_dns – DNS resolution utilities¶
This module contains a few experimental utilities to interact with the DNS server before performing a connection.
This module is experimental and its interface could change in the future, without warning or respect for the version scheme. It is provided here to allow experimentation before making it more stable.
This module depends on the dnspython package. The package is currently not installed automatically as a Psycopg dependency and must be installed manually:
$ pip install "dnspython >= 2.1"
- async psycopg._dns.resolve_hostaddr_async(params)¶
Perform async DNS lookup of the hosts and return a new params dict.
hostparam is present but not
hostname, resolve the host addresses dynamically.
The function may change the input
portto allow connecting without further DNS lookups, eventually removing hosts that are not resolved, keeping the lists of hosts and ports consistent.
OperationalErrorif connection is not possible (e.g. no host resolve, inconsistent lists length).
See the PostgreSQL docs for explanation of how these params are used, and how they support multiple entries.
This function currently doesn’t handle the
import psycopg._dns # not imported automatically class AsyncDnsConnection(psycopg.AsyncConnection): @classmethod async def _get_connection_params(cls, conninfo, **kwargs): params = await super()._get_connection_params(conninfo, **kwargs) params = await psycopg._dns.resolve_hostaddr_async(params) return params
Apply SRV DNS lookup as defined in RFC 2782.
- Return type
An updated list of connection parameters.
For every host defined in the
params["host"]list (comma-separated), perform SRV lookup if the host is in the form
_Service._Proto.Target. If lookup is successful, return a params dict with hosts and ports replaced with the looked-up entries.
OperationalErrorif no lookup is successful and no host (looked up or unchanged) could be returned.
In addition to the rules defined by RFC 2782 about the host name pattern, perform SRV lookup also if the the port is the string
This is an experimental functionality.
import psycopg._dns # not imported automatically class SrvCognizantConnection(psycopg.Connection): @classmethod def _get_connection_params(cls, conninfo, **kwargs): params = super()._get_connection_params(conninfo, **kwargs) params = psycopg._dns.resolve_srv(params) return params # The name will be resolved to db1.example.com cnn = SrvCognizantConnection.connect("host=_postgres._tcp.db.psycopg.org")
- async psycopg._dns.resolve_srv_async(params)¶
Async equivalent of
- classmethod Connection._get_connection_params(conninfo, **kwargs)¶
Manipulate connection parameters before connecting.
- Return type
Connection arguments merged and eventually modified, in a format similar to
This is an experimental method.
This method is a subclass hook allowing to manipulate the connection parameters before performing the connection. Make sure to call the
super()implementation before further manipulation of the arguments:
@classmethod def _get_connection_params(cls, conninfo, **kwargs): params = super()._get_connection_params(conninfo, **kwargs) # do something with the params return params