pvc/daemon-common/zkhandler.py

#!/usr/bin/env python3

# zkhandler.py - Secure versioned ZooKeeper updates
# Part of the Parallel Virtual Cluster (PVC) system
#
#    Copyright (C) 2018-2024 Joshua M. Boniface <joshua@boniface.me>
#
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, version 3.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <https://www.gnu.org/licenses/>.
#
###############################################################################

import asyncio
import os
import time
import uuid
import json
import re
from functools import wraps
from kazoo.client import KazooClient, KazooState
from kazoo.exceptions import NoNodeError


DEFAULT_ROOT_PATH = "/usr/share/pvc"
SCHEMA_PATH = "daemon_lib/migrations/versions"


#
# Function decorators
#
class ZKConnection(object):
    """
    Decorates a function with a Zookeeper connection before and after the main call.

    The decorated function must accept the `zkhandler` argument as its first argument, and
    then use this to access the connection.
    """

    def __init__(self, config):
        self.config = config

    def __call__(self, function):
        if not callable(function):
            return

        @wraps(function)
        def connection(*args, **kwargs):
            zkhandler = ZKHandler(self.config)
            zkhandler.connect()
            schema_version = zkhandler.read("base.schema.version")
            if schema_version is None:
                schema_version = 0
            zkhandler.schema.load(schema_version, quiet=True)

            try:
                ret = function(zkhandler, *args, **kwargs)
            finally:
                zkhandler.disconnect()
                del zkhandler

            return ret

        return connection


#
# Exceptions
#
class ZKConnectionException(Exception):
    """
    A exception when connecting to the cluster
    """

    def __init__(self, zkhandler, error=None):
        if error is not None:
            self.message = "Failed to connect to Zookeeper at {}: {}".format(
                zkhandler.coordinators(), error
            )
        else:
            self.message = "Failed to connect to Zookeeper at {}".format(
                zkhandler.coordinators()
            )
        zkhandler.disconnect()

    def __str__(self):
        return str(self.message)


#
# Handler class
#
class ZKHandler(object):
    def __init__(self, config, logger=None):
        """
        Initialize an instance of the ZKHandler class with config

        A zk_conn object will be created but not started

        A ZKSchema instance will be created
        """
        self.encoding = "utf8"
        self.coordinators = config["coordinators"]
        self.logger = logger
        self.zk_conn = KazooClient(hosts=self.coordinators)
        self._schema = ZKSchema()

    #
    # Class meta-functions
    #
    def coordinators(self):
        return str(self.coordinators)

    def log(self, message, state=""):
        if self.logger is not None:
            self.logger.out(message, state)
        else:
            print(message)

    #
    # Properties
    #
    @property
    def schema(self):
        return self._schema

    #
    # State/connection management
    #
    def listener(self, state):
        """
        Listen for KazooState changes and log accordingly.

        This function does not do anything except for log the state, and Kazoo handles the rest.
        """
        if state == KazooState.CONNECTED:
            self.log("Connection to Zookeeper resumed", state="o")
        else:
            self.log(
                "Connection to Zookeeper lost with state {}".format(state), state="w"
            )

    def connect(self, persistent=False):
        """
        Start the zk_conn object and connect to the cluster
        """
        try:
            self.zk_conn.start()
            if persistent:
                self.log("Connection to Zookeeper started", state="o")
                self.zk_conn.add_listener(self.listener)
        except Exception as e:
            raise ZKConnectionException(self, e)

    def disconnect(self, persistent=False):
        """
        Stop and close the zk_conn object and disconnect from the cluster

        The class instance may be reused later (avoids persistent connections)
        """
        self.zk_conn.stop()
        self.zk_conn.close()
        if persistent:
            self.log("Connection to Zookeeper terminated", state="o")

    #
    # Schema helper actions
    #
    def get_schema_path(self, key):
        """
        Get the Zookeeper path for {key} from the current schema based on its format.

        If {key} is a tuple of length 2, it's treated as a path plus an item instance of that path (e.g. a node, a VM, etc.).

        If {key} is a tuple of length 4, it is treated as a path plus an item instance, as well as another item instance of the subpath.

        If {key} is just a string, it's treated as a lone path (mostly used for the 'base' schema group.

        Otherwise, returns None since this is not a valid key.

