70 lines
2.3 KiB
Python
70 lines
2.3 KiB
Python
 
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import fcntl
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import json
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import logging
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import os
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import tempfile
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import time
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from contextlib import contextmanager
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logger = logging.getLogger(__name__)
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class StorageError(Exception):
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"""Файл данных повреждён или недоступен."""
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def load_json(path, default):
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"""Читает JSON. Битый файл переименовывается в *.corrupt-<ts>, чтобы его не затёрли."""
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if not os.path.exists(path):
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return default
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try:
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with open(path, 'r') as f:
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return json.load(f)
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except json.JSONDecodeError as e:
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backup = f"{path}.corrupt-{int(time.time())}"
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os.replace(path, backup)
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logger.error("Corrupted JSON in %s (%s); moved to %s", path, e, backup)
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raise StorageError(f"{path} is corrupted") from e
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except OSError as e:
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raise StorageError(f"Cannot read {path}: {e}") from e
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def save_json_atomic(path, data):
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"""Пишет во временный файл в том же каталоге и подменяет оригинал через os.replace."""
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directory = os.path.dirname(os.path.abspath(path))
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fd, tmp_path = tempfile.mkstemp(dir=directory, prefix=os.path.basename(path) + ".", suffix=".tmp")
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try:
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with os.fdopen(fd, 'w') as f:
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json.dump(data, f, indent=4)
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f.flush()
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os.fsync(f.fileno())
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os.replace(tmp_path, path)
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except BaseException:
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if os.path.exists(tmp_path):
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os.unlink(tmp_path)
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raise
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@contextmanager
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def file_lock(path):
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"""Межпроцессная блокировка (сборщик, CLI и API) через <path>.lock."""
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with open(path + ".lock", 'w') as lock_file:
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fcntl.flock(lock_file, fcntl.LOCK_EX)
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try:
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yield
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finally:
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fcntl.flock(lock_file, fcntl.LOCK_UN)
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def try_lock(path):
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"""Неблокирующая эксклюзивная блокировка (singleton-процесс).
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Возвращает открытый файл (блокировка держится, пока он жив) или None, если занято.
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"""
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lock_file = open(path, 'w')
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try:
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fcntl.flock(lock_file, fcntl.LOCK_EX | fcntl.LOCK_NB)
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except BlockingIOError:
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lock_file.close()
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return None
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return lock_file
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