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Diffstat (limited to '')
-rw-r--r-- | src/pybind/mgr/volumes/fs/operations/lock.py | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/src/pybind/mgr/volumes/fs/operations/lock.py b/src/pybind/mgr/volumes/fs/operations/lock.py new file mode 100644 index 000000000..7ef6923e1 --- /dev/null +++ b/src/pybind/mgr/volumes/fs/operations/lock.py @@ -0,0 +1,43 @@ +from contextlib import contextmanager +import logging +from threading import Lock +from typing import Dict + +log = logging.getLogger(__name__) + +# singleton design pattern taken from http://www.aleax.it/5ep.html + +class GlobalLock(object): + """ + Global lock to serialize operations in mgr/volumes. This lock + is currently held when accessing (opening) a volume to perform + group/subvolume operations. Since this is a big lock, it's rather + inefficient -- but right now it's ok since mgr/volumes does not + expect concurrent operations via its APIs. + + As and when features get added (such as clone, where mgr/volumes + would maintain subvolume states in the filesystem), there might + be a need to allow concurrent operations. In that case it would + be nice to implement an efficient path based locking mechanism. + + See: https://people.eecs.berkeley.edu/~kubitron/courses/cs262a-F14/projects/reports/project6_report.pdf + """ + _shared_state = { + 'lock' : Lock(), + 'init' : False + } # type: Dict + + def __init__(self): + with self._shared_state['lock']: + if not self._shared_state['init']: + self._shared_state['init'] = True + # share this state among all instances + self.__dict__ = self._shared_state + + @contextmanager + def lock_op(self): + log.debug("entering global lock") + with self._shared_state['lock']: + log.debug("acquired global lock") + yield + log.debug("exited global lock") |