        This function also handles the special case where a string that looks like an existing path (i.e. starts with '/') is passed;
        in that case it will silently return the same path back. This was mostly a migration functionality and is deprecated.
        """
        if isinstance(key, tuple):
            # This is a key tuple with both an ipath and an item
            if len(key) == 2:
                # 2-length normal tuple
                ipath, item = key
            elif len(key) == 4:
                # 4-length sub-level tuple
                ipath, item, sub_ipath, sub_item = key
                return self.schema.path(ipath, item=item) + self.schema.path(
                    sub_ipath, item=sub_item
                )
            else:
                # This is an invalid key
                return None
        elif isinstance(key, str):
            # This is a key string with just an ipath
            ipath = key
            item = None

            # This is a raw key path, used by backup/restore functionality
            if re.match(r"^/", ipath):
                return ipath
        else:
            # This is an invalid key
            return None

        return self.schema.path(ipath, item=item)

    #
    # Key Actions
    #
    def exists(self, key):
        """
        Check if a key exists
        """
        path = self.get_schema_path(key)
        if path is None:
            # This path is invalid, this is likely due to missing schema entries, so return False
            return False

        stat = self.zk_conn.exists(path)
        if stat:
            return True
        else:
            return False

    def read(self, key):
        """
        Read data from a key
        """
        try:
            path = self.get_schema_path(key)
            if path is None:
                # This path is invalid; this is likely due to missing schema entries, so return None
                return None

            res = self.zk_conn.get(path)
            return res[0].decode(self.encoding)
        except NoNodeError:
            return None

    async def read_async(self, key):
        """
        Read data from a key asynchronously
        """
        try:
            path = self.get_schema_path(key)
            if path is None:
                # This path is invalid; this is likely due to missing schema entries, so return None
                return None

            val = self.zk_conn.get_async(path)
            data = val.get()
            return data[0].decode(self.encoding)
        except NoNodeError:
            return None

    async def _read_many(self, keys):
        """
        Async runner for read_many
        """
        res = await asyncio.gather(*(self.read_async(key) for key in keys))
        return tuple(res)

    def read_many(self, keys):
        """
        Read data from several keys, asynchronously. Returns a tuple of all key values once all
        reads are complete.
        """
        return asyncio.run(self._read_many(keys))

    def write(self, kvpairs):
        """
        Create or update one or more keys' data
        """
        if type(kvpairs) is not list:
            self.log("ZKHandler error: Key-value sequence is not a list", state="e")
            return False

        transaction = self.zk_conn.transaction()

        for kvpair in kvpairs:
            if type(kvpair) is not tuple:
                self.log(
                    "ZKHandler error: Key-value pair '{}' is not a tuple".format(
                        kvpair
                    ),
                    state="e",
                )
                return False

            key = kvpair[0]
            value = kvpair[1]

            path = self.get_schema_path(key)
            if path is None:
                # This path is invalid; this is likely due to missing schema entries, so continue
                continue

            if not self.exists(key):
                # Creating a new key
                transaction.create(path, str(value).encode(self.encoding))

            else:
                # Updating an existing key
                data = self.zk_conn.get(path)
                version = data[1].version

                # Validate the expected version after the execution
                new_version = version + 1

                # Update the data
                transaction.set_data(path, str(value).encode(self.encoding))

                # Check the data
                try:
                    transaction.check(path, new_version)
                except TypeError:
                    self.log(
                        "ZKHandler error: Key '{}' does not match expected version".format(
                            path
                        ),
                        state="e",
                    )
                    return False

        try:
            transaction.commit()
            return True
        except Exception as e:
            self.log(
                "ZKHandler error: Failed to commit transaction: {}".format(e), state="e"
            )
            return False

    def delete(self, keys, recursive=True):
        """
        Delete a key or list of keys (defaults to recursive)
        """
        if type(keys) is not list:
            keys = [keys]

        for key in keys:
            if self.exists(key):
                try:
                    path = self.get_schema_path(key)
                    self.zk_conn.delete(path, recursive=recursive)
                except Exception as e:
                    self.log(
                        "ZKHandler error: Failed to delete key {}: {}".format(path, e),
                        state="e",
                    )
                    return False

        return True

    def children(self, key):
        """
        Lists all children of a key
        """
        try:
            path = self.get_schema_path(key)
            if path is None:
                raise NoNodeError

            return self.zk_conn.get_children(path)
        except NoNodeError:
            # This path is invalid; this is likely due to missing schema entries, so return None
            return None

    def rename(self, kkpairs):
        """
        Rename one or more keys to a new value
        """
        if type(kkpairs) is not list:
            self.log("ZKHandler error: Key-key sequence is not a list", state="e")
            return False

        transaction = self.zk_conn.transaction()

        def rename_element(transaction, source_path, destination_path):
            data = self.zk_conn.get(source_path)[0]
            transaction.create(destination_path, data)

