275 lines
9.8 KiB
Python
275 lines
9.8 KiB
Python
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import asyncio
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import socket
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import weakref
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from typing import Any, Dict, Final, List, Optional, Tuple, Type, Union
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from .abc import AbstractResolver, ResolveResult
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__all__ = ("ThreadedResolver", "AsyncResolver", "DefaultResolver")
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try:
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import aiodns
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aiodns_default = hasattr(aiodns.DNSResolver, "getaddrinfo")
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except ImportError: # pragma: no cover
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aiodns = None # type: ignore[assignment]
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aiodns_default = False
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_NUMERIC_SOCKET_FLAGS = socket.AI_NUMERICHOST | socket.AI_NUMERICSERV
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_NAME_SOCKET_FLAGS = socket.NI_NUMERICHOST | socket.NI_NUMERICSERV
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_AI_ADDRCONFIG = socket.AI_ADDRCONFIG
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if hasattr(socket, "AI_MASK"):
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_AI_ADDRCONFIG &= socket.AI_MASK
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class ThreadedResolver(AbstractResolver):
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"""Threaded resolver.
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Uses an Executor for synchronous getaddrinfo() calls.
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concurrent.futures.ThreadPoolExecutor is used by default.
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"""
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def __init__(self, loop: Optional[asyncio.AbstractEventLoop] = None) -> None:
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self._loop = loop or asyncio.get_running_loop()
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async def resolve(
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self, host: str, port: int = 0, family: socket.AddressFamily = socket.AF_INET
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) -> List[ResolveResult]:
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infos = await self._loop.getaddrinfo(
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host,
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port,
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type=socket.SOCK_STREAM,
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family=family,
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flags=_AI_ADDRCONFIG,
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)
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hosts: List[ResolveResult] = []
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for family, _, proto, _, address in infos:
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if family == socket.AF_INET6:
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if len(address) < 3:
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# IPv6 is not supported by Python build,
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# or IPv6 is not enabled in the host
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continue
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if address[3]:
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# This is essential for link-local IPv6 addresses.
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# LL IPv6 is a VERY rare case. Strictly speaking, we should use
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# getnameinfo() unconditionally, but performance makes sense.
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resolved_host, _port = await self._loop.getnameinfo(
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address, _NAME_SOCKET_FLAGS
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)
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port = int(_port)
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else:
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resolved_host, port = address[:2]
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else: # IPv4
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assert family == socket.AF_INET
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resolved_host, port = address # type: ignore[misc]
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hosts.append(
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ResolveResult(
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hostname=host,
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host=resolved_host,
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port=port,
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family=family,
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proto=proto,
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flags=_NUMERIC_SOCKET_FLAGS,
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)
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)
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return hosts
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async def close(self) -> None:
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pass
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class AsyncResolver(AbstractResolver):
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"""Use the `aiodns` package to make asynchronous DNS lookups"""
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def __init__(
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self,
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loop: Optional[asyncio.AbstractEventLoop] = None,
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*args: Any,
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**kwargs: Any,
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) -> None:
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if aiodns is None:
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raise RuntimeError("Resolver requires aiodns library")
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self._loop = loop or asyncio.get_running_loop()
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self._manager: Optional[_DNSResolverManager] = None
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# If custom args are provided, create a dedicated resolver instance
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# This means each AsyncResolver with custom args gets its own
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# aiodns.DNSResolver instance
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if args or kwargs:
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self._resolver = aiodns.DNSResolver(*args, **kwargs)
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return
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# Use the shared resolver from the manager for default arguments
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self._manager = _DNSResolverManager()
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self._resolver = self._manager.get_resolver(self, self._loop)
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if not hasattr(self._resolver, "gethostbyname"):
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# aiodns 1.1 is not available, fallback to DNSResolver.query
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self.resolve = self._resolve_with_query # type: ignore
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async def resolve(
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self, host: str, port: int = 0, family: socket.AddressFamily = socket.AF_INET
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) -> List[ResolveResult]:
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try:
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resp = await self._resolver.getaddrinfo(
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host,
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port=port,
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type=socket.SOCK_STREAM,
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family=family,
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flags=_AI_ADDRCONFIG,
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)
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except aiodns.error.DNSError as exc:
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msg = exc.args[1] if len(exc.args) >= 1 else "DNS lookup failed"
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raise OSError(None, msg) from exc
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hosts: List[ResolveResult] = []
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for node in resp.nodes:
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address: Union[Tuple[bytes, int], Tuple[bytes, int, int, int]] = node.addr
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family = node.family
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if family == socket.AF_INET6:
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if len(address) > 3 and address[3]:
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# This is essential for link-local IPv6 addresses.
