Handle two-frame Ego4D bbox tails and preserve worker errors

test_ego4d_local_multigpu.py

@@ -98,6 +98,47 @@ class MultiGPUExtractionTests(unittest.TestCase):
         self.assertEqual((self.root / "gpu2.log").read_text().strip(), "2 2")
         self.assertEqual((self.root / "gpu5.log").read_text().strip(), "5 2")
 
+    def test_failure_tail_keeps_traceback_and_long_diagnostics_but_progress_is_short(self):
+        path = self.root / "worker.log"
+        message = ("ValueError: Ego4D annotation frame exceeds source clip: " + self.names[0]
+                   + "; source_frames=8998; " + "diagnostic " * 100 + "first_10=[8998, 8999]")
+        traceback = "Traceback (most recent call last):\n  File 'extract.py', line 200\n" + message
+        path.write_text("old progress\n" * 10000 + traceback + "\n")
+        self.assertEqual(launch.log_tail(path, failure=True), traceback)
+        self.assertLessEqual(len(launch.log_tail(path)), 300)
+        path.write_text(message + "\n")
+        self.assertEqual(launch.log_tail(path, failure=True), message)
+        self.assertEqual(launch.log_tail(self.root / "missing.log", failure=True), "starting")
+
+    def test_failure_diagnostics_survive_both_startup_and_polling_errors(self):
+        message = f"clip={self.names[0]}; source_frames=8998; " + "detail " * 100 + "outliers=[8998, 8999]"
+        for startup in (True, False):
+            with self.subTest(startup=startup):
+                folder = self.root / str(startup)
+                folder.mkdir()
+                # Simulate a flushed failing worker at startup or in the poll
+                # loop without scheduler-dependent sleep/timing assertions.
+                process = SimpleNamespace(returncode=1)
+                process.poll = lambda: 1
+                process.wait = lambda **kwargs: 1
+                process.pid = None  # Stub only; must never be passed to a real signal call.
+
+                def start(command, **kwargs):
+                    kwargs["stdout"].write(("Traceback (most recent call last):\nValueError: " + message + "\n").encode())
+                    kwargs["stdout"].flush()
+                    if not startup:
+                        polls = iter([None, 1, 1])
+                        process.poll = lambda: next(polls, 1)
+                    return process
+
+                args = SimpleNamespace(cpu_threads=1, startup_delay=0., status_interval=.01)
+                plans = [{"gpu": 7, "samples": [self.names[0]], "command": ["unused"]}]
+                with patch("extract_ego4d_local_multigpu.subprocess.Popen", side_effect=start), \
+                     contextlib.redirect_stdout(io.StringIO()), self.assertRaises(RuntimeError) as raised:
+                    launch.run_workers(plans, args, folder)
+                self.assertIn(message, str(raised.exception))
+                self.assertIn("Traceback (most recent call last):", str(raised.exception))
+
     def test_failing_worker_stops_only_its_launched_peers(self):
         args = SimpleNamespace(cpu_threads=1, startup_delay=0., status_interval=.01)
         plans = [{"gpu": 0, "samples": ["dummy"], "command": [sys.executable, "-c", "import time; time.sleep(60)"]},