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|
#!/usr/bin/env python3
from abc import ABC, abstractmethod
import atexit
import functools
import logging
import dill
import file_utils
logger = logging.getLogger(__name__)
class Persistent(ABC):
@abstractmethod
def save(self):
pass
@abstractmethod
def load(self):
pass
class persistent_autoload_singleton(Persistent):
def __init__(self, filename: str, *, max_age_sec: int = 0):
self.filename = filename
self.max_age_sec = max_age_sec
self.instance = None
def __call__(self, cls):
@functools.wraps(cls)
def _load(*args, **kwargs):
# If class has already been loaded, act like a singleton
# and return a reference to the one and only instance in
# memory.
if self.instance is not None:
logger.debug(
f'Returning already instantiated singleton instance of {cls.__name__}.'
)
return self.instance
if not self.load():
assert self.instance is None
logger.debug(
f'Instantiating {cls.__name__} directly.'
)
self.instance = cls(*args, **kwargs)
# On program exit, save state to disk.
atexit.register(self.save)
assert self.instance is not None
return self.instance
return _load
def load(self) -> bool:
if (
file_utils.does_file_exist(self.filename)
and (
self.max_age_sec == 0 or
file_utils.get_file_mtime_age_seconds(self.filename) <= self.max_age_sec
)
):
logger.debug(
f'Attempting to load from file {self.filename}'
)
try:
with open(self.filename, 'rb') as f:
self.instance = dill.load(f)
return True
except Exception:
self.instance = None
return False
return False
def save(self) -> bool:
if self.instance is not None:
logger.debug(
f'Attempting to save {type(self.instance).__name__} to file {self.filename}'
)
try:
with open(self.filename, 'wb') as f:
dill.dump(self.instance, f, dill.HIGHEST_PROTOCOL)
return True
except Exception:
return False
return False
|
