asyncio version of ntptime?

[bulletmark]

Does anybody know of an implementation of ntptime for asyncio? i.e. so I can:

await ntptime.settime()

[peterhinch]

Such a version would need to address a known problem. The line

addr = socket.getaddrinfo(host, 123)[0][-1]

blocks because nobody has yet written a nonblocking DNS lookup (AFAIK of course).

[bulletmark]

I read this and thought, what does that mean my use of uaiohttpclient() from micropython-lib is actually blocking as well? So I followed it down and found this TODO in micropython/extmod/asyncio/stream.py:

# Create a TCP stream connection to a remote host
#
# async
def open_connection(host, port):
    from errno import EINPROGRESS
    import socket

    ai = socket.getaddrinfo(host, port, 0, socket.SOCK_STREAM)[0]  # TODO this is blocking!
..

Doh! Although I guess this problem is lessened somewhat by the fact that host name lookups are cached at various levels.

@peterhinch do you know if there is an MP issue tracking this TODO?

[peterhinch]

host name lookups are cached at various levels

Caching is fine when the host is fixed. I'm no expert on NTP, but I think you're supposed to do a DNS lookup on each access. A potentially different IP is retrieved from the pool each time.

I'm not aware of an issue, and a quick lookup drew a blank.

[karfas]

See e.g. asy_udp_client and asy_ntp_client

This will block during name lookup but provides async NTP time setting.
I'm pretty sure there are better ways to do it (especially the udp client thing), but it could be a starting point.

Edit: fixed second link.

[bulletmark]

Thanks for pushing that entire little repo up to github. I'll try those 2 files out in my app.

[peterhinch]

The second link is a 404 here.