            if self.children(source_path):
                for child_path in self.children(source_path):
                    child_source_path = "{}/{}".format(source_path, child_path)
                    child_destination_path = "{}/{}".format(
                        destination_path, child_path
                    )
                    rename_element(
                        transaction, child_source_path, child_destination_path
                    )

            transaction.delete(source_path)

        for kkpair in kkpairs:
            if type(kkpair) is not tuple:
                self.log(
                    "ZKHandler error: Key-key pair '{}' is not a tuple".format(kkpair),
                    state="e",
                )
                return False

            source_key = kkpair[0]
            source_path = self.get_schema_path(source_key)
            if source_path is None:
                # This path is invalid; this is likely due to missing schema entries, so continue
                continue

            destination_key = kkpair[1]
            destination_path = self.get_schema_path(destination_key)
            if destination_path is None:
                # This path is invalid; this is likely due to missing schema entries, so continue
                continue

            if not self.exists(source_key):
                self.log(
                    "ZKHander error: Source key '{}' does not exist".format(
                        source_path
                    ),
                    state="e",
                )
                return False

            if self.exists(destination_key):
                self.log(
                    "ZKHander error: Destination key '{}' already exists".format(
                        destination_path
                    ),
                    state="e",
                )
                return False

            rename_element(transaction, source_path, destination_path)

        try:
            transaction.commit()
            return True
        except Exception as e:
            self.log(
                "ZKHandler error: Failed to commit transaction: {}".format(e), state="e"
            )
            return False

    #
    # Lock actions
    #
    def readlock(self, key):
        """
        Acquires a read lock on a key
        """
        count = 1
        lock = None

        path = self.get_schema_path(key)

        while True:
            try:
                lock_id = str(uuid.uuid1())
                lock = self.zk_conn.ReadLock(path, lock_id)
                break
            except NoNodeError:
                self.log(
                    "ZKHandler warning: Failed to acquire read lock on nonexistent path {}".format(
                        path
                    ),
                    state="e",
                )
                return None
            except Exception as e:
                if count > 5:
                    self.log(
                        "ZKHandler warning: Failed to acquire read lock after 5 tries: {}".format(
                            e
                        ),
                        state="e",
                    )
                    break
                else:
                    time.sleep(0.5)
                    count += 1
                    continue

        return lock

    def writelock(self, key):
        """
        Acquires a write lock on a key
        """
        count = 1
        lock = None

        path = self.get_schema_path(key)

        while True:
            try:
                lock_id = str(uuid.uuid1())
                lock = self.zk_conn.WriteLock(path, lock_id)
                break
            except NoNodeError:
                self.log(
                    "ZKHandler warning: Failed to acquire write lock on nonexistent path {}".format(
                        path
                    ),
                    state="e",
                )
                return None
            except Exception as e:
                if count > 5:
                    self.log(
                        "ZKHandler warning: Failed to acquire write lock after 5 tries: {}".format(
                            e
                        ),
                        state="e",
                    )
                    break
                else:
                    time.sleep(0.5)
                    count += 1
                    continue

        return lock

    def exclusivelock(self, key):
        """
        Acquires an exclusive lock on a key
        """
        count = 1
        lock = None

        path = self.get_schema_path(key)

        while True:
            try:
                lock_id = str(uuid.uuid1())
                lock = self.zk_conn.Lock(path, lock_id)
                break
            except NoNodeError:
                self.log(
                    "ZKHandler warning: Failed to acquire exclusive lock on nonexistent path {}".format(
                        path
                    ),
                    state="e",
                )
                return None
            except Exception as e:
                if count > 5:
                    self.log(
                        "ZKHandler warning: Failed to acquire exclusive lock after 5 tries: {}".format(
                            e
                        ),
                        state="e",
                    )
                    break
                else:
                    time.sleep(0.5)
                    count += 1
                    continue

