CroneKorkN
9d9ac7ac5e
Clients deleted every auto-backup_ snapshot on the server except the newest, so the backup held one state only. prune-snapshots now keeps the newest per day, week and month (14/8/24 by default) independent of the source, and the clients call it after each receive. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01RywMtsL8qXG7GDY3MHq9Uh
85 lines
3.3 KiB
Python
85 lines
3.3 KiB
Python
#!/usr/bin/env python3
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"""Thin out the auto-backup_ snapshots of one received dataset, independent of the source.
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Usage: prune-snapshots [--dry-run] DATASET
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Keeps the newest snapshot per day, ISO week and month for the most recent days, weeks and months
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in /etc/backup-server/retention.json, and always the newest snapshot, which the next incremental
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receive builds on. Other snapshots of the dataset are never touched. Called by the clients'
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backup_path_via_zfs after each successful receive, so it runs while this server is awake.
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Exit codes: 0 ok, 1 zfs failed, 2 usage.
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"""
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from __future__ import annotations
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import datetime
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import json
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import re
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import subprocess
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import sys
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PREFIX = "auto-backup_"
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CONFIG = "/etc/backup-server/retention.json"
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# only datasets received from clients (tank/<client uuid>/...), as the backup user calls this via sudo
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DATASET_RE = re.compile(r"\Atank/[0-9a-f-]{36}/[A-Za-z0-9._/-]+\Z")
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BUCKETS = {
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"daily": lambda d: d.strftime("%Y-%m-%d"),
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"weekly": lambda d: "%d-W%02d" % d.isocalendar()[:2],
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"monthly": lambda d: d.strftime("%Y-%m"),
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}
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def zfs(*args: str) -> str:
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return subprocess.run(["zfs", *args], capture_output=True, text=True, check=True, timeout=120).stdout
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def keep(snapshots: list[tuple[str, int]], retention: dict[str, int]) -> set[str]:
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"""Names to keep from (name, creation epoch) pairs: per granularity the newest snapshot of each
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of the most recent buckets, plus the newest snapshot overall."""
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newest_first = sorted(snapshots, key=lambda s: s[1], reverse=True)
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kept = {newest_first[0][0]} if newest_first else set()
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for granularity, count in retention.items():
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seen: set[str] = set()
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for name, creation in newest_first:
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bucket = BUCKETS[granularity](datetime.datetime.fromtimestamp(creation))
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if bucket not in seen and len(seen) < count:
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seen.add(bucket)
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kept.add(name)
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return kept
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def main(argv: list[str]) -> int:
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dry_run = "--dry-run" in argv
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args = [a for a in argv if a != "--dry-run"]
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if len(args) != 1 or not DATASET_RE.match(args[0]):
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print(__doc__, file=sys.stderr)
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return 2
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dataset = args[0]
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with open(CONFIG, encoding="utf-8") as fh:
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retention = {k: int(v) for k, v in json.load(fh).items() if k in BUCKETS}
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try:
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lines = zfs("list", "-H", "-p", "-t", "snapshot", "-d", "1", "-o", "name,creation", dataset).splitlines()
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except subprocess.CalledProcessError as e:
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print(f"prune-snapshots: {e.stderr.strip()}", file=sys.stderr)
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return 1
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snapshots = []
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for line in lines:
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name, creation = line.split("\t")
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if name.split("@", 1)[1].startswith(PREFIX):
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snapshots.append((name, int(creation)))
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kept = keep(snapshots, retention)
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for name, _ in snapshots:
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if name in kept:
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continue
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print(f"{'would destroy' if dry_run else 'destroying'} {name}")
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if not dry_run:
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try:
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zfs("destroy", name)
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except subprocess.CalledProcessError as e:
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print(f"prune-snapshots: {e.stderr.strip()}", file=sys.stderr)
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return 1
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print(f"{dataset}: {len(kept)} of {len(snapshots)} {PREFIX} snapshots kept")
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return 0
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if __name__ == "__main__":
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sys.exit(main(sys.argv[1:]))
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