snap-strip.py

#!/usr/bin/env python3

# snap-strip.py by Arno Hautala <arno@alum.wpi.edu>
# modifications by Arno Hautala
#   This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.
#   (CC BY-SA-3.0) http://creativecommons.org/licenses/by-sa/3.0/

# This script removes empty snapshots, based on their 'used' property.
# Note that one snapshot's 'used' value may change when another snapshot is
# destroyed. This script iteratively destroys the oldest empty snapshot. It
# does not remove the latest snapshot of each dataset or manual snapshots

import subprocess
import argparse
from collections import defaultdict

parser = argparse.ArgumentParser(description='Removes empty auto snapshots.')
parser.add_argument('datasets', nargs='+', help='the root dataset(s) from which to remove snapshots')
parser.add_argument('--test', '-t', action="store_true", default=False, help='only display the snapshots that would be deleted, without actually deleting them. Note that due to dependencies between snapshots, this may not match what would really happen.')
parser.add_argument('--verbose', '-v', action="store_true", default=False, help='be verbose about what snapshots will be deleted and how much space will be freed.')
parser.add_argument('--recursive', '-r', action="store_true", default=False, help='recursively removes snapshots from nested datasets')
parser.add_argument('--prefix', '-p', action='append', help='list of snapshot name prefixes that will be considered')

args = parser.parse_args()

if not args.prefix:
    args.prefix = ['auto']

args.prefix = [prefix+"-" for prefix in set(args.prefix)]

deleted = defaultdict(lambda : defaultdict(lambda : defaultdict(int)))

snapshots = defaultdict(lambda : defaultdict(lambda : defaultdict(int)))

# Get properties of all snapshots of the selected datasets
for dataset in args.datasets:
    subp = subprocess.Popen(["zfs", "get", "-t", "snapshot", "-Hrpo", "name,property,value", "type,creation,used,freenas:state", dataset], stdout=subprocess.PIPE)
    zfs_snapshots = subp.communicate()[0]
    if subp.returncode:
        print("zfs get failed with RC=%s" % subp.returncode)
        sys.exit(1)

    for snapshot in zfs_snapshots.splitlines():
        name,property,value = snapshot.decode().split('\t',3)

        # if the rollup isn't recursive, skip any snapshots from child datasets
        if not args.recursive and not name.startswith(dataset+"@"):
            continue

        try:
            dataset,snapshot = name.split('@',2)
        except ValueError:
            continue

        snapshots[dataset][snapshot][property] = value

# Ignore non-snapshots and snapshots that don't include the requested prefix(es)
# Remove already destroyed snapshots
for dataset in list(snapshots.keys()):
    latest = None
    latestNEW = None
    for snapshot in sorted(snapshots[dataset], key=lambda snapshot: snapshots[dataset][snapshot]['creation'], reverse=True):
        if "snapshot" != snapshots[dataset][snapshot]['type']:
            del snapshots[dataset][snapshot]
            continue
        if not latest:
            latest = snapshot
            del snapshots[dataset][snapshot]
            continue
        if not latestNEW and snapshots[dataset][snapshot]['freenas:state'] == 'NEW':
            latestNEW = snapshot
            del snapshots[dataset][snapshot]
            continue
        if snapshots[dataset][snapshot]['freenas:state'] == 'LATEST':
            del snapshots[dataset][snapshot]
            continue

    # Stop if no snapshots are in the list
    if not snapshots[dataset]:
        del snapshots[dataset]
        continue

def end_range(r_start, r_end):
    if not r_start:
        return None
    if r_start == r_end or not r_end:
        return r_start
    return r_start + "%" + r_end

delete_targets = list()

# now build lists of snapshots that match the requested prefixes
for dataset in sorted(snapshots.keys()):
    range_start = None
    range_end = None
    for snapshot in sorted(snapshots[dataset], key=lambda snapshot: snapshots[dataset][snapshot]['creation'], reverse=False):
        if not any(map(snapshot.startswith, args.prefix)):
            range = end_range(range_start, range_end)
            if range:
                delete_targets.append(dataset + "@" + range)
            range_start = None
            range_end = None
            continue
        if not range_start:
            range_start = snapshot
        range_end = snapshot
    range = end_range(range_start, range_end)
    if range:
        delete_targets.append(dataset + "@" + range)
    range_start = None
    range_end = None

command = "zfs destroy "
if args.test:
    command += "-n "
if args.verbose:
    command += "-v "
for target in delete_targets:
    print(command + target)