
| name=f"evolve-hook-{self._name}", | ||
| daemon=True, | ||
| ) | ||
| thread.start() |
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Minor, for the record: one thread per native call costs about 0.2 ms per plugin per dispatch here. That's more than the PR body's "about 0.05 ms", which measured one plugin. With 5 sequential no-op native plugins, the best of 7×300 dispatches was 0.40–0.86 ms on main and 1.58–1.87 ms on this head. 16 callers × 100 dispatches over 5 concurrent plugins took 1.3–2.4s on main and 4.9–5.6s here. This is a noisy host, so treat the figures as rough. It's negligible next to LLM calls, but memory_post_read fires on every public search. If it shows up in profiles, a small module-level pool of daemon threads that no event loop owns would amortize it, at the cost of some of the complexity you just removed.
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Thanks, corrected in the PR body. n1b here (best of 7×300, host load around 40) puts it at about 0.15–0.2 ms per native plugin per dispatch:
- 5 plugins: main 0.36–0.66 ms, this head 1.09–2.08 ms.
- 1 plugin: within noise.
I've kept per-call threads for now, because a pool would bring back the lifetime and fork state that 8e0596a removed. The pool idea is noted in the body as the follow-up if this shows up in profiles.
| # check after the patch hooks, right before the write starts. | ||
| patch = dispatch_memory_pre_metadata_patch(self.__backend, namespace_id, entity_id, metadata_patch) | ||
| self._check(namespace_id) | ||
| entity = self.__backend._update_entity_metadata_impl(namespace_id, entity_id, patch) |
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Low: this inlines BaseEntityBackend.update_entity_metadata so a revocation check can sit before the impl. A backend or wrapper that overrides the public template is now bypassed for hook-originated direct writes. base.py's docstring allows a "retry wrapper [that] may delegate to this entire method to include hook work in the attempt". Nothing in-tree overrides it today, so a one-line comment pointing at the base template, or a test asserting the two stay in sync, would keep the copy from drifting.
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Addressed in 81e3ca9. The direct path calls the public self.__backend.update_entity_metadata(...) again, so overrides and wrappers apply. The revocation re-check after the patch hooks moved to the end of dispatch_memory_pre_metadata_patch, through _check_calling_view(). It only acts while a HookBackend method is dispatching, so it still runs after the patch hooks and before the write.
test_hook_direct_writes_go_through_the_public_template uses a FilesystemEntityBackend subclass that overrides the public method. A mutant that calls BaseEntityBackend.update_entity_metadata directly fails it. test_direct_write_is_refused_if_the_call_timed_out_during_the_patch_hooks still kills removal of the re-check.
cpex cancels a running call both when it times out and when a sibling halts the pipeline in concurrent mode. Both were recorded as a timed-out call, so after a policy block the next call to a slow but healthy plugin failed fast with "still running a call that timed out". A cancelled call now counts as abandoned only if it had used up plugin_timeout. An early cancellation still discards the call's result and revokes its backend view, but it doesn't refuse new calls: the plugin isn't stuck.
… thread The parent link for transitive revocation came from a contextvar set for the whole native call. That tied it to the call's thread and context, not to the capability. A view created by a hook dispatched from the plugin's own pool thread had no parent, so its late patch was committed. Work the call handed off with a copied context stayed linked after the call finished normally, so a later, unrelated public write failed closed. The link is now set only while a HookBackend method dispatches nested hooks. It follows context.backend onto whatever thread uses it, and nothing outside a context.backend call is linked.
Hold the revoke lock on a parent thread across os.fork. Without the reset, the child's first revocation never returns.
Outside preparation, HookBackend.update_entity_metadata had inlined BaseEntityBackend.update_entity_metadata, to place a revocation check before the write. That bypassed any backend or wrapper override of the public template, which base.py allows (for example, a retry wrapper). It now calls the public method again. The re-check runs at the end of dispatch_memory_pre_metadata_patch instead, against the view that is currently dispatching. That is still after the patch hooks and before the write.
Calls admitted concurrently can each time out, so the abandoned-call limit does not cap stuck threads, and early cancellations do not count. Also say that revocation follows views created through context.backend on any thread.
