Synchronous Python implementation of the Happy Eyeballs Algorithm described in RFC 6555. Provided with a single file and dead-simple API to allow easy vendoring and integration into other projects.
When a server's IPv4 path and protocol are working, but the server's IPv6 path and protocol are not working, a dual-stack client application experiences significant connection delay compared to an IPv4-only client. This is undesirable because it causes the dual- stack client to have a worse user experience. This document specifies requirements for algorithms that reduce this user-visible delay and provides an algorithm.
$ python -m pip install rfc6555
The main API for the rfc6555 module is via rfc6555.create_connection() which
functions identically to socket.create_connection() with the same arguments.
This function will automatically fall back on a socket.create_connection() call if
RFC 6555 is not supported (for instance on platforms not capable of IPv6) or if
RFC 6555 is disabled via setting rfc6555.RFC6555_ENABLED equal to False.
IMPORTANT: Caching is NOT thread-safe by default. If you require thread-safe caching
one should create their own implementation of rfc6555._RFC6555CacheManager object that
is thread-safe and assign an instance to rfc6555.cache.
import rfc6555 sock = rfc6555.create_connection(('www.google.com', 80), timeout=10, source_address=('::1', 0)) # This will disable the Happy Eyeballs algorithm for future # calls to create_connection() rfc6555.RFC6555_ENABLED = False # Use this to set a different duration for cache entries. rfc6555.cache.validity_duration = 10 # 10 second validity time. # Use this to disable caching. rfc6555.cache.enabled = False
This module supports Python 2.7 or newer and supports all major platforms.
Additionally if you have selectors2>=2.0.0 installed this module will
also support Jython in addition to CPython.
The rfc6555 package is released under the Apache-2.0 license.
See full license text in LICENSE file for more information.