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authorzsdc <taras@vyos.io>2024-07-03 22:45:52 +0300
committerzsdc <taras@vyos.io>2024-07-03 22:45:52 +0300
commit0160823d084d141be71299c0e51d9dd3c27ede94 (patch)
tree96f6c994a2f900ee0ed1c5b9d419a46d6a02dac8 /python
parent2eb80002145bbd4b4d965b14ba401378b45bfc80 (diff)
downloadvyos-1x-0160823d084d141be71299c0e51d9dd3c27ede94.tar.gz
vyos-1x-0160823d084d141be71299c0e51d9dd3c27ede94.zip
locking: T6544: Added locking util
Sometimes we need a reliable way to lock an execution until some other operation is not done. This commit introduces locking util, which can be used as a common lock, even between different processes. Usage example: ``` from vyos.utils.locking import Lock lock = Lock('my_lock_id') lock.acquire(timeout=10) print(f'Lock acquired: {lock.is_locked}') lock.release() ```
Diffstat (limited to 'python')
-rw-r--r--python/vyos/utils/__init__.py1
-rw-r--r--python/vyos/utils/locking.py115
2 files changed, 116 insertions, 0 deletions
diff --git a/python/vyos/utils/__init__.py b/python/vyos/utils/__init__.py
index 90620071b..3759b2125 100644
--- a/python/vyos/utils/__init__.py
+++ b/python/vyos/utils/__init__.py
@@ -25,6 +25,7 @@ from vyos.utils import file
from vyos.utils import io
from vyos.utils import kernel
from vyos.utils import list
+from vyos.utils import locking
from vyos.utils import misc
from vyos.utils import network
from vyos.utils import permission
diff --git a/python/vyos/utils/locking.py b/python/vyos/utils/locking.py
new file mode 100644
index 000000000..63cb1a816
--- /dev/null
+++ b/python/vyos/utils/locking.py
@@ -0,0 +1,115 @@
+# Copyright 2024 VyOS maintainers and contributors <maintainers@vyos.io>
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library. If not, see <http://www.gnu.org/licenses/>.
+
+import fcntl
+import re
+import time
+from pathlib import Path
+
+
+class LockTimeoutError(Exception):
+ """Custom exception raised when lock acquisition times out."""
+
+ pass
+
+
+class InvalidLockNameError(Exception):
+ """Custom exception raised when the lock name is invalid."""
+
+ pass
+
+
+class Lock:
+ """Lock class to acquire and release a lock file"""
+
+ def __init__(self, lock_name: str) -> None:
+ """Lock class constructor
+
+ Args:
+ lock_name (str): Name of the lock file
+
+ Raises:
+ InvalidLockNameError: If the lock name is invalid
+ """
+ # Validate lock name
+ if not re.match(r'^[a-zA-Z0-9_\-]+$', lock_name):
+ raise InvalidLockNameError(f'Invalid lock name: {lock_name}')
+
+ self.__lock_dir = Path('/run/vyos/lock')
+ self.__lock_dir.mkdir(parents=True, exist_ok=True)
+
+ self.__lock_file_path: Path = self.__lock_dir / f'{lock_name}.lock'
+ self.__lock_file = None
+
+ self._is_locked = False
+
+ def __del__(self) -> None:
+ """Ensure the lock file is removed when the object is deleted"""
+ self.release()
+
+ @property
+ def is_locked(self) -> bool:
+ """Check if the lock is acquired
+
+ Returns:
+ bool: True if the lock is acquired, False otherwise
+ """
+ return self._is_locked
+
+ def __unlink_lockfile(self) -> None:
+ """Remove the lock file if it is not currently locked."""
+ try:
+ with self.__lock_file_path.open('w') as f:
+ fcntl.flock(f, fcntl.LOCK_EX | fcntl.LOCK_NB)
+ self.__lock_file_path.unlink(missing_ok=True)
+ except IOError:
+ # If we cannot acquire the lock, it means another process has it, so we do nothing.
+ pass
+
+ def acquire(self, timeout: int = 0) -> None:
+ """Acquire a lock file
+
+ Args:
+ timeout (int, optional): A time to wait for lock. Defaults to 0.
+
+ Raises:
+ LockTimeoutError: If lock could not be acquired within timeout
+ """
+ start_time: float = time.time()
+ while True:
+ try:
+ self.__lock_file = self.__lock_file_path.open('w')
+ fcntl.flock(self.__lock_file, fcntl.LOCK_EX | fcntl.LOCK_NB)
+ self._is_locked = True
+ return
+ except IOError:
+ if timeout > 0 and (time.time() - start_time) >= timeout:
+ if self.__lock_file:
+ self.__lock_file.close()
+ raise LockTimeoutError(
+ f'Could not acquire lock within {timeout} seconds'
+ )
+ time.sleep(0.1)
+
+ def release(self) -> None:
+ """Release a lock file"""
+ if self.__lock_file and self._is_locked:
+ try:
+ fcntl.flock(self.__lock_file, fcntl.LOCK_UN)
+ self._is_locked = False
+ finally:
+ self.__lock_file.close()
+ self.__lock_file = None
+ self.__unlink_lockfile()