btrfs dedupe and backup scripts

btrfsborg.py

#!/usr/bin/env python3

from argparse import ArgumentParser
from contextlib import suppress
from datetime import datetime, timezone
from functools import cached_property
from sys import argv, stderr
from time import time
import json
import os
import re
import shlex
import subprocess as sp
import yaml

CONFIG_DEFAULT = '''\
## btrfs borg configuration

#subvolume: subvolume # path to target subvolume
#retention:
#  - span: 1d
#    interval: 1h
#  - span: 1w
#    interval: 1d
#  - span: 1M
#    interval: 1w
#borg:
#  - repo:
#    name: # backup name
#    compression: zstd
#    options: # options as sh commandline, for borg-create and borg-list
#    create-options:
#    retention:
#      - span: 1d
#        interval: 4h
#      - span: 1w
#        interval: 1d
#      - span: 6M
#        interval: 1w
'''

class RetentionRule:
    @staticmethod
    def parse_span(span):
        units = {
                'usec': 1e-6,
                'us': 1e-6,
                'μs': 1e-6,
                'msec': 1e-3,
                'ms': 1e-3,
                'seconds': 1,
                'second': 1,
                'sec': 1,
                's': 1,
                'minutes': 60,
                'minute': 60,
                'min': 60,
                'm': 60,
                'hours': 3600,
                'hour': 3600,
                'hr': 3600,
                'h': 3600,
                'days': 86400,
                'day': 86400,
                'd': 86400,
                'weeks': 86400 * 7,
                'week': 86400 * 7,
                'w': 86400 * 7,
                'months': 86400 * 365.25 / 12,
                'month': 86400 * 365.25 / 12,
                'M': 86400 * 365.25 / 12,
                'years': 86400 * 365.25,
                'year': 86400 * 365.25,
                'y': 86400 * 365.25,
                }
        s = 0
        n = None
        for p in re.findall(r'[0-9.]+|[a-zA-Z]+', span):
            if p[0].isalpha():
                s += n * units[p]
                n = None
            else:
                n = float(p)
        if n is not None:
            s += n
        return s

    def __init__(self, rules):
        self.rules = sorted([
            (self.parse_span(r['span']), self.parse_span(r['interval']))
            for r in rules
            ])

    @staticmethod
    def interval_adjust(i):
        if i > 600:
            i -= min(i / 10, 3600)
        return i

    def filter_expired(self, objs, key=float, now=None):
        if now is None:
            now = time()
        lastts = None
        for ts, obj in sorted([(key(o), o) for o in objs]):
            age = now - ts
            if age <= 0:
                continue
            interval = None
            for span, spanint in self.rules:
                if span >= age:
                    interval = spanint
                    break
            if interval is None:
                yield obj
                continue
            interval = self.interval_adjust(interval)
            if lastts is not None and ts - lastts < interval:
                yield obj
                continue
            lastts = ts

class BtrfsBorgConfig:
    def __init__(self, snapvol):
        d = None
        with open(os.path.join(snapvol, 'config.yaml'), 'rb') as f:
            d = yaml.safe_load(f)

        self.subvolume = self._parse_subvolume(d.get('subvolume', 'subvolume'), snapvol)

        self.retention = RetentionRule(d.get('retention', [
            { 'span': '1d', 'interval': '1h' },
            { 'span': '1w', 'interval': '1d' },
            { 'span': '1M', 'interval': '1w' },
            ]))

        self.borg = [self.BorgRepo(c) for c in d.get('borg', [])]

    @staticmethod
    def _parse_subvolume(v, snapvol):
        if os.path.isabs(v):
            return v
        return os.path.realpath(os.path.join(snapvol, v))

    class BorgRepo:
        def __init__(self, r):
            self.repo = r['repo']
            self.name = r['name']
            self.compression = r.get('compression', 'zstd')
            self.options = shlex.split(r.get('options', ''))
            self.create_options = shlex.split(r.get('create-options', ''))
            self.retention = RetentionRule(r.get('retention', [
                { 'span': '1d', 'interval': '4h' },
                { 'span': '1w', 'interval': '1d' },
                { 'span': '6M', 'interval': '1w' },
                ]))

class FileLock:
    def __init__(self, path):
        self.f = open(path, 'ab')

    def __enter__(self):
        try:
            os.lockf(self.f.fileno(), os.F_TLOCK, 0)
            return self
        except OSError:
            self.f.close()
            raise

    def __exit__(self, *a):
        self.f.close()

class BtrfsBorg:
    @staticmethod
    def unshared_main(target_path, src_path, *cmd):
        sp.run(['mount', '--rbind', src_path, target_path], check=True)
        os.execvp(cmd[0], cmd)

