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https://github.com/retspen/webvirtcloud
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feat(instances): external snapshots use libvirt's snapshot API
Create, revert and delete are one libvirt call each. The pflash-to-rom loader rewrite, the hand-written block commit and the s1./s2. names are gone, so UEFI VMs can take external snapshots, a revert keeps disks added later, and deleting an older snapshot keeps the newer one. Create refuses what libvirt could not revert or delete later: internal snapshots on the VM, a saved state, a running snapshot job, disks that are not files, CD-ROM media, a branch after a revert, and memory without a running VM or room in the first disk's pool. A disk-only revert keeps the VM running, paused or shut off; one with memory resumes it as saved. A revert in the same second as the previous one, which libvirt fails after stopping the VM, is retried once. A snapshot the old code took of a UEFI VM saved the loader as rom; its revert is refused (deleting it still works). The snapshots tab lists internal and external snapshots separately, can save memory too, shows running snapshot jobs, and the revert confirmation names the disks it detaches and that NVRAM is not restored.
This commit is contained in:
catborise
parent
c55f52f025
commit
ff1508b3c2
13 changed files with 994 additions and 311 deletions
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@ -3,6 +3,7 @@ import ipaddress
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import json
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import logging
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import os.path
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import re
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import string
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import threading
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import time
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@ -31,14 +32,13 @@ try:
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VIR_MIGRATE_PERSIST_DEST,
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VIR_MIGRATE_UNDEFINE_SOURCE,
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VIR_MIGRATE_UNSAFE,
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VIR_DOMAIN_SNAPSHOT_CREATE_ATOMIC,
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VIR_DOMAIN_SNAPSHOT_CREATE_DISK_ONLY,
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VIR_DOMAIN_SNAPSHOT_DELETE_METADATA_ONLY,
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VIR_DOMAIN_SNAPSHOT_REVERT_PAUSED,
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VIR_DOMAIN_SNAPSHOT_REVERT_RUNNING,
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VIR_ERR_CONFIG_UNSUPPORTED,
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VIR_DOMAIN_SNAPSHOT_LIST_INTERNAL,
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VIR_DOMAIN_SNAPSHOT_LIST_EXTERNAL,
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VIR_DOMAIN_BLOCK_COMMIT_DELETE,
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VIR_DOMAIN_BLOCK_COMMIT_ACTIVE,
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VIR_DOMAIN_BLOCK_JOB_ABORT_PIVOT,
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VIR_DOMAIN_START_PAUSED,
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libvirtError,
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)
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from libvirt_qemu import VIR_DOMAIN_QEMU_AGENT_COMMAND_DEFAULT, qemuAgentCommand
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@ -59,6 +59,9 @@ from vrtManager.storage import wvmStorage, wvmStorages
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# with secrets. Live XML would drop pending changes, non-secure XML the VNC
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# password.
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PERSISTENT_XML = VIR_DOMAIN_XML_INACTIVE | VIR_DOMAIN_XML_SECURE
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# External snapshot names become part of overlay and memory file names.
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SNAPSHOT_NAME = re.compile(r"[A-Za-z0-9_-][A-Za-z0-9._-]{0,63}")
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# the longest window wvmInstance.usage() averages over
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USAGE_MAX_WINDOW = 30
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@ -1509,17 +1512,12 @@ class wvmInstance(wvmConnect):
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[path for path in own if path in used_elsewhere],
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)
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def delete_all_disks(self):
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self.refresh_instance_pools()
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disks = self.get_disk_devices()
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for disk in disks:
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vol = self.get_volume_by_path(disk.get("path"))
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vol.delete(0)
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def _snapshotCreateXML(self, xml, flag):
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self.instance.snapshotCreateXML(xml, flag)
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def create_snapshot(self, name, desc=None):
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if self.instance.snapshotListNames(VIR_DOMAIN_SNAPSHOT_LIST_EXTERNAL):
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raise util.OperationError("The VM has external snapshots; internal snapshots cannot be mixed with them")
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state = "shutoff" if self.get_status() == 5 else "running"
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name_esc = util.xml_escape(name)
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desc_esc = util.xml_escape(desc) if desc else ""
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@ -1540,139 +1538,184 @@ class wvmInstance(wvmConnect):
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</domainsnapshot>"""
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self._snapshotCreateXML(xml, 0)
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def change_snapshot_xml(self):
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try:
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raw_xml = self._XMLDesc(VIR_DOMAIN_XML_SECURE)
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tree = ElementTree.fromstring(raw_xml)
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loader = tree.find("./os/loader")
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if loader is not None and loader.get("type") == "pflash":
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loader.set("type", "rom")
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self._defineXML(ElementTree.tostring(tree, encoding="unicode"))
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return True
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return False
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except Exception as e:
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logger.error("Failed to change snapshot XML loader: %s", e)