        return lock


#
# Schema classes
#
class ZKSchema(object):
    # Current version
    _version = 15

    # Root for doing nested keys
    _schema_root = ""

    # Primary schema definition for the current version
    _schema = {
        "version": f"{_version}",
        "root": f"{_schema_root}",
        # Base schema defining core keys; this is all that is initialized on cluster init()
        "base": {
            "root": f"{_schema_root}",
            "schema": f"{_schema_root}/schema",
            "schema.version": f"{_schema_root}/schema/version",
            "config": f"{_schema_root}/config",
            "config.maintenance": f"{_schema_root}/config/maintenance",
            "config.fence_lock": f"{_schema_root}/config/fence_lock",
            "config.primary_node": f"{_schema_root}/config/primary_node",
            "config.primary_node.sync_lock": f"{_schema_root}/config/primary_node/sync_lock",
            "config.upstream_ip": f"{_schema_root}/config/upstream_ip",
            "config.migration_target_selector": f"{_schema_root}/config/migration_target_selector",
            "logs": f"{_schema_root}/logs",
            "faults": f"{_schema_root}/faults",
            "node": f"{_schema_root}/nodes",
            "domain": f"{_schema_root}/domains",
            "network": f"{_schema_root}/networks",
            "storage": f"{_schema_root}/ceph",
            "storage.health": f"{_schema_root}/ceph/health",
            "storage.util": f"{_schema_root}/ceph/util",
            "osd": f"{_schema_root}/ceph/osds",
            "pool": f"{_schema_root}/ceph/pools",
            "volume": f"{_schema_root}/ceph/volumes",
            "snapshot": f"{_schema_root}/ceph/snapshots",
        },
        # The schema of an individual logs entry (/logs/{node_name})
        "logs": {
            "node": "",  # The root key
            "messages": "/messages",
        },
        # The schema of an individual logs entry (/logs/{id})
        "faults": {
            "id": "",  # The root key
            "last_time": "/last_time",
            "first_time": "/first_time",
            "ack_time": "/ack_time",
            "status": "/status",
            "delta": "/delta",
            "message": "/message",
        },
        # The schema of an individual node entry (/nodes/{node_name})
        "node": {
            "name": "",  # The root key
            "keepalive": "/keepalive",
            "mode": "/daemonmode",
            "data.active_schema": "/activeschema",
            "data.latest_schema": "/latestschema",
            "data.static": "/staticdata",
            "data.pvc_version": "/pvcversion",
            "running_domains": "/runningdomains",
            "count.provisioned_domains": "/domainscount",
            "count.networks": "/networkscount",
            "state.daemon": "/daemonstate",
            "state.router": "/routerstate",
            "state.domain": "/domainstate",
            "cpu.load": "/cpuload",
            "vcpu.allocated": "/vcpualloc",
            "memory.total": "/memtotal",
            "memory.used": "/memused",
            "memory.free": "/memfree",
            "memory.allocated": "/memalloc",
            "memory.provisioned": "/memprov",
            "ipmi.hostname": "/ipmihostname",
            "ipmi.username": "/ipmiusername",
            "ipmi.password": "/ipmipassword",
            "sriov": "/sriov",
            "sriov.pf": "/sriov/pf",
            "sriov.vf": "/sriov/vf",
            "monitoring.plugins": "/monitoring_plugins",
            "monitoring.data": "/monitoring_data",
            "monitoring.health": "/monitoring_health",
            "network.stats": "/network_stats",
        },
        # The schema of an individual monitoring plugin data entry (/nodes/{node_name}/monitoring_data/{plugin})
        "monitoring_plugin": {
            "name": "",  # The root key
            "last_run": "/last_run",
            "health_delta": "/health_delta",
            "message": "/message",
            "data": "/data",
            "runtime": "/runtime",
        },
        # The schema of an individual SR-IOV PF entry (/nodes/{node_name}/sriov/pf/{pf})
        "sriov_pf": {
            "phy": "",
            "mtu": "/mtu",
            "vfcount": "/vfcount",
        },  # The root key
        # The schema of an individual SR-IOV VF entry (/nodes/{node_name}/sriov/vf/{vf})
        "sriov_vf": {
            "phy": "",  # The root key
            "pf": "/pf",
            "mtu": "/mtu",
            "mac": "/mac",
            "phy_mac": "/phy_mac",
            "config": "/config",
            "config.vlan_id": "/config/vlan_id",
            "config.vlan_qos": "/config/vlan_qos",
            "config.tx_rate_min": "/config/tx_rate_min",