    @staticmethod
    def init_vol(subvol, snapvol):
        sp.run(['btrfs', 'subvolume', 'create', snapvol], check=True)
        os.mkdir(os.path.join(snapvol, 'snapshots'))
        if not os.path.isabs(subvol):
            subvol = os.path.relpath(subvol, snapvol)
        os.symlink(subvol, os.path.join(snapvol, 'subvolume'))
        with open(os.path.join(snapvol, 'config.yaml'), 'w', encoding='utf-8') as f:
            f.write(CONFIG_DEFAULT)

    @staticmethod
    def eprint(*a):
        print(*a, file=stderr)
        stderr.flush()

    @classmethod
    def run_backup(cls, vols, dry):
        failed = False
        compact_repos = set()
        for vol in sorted(vols):
            cls.eprint(f'Backing up {vol}')
            succeed = False
            with suppress(Exception):
                if dry:
                    cls.eprint(f'would back up {vol}')
                else:
                    bb = cls(vol, compact_repos)
                    bb.do_backup()
                succeed = True
            cls.eprint(f'Backing up of {vol} ' + ('succeeded' if succeed else 'failed'))
            if not succeed:
                failed = True
        for repo in sorted(compact_repos):
            cls.eprint(f'Compacting repo {repo}')
            sp.run(['borg', 'compact', repo], check=True)

        if failed:
            exit(1)

    @classmethod
    def main(cls):
        if len(argv) >= 2 and argv[1] == '--unshared':
            return cls.unshared_main(*argv[2:])

        a = ArgumentParser(description='Btrfs backup tool')
        a.add_argument('--init', metavar='SUBVOLUME', help='initialize new snapshot path')
        a.add_argument('--dry', action='store_true', help='dry run')
        a.add_argument('snapshot_vol', nargs='+', help='snapshot path or directory of snapshot vols')
        a = a.parse_args()

        if a.init:
            if len(a.snapshot_vol) != 1:
                raise RuntimeError('only one volume could be initialized')
            if a.dry:
                vol = a.snapshot_vol[0]
                cls.eprint(f'would initialize {vol}')
            else:
                cls.init_vol(a.init, vol)
        else:
            vols = []
            for v in a.snapshot_vol:
                if os.path.exists(os.path.join(v, 'config.yaml')):
                    vols.append(os.path.realpath(v))
                else:
                    for e in os.listdir(v):
                        p = os.path.realpath(os.path.join(v, e))
                        if os.path.isdir(p):
                            vols.append(p)
            cls.run_backup(vols, a.dry)

    def __init__(self, vol, compact_repo=None):
        self.snapvol = vol
        if compact_repo is None:
            compact_repo = set()
        self.compact_repo = compact_repo

    @cached_property
    def config(self):
        return BtrfsBorgConfig(self.snapvol)

    @staticmethod
    def parse_ts(s):
        return datetime.fromisoformat(s).timestamp()

    @staticmethod
    def format_ts(ts):
        return datetime.fromtimestamp(ts, timezone.utc).isoformat()

    def do_backup(self):
        with FileLock(os.path.join(self.snapvol, 'lock')):
            newvol = os.path.join(self.snapvol, 'snapshots', '.new')
            if os.path.exists(newvol):
                sp.run(['btrfs', 'subvolume', 'delete', newvol], stdout=sp.DEVNULL, stderr=sp.DEVNULL, check=False)
            ts = time()
            sp.run(['btrfs', 'subvolume', 'snapshot', '-r', self.config.subvolume, newvol], stdout=sp.DEVNULL, check=True)
            for s in self.config.retention.filter_expired(filter(
                lambda x: not x.startswith('.'),
                os.listdir(os.path.join(self.snapvol, 'snapshots'))),
                                                          key=self.parse_ts, now=ts):
                sp.run(['btrfs', 'subvolume', 'delete', os.path.join(self.snapvol, 'snapshots', s)], check=True)
            curvol = os.path.join(self.snapvol, 'snapshots', self.format_ts(ts))
            os.rename(newvol, curvol)

