DESKTOP-CONVERT-KILL: the IFC converter runs in a child process the server can kill - #576
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…r can kill The cooperative deadline shipped in #574 is checked between elements and every 4,096 entities, which bounds a model that overran because it had a lot in it. Two costs sit outside every checkpoint and nothing inside the process can reach them: `ifcopenshell.open`, one call whose time scales with file size and is paid in full before the first check, and any single `create_shape` that never returns. On the desktop app -- no Node runtime, so the Python path is the only one -- `edit_preview` passes `timeout=120` on a SYNCHRONOUS route, so a model hitting either cost held a request worker indefinitely instead of returning the 503 the caller is written to expect. **The blocker this entry was filed on did not hold, and the shape of that is the point.** It said process isolation needed `multiprocessing`, which under PyInstaller re-execs the frozen executable unless `freeze_support()` is wired -- net-new machinery for a frozen app with no pattern in this tree to copy. True of `multiprocessing`, and not of process isolation. `desktop_entry.py` is a three-line launcher and is the `Analysis` script for BOTH `sidecar.spec` and `desktop.spec`, so it can branch on an argv sentinel before importing the server, and `sys.executable` then means "this bundle" when frozen and "this interpreter" when not. One mechanism, both environments, no `multiprocessing` at all. *A blocker recorded as a property of the platform turned out to be a property of one approach to it* -- and written as the former, it stopped anyone looking for a fortnight. This is the SECOND reason-shaped error on this one entry: the lane table's "process/packaging shape" was the first and cost thirteen days. Both were accurate about the work and wrong about why it could not be done, which is the form that stops a reader before they check. The child writes the `.frag` itself rather than piping bytes back: a model is tens of megabytes and a pipe the parent is not draining while it waits would deadlock. It gets the caller's FULL budget, so an ordinary overrun still returns from its own checkpoint naming the phase; the parent's kill fires `_KILL_GRACE_S` later. The outer bound is therefore `timeout + 5s` rather than `timeout`, which is stated rather than hidden -- shortening the child's deadline to keep the bound exact would make the two branches disagree about what the parameter means, and a backstop that pre-empts the thing it backs up is not a backstop. **No in-process fallback, deliberately.** Spawning failures are not an error anyone reports, so a fallback would mean the conversion silently returned to being uninterruptible while the reader believed it was bounded -- the same shape as the advisory-lock degrade that nearly shipped in #575. Measured, not argued. A real conversion through the child produces a 697-byte fragment in 0.61 s. A stub child that ignores every checkpoint and sleeps 25 s is killed at 7.0 s against a 2 s budget. The stub SELF-EXITS, so deleting `timeout=` from the spawn makes the gate fail in 25 s rather than hang for ever -- a hang is reported as nothing, which `test_fragconvert_timeout.py` section 4 had to learn the same way. Gate: 12/12, with three mutations each redding the check that names them -- dropping the spawn timeout (3 red, and the run still TERMINATES), moving the sentinel dispatch after the server import (1 red), and restoring the in-process call (1 red). The sentinel is matched by NAME rather than by string literal, so an entry point that drifted to its own hardcoded copy reds rather than passing. `test_fragconvert_timeout`, `test_fragments_python` and `test_fragments_schema` all still pass through the new path; ruff clean tree-wide. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Tt2XKB83wwNt2nrMbK6eEA
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Included review availability: Your plan provides up to 2 included reviews per hour; 0 remain after this review. 📝 WalkthroughWalkthroughPython IFC-to-Fragments conversion now runs in a child process. The parent applies a cooperative timeout and a five-second kill grace after the child starts. The desktop launcher dispatches child invocations by sentinel. Tests cover conversion output, cooperative timeout, and parent-enforced termination. ChangesIFC conversion timeout handling
Priority: ➖ Normal Estimated code review effort: 3 (Moderate) | ~25 minutes Change: Bug fix · Severity of issue fixed: Medium Sequence Diagram(s)sequenceDiagram