            "config.tx_rate_max": "/config/tx_rate_max",
            "config.spoof_check": "/config/spoof_check",
            "config.link_state": "/config/link_state",
            "config.trust": "/config/trust",
            "config.query_rss": "/config/query_rss",
            "pci": "/pci",
            "pci.domain": "/pci/domain",
            "pci.bus": "/pci/bus",
            "pci.slot": "/pci/slot",
            "pci.function": "/pci/function",
            "used": "/used",
            "used_by": "/used_by",
        },
        # The schema of an individual domain entry (/domains/{domain_uuid})
        "domain": {
            "name": "",  # The root key
            "xml": "/xml",
            "state": "/state",
            "profile": "/profile",
            "stats": "/stats",
            "node": "/node",
            "last_node": "/lastnode",
            "failed_reason": "/failedreason",
            "storage.volumes": "/rbdlist",
            "console.log": "/consolelog",
            "console.vnc": "/vnc",
            "meta.autostart": "/node_autostart",
            "meta.migrate_method": "/migration_method",
            "meta.migrate_max_downtime": "/migration_max_downtime",
            "meta.node_selector": "/node_selector",
            "meta.node_limit": "/node_limit",
            "meta.tags": "/tags",
            "migrate.sync_lock": "/migrate_sync_lock",
            "snapshots": "/snapshots",
        },
        # The schema of an individual domain tag entry (/domains/{domain}/tags/{tag})
        "tag": {
            "name": "",  # The root key
            "type": "/type",
            "protected": "/protected",
        },
        # The schema of an individual domain snapshot entry (/domains/{domain}/snapshots/{snapshot})
        "domain_snapshot": {
            "name": "",  # The root key
            "timestamp": "/timestamp",
            "xml": "/xml",
            "rbd_snapshots": "/rbdsnaplist",
        },
        # The schema of an individual network entry (/networks/{vni})
        "network": {
            "vni": "",  # The root key
            "type": "/nettype",
            "mtu": "/mtu",
            "rule": "/firewall_rules",
            "rule.in": "/firewall_rules/in",
            "rule.out": "/firewall_rules/out",
            "nameservers": "/name_servers",
            "domain": "/domain",
            "reservation": "/dhcp4_reservations",
            "lease": "/dhcp4_leases",
            "ip4.gateway": "/ip4_gateway",
            "ip4.network": "/ip4_network",
            "ip4.dhcp": "/dhcp4_flag",
            "ip4.dhcp_start": "/dhcp4_start",
            "ip4.dhcp_end": "/dhcp4_end",
            "ip6.gateway": "/ip6_gateway",
            "ip6.network": "/ip6_network",
            "ip6.dhcp": "/dhcp6_flag",
        },
        # The schema of an individual network DHCP(v4) reservation entry (/networks/{vni}/dhcp4_reservations/{mac})
        "reservation": {
            "mac": "",  # The root key
            "ip": "/ipaddr",
            "hostname": "/hostname",
        },
        # The schema of an individual network DHCP(v4) lease entry (/networks/{vni}/dhcp4_leases/{mac})
        "lease": {
            "mac": "",  # The root key
            "ip": "/ipaddr",
            "hostname": "/hostname",
            "expiry": "/expiry",
            "client_id": "/clientid",
        },
        # The schema for an individual network ACL entry (/networks/{vni}/firewall_rules/(in|out)/{acl}
        "rule": {
            "description": "",
            "rule": "/rule",
            "order": "/order",
        },  # The root key
        # The schema of an individual OSD entry (/ceph/osds/{osd_id})
        "osd": {
            "id": "",  # The root key
            "node": "/node",
            "device": "/device",
            "db_device": "/db_device",
            "fsid": "/fsid",
            "ofsid": "/fsid/osd",
            "cfsid": "/fsid/cluster",
            "lvm": "/lvm",
            "vg": "/lvm/vg",
            "lv": "/lvm/lv",
            "is_split": "/is_split",
            "stats": "/stats",
        },
        # The schema of an individual pool entry (/ceph/pools/{pool_name})
        "pool": {
            "name": "",
            "pgs": "/pgs",
            "tier": "/tier",
            "stats": "/stats",
        },  # The root key
        # The schema of an individual volume entry (/ceph/volumes/{pool_name}/{volume_name})
        "volume": {
            "name": "",
            "stats": "/stats",
        },  # The root key
        # The schema of an individual snapshot entry (/ceph/volumes/{pool_name}/{volume_name}/{snapshot_name})
        "snapshot": {
            "name": "",
            "stats": "/stats",
        },  # The root key
    }

