94 lines
3 KiB
Python
94 lines
3 KiB
Python
"""Persistent, encrypted retry buffer for offline periods.
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When the upstream is unreachable, signed payloads are written to ``buffer_dir``
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as individual ``{timestamp}-{router_id}.json.enc`` files, encrypted with a key
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derived from the tenant API key (see compliance.crypto). On reconnection they
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are replayed oldest-first; each is deleted only after a ``202 Accepted``.
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The buffer is bounded (``max_buffer_payloads``); the oldest file is dropped
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when the limit is exceeded.
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"""
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import json
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import re
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from pathlib import Path
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from typing import Optional
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from compliance import crypto
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from compliance.settings import ComplianceSettings
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_SAFE = re.compile(r"[^A-Za-z0-9_.-]")
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def _safe(s: str) -> str:
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return _SAFE.sub("_", s)
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class BufferStore:
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def __init__(self, cfg: ComplianceSettings):
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self._cfg = cfg
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self._dir = Path(cfg.buffer_dir)
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def _ensure_dir(self) -> None:
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self._dir.mkdir(parents=True, exist_ok=True)
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def _files(self) -> list[Path]:
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if not self._dir.exists():
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return []
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# Filenames are ``{epoch_ms}-{router_id}.json.enc``; lexical sort on the
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# zero-padded epoch prefix is chronological.
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return sorted(self._dir.glob("*.json.enc"))
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def count(self) -> int:
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return len(self._files())
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def save(self, payload: dict, timestamp_ms: int) -> Optional[Path]:
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"""Encrypt and persist ``payload``. Returns the path, or None on failure."""
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if not self._cfg.api_key:
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return None
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self._ensure_dir()
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self._enforce_limit(reserve=1)
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name = f"{timestamp_ms:020d}-{_safe(self._cfg.router_id)}.json.enc"
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path = self._dir / name
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token = crypto.encrypt(json.dumps(payload).encode("utf-8"), self._cfg.api_key)
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path.write_bytes(token)
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return path
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def load(self, path: Path) -> Optional[dict]:
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"""Decrypt and parse a buffer file. Returns None (and deletes) on corruption."""
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if not self._cfg.api_key:
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return None
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try:
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token = path.read_bytes()
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except OSError:
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return None
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plaintext = crypto.decrypt(token, self._cfg.api_key)
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if plaintext is None:
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# Wrong key or corrupt file — unrecoverable, drop it.
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self.delete(path)
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return None
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try:
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return json.loads(plaintext)
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except json.JSONDecodeError:
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self.delete(path)
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return None
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def pending(self) -> list[Path]:
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"""Buffered files, oldest first."""
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return self._files()
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def delete(self, path: Path) -> None:
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try:
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path.unlink()
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except OSError:
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pass
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def clear(self) -> None:
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for p in self._files():
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self.delete(p)
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def _enforce_limit(self, reserve: int = 0) -> None:
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"""Drop oldest files until under (max - reserve)."""
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limit = max(self._cfg.max_buffer_payloads - reserve, 0)
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files = self._files()
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while len(files) > limit:
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self.delete(files.pop(0))
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