72 lines
2.9 KiB
Python
72 lines
2.9 KiB
Python
import json
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import os
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from backup.logger import getLogger
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from os.path import exists
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logger = getLogger(__name__)
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class JsonFileSaver:
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"""
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The envrionment Home Assistant runs in is notorious for disk-related failures, often from running completely out of space and SD card corruption.
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Both of these can leave the addon in a state where the files it need to run are either corrupted or empty. This class attempts to mitigate that
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by writing all config files twice, first to a backup file and then to the "real" file path. Then when reading it will check both locations to try
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and find a copy of the file that isn't corrupted or deleted.
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This avoids a number of common failures, namely:
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- A power failure while writing a file can leave it empty or malformed.
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- Overwriting a file while the disk is full can truncateit without writing the new data
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- HD corruption cna make a file malformed, but its less likely to affect both files.
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"""
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@classmethod
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def _read(cls, path):
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with open(path, "r") as f:
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return json.load(f)
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@classmethod
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def read(cls, path):
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try:
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return JsonFileSaver._read(path)
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except json.decoder.JSONDecodeError:
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logger.error(f"The configuration file {path} had an invalid format. This could be caused by hard drive corruption or an unstable power event. We'll attempt to load from a backup file instead.")
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backup = JsonFileSaver._backup_path(path)
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if not exists(backup):
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logger.error("Unable to locate a backup path")
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raise
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return JsonFileSaver._read(backup)
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except FileNotFoundError:
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logger.error(f"The configuration file {path} was not found. This could be caused by hard drive corruption or an unstable power event. We'll attempt to load from a backup file instead.")
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backup = JsonFileSaver._backup_path(path)
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if not exists(backup):
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logger.error("Unable to locate a backup path")
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raise
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return JsonFileSaver._read(backup)
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@classmethod
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def _write(cls, path, data):
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with open(path, "w") as f:
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json.dump(data, f, indent=4)
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@classmethod
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def write(cls, path, data):
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# Crete the backup (rcovery) file first. This ensures its present if the subsequent write is corrupted.
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JsonFileSaver._write(JsonFileSaver._backup_path(path), data)
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JsonFileSaver._write(path, data)
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@classmethod
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def exists(cls, path):
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if exists(path):
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return True
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return exists(JsonFileSaver._backup_path(path))
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@classmethod
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def delete(sels, path):
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if exists(JsonFileSaver._backup_path(path)):
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os.remove(JsonFileSaver._backup_path(path))
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if exists(path):
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os.remove(path)
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@classmethod
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def _backup_path(cls, path):
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return path + ".backup"
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