mirror of
https://github.com/kevinveenbirkenbach/docker-volume-backup.git
synced 2026-08-20 13:12:48 +00:00
Kevin Veen-Birkenbach
da9c3a1e6f
A volume with a backing store of its own is not in a snapshot of the docker data root: it appears there as an existing empty directory, so the copy succeeds, the generation is stamped complete, and the volume is empty in it. The existing check only asked whether the path was inside the snapshot, which that empty directory answers with yes. The driver, its options and the filesystem the mountpoint sits on now decide, per volume. An uncaptured volume is copied live - correct data without the point in time - while every other volume of the same run keeps its snapshot. One NFS volume no longer costs the whole host its consistent backup. A volume resolving outside the subject degrades the same way instead of aborting the run. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
93 lines
2.7 KiB
Python
93 lines
2.7 KiB
Python
"""Show what a real snapshot holds for a volume that has its own storage.
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Runs inside the privileged container that built the btrfs subject. Prints one
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PASS/FAIL line per assertion and exits non-zero on the first failure.
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"""
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from __future__ import annotations
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import subprocess
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import sys
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from pathlib import Path
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sys.path.insert(0, "/src")
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from baudolo.backup.snapshot import (
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SnapshotError,
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snapshot_source,
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unsnapshotted,
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volume_snapshot,
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)
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from baudolo.backup.volume import Backing
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SUBJECT = sys.argv[1]
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def shell(command: str) -> list[str]:
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proc = subprocess.run(
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command, shell=True, capture_output=True, text=True, check=False
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)
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if proc.returncode != 0:
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raise SnapshotError(
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f"{command} exited {proc.returncode}: {proc.stderr.strip()}"
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)
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return proc.stdout.splitlines()
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def check(label: str, condition: bool) -> None:
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print(f"{'PASS' if condition else 'FAIL'} {label}", flush=True)
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if not condition:
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sys.exit(1)
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def volume(name: str, payload: str) -> Path:
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path = Path(SUBJECT) / "volumes" / name / "_data"
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path.mkdir(parents=True, exist_ok=True)
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(path / "state").write_text(payload)
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return path
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plain = volume("plain", "plain-payload")
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own = Path(SUBJECT) / "volumes" / "own" / "_data"
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own.mkdir(parents=True, exist_ok=True)
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shell(f"mount -t tmpfs tmpfs {own}")
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(own / "state").write_text("own-payload")
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check("a plain volume is captured", unsnapshotted(Backing(str(plain)), SUBJECT) is None)
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check(
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"a volume on a mount of its own is not",
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unsnapshotted(Backing(str(own)), SUBJECT) is not None,
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)
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check(
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"a declared backing store is not, mounted or not",
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unsnapshotted(Backing(str(plain), options={"type": "nfs"}), SUBJECT) is not None,
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)
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check(
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"a foreign driver is not",
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unsnapshotted(Backing(str(plain), driver="rexray"), SUBJECT) is not None,
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)
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with volume_snapshot("btrfs", SUBJECT, "e2e", run=shell) as resolve:
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frozen_plain = Path(resolve(str(plain)))
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frozen_own = Path(resolve(str(own)))
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check(
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"the snapshot carries the plain volume",
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(frozen_plain / "state").read_text() == "plain-payload",
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)
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check(
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"the snapshot shows the other volume as an empty directory",
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frozen_own.is_dir() and not any(frozen_own.iterdir()),
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)
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source, reason = snapshot_source(resolve, Backing(str(plain)), SUBJECT)
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check(
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"the plain volume is read from the snapshot",
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source is not None and source.rstrip("/") == str(frozen_plain),
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)
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source, reason = snapshot_source(resolve, Backing(str(own)), SUBJECT)
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check(f"the other volume degrades to live: {reason[:60]}", source is None)
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print("ALL OK", flush=True)
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