participant convert_ifc
participant subprocess.run
participant desktop_entry
participant fragconvert_child
participant from_ifc.convert
participant fragmentFile
convert_ifc->>subprocess.run: Launch child with timeout plus five-second grace
alt Frozen application
subprocess.run->>desktop_entry: Start with child sentinel and arguments
desktop_entry->>fragconvert_child: Dispatch to main
else Unfrozen application
subprocess.run->>fragconvert_child: Start module with source, destination, and budget
end
fragconvert_child->>from_ifc.convert: Convert source with cooperative deadline
from_ifc.convert-->>fragconvert_child: Return conversion result
fragconvert_child->>fragmentFile: Write fragment data
fragconvert_child-->>subprocess.run: Return status JSON
subprocess.run-->>convert_ifc: Return status and output, or kill child at timeout
Merge Risk: ⚪ Minimal · up to The child-process conversion change and its updated reconversion test have no identified issue that should block merging after normal checks. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
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Inline comments:
In `@docs/roadmap.md`:
- Line 1426: Qualify the `timeout + 5s` bound in the roadmap text as applying
after the subprocess has spawned; clarify that process creation may take longer
and is not covered by `subprocess.run(timeout=...)`.
In `@services/api/test_fragconvert_kill.py`:
- Line 180: Set _HANG_S to just above the seven-second kill window so the stub
still verifies parent termination while the second subprocess.run invocation
exits promptly.
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CHANGELOG.mddocs/roadmap.mdservices/api/desktop_entry.pyservices/api/run_tests.pyservices/api/src/aec_api/fragconvert.pyservices/api/src/aec_api/fragconvert_child.pyservices/api/test_fragconvert_kill.py
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…a 25s tax **1. `timeout + 5s` was claimed as a total; it is post-spawn.** Checked against CPython's source rather than reasoned about: `subprocess.run` constructs `Popen(...)` and only then hands `timeout=` to `communicate()`, so the clock starts once the process exists and creating it -- fork/exec, `CreateProcess` on Windows -- sits outside the window. That cost is bounded by the OS and nothing here can bound it, so the honest form is "`timeout + 5s` after the child starts". *This is the same overclaim the item exists to remove, one layer up.* The change is about a parameter that was documented as bounding more than it bounded; describing its replacement as bounding more than IT bounds would have reproduced the defect in the prose that explains the fix. Corrected in the code comment and in the roadmap entry together -- the roadmap is where a reader plans against it. **2. The self-exit probe cost 25 s on every full-suite run.** Real, and the suite runs this file now. But the suggested fix was to shorten `_HANG_S` itself, and that pays for the time by NARROWING the margin the kill arm depends on: the arm distinguishes "killed at ~7 s" from "the stub finished by itself", and at `_HANG_S = 10` those are three seconds apart on a loaded runner. The arm would still pass -- for the wrong reason. So the stub's sleep is parameterised instead. The kill arm asks for 25 s and keeps its margin; the self-exit probe asks for 0.2 s, because it is establishing that `sleep(x); sys.exit(0)` returns at all, which holds for every x. *Make the cheap check cheap without making the expensive one weaker.* Gate 12/12, and the run drops 35s -> 9.5s. Re-measured the mutation that matters against the parameterised stub: dropping `timeout=` from the spawn still reds 3 checks and still TERMINATES (26.7 s) rather than hanging, which is the property the probe exists to keep true. ruff clean tree-wide. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Tt2XKB83wwNt2nrMbK6eEA