    # Properties
    @property
    def schema_root(self):
        return self._schema_root

    @schema_root.setter
    def schema_root(self, schema_root):
        self._schema_root = schema_root

    @property
    def version(self):
        return int(self._version)

    @version.setter
    def version(self, version):
        self._version = int(version)

    @property
    def schema(self):
        return self._schema

    @schema.setter
    def schema(self, schema):
        self._schema = schema

    def __init__(self, root_path=DEFAULT_ROOT_PATH):
        self.schema_path = f"{root_path}/{SCHEMA_PATH}"

    def __repr__(self):
        return f"ZKSchema({self.version})"

    def __lt__(self, other):
        if self.version < other.version:
            return True
        else:
            return False

    def __le__(self, other):
        if self.version <= other.version:
            return True
        else:
            return False

    def __gt__(self, other):
        if self.version > other.version:
            return True
        else:
            return False

    def __ge__(self, other):
        if self.version >= other.version:
            return True
        else:
            return False

    def __eq__(self, other):
        if self.version == other.version:
            return True
        else:
            return False

    # Load the schema of a given version from a file
    def load(self, version, quiet=False):
        if not quiet:
            print(f"Loading schema version {version}")

        with open(f"{self.schema_path}/{version}.json", "r") as sfh:
            self.schema = json.load(sfh)
            self.version = self.schema.get("version")

    # Get key paths
    def path(self, ipath, item=None):
        itype, *ipath = ipath.split(".")

        if item is None:
            return self.schema.get(itype).get(".".join(ipath))
        else:
            base_path = self.schema.get("base").get(itype, None)
            if base_path is None:
                # This should only really happen for second-layer key types where the helper functions join them together
                base_path = ""

            if not ipath:
                # This is a root path
                return f"{base_path}/{item}"

            sub_path = self.schema.get(itype).get(".".join(ipath))
            if sub_path is None:
                # We didn't find the path we're looking for, so we don't want to do anything
                return None

            return f"{base_path}/{item}{sub_path}"

    # Get keys of a schema location
    def keys(self, itype=None):
        if itype is None:
            return list(self.schema.get("base").keys())
        else:
            return list(self.schema.get(itype).keys())

    # Get the active version of a cluster's schema
    def get_version(self, zkhandler):
        try:
            current_version = zkhandler.read(self.path("base.schema.version"))
        except NoNodeError:
            current_version = 0
        return current_version

    # Validate an active schema against a Zookeeper cluster
    def validate(self, zkhandler, logger=None):
        result = True

        # Walk the entire tree checking our schema
        for elem in ["base"]:
            for key in self.keys(elem):
                kpath = f"{elem}.{key}"
                if not zkhandler.zk_conn.exists(self.path(kpath)):
                    if logger is not None:
                        logger.out(f"Key not found: {self.path(kpath)}", state="w")
                    result = False

        for elem in ["node", "domain", "network", "osd", "pool"]:
            # First read all the subelements of the key class
            for child in zkhandler.zk_conn.get_children(self.path(f"base.{elem}")):
                # For each key in the schema for that particular elem
                for ikey in self.keys(elem):
                    kpath = f"{elem}.{ikey}"
                    # Validate that the key exists for that child
                    if not zkhandler.zk_conn.exists(self.path(kpath, child)):
                        if logger is not None:
                            logger.out(
                                f"Key not found: {self.path(kpath, child)}", state="w"
                            )
                        result = False

                    # Continue for child keys under network (reservation, acl)
                    if elem in ["network"] and ikey in [
                        "reservation",
                        "rule.in",
                        "rule.out",
                    ]:
                        if ikey in ["rule.in", "rule.out"]:
                            sikey = "rule"
                        else:
                            sikey = ikey
                        npath = self.path(f"{elem}.{ikey}", child)
                        for nchild in zkhandler.zk_conn.get_children(npath):
                            nkpath = f"{npath}/{nchild}"
                            for esikey in self.keys(sikey):
                                nkipath = f"{nkpath}/{esikey}"
                                if not zkhandler.zk_conn.exists(nkipath):
                                    result = False

                    # One might expect child keys under node (specifically, sriov.pf, sriov.vf,
                    # monitoring.data) to be managed here as well, but those are created
                    # automatically every time pvcnoded started and thus never need to be validated
                    # or applied.

        # These two have several children layers that must be parsed through
        for elem in ["volume"]:
            # First read all the subelements of the key class (pool layer)
            for pchild in zkhandler.zk_conn.get_children(self.path(f"base.{elem}")):
                # Finally read all the subelements of the key class (volume layer)
                for vchild in zkhandler.zk_conn.get_children(
                    self.path(f"base.{elem}") + f"/{pchild}"
                ):
                    child = f"{pchild}/{vchild}"
                    # For each key in the schema for that particular elem
                    for ikey in self.keys(elem):
                        kpath = f"{elem}.{ikey}"
                        # Validate that the key exists for that child
                        if not zkhandler.zk_conn.exists(self.path(kpath, child)):
                            if logger is not None:
                                logger.out(
                                    f"Key not found: {self.path(kpath, child)}",
                                    state="w",
                                )
                            result = False

