Isolate STL analysis in child process; fix 3MF memory usage

- _load_geometry(): compute extents/volume from individual Scene meshes
  without concatenating — avoids the RAM spike that crashed the container
- analyse_in_background(): spawns a child process (spawn context, not fork)
  with a 120s timeout; OOM/crash in child no longer takes down the app
- _failed set: tracks files that timed out or crashed; spinner stops and
  a warning with inline override form is shown instead of looping forever
- analysis_failed state passed to template; override form shown immediately
  when analysis failed (no expand needed)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/routers/ui.py

@@ -26,7 +26,7 @@ from app.estimation import estimate  # also used in start_job
 from app.filamentdb import (available_colors, available_materials, find_matching_ams_roll,
                              get_stock, log_print_on_roll, spool_counts)
 from app.stl import get_stl_dir, list_stl_files
-from app.stl_analysis import analyse_in_background, get_cache_map, is_computing  # noqa: F401
+from app.stl_analysis import analyse_in_background, get_cache_map, is_computing, is_failed  # noqa: F401
 
 router = APIRouter()
 templates = Jinja2Templates(directory="app/templates")
@@ -276,9 +276,11 @@ def job_detail(job_id: int, request: Request, background_tasks: BackgroundTasks,
         else:
             stl = db.query(StlCache).filter_by(filename=job.file_name).first()
             if stl is None and not job.file_name.endswith(".gcode"):
-                if not is_computing(job.file_name):
+                if is_failed(job.file_name):
+                    file_missing = False  # file exists, analysis just failed
+                elif not is_computing(job.file_name):
                     background_tasks.add_task(analyse_in_background, job.file_name)
-                computing = True
+                computing = not is_failed(job.file_name)
 
     estimation = estimate(stl.volume_ccm, job.job_material) if stl and stl.volume_ccm else None
     return templates.TemplateResponse("job_detail.html", {
@@ -288,6 +290,7 @@ def job_detail(job_id: int, request: Request, background_tasks: BackgroundTasks,
         "stl": stl,
         "file_missing": file_missing,
         "computing": computing,
+        "analysis_failed": job.file_name and is_failed(job.file_name),
         "estimation": estimation,
         "printers": db.query(Printer).order_by(Printer.name).all(),
         "brackets": db.query(JobBracket).order_by(JobBracket.name).all(),

app/stl_analysis.py

@@ -1,6 +1,9 @@
+"""STL/3MF geometry analysis with background process isolation."""
 import logging
+import multiprocessing as _mp
 from pathlib import Path
 
+import numpy as np
 from sqlalchemy.orm import Session
 
 from app.models.stl_cache import StlCache
@@ -8,7 +11,27 @@ from app.models.stl_cache import StlCache
 logger = logging.getLogger("pops")
 
 _ANALYSABLE = {".stl", ".3mf"}
+_TIMEOUT = 120  # seconds before we give up
+
 _in_progress: set[str] = set()
+_failed: set[str] = set()
+
+
+def _load_geometry(filepath: str):
+    """Return (extents_array, volume_mm3). Handles Scene without concatenating."""
+    import trimesh
+    loaded = trimesh.load(filepath)
+    if isinstance(loaded, trimesh.Scene):
+        meshes = list(loaded.geometry.values())
+        if not meshes:
+            raise ValueError("3MF scene contains no meshes")
+        bounds = np.array([m.bounds for m in meshes])  # (N, 2, 3)
+        extents = bounds[:, 1, :].max(axis=0) - bounds[:, 0, :].min(axis=0)
+        volume_mm3 = sum(abs(float(m.volume)) for m in meshes)
+    else:
+        extents = np.array(loaded.extents)
+        volume_mm3 = abs(float(loaded.volume))
+    return extents, volume_mm3
 
 
 def analyse(filename: str, db: Session) -> StlCache | None:
@@ -23,14 +46,7 @@ def analyse(filename: str, db: Session) -> StlCache | None:
         return None
 
     try:
-        import trimesh
-        loaded = trimesh.load(str(filepath))
-        if isinstance(loaded, trimesh.Scene):
-            mesh = trimesh.util.concatenate(list(loaded.geometry.values()))
-        else:
-            mesh = loaded
-        extents = mesh.extents          # [size_x, size_y, size_z] in mm
-        volume_mm3 = abs(mesh.volume)   # mm³ (negative for inverted normals)
+        extents, volume_mm3 = _load_geometry(str(filepath))
         entry = StlCache(
             filename=filename,
             cube_x=round(float(extents[0]), 2),
@@ -46,18 +62,38 @@ def analyse(filename: str, db: Session) -> StlCache | None:
         return None
 