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raise
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def recover_snapshot_xml(self):
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try:
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raw_xml = self._XMLDesc(VIR_DOMAIN_XML_SECURE)
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tree = ElementTree.fromstring(raw_xml)
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loader = tree.find("./os/loader")
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if loader is not None and loader.get("type") == "rom":
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loader.set("type", "pflash")
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self._defineXML(ElementTree.tostring(tree, encoding="unicode"))
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return True
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return False
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except Exception as e:
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logger.error("Failed to recover snapshot XML loader: %s", e)
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raise
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def create_external_snapshot(self, name, date=None, desc=None):
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creation_time = time.time()
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state = "shutoff" if self.get_status() == 5 else "running"
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name_esc = util.xml_escape(name)
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desc_esc = util.xml_escape(desc) if desc else ""
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#<seclabel type='none' model='dac' relabel='no'/>
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xml = """<domainsnapshot>
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<name>%s</name>
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<description>%s</description>
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<state>%s</state>
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<creationTime>%d</creationTime>
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""" % (
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name_esc,
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desc_esc,
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state,
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creation_time,
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def create_external_snapshot(self, name, desc="", memory=False):
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"""A disk-only snapshot, or with memory too (running VMs only). Every
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disk gets a libvirt-named overlay next to it; the memory file goes
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next to the first disk."""
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if not SNAPSHOT_NAME.fullmatch(name):
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raise util.OperationError(
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"Snapshot names are 1-64 letters, digits, '.', '_' or '-' and do not start with '.'"
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)
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self._check_snapshot_state()
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if self.instance.snapshotListNames(VIR_DOMAIN_SNAPSHOT_LIST_INTERNAL):
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raise util.OperationError("The VM has internal snapshots; external snapshots cannot be mixed with them")
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if name in self.instance.snapshotListNames(0):
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raise util.OperationError(f"A snapshot named {name} already exists")
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if self.instance.hasCurrentSnapshot(0):
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if self.instance.snapshotCurrent(0).numChildren(0):
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raise util.OperationError("Newer snapshots exist after the last revert; delete them first")
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elif self.instance.snapshotListNames(0):
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# only after changes outside WebVirtCloud; a create would start a second root
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raise util.OperationError("No snapshot is current; revert to a snapshot first")
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tree = etree.fromstring(self._XMLDesc(0))
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for disk in tree.xpath("devices/disk"):
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dev = disk.xpath("string(target/@dev)")
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if disk.get("device") in ("cdrom", "floppy"):
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if disk.xpath("source/@file|source/@dev|source/@name"):
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raise util.OperationError(f"Eject the media from {dev} first")
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elif disk.get("type") != "file":
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raise util.OperationError(f"Disk {dev} is not a file; external snapshots need file disks")
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memory_xml = self._snapshot_memory_xml(name, tree) if memory else ""
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xml = (
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f"<domainsnapshot><name>{name}</name>"
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f"<description>{util.xml_escape(desc)}</description>{memory_xml}</domainsnapshot>"
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)
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changed = self.change_snapshot_xml()
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try:
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xml += self._XMLDesc(VIR_DOMAIN_XML_SECURE)
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xml += """<active>0</active>
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</domainsnapshot>"""
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self._snapshotCreateXML(xml, VIR_DOMAIN_SNAPSHOT_CREATE_DISK_ONLY)
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finally:
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if changed:
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self.recover_snapshot_xml()
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flags = VIR_DOMAIN_SNAPSHOT_CREATE_ATOMIC
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if not memory:
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flags |= VIR_DOMAIN_SNAPSHOT_CREATE_DISK_ONLY
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self._snapshotCreateXML(xml, flags)
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self.refresh_instance_pools()
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def _snapshot_memory_xml(self, name, tree):
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"""The <memory> element of a snapshot that saves memory: a file in the
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storage pool of the first disk, which must have room for it."""
