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178 | class MemoryRecordStore(RecordStore):
"""
A record store that stores data in memory.
"""
_instance = None
def __new__(cls, *args, **kwargs):
if cls._instance is None:
cls._instance = super().__new__(cls)
return cls._instance
def __init__(self):
self._locks_dict_lock = threading.Lock()
self._locks: Dict[str, _LockInfo] = {}
self._records: Dict[str, TransactionRecord] = {}
def read(
self, key: str, holder: Optional[str] = None
) -> Optional[TransactionRecord]:
holder = holder or self.generate_default_holder()
if self.is_locked(key) and not self.is_lock_holder(key, holder):
self.wait_for_lock(key)
return self._records.get(key)
def write(self, key: str, result: BaseResult, holder: Optional[str] = None) -> None:
holder = holder or self.generate_default_holder()
with self._locks_dict_lock:
if self.is_locked(key) and not self.is_lock_holder(key, holder):
raise ValueError(
f"Cannot write to transaction with key {key} because it is locked by another holder."
)
self._records[key] = TransactionRecord(key=key, result=result)
def exists(self, key: str) -> bool:
return key in self._records
def supports_isolation_level(self, isolation_level: IsolationLevel) -> bool:
return isolation_level in {
IsolationLevel.READ_COMMITTED,
IsolationLevel.SERIALIZABLE,
}
def _expire_lock(self, key: str):
"""
Expire the lock for the given key.
Used as a callback for the expiration timer of a lock.
Args:
key: The key of the lock to expire.
"""
with self._locks_dict_lock:
if key in self._locks:
lock_info = self._locks[key]
if lock_info["lock"].locked():
lock_info["lock"].release()
if lock_info["expiration_timer"]:
lock_info["expiration_timer"].cancel()
del self._locks[key]
def acquire_lock(
self,
key: str,
holder: Optional[str] = None,
acquire_timeout: Optional[float] = None,
hold_timeout: Optional[float] = None,
) -> bool:
holder = holder or self.generate_default_holder()
with self._locks_dict_lock:
if key not in self._locks:
lock = threading.Lock()
lock.acquire()
expiration_timer = None
if hold_timeout is not None:
expiration_timer = threading.Timer(
hold_timeout, self._expire_lock, args=(key,)
)
expiration_timer.start()
self._locks[key] = _LockInfo(
holder=holder, lock=lock, expiration_timer=expiration_timer
)
return True
elif self._locks[key]["holder"] == holder:
return True
else:
existing_lock_info = self._locks[key]
if acquire_timeout is not None:
existing_lock_acquired = existing_lock_info["lock"].acquire(
timeout=acquire_timeout
)
else:
existing_lock_acquired = existing_lock_info["lock"].acquire()
if existing_lock_acquired:
with self._locks_dict_lock:
if (
expiration_timer := existing_lock_info["expiration_timer"]
) is not None:
expiration_timer.cancel()
expiration_timer = None
if hold_timeout is not None:
expiration_timer = threading.Timer(
hold_timeout, self._expire_lock, args=(key,)
)
expiration_timer.start()
self._locks[key] = _LockInfo(
holder=holder,
lock=existing_lock_info["lock"],
expiration_timer=expiration_timer,
)
return True
return False
def release_lock(self, key: str, holder: Optional[str] = None) -> None:
holder = holder or self.generate_default_holder()
with self._locks_dict_lock:
if key in self._locks and self._locks[key]["holder"] == holder:
if (
expiration_timer := self._locks[key]["expiration_timer"]
) is not None:
expiration_timer.cancel()
self._locks[key]["lock"].release()
del self._locks[key]
else:
raise ValueError(
f"No lock held by {holder} for transaction with key {key}"
)
def is_locked(self, key: str) -> bool:
return key in self._locks and self._locks[key]["lock"].locked()
def is_lock_holder(self, key: str, holder: Optional[str] = None) -> bool:
holder = holder or self.generate_default_holder()
lock_info = self._locks.get(key)
return (
lock_info is not None
and lock_info["lock"].locked()
and lock_info["holder"] == holder
)
def wait_for_lock(self, key: str, timeout: Optional[float] = None) -> bool:
if lock := self._locks.get(key, {}).get("lock"):
if timeout is not None:
lock_acquired = lock.acquire(timeout=timeout)
else:
lock_acquired = lock.acquire()
if lock_acquired:
lock.release()
return lock_acquired
return True
|