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# LL IPv6 is a VERY rare case. Strictly speaking, we should use
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# getnameinfo() unconditionally, but performance makes sense.
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result = await self._resolver.getnameinfo(
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(address[0].decode("ascii"), *address[1:]),
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_NAME_SOCKET_FLAGS,
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)
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resolved_host = result.node
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else:
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resolved_host = address[0].decode("ascii")
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port = address[1]
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else: # IPv4
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assert family == socket.AF_INET
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resolved_host = address[0].decode("ascii")
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port = address[1]
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hosts.append(
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ResolveResult(
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hostname=host,
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host=resolved_host,
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port=port,
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family=family,
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proto=0,
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flags=_NUMERIC_SOCKET_FLAGS,
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)
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)
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if not hosts:
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raise OSError(None, "DNS lookup failed")
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return hosts
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async def _resolve_with_query(
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self, host: str, port: int = 0, family: int = socket.AF_INET
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) -> List[Dict[str, Any]]:
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qtype: Final = "AAAA" if family == socket.AF_INET6 else "A"
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try:
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resp = await self._resolver.query(host, qtype)
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except aiodns.error.DNSError as exc:
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msg = exc.args[1] if len(exc.args) >= 1 else "DNS lookup failed"
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raise OSError(None, msg) from exc
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hosts = []
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for rr in resp:
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hosts.append(
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{
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"hostname": host,
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"host": rr.host,
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"port": port,
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"family": family,
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"proto": 0,
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"flags": socket.AI_NUMERICHOST,
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}
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)
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if not hosts:
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raise OSError(None, "DNS lookup failed")
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return hosts
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async def close(self) -> None:
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if self._manager:
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# Release the resolver from the manager if using the shared resolver
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self._manager.release_resolver(self, self._loop)
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self._manager = None # Clear reference to manager
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self._resolver = None # type: ignore[assignment] # Clear reference to resolver
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return
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# Otherwise cancel our dedicated resolver
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if self._resolver is not None:
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self._resolver.cancel()
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self._resolver = None # type: ignore[assignment] # Clear reference
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class _DNSResolverManager:
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"""Manager for aiodns.DNSResolver objects.
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This class manages shared aiodns.DNSResolver instances
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with no custom arguments across different event loops.
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"""
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_instance: Optional["_DNSResolverManager"] = None
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def __new__(cls) -> "_DNSResolverManager":
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if cls._instance is None:
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cls._instance = super().__new__(cls)
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cls._instance._init()
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return cls._instance
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def _init(self) -> None:
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# Use WeakKeyDictionary to allow event loops to be garbage collected
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self._loop_data: weakref.WeakKeyDictionary[
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asyncio.AbstractEventLoop,
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tuple["aiodns.DNSResolver", weakref.WeakSet["AsyncResolver"]],
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] = weakref.WeakKeyDictionary()
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def get_resolver(
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self, client: "AsyncResolver", loop: asyncio.AbstractEventLoop
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) -> "aiodns.DNSResolver":
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"""Get or create the shared aiodns.DNSResolver instance for a specific event loop.
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Args:
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client: The AsyncResolver instance requesting the resolver.
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This is required to track resolver usage.
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loop: The event loop to use for the resolver.
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"""
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# Create a new resolver and client set for this loop if it doesn't exist
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if loop not in self._loop_data:
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resolver = aiodns.DNSResolver(loop=loop)
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client_set: weakref.WeakSet["AsyncResolver"] = weakref.WeakSet()
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self._loop_data[loop] = (resolver, client_set)
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else:
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# Get the existing resolver and client set
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resolver, client_set = self._loop_data[loop]
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# Register this client with the loop
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client_set.add(client)
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return resolver
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def release_resolver(
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self, client: "AsyncResolver", loop: asyncio.AbstractEventLoop
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) -> None:
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"""Release the resolver for an AsyncResolver client when it's closed.
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Args:
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client: The AsyncResolver instance to release.
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loop: The event loop the resolver was using.
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"""
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# Remove client from its loop's tracking
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current_loop_data = self._loop_data.get(loop)
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if current_loop_data is None:
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return
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resolver, client_set = current_loop_data
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client_set.discard(client)
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# If no more clients for this loop, cancel and remove its resolver
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if not client_set:
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if resolver is not None:
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resolver.cancel()
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del self._loop_data[loop]
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_DefaultType = Type[Union[AsyncResolver, ThreadedResolver]]
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DefaultResolver: _DefaultType = AsyncResolver if aiodns_default else ThreadedResolver
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