        for elem in ["snapshot"]:
            # First read all the subelements of the key class (pool layer)
            for pchild in zkhandler.zk_conn.get_children(self.path(f"base.{elem}")):
                # Next read all the subelements of the key class (volume layer)
                for vchild in zkhandler.zk_conn.get_children(
                    self.path(f"base.{elem}") + f"/{pchild}"
                ):
                    # Finally read all the subelements of the key class (volume layer)
                    for schild in zkhandler.zk_conn.get_children(
                        self.path(f"base.{elem}") + f"/{pchild}/{vchild}"
                    ):
                        child = f"{pchild}/{vchild}/{schild}"
                        # For each key in the schema for that particular elem
                        for ikey in self.keys(elem):
                            kpath = f"{elem}.{ikey}"
                            # Validate that the key exists for that child
                            if not zkhandler.zk_conn.exists(self.path(kpath, child)):
                                if logger is not None:
                                    logger.out(
                                        f"Key not found: {self.path(kpath, child)}",
                                        state="w",
                                    )
                                result = False

        return result

    # Apply the current schema to the cluster
    def apply(self, zkhandler):
        # Walk the entire tree checking our schema
        for elem in ["base"]:
            for key in self.keys(elem):
                kpath = f"{elem}.{key}"
                if not zkhandler.zk_conn.exists(self.path(kpath)):
                    # Ensure that we create base.schema.version with the current valid version value
                    if kpath == "base.schema.version":
                        data = str(self.version)
                    else:
                        data = ""
                    zkhandler.zk_conn.create(
                        self.path(kpath), data.encode(zkhandler.encoding)
                    )

        for elem in ["node", "domain", "network", "osd", "pool"]:
            # First read all the subelements of the key class
            for child in zkhandler.zk_conn.get_children(self.path(f"base.{elem}")):
                # For each key in the schema for that particular elem
                for ikey in self.keys(elem):
                    kpath = f"{elem}.{ikey}"
                    # Validate that the key exists for that child
                    if not zkhandler.zk_conn.exists(self.path(kpath, child)):
                        if elem == "osd" and ikey == "is_split":
                            default_data = "False"
                        elif elem == "pool" and ikey == "tier":
                            default_data = "default"
                        elif elem == "domain" and ikey == "meta.migrate_max_downtime":
                            default_data = "300"
                        else:
                            default_data = ""
                        zkhandler.zk_conn.create(
                            self.path(kpath, child),
                            default_data.encode(zkhandler.encoding),
                        )

                    # Continue for child keys under network (reservation, acl)
                    if elem in ["network"] and ikey in [
                        "reservation",
                        "rule.in",
                        "rule.out",
                    ]:
                        if ikey in ["rule.in", "rule.out"]:
                            sikey = "rule"
                        else:
                            sikey = ikey
                        npath = self.path(f"{elem}.{ikey}", child)
                        for nchild in zkhandler.zk_conn.get_children(npath):
                            nkpath = f"{npath}/{nchild}"
                            for esikey in self.keys(sikey):
                                nkipath = f"{nkpath}/{esikey}"
                                if not zkhandler.zk_conn.exists(nkipath):
                                    zkhandler.zk_conn.create(
                                        nkipath, "".encode(zkhandler.encoding)
                                    )

                    # One might expect child keys under node (specifically, sriov.pf and sriov.vf) to be
                    # managed here as well, but those are created automatically every time pvcnoded starts
                    # and thus never need to be validated or applied.

        # These two have several children layers that must be parsed through
        for elem in ["volume"]:
            # First read all the subelements of the key class (pool layer)
            for pchild in zkhandler.zk_conn.get_children(self.path(f"base.{elem}")):
                # Finally read all the subelements of the key class (volume layer)
                for vchild in zkhandler.zk_conn.get_children(
                    self.path(f"base.{elem}") + f"/{pchild}"
                ):
                    child = f"{pchild}/{vchild}"
                    # For each key in the schema for that particular elem
                    for ikey in self.keys(elem):
                        kpath = f"{elem}.{ikey}"
                        # Validate that the key exists for that child
                        if not zkhandler.zk_conn.exists(self.path(kpath, child)):
                            zkhandler.zk_conn.create(
                                self.path(kpath, child), "".encode(zkhandler.encoding)
                            )

        for elem in ["snapshot"]:
            # First read all the subelements of the key class (pool layer)
            for pchild in zkhandler.zk_conn.get_children(self.path(f"base.{elem}")):
                # Next read all the subelements of the key class (volume layer)
                for vchild in zkhandler.zk_conn.get_children(
                    self.path(f"base.{elem}") + f"/{pchild}"
                ):
                    # Finally read all the subelements of the key class (volume layer)
                    for schild in zkhandler.zk_conn.get_children(
                        self.path(f"base.{elem}") + f"/{pchild}/{vchild}"
                    ):
                        child = f"{pchild}/{vchild}/{schild}"
                        # For each key in the schema for that particular elem
                        for ikey in self.keys(elem):
                            kpath = f"{elem}.{ikey}"
                            # Validate that the key exists for that child
                            if not zkhandler.zk_conn.exists(self.path(kpath, child)):
                                zkhandler.zk_conn.create(
                                    self.path(kpath, child),
                                    "".encode(zkhandler.encoding),
                                )

