Proof of concept for blockRebase-based snapshots

snapshot-via-rebase

#!/usr/bin/python

import libvirt
import os
import sys
import time
import uuid

try:
    instance_name = sys.argv[1]
except:
    sys.exit(1)

conn = libvirt.open('qemu:///system')
domain = conn.lookupByName(instance_name)

try:
    domain.undefine()
except:
    pass

try:
    domain.blockJobAbort('vda', 0)
except:
    pass

snapshot_name = os.path.join('/tmp', 'snap-' + str(uuid.uuid4()))
domain.blockRebase('vda', snapshot_name, 0, libvirt.VIR_DOMAIN_BLOCK_REBASE_COPY)

def wait_for_block_job(domain):
    status = domain.blockJobInfo('vda', 0)
    if status is None:
        return False

    print status
    cur = status.get('cur', 0)
    end = status.get('end', 0)

    if cur == end and cur != 0 and end != 0:
        return False
    else:
        return True

while wait_for_block_job(domain):
    print "Sleeping ... "
    time.sleep(0.5)

domain.blockJobAbort('vda', 0)