getaddrinfo in a thread

[kjm]

DNS lookups via 4G on a GPY can take up to 20s if things don't go well

import time, usocket, _thread
def _dns(host, port):
  ai = usocket.getaddrinfo(host, port); ai=ai[0]; return ai

start=time.time()
ai=_dns('some url', 443)
stop=time.time(); wait=stop-start; print('wait =', wait, ' dns =', ai)

for example, returns

wait = 14  dns = (2, 1, 0, '', ('0.0.0.0', 443))

Since we can't wait that long in a battery powered GPY we tried a thread

import time, usocket, _thread
def _dns(host, port):
  global ai; ai=usocket.getaddrinfo(host, port); ai=ai[0]

start=time.time(); ai=0
_thread.start_new_thread(_dns, ('some url', 443))
for i in range(5):
  print(i, ai), time.sleep(1)
  if ai: break
stop=time.time(); wait=stop-start; print('wait =', wait, ' dns =', ai)

more or less the same result

0 0
wait = 13  dns = (2, 1, 0, '', ('0.0.0.0', 443))

We don't get it. Why doesn't the main program timeout after 5s? Why does it pause after the first iteration of the loop & wait for the thread? Isn't the idea of a thread that it allows the main program to continue regardless of what the thread is doing?

[andreas]

Just retyped this for the sake of improved readability. You might want to save it as /flash/lib/dnstest.py.

import time
import usocket
import machine
import _thread
"""
>>> import dnstest; dnstest.dns_lookup('google.com')
0 None
1 (2, 1, 0, '', ('172.217.18.14', 443))
2 (2, 1, 0, '', ('172.217.18.14', 443))
3 (2, 1, 0, '', ('172.217.18.14', 443))
4 (2, 1, 0, '', ('172.217.18.14', 443))
"""

response = None


def run_getaddrinfo(host, port):
    global response
    response = usocket.getaddrinfo(host, port)[0]


def dns_lookup(hostname, timeout=5):

    _thread.start_new_thread(run_getaddrinfo, (hostname, 443))

    for i in range(timeout):
        print(i, response)
        machine.idle()
        time.sleep(1)

    print('Ready.')

It works flawlessly over a WiFi connection, but LTE might well have its delicacies.

[andreas]

What should print(i, ai), time.sleep(1) actually do? I believe your thread might crash without notice.

@andreas said in urequests timeouts:

I can't decipher your code

However, you might want to add machine.idle() while you are waiting for the thread outcome in order to feed the OS scheduler.

[andreas]

getaddrinfo does not only have issues on MicroPython when used in a thread [1]. These things are tricky.

[1] https://emptysqua.re/blog/getaddrinfo-deadlock/

[kjm]

This post is deleted!

[kjm]

Is this guy for real?!

[oligauc]

@kjm GPY works with the 5G LTE CAT M1 and NB-Iot. You need to buy a 5G sim card from a service provider and follow the examples found on our website: CAT M1 and NB-Iot