aiodns (original) (raw)

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

Example

import asyncio
import aiodns

loop = asyncio.get_event_loop()
resolver = aiodns.DNSResolver(loop=loop)

async def query(name, query_type):
    return await resolver.query(name, query_type)

coro = query('google.com', 'A')
result = loop.run_until_complete(coro)

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

API

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

• query(host, type): Do a DNS resolution of the given type for the given hostname. It returns an instance of asyncio.Future. The actual result of the DNS query is taken directly from pycares. As of version 1.0.0 of aiodns (and pycares, for that matter) results are always namedtuple-like objects with different attributes. Please check the documentationfor the result fields.
• gethostbyname(host, socket_family): Do a DNS resolution for the given hostname and the desired type of address family (i.e. socket.AF_INET). While query() always performs a request to a DNS server,gethostbyname() first looks into /etc/hosts and thus can resolve local hostnames (such as localhost). Please check the documentationfor the result fields. The actual result of the call is a asyncio.Future.
• gethostbyaddr(name): Make a reverse lookup for an address.
• cancel(): Cancel all pending DNS queries. All futures will get DNSError exception set, withARES_ECANCELLED errno.

Note for Windows users

This library requires the use of an asyncio.SelectorEventLoop on Windowsonly 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 defaultProactorEventLoop 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 doesnot 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 tests.py

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 :-)