 
+def _worker(filename: str) -> None:
+    """Child process entry point — creates its own DB session."""
+    from app.db import SessionLocal
+    db = SessionLocal()
+    try:
+        analyse(filename, db)
+    finally:
+        db.close()
+
+
 def analyse_in_background(filename: str) -> None:
-    """Run analyse() in a background task with its own DB session."""
+    """Spawn an isolated child process for analysis; kill it after _TIMEOUT."""
     if filename in _in_progress:
         return
     _in_progress.add(filename)
+    _failed.discard(filename)
     try:
-        from app.db import SessionLocal
-        db = SessionLocal()
-        try:
-            analyse(filename, db)
-        finally:
-            db.close()
+        ctx = _mp.get_context("spawn")
+        p = ctx.Process(target=_worker, args=(filename,), daemon=True)
+        p.start()
+        p.join(timeout=_TIMEOUT)
+        if p.is_alive():
+            logger.warning("STL analysis timed out for %s — killing process", filename)
+            p.kill()
+            p.join()
+            _failed.add(filename)
+        elif p.exitcode != 0:
+            logger.warning("STL analysis process exited with code %s for %s", p.exitcode, filename)
+            _failed.add(filename)
+    except Exception:
+        logger.exception("STL background task error for %s", filename)
+        _failed.add(filename)
     finally:
         _in_progress.discard(filename)
 
@@ -66,6 +102,10 @@ def is_computing(filename: str) -> bool:
     return filename in _in_progress
 
 
+def is_failed(filename: str) -> bool:
+    return filename in _failed
+
+
 def get_cache_map(filenames: list[str], db: Session) -> dict[str, StlCache]:
     """Bulk-fetch cached entries for a list of filenames."""
     rows = db.query(StlCache).filter(StlCache.filename.in_(filenames)).all()

app/templates/job_detail.html

@@ -127,6 +127,34 @@
           <i class="bi bi-exclamation-triangle-fill me-2"></i>
           File <code>{{ job.file_name }}</code> not found on disk.
         </div>
+        {% elif analysis_failed %}
+        <div class="alert alert-warning py-2 px-3 mb-2" style="font-size:.875rem">
+          <i class="bi bi-exclamation-triangle me-2"></i>
+          Analysis failed or timed out — enter values from your slicer below.
+        </div>
+        <form method="POST" action="/jobs/{{ job.id }}/geometry" class="d-flex flex-column gap-2" style="font-size:.8rem">
+          <div class="d-flex gap-2 align-items-center">
+            <label class="text-secondary" style="width:70px">X mm</label>
+            <input type="number" step="0.1" name="cube_x" value="" required
+                   class="form-control form-control-sm bg-dark border-secondary text-white" style="width:100px">
+          </div>
+          <div class="d-flex gap-2 align-items-center">
+            <label class="text-secondary" style="width:70px">Y mm</label>
+            <input type="number" step="0.1" name="cube_y" value="" required
+                   class="form-control form-control-sm bg-dark border-secondary text-white" style="width:100px">
+          </div>
+          <div class="d-flex gap-2 align-items-center">
+            <label class="text-secondary" style="width:70px">Z mm</label>
+            <input type="number" step="0.1" name="cube_z" value="" required
+                   class="form-control form-control-sm bg-dark border-secondary text-white" style="width:100px">
+          </div>
+          <div class="d-flex gap-2 align-items-center">
+            <label class="text-secondary" style="width:70px">Vol cm³</label>
+            <input type="number" step="0.001" name="volume_ccm" value="" required
+                   class="form-control form-control-sm bg-dark border-secondary text-white" style="width:100px">
+          </div>
+          <div><button type="submit" class="btn btn-sm btn-outline-secondary py-0 px-2">Save</button></div>
+        </form>
         {% elif computing %}
         <div class="text-secondary small d-flex align-items-center gap-2" id="computing-state">
           <div class="spinner-border spinner-border-sm text-secondary" role="status"></div>