[PATCH 2/2] tests: Evict stale files in the functional download cache after a while

[Thomas Huth <thuth@redhat.com>]

From: Thomas Huth <thuth@redhat.com>

The download cache of the functional tests is currently only growing.
But sometimes tests get removed or changed to use different assets,
thus we should clean up the stale old assets after a while when they
are not in use anymore. So add a script that looks at the time stamps
of the assets and removes them if they haven't been touched for more
than half of a year. Since there might also be some assets around that
have been added to the cache before we added the time stamp files,
assume a default time stamp that is close to the creation date of this
patch, so that we don't delete these files too early.

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 MAINTAINERS                       |  1 +
 scripts/clean_functional_cache.py | 47 +++++++++++++++++++++++++++++++
 tests/Makefile.include            |  1 +
 3 files changed, 49 insertions(+)
 create mode 100755 scripts/clean_functional_cache.py

diff --git a/MAINTAINERS b/MAINTAINERS
index 84cfd85e1fa..4c468d45337 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4398,6 +4398,7 @@ M: Thomas Huth <thuth@redhat.com>
 R: Philippe Mathieu-Daudé <philmd@linaro.org>
 R: Daniel P. Berrange <berrange@redhat.com>
 F: docs/devel/testing/functional.rst
+F: scripts/clean_functional_cache.py
 F: tests/functional/qemu_test/
 
 Windows Hosted Continuous Integration
diff --git a/scripts/clean_functional_cache.py b/scripts/clean_functional_cache.py
new file mode 100755
index 00000000000..e5c4d1acaf3
--- /dev/null
+++ b/scripts/clean_functional_cache.py
@@ -0,0 +1,47 @@
+#!/usr/bin/env python3
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+"""Delete stale assets from the download cache of the functional tests"""
+
+import os
+import stat
+import sys
+import time
+from pathlib import Path
+
+
+cache_dir_env = os.getenv('QEMU_TEST_CACHE_DIR')
+if cache_dir_env:
+    cache_dir = Path(cache_dir_env, "download")
+else:
+    cache_dir = Path(Path("~").expanduser(), ".cache", "qemu", "download")
+
+if not os.path.exists(cache_dir):
+    print(f"Cache dir {cache_dir} does not exist!", file=sys.stderr)
+    sys.exit(1)
+
+os.chdir(cache_dir)
+
+for file in os.listdir(cache_dir):
+    filename = os.fsdecode(file)
+    # Only consider the files that use a sha256 as filename:
+    if len(filename) != 64:
+        continue
+
+    try:
+        with open(filename + ".stamp", "r", encoding='utf-8') as fh:
+            timestamp = int(fh.read())
+    except FileNotFoundError:
+        # Assume it's an old file that was already in the cache before we
+        # added the code for evicting stale assets. Use the release date
+        # of QEMU v10.1 as a default timestamp.
+        timestamp = time.mktime((2025, 8, 26, 0, 0, 0, 0, 0, 0))
+
+    age = time.time() - timestamp
+
+    # Delete files older than half of a year (183 days * 24h * 60m * 60s)
+    if age > 15811200:
+        print(f"Removing {cache_dir}/{filename}.")
+        os.chmod(filename, stat.S_IWRITE)
+        os.remove(filename)
diff --git a/tests/Makefile.include b/tests/Makefile.include
index e47ef4d45c9..d4dfbf3716d 100644
--- a/tests/Makefile.include
+++ b/tests/Makefile.include
@@ -111,6 +111,7 @@ $(FUNCTIONAL_TARGETS): check-venv
 .PHONY: check-functional
 check-functional: check-venv
 	@$(NINJA) precache-functional
+	@$(PYTHON) $(SRC_PATH)/scripts/clean_functional_cache.py
 	@QEMU_TEST_NO_DOWNLOAD=1 $(MAKE) SPEED=thorough check-func check-func-quick
 
 .PHONY: check-func check-func-quick
-- 
2.51.0