Class OverrideResolver

python/python3/tornado/netutil.py:539–578

Wraps a resolver with a mapping of overrides. This can be used to make local DNS changes (e.g. for testing) without modifying system-wide settings. The mapping can be in three formats:: { # Hostname to host or ip "example.com": "127.0.1.1",

class OverrideResolver(Resolver):
    """Wraps a resolver with a mapping of overrides.

    This can be used to make local DNS changes (e.g. for testing)
    without modifying system-wide settings.

    The mapping can be in three formats::

        {
            # Hostname to host or ip
            "example.com": "127.0.1.1",

            # Host+port to host+port
            ("login.example.com", 443): ("localhost", 1443),

            # Host+port+address family to host+port
            ("login.example.com", 443, socket.AF_INET6): ("::1", 1443),
        }

    .. versionchanged:: 5.0
       Added support for host-port-family triplets.
    """

    def initialize(self, resolver: Resolver, mapping: dict) -> None:
        self.resolver = resolver
        self.mapping = mapping

    def close(self) -> None:
        self.resolver.close()

    def resolve(
        self, host: str, port: int, family: socket.AddressFamily = socket.AF_UNSPEC
    ) -> Awaitable[List[Tuple[int, Any]]]:
        if (host, port, family) in self.mapping:
            host, port = self.mapping[(host, port, family)]
        elif (host, port) in self.mapping:
            host, port = self.mapping[(host, port)]
        elif host in self.mapping:
            host = self.mapping[host]
        return self.resolver.resolve(host, port, family)


# These are the keyword arguments to ssl.wrap_socket that must be translated