aiodns provides a simple way for doing asynchronous DNS resolutions using pycares.
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.
The API is pretty simple, the following 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 ofasyncio.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 documentation for 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). Whilequery()always performs a request to a DNS server,gethostbyname()first looks into/etc/hostsand thus can resolve local hostnames (such aslocalhost). Please check the documentation for the result fields. The actual result of the call is aasyncio.Future.gethostbyaddr(name): Make a reverse lookup for an address.cancel(): Cancel all pending DNS queries. All futures will getDNSErrorexception set, withARES_ECANCELLEDerrno.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.
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('example.com', 'A')
# resolver.close() is called automatically when exiting the contextImportant: 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.
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.
To run the test suite: python tests.py
Saúl Ibarra Corretgé <s@saghul.net>
aiodns uses the MIT license, check LICENSE file.
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 :-)