refactor: singleton is now a context manager

src/tendo/singleton.py

@@ -40,7 +40,9 @@ def __init__(self, flavor_id="", lockfile=""):
  self.lockfile = os.path.normpath(
  tempfile.gettempdir() + '/' + basename)
 
- logger.debug("SingleInstance lockfile: " + self.lockfile)
+ logger.debug(f"SingleInstance lockfile: {self.lockfile}")
+
+ def __enter__(self):
  if sys.platform == 'win32':
  try:
  # file already exists, we try to remove (in case previous
@@ -67,10 +69,13 @@ def __init__(self, flavor_id="", lockfile=""):
  "Another instance is already running, quitting.")
  raise SingleInstanceException()
  self.initialized = True
+ return self
 
- def __del__(self):
+ def __exit__(self, exc_type, exc_value, exc_tb):
  if not self.initialized:
  return
+ if exc_value is not None:
+ logger.warning("Error: %s" % exc_value, exc_info=True)
  try:
  if sys.platform == 'win32':
  if hasattr(self, 'fd'):
@@ -85,7 +90,9 @@ def __del__(self):
  if logger:
  logger.warning(e)
  else:
- print("Unloggable error: %s" % e)
+ print(f"Unloggable error: {e}")
+ if exc_value is not None:
+ raise e from exc_value
  sys.exit(-1)
 
 

src/tendo/tests/test_singleton.py

@@ -13,46 +13,48 @@ def f(name):
  tmp = logger.level
  logger.setLevel(logging.CRITICAL) # we do not want to see the warning
  try:
- me2 = SingleInstance(flavor_id=name) # noqa
+ with SingleInstance(flavor_id=name):
+ pass
  except SingleInstanceException:
  sys.exit(-1)
  logger.setLevel(tmp)
- pass
 
 
-def test_1():
- me = SingleInstance(flavor_id="test-1")
- del me # now the lock should be removed
+def test_singleton_from_script():
+ with SingleInstance(flavor_id="test-1"):
+ pass
+ # now the lock should be removed
  assert True
 
 
-def test_2():
+def test_singleton_from_process():
  p = Process(target=f, args=("test-2",))
  p.start()
  p.join()
  # the called function should succeed
  assert p.exitcode == 0, "%s != 0" % p.exitcode
 
 
-def test_3():
- me = SingleInstance(flavor_id="test-3") # noqa -- me should still kept
- p = Process(target=f, args=("test-3",))
- p.start()
- p.join()
- # the called function should fail because we already have another
- # instance running
- assert p.exitcode != 0, "%s != 0 (2nd execution)" % p.exitcode
- # note, we return -1 but this translates to 255 meanwhile we'll
- # consider that anything different from 0 is good
- p = Process(target=f, args=("test-3",))
- p.start()
- p.join()
- # the called function should fail because we already have another
- # instance running
- assert p.exitcode != 0, "%s != 0 (3rd execution)" % p.exitcode
-
-
-def test_4():
+def test_multiple_singletons_from_process():
+ with SingleInstance(flavor_id="test-3"):
+  p = Process(target=f, args=("test-3",))
+  p.start()
+  p.join()
+  # the called function should fail because we already have another
+  # instance running
+  assert p.exitcode != 0, "%s != 0 (2nd execution)" % p.exitcode
+  # note, we return -1 but this translates to 255 meanwhile we'll
+  # consider that anything different from 0 is good
+  p = Process(target=f, args=("test-3",))
+  p.start()
+  p.join()
+  # the called function should fail because we already have another
+  # instance running
+  assert p.exitcode != 0, "%s != 0 (3rd execution)" % p.exitcode
+
+
+def test_singleton_lock_file():
  lockfile = '/tmp/foo.lock'
- me = SingleInstance(lockfile=lockfile)
- assert me.lockfile == lockfile
+ with SingleInstance(lockfile=lockfile) as me:
+ print(me)
+ assert me.lockfile == lockfile