From 2f19908d9a78e615ba061e5616f1fcd35a944dbc Mon Sep 17 00:00:00 2001
From: Vito Sansevero <vito.sansevero@gmail.com>
Date: Tue, 27 Oct 2026 09:57:38 -0700
Subject: [PATCH] fix(test): remove /dev/shm reset scratch left by killed
 browser servers (#384)

A server killed outright never runs its cleanup, and tmpfs keeps the
scratch folder in memory until reboot: the Python suite's server tests
left one per killed server. Scratch folders now carry the owner's pid,
and each new one first removes those whose process is gone (POSIX only).
---
 tests/browser/fast_reset.py      | 39 ++++++++++++++++++++++++++------
 tests/test_browser_fast_reset.py | 24 ++++++++++++++++++++
 2 files changed, 56 insertions(+), 7 deletions(-)

diff --git a/tests/browser/fast_reset.py b/tests/browser/fast_reset.py
index 5f2634bc..c305c686 100644
--- a/tests/browser/fast_reset.py
+++ b/tests/browser/fast_reset.py
@@ -43,6 +43,8 @@ MEMORY_ROOT = Path("/dev/shm")
 # the browsers and the other workers; with less free than this, the scratch
 # copy goes on disk instead.
 MEMORY_FREE_BYTES = 32 * 1024 * 1024
+# Scratch folders are named <prefix><owner pid>-<random>.
+SCRATCH_PREFIX = "pm-reset-"
 
 
 def _quote(name: str) -> str:
@@ -94,6 +96,31 @@ def table_digests(conn: sqlite3.Connection, schema: str = "main") -> dict[str, s
     return result
 
 
+def _process_alive(pid: int) -> bool:
+    try:
+        os.kill(pid, 0)
+    except ProcessLookupError:
+        return False
+    except OSError:
+        return True  # it exists but belongs to someone else
+    return True
+
+
+def remove_orphaned_scratch(root: Path) -> None:
+    """Remove scratch folders of servers that died without cleaning up.
+
+    A server killed outright (SIGKILL, a crash) never runs ``close``, and
+    tmpfs keeps its folder in memory until reboot. The folder name carries
+    the owner's process id; a folder whose process is gone is removed.
+    """
+    if os.name != "posix":
+        return  # os.kill(pid, 0) would terminate the process on Windows
+    for folder in root.glob(f"{SCRATCH_PREFIX}*-*"):
+        pid = folder.name[len(SCRATCH_PREFIX) :].split("-", 1)[0]
+        if pid.isdigit() and not _process_alive(int(pid)):
+            shutil.rmtree(folder, ignore_errors=True)
+
+
 class _SeedApi:
     """The live API, except that ``db`` is the scratch database.
 
@@ -247,12 +274,10 @@ class ScratchSeeder:
         kernel is writing back the pages they rewrite.
         """
         root = self._memory_root
-        if (
-            root is not None
-            and root.is_dir()
-            and os.access(root, os.W_OK)
-            and shutil.disk_usage(root).free >= MEMORY_FREE_BYTES
-        ):
-            return Path(tempfile.mkdtemp(prefix="pm-reset-", dir=root))
+        if root is not None and root.is_dir() and os.access(root, os.W_OK):
+            remove_orphaned_scratch(root)
+            if shutil.disk_usage(root).free >= MEMORY_FREE_BYTES:
+                prefix = f"{SCRATCH_PREFIX}{os.getpid()}-"
+                return Path(tempfile.mkdtemp(prefix=prefix, dir=root))
         self._fallback.mkdir(parents=True, exist_ok=True)
         return self._fallback
diff --git a/tests/test_browser_fast_reset.py b/tests/test_browser_fast_reset.py
index ba53a41c..6be9a54a 100644
--- a/tests/test_browser_fast_reset.py
+++ b/tests/test_browser_fast_reset.py
@@ -1,7 +1,10 @@
 """Browser-test resets seed a scratch copy and publish it in one commit (#384)."""
 
 import hashlib
+import os
 import sqlite3
+import subprocess
+import sys
 import tempfile
 import threading
 import time
@@ -300,6 +303,27 @@ class TestScratchSeeder(unittest.TestCase):
         self.assertEqual(list(memory.iterdir()), [])
         self.assertTrue((self.root / "fallback" / "seed.db").exists())
 
+    @unittest.skipUnless(os.name == "posix", "process probe is POSIX only")
+    def test_scratch_folders_of_dead_servers_are_removed(self):
+        memory = self.root / "memory"
+        memory.mkdir()
+        dead = subprocess.Popen([sys.executable, "-c", "pass"])
+        dead.wait()
+        orphan = memory / f"pm-reset-{dead.pid}-abc"
+        alive = memory / f"pm-reset-{os.getpid()}-def"
+        other = memory / "pm-reset-notapid"
+        for folder in (orphan, alive, other):
+            folder.mkdir()
+            (folder / "seed.db").write_bytes(b"x")
+        seeder = ScratchSeeder(self.api, self.root / "fallback", memory_root=memory)
+        self.addCleanup(seeder.close)
+        seeder.run(reseed)
+        self.assertFalse(orphan.exists())
+        self.assertTrue(alive.exists())
+        self.assertTrue(other.exists())
+        own = [p for p in memory.glob(f"pm-reset-{os.getpid()}-*") if p != alive]
+        self.assertEqual(len(own), 1)
+
     def test_close_releases_the_scratch_files(self):
         self.seeder.run(reseed)
         self.seeder.close()