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if self.get_status() != 1:
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raise util.OperationError("Memory is saved only from a running VM")
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disks = list(self._disk_sources(tree).values())
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if not disks:
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raise util.OperationError("The VM has no disk to keep its memory next to")
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# the top overlay is known to its pool only after a refresh
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self.refresh_instance_pools()
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try:
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pool = self.get_volume_by_path(disks[0]).storagePoolLookupByVolume()
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except libvirtError:
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raise util.OperationError(f"{disks[0]} is not in a storage pool; memory is saved only into one") from None
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if pool.info()[3] < self.get_cur_memory() * 1024 * 1024:
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raise util.OperationError(f"Storage pool {pool.name()} has less free space than the VM's memory")
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path = os.path.join(os.path.dirname(disks[0]), f"{self.get_uuid()}.{name}.mem")
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return f"<memory snapshot='external' file='{util.xml_escape(path)}'/>"
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def revert_external_snapshot(self, name):
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"""libvirt returns the disks and the definition to the snapshot's. A
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disk-only snapshot keeps the VM running, paused or shut off as it is;
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a snapshot with memory resumes the VM as it was saved."""
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snap = self._snapshot(name, external=True)
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self._check_snapshot_state()
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tree = etree.fromstring(snap.getXMLDesc(0))
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# Snapshots of UEFI VMs taken before WebVirtCloud used libvirt's
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# snapshot API saved the loader switched to rom; a revert would
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# restore that.
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saved = self._saved_definition(tree)
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saved_loader = saved.xpath("string(os/loader/@type)") if saved is not None else ""
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current_loader = util.get_xml_path(self._XMLDesc(PERSISTENT_XML), "/domain/os/loader/@type")
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if saved_loader == "rom" and current_loader == "pflash":
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raise util.OperationError(
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"This snapshot was taken by an older version on a UEFI VM and cannot be reverted; delete it instead"
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)
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if tree.find("memory[@snapshot='external']") is not None:
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flags = 0
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else:
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flags = {1: VIR_DOMAIN_SNAPSHOT_REVERT_RUNNING, 3: VIR_DOMAIN_SNAPSHOT_REVERT_PAUSED}.get(
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self.get_status(), 0
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)
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# libvirt names the new overlays after the second, so a revert within
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# the second of the previous one finds them taken, after it has
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# already stopped a running VM; one retry a second later finishes it.
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try:
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self.instance.revertToSnapshot(snap, flags)
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except libvirtError as err:
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if err.get_error_code() != VIR_ERR_CONFIG_UNSUPPORTED or "already exists" not in str(err):
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raise
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time.sleep(1)
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try:
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self.instance.revertToSnapshot(snap, flags)
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except libvirtError as retry_err:
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state = "running" if self.instance.isActive() else "shut off"
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raise util.OperationError(
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f"The revert failed twice; try again in a moment ({retry_err}). The VM is {state}."
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) from None
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self.refresh_instance_pools()
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def get_external_snapshots(self):
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return self.get_snapshot(VIR_DOMAIN_SNAPSHOT_LIST_EXTERNAL)
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def delete_external_snapshot(self, name):
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disk_info = self.get_disk_devices()
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for disk in disk_info:
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target_dev = disk["dev"]
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backing_file = disk["backing_file"]
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snap_source_file = disk["path"]
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self.instance.blockCommit(target_dev, backing_file, snap_source_file,
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flags=VIR_DOMAIN_BLOCK_COMMIT_DELETE|
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VIR_DOMAIN_BLOCK_COMMIT_ACTIVE)
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while True:
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info = self.instance.blockJobInfo(target_dev, 0)
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if info.get('cur') == info.get('end'):
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self.instance.blockJobAbort(target_dev,flags=VIR_DOMAIN_BLOCK_JOB_ABORT_PIVOT)
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time.sleep(2)
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break
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# Check again pool for snapshot delta volume; if it exist, remove it manually
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with contextlib.suppress(libvirtError):
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vol_snap = self.get_volume_by_path(snap_source_file)
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pool = vol_snap.storagePoolLookupByVolume()
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pool.refresh(0)
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vol_snap.delete(0)
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"""libvirt merges the snapshot's overlays and removes its files."""
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snap = self._snapshot(name, external=True)
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self._check_snapshot_state()
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snap.delete(0)
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self.refresh_instance_pools()
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snap = self.instance.snapshotLookupByName(name, 0)
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snap.delete(VIR_DOMAIN_SNAPSHOT_DELETE_METADATA_ONLY)
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@staticmethod
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def _disk_sources(xml):
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"""Target dev -> source file of the disks (not CD-ROMs) in a domain definition."""
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tree = etree.fromstring(xml) if isinstance(xml, str) else xml
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return {
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disk.xpath("string(target/@dev)"): disk.xpath("string(source/@file|source/@dev|source/@name)")
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for disk in tree.xpath("devices/disk[@device='disk']")
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}
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def revert_external_snapshot(self, name, date, desc):
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snap = self.instance.snapshotLookupByName(name, 0)
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snap_xml = snap.getXMLDesc(0)
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snapXML = ElementTree.fromstring(snap_xml)
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@staticmethod
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def _saved_definition(tree):
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"""The definition a revert to this snapshot restores as the persistent one."""
