mirror of
https://github.com/kevinveenbirkenbach/docker-volume-backup.git
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Kevin Veen-Birkenbach
d4317827bd
Backing up a live volume with rsync copies a moving target: a database
written to mid-copy lands on disk in a state no engine ever committed.
Stopping the container avoids that at the cost of downtime.
A snapshot removes both. `--snapshot {btrfs,zfs}` with `--snapshot-subject`
freezes the docker root once per run, and every volume copy is then read
from that frozen tree while the containers keep serving. A restore of such
a copy is an ordinary crash recovery, which every supported engine performs
on its own at startup.
An unsupported filesystem or an unknown snapshot kind fails loudly rather
than degrading to a live copy, since a silent fallback would return exactly
the torn backup the mode exists to prevent. `--shutdown` is rejected
alongside `--snapshot` instead of being ignored: under a snapshot no
container is ever stopped, so accepting the flag would promise downtime
semantics the run does not deliver.
Copies out of a snapshot skip rsync's --checksum verification. The source
is immutable for the lifetime of the copy, so size-and-mtime cannot race,
and dropping the second full read roughly halves the I/O per volume.
backup/app.py grew past what one module could carry and is split into
layout, policy and dumps along the lines it already had internally.
Tests: unit coverage for the new snapshot, layout, policy, volume and cli
units; e2e cases drive real btrfs, zfs and ext4 filesystems on loop devices
in a privileged container, including a MariaDB that is written to across
the snapshot and must recover from the restored copy without losing a
committed row. CI installs zfs and sets E2E_REQUIRE_FILESYSTEMS so a
missing kernel module fails the build instead of silently skipping a
filesystem.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
45 lines
1.0 KiB
Python
45 lines
1.0 KiB
Python
"""Builds the on-disk compose directories the compose tests discover."""
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from __future__ import annotations
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import shutil
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from pathlib import Path
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def touch(p: Path) -> None:
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p.parent.mkdir(parents=True, exist_ok=True)
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# ".env/env" leaves ".env" behind as a directory, which blocks a later ".env" file.
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if p.exists() and p.is_dir():
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shutil.rmtree(p)
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p.write_text("x", encoding="utf-8")
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def setup_compose_dir(
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tmp_path: Path,
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name: str = "mailu",
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*,
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compose_name: str = "docker-compose.yml",
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with_override: bool = False,
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with_ca_override: bool = False,
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env_layout: str | None = None, # None | ".env" | ".env/env"
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) -> Path:
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d = tmp_path / name
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d.mkdir(parents=True, exist_ok=True)
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touch(d / compose_name)
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if with_override:
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touch(d / "docker-compose.override.yml")
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if with_ca_override:
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touch(d / "docker-compose.ca.override.yml")
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if env_layout == ".env":
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touch(d / ".env")
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elif env_layout == ".env/env":
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touch(d / ".env" / "env")
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return d
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