    # Migrate key diffs
    def run_migrate(self, zkhandler, changes):
        diff_add = changes["add"]
        diff_remove = changes["remove"]
        diff_rename = changes["rename"]
        add_tasks = list()
        for key in diff_add.keys():
            add_tasks.append((diff_add[key], ""))
        remove_tasks = list()
        for key in diff_remove.keys():
            remove_tasks.append(diff_remove[key])
        rename_tasks = list()
        for key in diff_rename.keys():
            rename_tasks.append((diff_rename[key]["from"], diff_rename[key]["to"]))

        zkhandler.write(add_tasks)
        zkhandler.delete(remove_tasks)
        zkhandler.rename(rename_tasks)

    # Migrate from older to newer schema
    def migrate(self, zkhandler, new_version):
        # Determine the versions in between
        versions = self.find_all(start=self.version, end=new_version)
        if versions is None:
            return

        for version in versions:
            # Create a new schema at that version
            zkschema_new = ZKSchema()
            zkschema_new.load(version)
            # Get a list of changes
            changes = ZKSchema.key_diff(self, zkschema_new)
            # Apply those changes
            self.run_migrate(zkhandler, changes)

    # Rollback from newer to older schema
    def rollback(self, zkhandler, old_version):
        # Determine the versions in between
        versions = self.find_all(start=old_version - 1, end=self.version - 1)
        if versions is None:
            return

        versions.reverse()

        for version in versions:
            # Create a new schema at that version
            zkschema_old = ZKSchema()
            zkschema_old.load(version)
            # Get a list of changes
            changes = ZKSchema.key_diff(self, zkschema_old)
            # Apply those changes
            self.run_migrate(zkhandler, changes)

    # Write the latest schema to a file
    def write(self):
        schema_file = f"{self.schema_path}/{self._version}.json"
        with open(schema_file, "w") as sfh:
            json.dump(self._schema, sfh)

    @classmethod
    def key_diff(cls, schema_a, schema_b):
        # schema_a = current
        # schema_b = new

        diff_add = dict()
        diff_remove = dict()
        diff_rename = dict()

        # Parse through each core element
        for elem in [
            "base",
            "node",
            "domain",
            "network",
            "osd",
            "pool",
            "volume",
            "snapshot",
        ]:
            set_a = set(schema_a.keys(elem))
            set_b = set(schema_b.keys(elem))
            diff_keys = set_a ^ set_b

            for item in diff_keys:
                elem_item = f"{elem}.{item}"
                if item not in schema_a.keys(elem) and item in schema_b.keys(elem):
                    diff_add[elem_item] = schema_b.path(elem_item)
                if item in schema_a.keys(elem) and item not in schema_b.keys(elem):
                    diff_remove[elem_item] = schema_a.path(elem_item)

            for item in set_b:
                elem_item = f"{elem}.{item}"
                if (
                    schema_a.path(elem_item) is not None
                    and schema_b.path(elem_item) is not None
                    and schema_a.path(elem_item) != schema_b.path(elem_item)
                ):
                    diff_rename[elem_item] = {
                        "from": schema_a.path(elem_item),
                        "to": schema_b.path(elem_item),
                    }

        return {"add": diff_add, "remove": diff_remove, "rename": diff_rename}

    # Static methods for reading information from the files
    def find_all(self, start=0, end=None):
        versions = list()
        for version in os.listdir(self.schema_path):
            sequence_id = int(version.split(".")[0])
            if end is None:
                if sequence_id > start:
                    versions.append(sequence_id)
            else:
                if sequence_id > start and sequence_id <= end:
                    versions.append(sequence_id)
        if len(versions) > 0:
            return versions
        else:
            return None

    def find_latest(self):
        latest_version = 0
        for version in os.listdir(self.schema_path):
            sequence_id = int(version.split(".")[0])
            if sequence_id > latest_version:
                latest_version = sequence_id
        return latest_version

    # Load in the schema of the current cluster
    @classmethod
    def load_current(cls, zkhandler):
        new_instance = cls()
        version = new_instance.get_version(zkhandler)
        new_instance.load(version)
        return new_instance