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definition = tree.find("inactiveDomain")
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return tree.find("domain") if definition is None else definition
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self.start(flags=VIR_DOMAIN_START_PAUSED) if self.get_status() == 5 else None
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self.delete_all_disks()
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self.force_shutdown()
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snap.delete(VIR_DOMAIN_SNAPSHOT_DELETE_METADATA_ONLY)
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disks = snapXML.findall('inactiveDomain/devices/disk')
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if not disks: disks = snapXML.findall('domain/devices/disk')
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for disk in disks:
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self.instance.updateDeviceFlags(ElementTree.tostring(disk).decode("UTF-8"))
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name = name.replace("s1", "s2")
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self.create_external_snapshot(name, date, desc)
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def get_snapshot(self, flag=VIR_DOMAIN_SNAPSHOT_LIST_INTERNAL|VIR_DOMAIN_SNAPSHOT_LIST_EXTERNAL):
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def get_snapshot(self, flag):
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"""Snapshots of one kind (VIR_DOMAIN_SNAPSHOT_LIST_INTERNAL or
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_EXTERNAL; both flags for all), with whether each saved memory, is the
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current one, and which disks of the persistent definition a revert to
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it detaches."""
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current_disks = self._disk_sources(self._XMLDesc(PERSISTENT_XML))
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snapshots = []
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snapshot_list = self.instance.snapshotListNames(flag)
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for snapshot in snapshot_list:
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snap = self.instance.snapshotLookupByName(snapshot, 0)
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snap_description = util.get_xml_path(
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snap.getXMLDesc(0), "/domainsnapshot/description"
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)
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snap_time_create = util.get_xml_path(
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snap.getXMLDesc(0), "/domainsnapshot/creationTime"
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)
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for snap in self.instance.listAllSnapshots(flag):
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tree = etree.fromstring(snap.getXMLDesc(0))
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definition = self._saved_definition(tree)
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saved_disks = self._disk_sources(definition) if definition is not None else {}
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snapshots.append(
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{
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"date": datetime.fromtimestamp(int(snap_time_create)),
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"name": snapshot,
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"description": snap_description,
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"date": datetime.fromtimestamp(int(tree.findtext("creationTime"))),
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"name": snap.getName(),
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"description": tree.findtext("description") or "",
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"memory": tree.find("memory[@snapshot='external']") is not None,
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"current": bool(snap.isCurrent(0)),
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"detaches": [
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{"dev": dev, "path": path} for dev, path in current_disks.items() if dev not in saved_disks
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],
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}
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)
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return snapshots
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def get_snapshot_jobs(self):
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"""Block jobs (snapshot merges) running on the VM's disks."""
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if not self.instance.isActive():
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return []
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jobs = []
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for dev in self._disk_sources(self._XMLDesc(0)):
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info = self.instance.blockJobInfo(dev, 0)
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if info:
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jobs.append({"dev": dev, "cur": info["cur"], "end": info["end"]})
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return jobs
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def _snapshot(self, name, external):
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"""The named snapshot; a snapshot of the other kind is refused."""
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flag = VIR_DOMAIN_SNAPSHOT_LIST_EXTERNAL if external else VIR_DOMAIN_SNAPSHOT_LIST_INTERNAL
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if name not in self.instance.snapshotListNames(flag):
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kind = "external" if external else "internal"
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raise util.OperationError(f"The VM has no {kind} snapshot named {name}")
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return self.instance.snapshotLookupByName(name, 0)
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def _check_snapshot_state(self):
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"""Refusals shared by external snapshot create, revert and delete. The
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internal/external mix is checked only on create, so a VM that is
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already mixed can still be cleaned up."""
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if self.instance.hasManagedSaveImage(0):
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raise util.OperationError("The VM has a saved state; start it or remove the saved state first")
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if self.get_snapshot_jobs():
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raise util.OperationError("A snapshot job is still running on this VM; try again when it ends")
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def snapshot_delete(self, snapshot):
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snap = self.instance.snapshotLookupByName(snapshot, 0)
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snap.delete(0)
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self._snapshot(snapshot, external=False).delete(0)
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def snapshot_revert(self, snapshot):
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snap = self.instance.snapshotLookupByName(snapshot, 0)
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self.instance.revertToSnapshot(snap, 0)
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self.instance.revertToSnapshot(self._snapshot(snapshot, external=False), 0)
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def get_managed_save_image(self):
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return self.instance.hasManagedSaveImage(0)
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