[Async-sig] async_stagger: Happy Eyeballs implementation in pure asyncio

[Pau Freixes]

Hi,

Great idea, I didn't know that it was already implemented by Trio and
I didn't know that there were two RFCs to specify how to make this.

In the case of the connection that strategy can bring many benefits in
networks that are dynamic, perhaps the case of the ELBs in AWS which
scale up or shrink the number of load balances that are in front of
your application taking into account the traffic that they have to
handle. That change gets reflected in the DNS answer, indeed AWS
suggests to the clients to save the DNS resolutions in the cache
client for not more than 60 seconds, obviously because the IP
addresses will be adaptative to the number of load balancers at some
specific time.

Having a "big" connection timeout the client experience till reaching
an available destination is proportional to the number of hosts
iterated and failed

for host in hosts:
    try:
        return await connect(host, timeout=1)
    except TimeoutError:
        logging.warning("Host not available, trying the next one")

So definitely the proposal of the Happy Eyeballs implementation
improves the latency needed to get a healthy connection.

Thanks for making it visible!


On Sun, May 13, 2018 at 7:40 AM, twisteroid ambassador
<twisteroid.ambassador at gmail.com> wrote:
> Repo: https://github.com/twisteroidambassador/async_stagger
> Docs: http://async-stagger.readthedocs.io/en/latest/
>
> Provides near drop-in replacements for open_connection() and
> create_connection() using Happy Eyeballs. Also exposes the underlying
> scheduling logic where you can plug in your own coroutines to run.
>
> I basically ported trio's implementation to asyncio, and it turned out
> to be not too difficult.
>
> Cheers,
>
> twistero
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-- 
--pau