File size: 2,381 Bytes
f8975ed | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 | #!/usr/bin/env python3
"""sqlite-stage: a consistent copy of live SQLite databases, for the backup to take.
sqlite-stage.py DEST_DIR DATABASE [DATABASE ...]
A backup that copies a database file while a service writes to it can catch the file and its write-ahead log
at different moments, and the copy may not open. SQLite's own backup API reads a consistent snapshot while
the writer keeps writing. Each database lands in DEST_DIR under its path with slashes as underscores, written
to a temporary name, checked (`quick_check`), synced and renamed: a half copy never has the final name.
A missing database is skipped; a failed one is reported and makes the exit status 1, and the others still run.
"""
from __future__ import annotations
import os
import sqlite3
import sys
from pathlib import Path
def stage(source: Path, dest_dir: Path) -> str:
name = str(source).replace(str(Path.home()), "").strip("/").replace("/", "_")
final = dest_dir / name
tmp = dest_dir / (name + ".tmp")
tmp.unlink(missing_ok=True)
try:
src = sqlite3.connect(f"file:{source}?mode=ro", uri=True, timeout=30)
dst = sqlite3.connect(tmp)
try:
src.backup(dst)
ok = dst.execute("PRAGMA quick_check").fetchone()[0]
finally:
dst.close()
src.close()
if ok != "ok":
raise sqlite3.DatabaseError(f"the copy does not pass quick_check: {ok}")
except sqlite3.Error:
tmp.unlink(missing_ok=True) # a half copy never stays, under any name
raise
with open(tmp, "rb") as fh:
os.fsync(fh.fileno())
os.replace(tmp, final)
return f"{source} -> {final} ({final.stat().st_size} bytes)"
def main(argv: list[str]) -> int:
if len(argv) < 2:
print(__doc__.strip().splitlines()[2].strip(), file=sys.stderr)
return 2
dest = Path(argv[0])
dest.mkdir(parents=True, exist_ok=True)
failed = 0
for arg in argv[1:]:
source = Path(arg)
if not source.exists():
continue
try:
print(stage(source, dest))
except sqlite3.Error as e:
failed = 1
print(f"sqlite-stage: {source}: {e}", file=sys.stderr)
fd = os.open(dest, os.O_RDONLY)
os.fsync(fd)
os.close(fd)
return failed
if __name__ == "__main__":
raise SystemExit(main(sys.argv[1:]))
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