def test_open_takes_exclusive_lock(self):
config_file = os.path.join(self.make_dir(), "config")
config_lock = RunLock(config_file)
self.assertFalse(config_lock.is_locked())
with ConfigurationFile.open_for_update(config_file):
self.assertTrue(config_lock.is_locked())
self.assertFalse(config_lock.is_locked())
def test_byte_path(self):
filename = b"/foo/bar/123:456.txt"
expected = get_tentative_data_path(
"/run/lock/maas@foo:bar:123::456.txt"
)
observed = RunLock(filename).path
self.assertEqual(expected, observed)
def open_for_update(cls, path: str):
"""Open a configuration file.
Locks are taken so that there can only be *one* reader or writer for a
configuration file at a time. Where configuration files can be read by
multiple concurrent processes it follows that each process should hold
the file open for the shortest time possible.
**Note** that this returns a context manager which will SAVE changes
to the configuration on a clean exit.
"""
time_opened = None
try:
# Only one reader or writer at a time.
with RunLock(path).wait(timeout=5.0):
time_opened = time()
# Ensure `path` exists...
touch(path)
# before loading it in.
configfile = cls(path, mutable=True)
configfile.load()
try:
yield configfile
except Exception:
raise
else:
if configfile.dirty:
configfile.save()
finally:
if time_opened is not None:
time_open = time() - time_opened
if time_open >= 2.5:
mini_stack = ", from ".join(
"%s:%d" % (fn, lineno)
for fn, lineno, _, _ in islice(
reversed(traceback.extract_stack()), 2, 5
)
)
logger.warn(
"Configuration file %s locked for %.1f seconds; this "
"may starve other processes. Called from %s.",
path,
time_open,
mini_stack,
)
def test__string_path(self):
filename = '/foo/bar/123:456.txt'
expected = get_tentative_data_path(
'/run/lock/maas@foo:bar:123::456.txt')
observed = RunLock(filename).path
self.assertEqual(expected, observed)
