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Diffstat (limited to '.venv/lib/python3.12/site-packages/dns/versioned.py')
| -rw-r--r-- | .venv/lib/python3.12/site-packages/dns/versioned.py | 318 |
1 files changed, 318 insertions, 0 deletions
diff --git a/.venv/lib/python3.12/site-packages/dns/versioned.py b/.venv/lib/python3.12/site-packages/dns/versioned.py new file mode 100644 index 00000000..fd78e674 --- /dev/null +++ b/.venv/lib/python3.12/site-packages/dns/versioned.py @@ -0,0 +1,318 @@ +# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license + +"""DNS Versioned Zones.""" + +import collections +import threading +from typing import Callable, Deque, Optional, Set, Union + +import dns.exception +import dns.immutable +import dns.name +import dns.node +import dns.rdataclass +import dns.rdataset +import dns.rdatatype +import dns.rdtypes.ANY.SOA +import dns.zone + + +class UseTransaction(dns.exception.DNSException): + """To alter a versioned zone, use a transaction.""" + + +# Backwards compatibility +Node = dns.zone.VersionedNode +ImmutableNode = dns.zone.ImmutableVersionedNode +Version = dns.zone.Version +WritableVersion = dns.zone.WritableVersion +ImmutableVersion = dns.zone.ImmutableVersion +Transaction = dns.zone.Transaction + + +class Zone(dns.zone.Zone): # lgtm[py/missing-equals] + __slots__ = [ + "_versions", + "_versions_lock", + "_write_txn", + "_write_waiters", + "_write_event", + "_pruning_policy", + "_readers", + ] + + node_factory = Node + + def __init__( + self, + origin: Optional[Union[dns.name.Name, str]], + rdclass: dns.rdataclass.RdataClass = dns.rdataclass.IN, + relativize: bool = True, + pruning_policy: Optional[Callable[["Zone", Version], Optional[bool]]] = None, + ): + """Initialize a versioned zone object. + + *origin* is the origin of the zone. It may be a ``dns.name.Name``, + a ``str``, or ``None``. If ``None``, then the zone's origin will + be set by the first ``$ORIGIN`` line in a zone file. + + *rdclass*, an ``int``, the zone's rdata class; the default is class IN. + + *relativize*, a ``bool``, determine's whether domain names are + relativized to the zone's origin. The default is ``True``. + + *pruning policy*, a function taking a ``Zone`` and a ``Version`` and returning + a ``bool``, or ``None``. Should the version be pruned? If ``None``, + the default policy, which retains one version is used. + """ + super().__init__(origin, rdclass, relativize) + self._versions: Deque[Version] = collections.deque() + self._version_lock = threading.Lock() + if pruning_policy is None: + self._pruning_policy = self._default_pruning_policy + else: + self._pruning_policy = pruning_policy + self._write_txn: Optional[Transaction] = None + self._write_event: Optional[threading.Event] = None + self._write_waiters: Deque[threading.Event] = collections.deque() + self._readers: Set[Transaction] = set() + self._commit_version_unlocked( + None, WritableVersion(self, replacement=True), origin + ) + + def reader( + self, id: Optional[int] = None, serial: Optional[int] = None + ) -> Transaction: # pylint: disable=arguments-differ + if id is not None and serial is not None: + raise ValueError("cannot specify both id and serial") + with self._version_lock: + if id is not None: + version = None + for v in reversed(self._versions): + if v.id == id: + version = v + break + if version is None: + raise KeyError("version not found") + elif serial is not None: + if self.relativize: + oname = dns.name.empty + else: + assert self.origin is not None + oname = self.origin + version = None + for v in reversed(self._versions): + n = v.nodes.get(oname) + if n: + rds = n.get_rdataset(self.rdclass, dns.rdatatype.SOA) + if rds and rds[0].serial == serial: + version = v + break + if version is None: + raise KeyError("serial not found") + else: + version = self._versions[-1] + txn = Transaction(self, False, version) + self._readers.add(txn) + return txn + + def writer(self, replacement: bool = False) -> Transaction: + event = None + while True: + with self._version_lock: + # Checking event == self._write_event ensures that either + # no one was waiting before we got lucky and found no write + # txn, or we were the one who was waiting and got woken up. + # This prevents "taking cuts" when creating a write txn. + if self._write_txn is None and event == self._write_event: + # Creating the transaction defers version setup + # (i.e. copying the nodes dictionary) until we + # give up the lock, so that we hold the lock as + # short a time as possible. This is why we call + # _setup_version() below. + self._write_txn = Transaction( + self, replacement, make_immutable=True + ) + # give up our exclusive right to make a Transaction + self._write_event = None + break + # Someone else is writing already, so we will have to + # wait, but we want to do the actual wait outside the + # lock. + event = threading.Event() + self._write_waiters.append(event) + # wait (note we gave up the lock!) + # + # We only wake one sleeper at a time, so it's important + # that no event waiter can exit this method (e.g. via + # cancellation) without returning a transaction or waking + # someone else up. + # + # This is not a problem with Threading module threads as + # they cannot be canceled, but could be an issue with trio + # tasks when we do the async version of writer(). + # I.e. we'd need to do something like: + # + # try: + # event.wait() + # except trio.Cancelled: + # with self._version_lock: + # self._maybe_wakeup_one_waiter_unlocked() + # raise + # + event.wait() + # Do the deferred version setup. + self._write_txn._setup_version() + return self._write_txn + + def _maybe_wakeup_one_waiter_unlocked(self): + if len(self._write_waiters) > 0: + self._write_event = self._write_waiters.popleft() + self._write_event.set() + + # pylint: disable=unused-argument + def _default_pruning_policy(self, zone, version): + return True + + # pylint: enable=unused-argument + + def _prune_versions_unlocked(self): + assert len(self._versions) > 0 + # Don't ever prune a version greater than or equal to one that + # a reader has open. This pins versions in memory while the + # reader is open, and importantly lets the reader open a txn on + # a successor version (e.g. if generating an IXFR). + # + # Note our definition of least_kept also ensures we do not try to + # delete the greatest version. + if len(self._readers) > 0: + least_kept = min(txn.version.id for txn in self._readers) + else: + least_kept = self._versions[-1].id + while self._versions[0].id < least_kept and self._pruning_policy( + self, self._versions[0] + ): + self._versions.popleft() + + def set_max_versions(self, max_versions: Optional[int]) -> None: + """Set a pruning policy that retains up to the specified number + of versions + """ + if max_versions is not None and max_versions < 1: + raise ValueError("max versions must be at least 1") + if max_versions is None: + + def policy(zone, _): # pylint: disable=unused-argument + return False + + else: + + def policy(zone, _): + return len(zone._versions) > max_versions + + self.set_pruning_policy(policy) + + def set_pruning_policy( + self, policy: Optional[Callable[["Zone", Version], Optional[bool]]] + ) -> None: + """Set the pruning policy for the zone. + + The *policy* function takes a `Version` and returns `True` if + the version should be pruned, and `False` otherwise. `None` + may also be specified for policy, in which case the default policy + is used. + + Pruning checking proceeds from the least version and the first + time the function returns `False`, the checking stops. I.e. the + retained versions are always a consecutive sequence. + """ + if policy is None: + policy = self._default_pruning_policy + with self._version_lock: + self._pruning_policy = policy + self._prune_versions_unlocked() + + def _end_read(self, txn): + with self._version_lock: + self._readers.remove(txn) + self._prune_versions_unlocked() + + def _end_write_unlocked(self, txn): + assert self._write_txn == txn + self._write_txn = None + self._maybe_wakeup_one_waiter_unlocked() + + def _end_write(self, txn): + with self._version_lock: + self._end_write_unlocked(txn) + + def _commit_version_unlocked(self, txn, version, origin): + self._versions.append(version) + self._prune_versions_unlocked() + self.nodes = version.nodes + if self.origin is None: + self.origin = origin + # txn can be None in __init__ when we make the empty version. + if txn is not None: + self._end_write_unlocked(txn) + + def _commit_version(self, txn, version, origin): + with self._version_lock: + self._commit_version_unlocked(txn, version, origin) + + def _get_next_version_id(self): + if len(self._versions) > 0: + id = self._versions[-1].id + 1 + else: + id = 1 + return id + + def find_node( + self, name: Union[dns.name.Name, str], create: bool = False + ) -> dns.node.Node: + if create: + raise UseTransaction + return super().find_node(name) + + def delete_node(self, name: Union[dns.name.Name, str]) -> None: + raise UseTransaction + + def find_rdataset( + self, + name: Union[dns.name.Name, str], + rdtype: Union[dns.rdatatype.RdataType, str], + covers: Union[dns.rdatatype.RdataType, str] = dns.rdatatype.NONE, + create: bool = False, + ) -> dns.rdataset.Rdataset: + if create: + raise UseTransaction + rdataset = super().find_rdataset(name, rdtype, covers) + return dns.rdataset.ImmutableRdataset(rdataset) + + def get_rdataset( + self, + name: Union[dns.name.Name, str], + rdtype: Union[dns.rdatatype.RdataType, str], + covers: Union[dns.rdatatype.RdataType, str] = dns.rdatatype.NONE, + create: bool = False, + ) -> Optional[dns.rdataset.Rdataset]: + if create: + raise UseTransaction + rdataset = super().get_rdataset(name, rdtype, covers) + if rdataset is not None: + return dns.rdataset.ImmutableRdataset(rdataset) + else: + return None + + def delete_rdataset( + self, + name: Union[dns.name.Name, str], + rdtype: Union[dns.rdatatype.RdataType, str], + covers: Union[dns.rdatatype.RdataType, str] = dns.rdatatype.NONE, + ) -> None: + raise UseTransaction + + def replace_rdataset( + self, name: Union[dns.name.Name, str], replacement: dns.rdataset.Rdataset + ) -> None: + raise UseTransaction |