happy_eyeballs_gevent.py

import gevent
import gevent.pool
import gevent.event
import gevent.socket
import gevent.monkey
gevent.monkey.patch_all()


class UnhappyEyeballs(Exception):
    pass


def map_staggered(group, func, targets, sleep_time, result):
    for t in targets:
        # Start the next attempt.
        group.spawn(func, t)

        # Wait until either ``sleep_time`` elapses, or one of the tasks
        # completes successfully.
        result.wait(timeout=sleep_time)

        # If the result is ready, we're done.
        if result.ready():
            return

    # If we get here, everyone failed (or took too long).
    result.set_exception(UnhappyEyeballs("Took too long to connect."))


def open_tcp_socket(hostname, port, *, timeout=0.250):
    group = gevent.pool.Group()
    result = gevent.event.AsyncResult()

    targets = gevent.socket.getaddrinfo(
        hostname, port, type=gevent.socket.SOCK_STREAM,
    )

    def attempt(target):
        *socket_config, _, socket_target = target
        socket = gevent.socket.socket(*socket_config)
        socket.connect(socket_target)
        result.set(socket)

    group.spawn(map_staggered, group, attempt, targets, timeout, result)

    try:
        return result.wait()
    finally:
        group.kill()


print(open_tcp_socket("debian.org", "https"))