44 lines
1.5 KiB
Python
44 lines
1.5 KiB
Python
"""Atomic JSON file writes.
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Use this everywhere a JSON config file is persisted. A plain `open("w") +
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json.dump` truncates the file on first write and only fills it with new
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content afterwards — a kill -9 / power loss / OOM in between produces a
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truncated or empty file. For password DBs (`auth.json`) and live state
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(`sessions.json`, `settings.json`, `integrations.json`, `cookbook_state.json`),
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that's a data-loss event.
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`atomic_write_json` writes to a sibling tmp file, fsyncs, then `os.replace`s
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into place. On POSIX `os.replace` is atomic on the same filesystem.
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"""
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from __future__ import annotations
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import json
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import os
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from typing import Any, Optional
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def atomic_write_json(path: str, data: Any, *, indent: Optional[int] = None) -> None:
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"""Atomically persist `data` as JSON at `path`.
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The temp file uses the live PID as a suffix so two processes saving the
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same file (e.g. unit tests) don't collide on the rename target.
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"""
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os.makedirs(os.path.dirname(path) or ".", exist_ok=True)
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tmp = f"{path}.tmp.{os.getpid()}"
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with open(tmp, "w", encoding="utf-8") as f:
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json.dump(data, f, indent=indent)
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f.flush()
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os.fsync(f.fileno())
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os.replace(tmp, path)
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def atomic_write_text(path: str, text: str) -> None:
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os.makedirs(os.path.dirname(path) or ".", exist_ok=True)
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tmp = f"{path}.tmp.{os.getpid()}"
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with open(tmp, "w", encoding="utf-8") as f:
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f.write(text)
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f.flush()
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os.fsync(f.fileno())
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os.replace(tmp, path)
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