            borgcount = 0
            borgfail = 0

            for b in self.config.borg:
                try:
                    self.run_borg(b, ts, curvol)
                except:
                    borgfail += 1
                finally:
                    borgcount += 1

            if borgcount > 0 and borgfail >= borgcount:
                raise RuntimeError('all backups to borg failed')

    def run_borg(self, conf, ts, path):
        arcs = list(filter(lambda n: n.startswith(conf.name + '-'),
                             [a['archive'] for a in json.loads(sp.run(
                                 ['borg', 'list', '--json'] + conf.options + [conf.repo],
                                 stdout=sp.PIPE, check=True).stdout)['archives']
                              ]))
        newarc = conf.name + '-' + self.format_ts(ts)
        if newarc in arcs:
            raise RuntimeError(f'archive {newarc} already exist')
        arcs.append(newarc)
        expired = list(conf.retention.filter_expired(arcs,
                                                     key=lambda n: self.parse_ts(n[len(conf.name) + 1:]), now=ts))

        if newarc not in expired:
            sp.run(['unshare', '-m', '--propagation', 'private', argv[0], '--unshared', self.config.subvolume, path] +
                   ['borg', 'create', '--checkpoint-interval', '600'] + conf.options + conf.create_options +
                   [conf.repo + '::' + newarc, self.config.subvolume], stdin=sp.DEVNULL, check=True)

        for n in expired:
            if n == newarc:
                continue
            sp.run(['borg', 'delete'] + conf.options + [conf.repo + '::' + n], check=True)
            self.compact_repo.add(conf.repo)

if __name__ == '__main__':
    BtrfsBorg.main()

btrfsborg.service

[Service]
ExecStart=/usr/bin/btrfsborg.py /etc/btrfsborg
Nice=19
CPUSchedulingPolicy=idle
IOSchedulingClass=idle

btrfsborg.timer

[Timer]
OnCalendar=hourly

[Install]
WantedBy=timers.target

[email protected]

[Service]
ExecStart=/usr/bin/btrfsborg.py %f
Nice=19
CPUSchedulingPolicy=idle
IOSchedulingClass=idle

[email protected]

[Timer]
OnCalendar=hourly

[Install]
WantedBy=timers.target

[email protected]

[Service]
ExecStart=/usr/bin/duperemove --dedupe-options=same -hqdr %f
Nice=19
CPUSchedulingPolicy=idle
IOSchedulingClass=idle

[email protected]

[Timer]
OnCalendar=weekly
Persistent=true

[Install]
WantedBy=timers.target

PKGBUILD

pkgname=btrfsmaint
pkgver=0.20231218.0
pkgrel=1
pkgdesc='extra btrfs maintenance and backup tools'
arch=(any)
license=(Unlicense)

depends=(
	borg
	btrfs-progs
	duperemove
	python
	python-yaml
	systemd
)

source=(
	btrfsborg.py
	btrfsborg.service
	btrfsborg.timer
	[email protected]
	[email protected]
	[email protected]
	[email protected]
)
cksums=(
	SKIP
	SKIP
	SKIP
	SKIP
	SKIP
	SKIP
	SKIP
)

package() {
	install -Dm755 -t "$pkgdir/usr/bin" "$srcdir/btrfsborg.py"
	install -Dm644 -t "$pkgdir/usr/lib/systemd/system" "$srcdir/btrfsborg.service"
	install -Dm644 -t "$pkgdir/usr/lib/systemd/system" "$srcdir/btrfsborg.timer"
	install -Dm644 -t "$pkgdir/usr/lib/systemd/system" "$srcdir/[email protected]"
	install -Dm644 -t "$pkgdir/usr/lib/systemd/system" "$srcdir/[email protected]"
	install -Dm644 -t "$pkgdir/usr/lib/systemd/system" "$srcdir/[email protected]"
	install -Dm644 -t "$pkgdir/usr/lib/systemd/system" "$srcdir/[email protected]"
}