CI red on 01e29ff: `test_publish_reconvert`, 713/714. ifcopenshell.Error: Unable to parse IFC SPF header The test intercepted the converter with `mock.patch("aec_data.fragments.from_ifc.convert", ...)`. That patch lives in THIS process. Moving the conversion into a child means the child imports and runs the real converter, which then met this file's stub `m.ifc` -- a fixture ifcopenshell cannot parse, and never had to, because nothing was previously asking it to. **The lesson is the general one, not the fixture.** *A seam a test holds has to be on the same side of the process boundary as the code it stands in for.* When that boundary moves, every patch that crosses it stops intercepting -- and nothing about the patch changes, so there is no diff to read and no warning to see. It failed loudly here only because the stub IFC could not be parsed; a fixture that happened to be a real model would have made this a silent performance regression, converting for real inside a test that believed it was mocked. Fixed by moving the seam to `fragconvert._py_convert_in_child`, which is the boundary. That keeps this file's subject -- whether the reconvert FLAG reaches the Python path -- while the child's own mechanics stay in `test_fragconvert_kill.py`, where they are measured against a real spawn. The stand-in also writes `dst`, because the real child does and the caller reads it. Derived rather than assumed: this is the ONLY site in the tree that patches the converter (`grep -rn 'patch.*from_ifc' --include=test_*.py` -> one hit), so the blast radius of the boundary move is one file. The other three tests that touch `from_ifc` call it directly in their own process, which is unaffected. Two things worth keeping. `test_fragconvert_kill` already asserts that `convert_ifc` no longer imports the converter in-process, so the structural guard for this class of breakage exists and is what makes the boundary explicit. And I found this by running the full suite rather than the files I had touched -- the targeted runs were all green, because the file that broke is not one this change edits. Reproduced locally before and after: 3 checks red, then `test_publish_reconvert OK`. ruff clean. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Tt2XKB83wwNt2nrMbK6eEA
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What
The cooperative deadline shipped in #574 is checked between elements and every 4,096 entities. That bounds a model that overran because it had a lot in it. Two costs sit outside every checkpoint and nothing inside the process can reach them:
ifcopenshell.open— one call, time scales with file size, paid in full before the first check.create_shapethat never returns — the loop never reaches the next check.On the desktop app there is no Node runtime, so the Python path is the only one, and
edit_previewpassestimeout=120on a synchronous route. A model hitting either cost held a request worker indefinitely instead of returning the 503 the caller is written to expect.The conversion now runs in a child process, and the parent kills it.
The filed blocker did not hold, and the shape of that is the point
The entry said process isolation needed
multiprocessing, which under PyInstaller re-execs the frozen executable unlessfreeze_support()is wired — net-new machinery for a frozen app with no pattern in this tree to copy.That is true of
multiprocessing. It is not true of process isolation.services/api/desktop_entry.pyis a three-line launcher and is theAnalysisscript for bothsidecar.specanddesktop.spec, so it can branch on an argv sentinel before importing the server.sys.executablethen means "this bundle" when frozen and "this interpreter" when not. One mechanism, both environments, nomultiprocessingat all.A blocker recorded as a property of the platform turned out to be a property of one approach to it — and written as the former, it stopped anyone looking for a fortnight.
This is the second reason-shaped error on this one entry. The lane-table row's "process/packaging shape" was the first, and cost thirteen days. Both were accurate about the work and wrong about why it could not be done, which is the form that stops a reader before they check.
Design decisions, each with its reason
.fragitself_KILL_GRACE_S(5 s) latertimeout + 5s, stated not hidden: shortening the child's deadline to keep it exact would make the two branches disagree about what the parameter means, and a backstop that pre-empts the thing it backs up is not a backstopMeasured, not argued
Mutations
timeout=from the spawnThe hang stub self-exits, which is load-bearing: without it, the first mutation would make the gate hang for ever rather than fail, and a hang is reported as nothing.
test_fragconvert_timeout.pysection 4 had to learn this the same way, so the gate also asserts the stub's self-exit rather than trusting the comment.Verification
test_fragconvert_kill12/12;test_fragconvert_timeout,test_fragments_python,test_fragments_schemaall still pass through the new pathtest_claude_md_gates,test_changelog_current,test_file_sizes,test_ruff_scope,test_declared_importsgreenruffclean tree-wideNot yet run at the time of opening: the full backend suite. It will run here in CI.
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