mirror of
https://github.com/kevinveenbirkenbach/docker-volume-backup.git
synced 2026-08-24 23:04:34 +00:00
Kevin Veen-Birkenbach
cd21f1fa67
Each volume is copied twice into the same destination: once hot with the container running, once cold after it is stopped (backup/app.py:127-131). rsync ran with -b, so --delete did not remove a file the source had dropped between the passes - it renamed it. Stopping a container is exactly what makes the source drop files: a graceful shutdown flushes, and the format rolls its commit point. For an opaque payload the twin is stale bytes nobody reads. For a format that enumerates its own directory it is corruption. Lucene resolves the current commit by parsing every file starting with segments as a radix-36 generation, so a restored segments_3~ raises NumberFormatException, the shard store cannot be read, and the primary is left NO_VALID_SHARD_COPY. With .security-7 unallocatable the reserved elastic user has no password hash, every probe gets HTTP 401, and the container never turns healthy. Seen in infinito-nexus-core CI run 30963648828: the restore drill waited 1200s on elasticsearch while all 29 other containers came back healthy; the generation held segments_3~ next to segments_4 in all three index directories. A run two days earlier passed the same drill because that stack was idle and nothing rolled between the passes - which is why this reads as flaky rather than broken. Reproduced with real rsync in all three shapes: two passes into the same destination with -b leave segments_3~ beside segments_4, without -b only segments_4 survives, and a single pass keeps segments_3. Measured on the same fixtures, dropping -b leaves the predecessor generation byte-identical and keeps the --link-dest hardlinks intact, so the incremental scheme is unaffected; generations get smaller, never larger. --link-dest already provides the cheap incrementals. -b contributed nothing on top of it but the twins, and no caller reads them: the restore path is an unfiltered rsync -avv --delete into the live volume (restore/files.py:35). Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
66 lines
2.0 KiB
Python
66 lines
2.0 KiB
Python
from __future__ import annotations
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import os
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import pathlib
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from .shell import BackupException, execute_shell_command
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def get_storage_path(volume_name: str) -> str:
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path = execute_shell_command(
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f"docker volume inspect --format '{{{{ .Mountpoint }}}}' {volume_name}"
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)[0]
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return f"{path}/"
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def get_last_backup_dir(
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versions_dir: str, volume_name: str, current_backup_dir: str
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) -> str | None:
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versions = sorted(os.listdir(versions_dir), reverse=True)
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for version in versions:
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candidate = os.path.join(versions_dir, version, volume_name, "files", "")
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if candidate != current_backup_dir and os.path.isdir(candidate):
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return candidate
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return None
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def backup_volume(
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versions_dir: str,
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volume_name: str,
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volume_dir: str,
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*,
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authoritative: bool,
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source: str,
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) -> None:
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"""Perform incremental file backup of a Docker volume.
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Args:
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authoritative: compare source and destination by content instead of by
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size and whole-second mtime. Required on a pass whose destination was
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already written from a live source, where a file can differ while
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both attributes still agree.
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source: directory to read from - the volume's mountpoint, or its path
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inside a snapshot.
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"""
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dest = os.path.join(volume_dir, "files") + "/"
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pathlib.Path(dest).mkdir(parents=True, exist_ok=True)
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last = get_last_backup_dir(versions_dir, volume_name, dest)
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link_dest = f"--link-dest='{last}'" if last else ""
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verify = "--checksum " if authoritative else ""
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cmd = (
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f"rsync -aP --no-D --delete --delete-excluded "
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f"{verify}{link_dest} {source} {dest}"
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)
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try:
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execute_shell_command(cmd)
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except BackupException as e:
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if "file has vanished" in str(e):
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print(
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"Warning: Some files vanished before transfer. Continuing.", flush=True
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)
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else:
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raise
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