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Follow-up to the second review at
All 10 new mutants are killed (G1–G10, table in the PR body). Reruns at
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Ready for review:
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Closes #422
Part of #420
Problem
_NativePluginAdapter._runcalled a native plugin's sync method inline inside the async dispatch. That blocked the event loop, so cpex'sasyncio.wait_fortimeout could not fire until the method returned. The late result was then applied to the payload.Change
The adapter now runs each native call on its own short-lived daemon thread (
_SyncHookRunner) and awaits the result, so cpex's timeout cancels the await on time. Raw cpex (async) plugins are unchanged.on_error, as for async plugins. Under the defaultfail, a write hook orllm_pre_callraisesMemoryPolicyViolation.ignorepasses the original payload through, anddisabletakes the plugin out of rotation. Amemory_post_readtimeout fails open:dispatch_memory_post_readreturns untransformed results and logs a warning, as it does for a crash or an async plugin.HookBackendview, revoked when the call ends or times out.update_entity_metadata, so overrides and wrappers apply. Revocation is re-checked after the patch hooks, before the write starts.HookBackendmethod dispatches nested hooks, it marks itself as the parent of any view they create, so those views are revoked with it. The link followscontext.backendonto any thread, including a plugin's own pool threads, and work outside acontext.backendcall is not linked.concurrentmode, doesn't refuse new calls, though its result is still discarded and its view revoked.asyncio.run's loop close nor interpreter exit. A plainasyncio.to_threadwould join the loop's default executor and wait (mutant F2 below).os.register_at_forkhook resets the runners' abandoned-call records and locks, and the revocation lock, in the child._in_write/_in_post_readguards, pending patches). Each thread exits when its call returns, so nothing keeps the plugin, payload or backend alive afterwards, and threads don't accumulate across re-initialization.Concurrency choice: unchanged from before. Inline, calls from different caller threads already ran a native plugin concurrently. This PR keeps that: no per-plugin serialization and no queue, so queue time never counts against
plugin_timeout. The first revision serialized calls per plugin, which made 3 of 8 concurrent callers of a 0.2s detector fail closed under a 1s timeout. Native plugins must therefore be thread-safe or lock internally; the docs say so, and READI already serializes inference with its owninference_lock. Time a plugin spends waiting on its own lock does count against the timeout. I didn't add a configurable concurrency limit, because the default would have to be "unlimited" to avoid a regression, and a plugin that needs a limit can lock internally.Evidence
The #420 repro: a native
llm_pre_callplugin that sleeps 2s, withplugin_timeout=1, and an async control:Dispatch overhead: about 0.2 ms per native plugin per dispatch for the per-call thread. R424's n1b (best of 7×300, on a loaded host) gives 5 no-op plugins 0.36–0.66 ms on main against 1.09–2.08 ms here; one plugin is within noise. This is small next to LLM calls, but
memory_post_readfires on every public search. If it shows up in profiles, a small module-level pool of daemon threads would amortize it.The review probes (R424) at base, the first revision
40e2d8d, and this head:40e2d8d0.0s TAGGED1.0stimeout0.0s TAGGEDPool, 4 tasksTAGGEDignore){'late': True}{'late': True}{}{'stamped_late': True}{}shutdown_hooks()['[REDACTED]']after 1.5s['alice@example.com']['alice@example.com']c05a830) 0.0s fail-fastc05a830)Y patched, stored{}c05a830)MemoryPolicyViolationc05a830) exit 0Tests
tests/unit/test_hooks_sync_timeout.py(32 tests). Sync cases are parametrized against an async control.on_errorignore/disablematch async plugins.fire_and_forgetis bounded.context.backendpatch is refused: after a gated wait; after a slow read underignore/disable; through a nested hook's view; and when the call times out during the patch hooks.memory_post_readguard holds.os.forkand a forkPool) is not blocked by the parent's timed-out call, or by a revoke lock a parent thread held at fork time.All 15 mutants of the first redesign are killed:
asyncio.to_thread_for_call)A second set of 10 mutants, covering the round-2 changes, is also all killed:
_dispatchingsets no linkChecks:
tests/unit/test_hooks*.py) passed 5 times in a row: 141 passed, 3 skipped each time.tests/unit: 1490 passed. Merged onto currentorigin/main(28fc0a5): 1530 passed, 2 failed. The 2 failures are fix(deps): deliberately bump cpex-secrets-detection to 0.3.11, with redaction regression tests #398's new secrets tests, which fail onorigin/maintoo in the shared venv: it hascpex-secrets-detection0.1.0, and they need a newer release.tests/e2e/test_processing_transactions.pyandtests/test_processing_storage_contract.pypass.ruff format --check,ruff checkandmypy .are clean.Caveats
detect, inside a timed call. On a cold start, setplugin_timeoutabove the load time or warm the model up first.memory_post_readtimeouts fail open (see above), consistent with crashes and async plugins.can't start new thread), the call fails closed. Before this PR it ran inline.Summary by CodeRabbit
Bug Fixes
Documentation