Simple DNS resolver for asyncio

aiodns provides a simple way for doing asynchronous DNS resolutions using pycares.

Example

import asyncio
import aiodns

async def main():
    resolver = aiodns.DNSResolver()
    result = await resolver.query_dns('google.com', 'A')
    for record in result.answer:
        print(record.data.addr)

asyncio.run(main())

The following query types are supported: A, AAAA, ANY, CAA, CNAME, MX, NAPTR, NS, PTR, SOA, SRV, TXT.

API

The API is pretty simple, the following functions are provided in the DNSResolver class:

• query_dns(host, type): Do a DNS resolution of the given type for the given hostname. It returns an instance of asyncio.Future. The result is a pycares.DNSResult object with answer, authority, and additional attributes containing lists of pycares.DNSRecord objects. Each record has type, ttl, and data attributes. Check the pycares documentation for details on the data attributes for each record type.
• query(host, type): Deprecated - use query_dns() instead. This method returns results in a legacy format compatible with aiodns 3.x for backward compatibility.
• gethostbyname(host, socket_family): Deprecated - use getaddrinfo() instead. Do a DNS resolution for the given hostname and the desired type of address family (i.e. socket.AF_INET). The actual result of the call is a asyncio.Future.
• gethostbyaddr(name): Make a reverse lookup for an address.
• getaddrinfo(host, family, port, proto, type, flags): Resolve a host and port into a list of address info entries.
• getnameinfo(sockaddr, flags): Resolve a socket address to a host and port.
• cancel(): Cancel all pending DNS queries. All futures will get DNSError exception set, with ARES_ECANCELLED errno.
• close(): Close the resolver. This releases all resources and cancels any pending queries. It must be called when the resolver is no longer needed (e.g., application shutdown). The resolver should only be closed from the event loop that created the resolver.

Migrating from aiodns 3.x

aiodns 4.x introduces a new query_dns() method that returns native pycares 5.x result types. See the pycares documentation for details on the result types. The old query() method is deprecated but continues to work for backward compatibility.

# Old API (deprecated)
result = await resolver.query('example.com', 'MX')
for record in result:
    print(record.host, record.priority)

# New API (recommended)
result = await resolver.query_dns('example.com', 'MX')
for record in result.answer:
    print(record.data.exchange, record.data.priority)

Future migration to aiodns 5.x

The temporary query_dns() naming allows gradual migration without breaking changes:

Version	query()	query_dns()
4.x	Deprecated, returns compat types	New API, returns pycares 5.x types
5.x	New API, returns pycares 5.x types	Alias to query() for back compat

In aiodns 5.x, query() will become the primary API returning native pycares 5.x types, and query_dns() will remain as an alias for backward compatibility. This allows downstream projects to migrate at their own pace.

Async Context Manager Support

While not recommended for typical use cases, DNSResolver can be used as an async context manager for scenarios where automatic cleanup is desired:

async with aiodns.DNSResolver() as resolver:
    result = await resolver.query_dns('example.com', 'A')
    # resolver.close() is called automatically when exiting the context

Important: This pattern is discouraged for most applications because DNSResolver instances are designed to be long-lived and reused for many queries. Creating and destroying resolvers frequently adds unnecessary overhead. Use the context manager pattern only when you specifically need automatic cleanup for short-lived resolver instances, such as in tests or one-off scripts.

Note for Windows users

This library requires the use of an asyncio.SelectorEventLoop or winloop on Windows only when using a custom build of pycares that links against a system- provided c-ares library without thread-safety support. This is because non-thread-safe builds of c-ares are incompatible with the default ProactorEventLoop on Windows.

If you're using the official prebuilt pycares wheels on PyPI (version 4.7.0 or later), which include a thread-safe version of c-ares, this limitation does not apply and can be safely ignored.

The default event loop can be changed as follows (do this very early in your application):

asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())

This may have other implications for the rest of your codebase, so make sure to test thoroughly.

Running the test suite

To run the test suite: python -m pytest tests/

Author

Saúl Ibarra Corretgé <s@saghul.net>

License

aiodns uses the MIT license, check LICENSE file.

Contributing

If you'd like to contribute, fork the project, make a patch and send a pull request. Have a look at the surrounding code and please, make yours look alike :-)