Add remove external lock files API in lockutils

when external lock are used, there will be a lock files which
is used for external file lock, it will not be removed and remain
forever. it will be a problem when tens of thousands of this kind
of actions. Add a API to allow other component to remove lock file
internal lock will be acquired before further action

Change-Id: I4d996b91bcc55becb0ebf4ec77ac80546f433ae9
Closes-Bug: 1256306

openstack/common/lockutils.py

@@ -143,26 +143,43 @@ _semaphores = weakref.WeakValueDictionary()
 _semaphores_lock = threading.Lock()
 
 
+def _get_lock_path(name, lock_file_prefix):
+    # NOTE(mikal): the lock name cannot contain directory
+    # separators
+    name = name.replace(os.sep, '_')
+    if lock_file_prefix:
+        sep = '' if lock_file_prefix.endswith('-') else '-'
+        name = '%s%s%s' % (lock_file_prefix, sep, name)
+
+    if not CONF.lock_path:
+        raise cfg.RequiredOptError('lock_path')
+
+    return os.path.join(CONF.lock_path, name)
+
+
 def external_lock(name, lock_file_prefix=None):
     with internal_lock(name):
         LOG.debug(_('Attempting to grab external lock "%(lock)s"'),
                   {'lock': name})
 
-        # NOTE(mikal): the lock name cannot contain directory
-        # separators
-        name = name.replace(os.sep, '_')
-        if lock_file_prefix:
-            sep = '' if lock_file_prefix.endswith('-') else '-'
-            name = '%s%s%s' % (lock_file_prefix, sep, name)
-
-        if not CONF.lock_path:
-            raise cfg.RequiredOptError('lock_path')
-
-        lock_file_path = os.path.join(CONF.lock_path, name)
+        lock_file_path = _get_lock_path(name, lock_file_prefix)
 
         return InterProcessLock(lock_file_path)
 
 
+def remove_external_lock_file(name, lock_file_prefix=None):
+    """Remove a external lock file when it's not used anymore
+    This will be helpful when we have a lot of lock files
+    """
+    with internal_lock(name):
+        lock_file_path = _get_lock_path(name, lock_file_prefix)
+        try:
+            os.remove(lock_file_path)
+        except OSError:
+            LOG.info(_('Failed to remove file %(file)s'),
+                     {'file': lock_file_path})
+
+
 def internal_lock(name):
     with _semaphores_lock:
         try:

tests/unit/test_lockutils.py

@@ -314,6 +314,21 @@ class LockTestCase(test.BaseTestCase):
 
         self.assertRaises(cfg.RequiredOptError, foo)
 
+    def test_remove_lock_external_file(self):
+        lock_name = 'mylock'
+        lock_pfix = 'mypfix-remove-lock-test-'
+
+        lock_dir = tempfile.mkdtemp()
+        self.config(lock_path=lock_dir)
+
+        lockutils.remove_external_lock_file(lock_name, lock_pfix)
+
+        for ent in os.listdir(lock_dir):
+            self.assertRaises(OSError, ent.startswith, lock_pfix)
+
+        if os.path.exists(lock_dir):
+            shutil.rmtree(lock_dir, ignore_errors=True)
+
 
 class LockutilsModuleTestCase(test.BaseTestCase):