socket.gaierror: [Errno -2] Name or service not known | Python

Question

I have closed my internet connection and want to catch that in code. I have set time out limit but it's not working. I am getting a huge bunch of error messages, that I have not understood.

Can anyone help to understand what these error messages mean?

My python code (simplified):

import requests
from requests.exceptions import Timeout

url = 'https://api.github.com'
try:
    resp = requests.get(url=url, timeout=7)
except Timeout:
    print('The request timed out')
else:
    entries = resp.json()
    print(entries)

---

Error messages:

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/urllib3/connection.py", line 141, in _new_conn
    (self.host, self.port), self.timeout, **extra_kw)
  File "/usr/lib/python3/dist-packages/urllib3/util/connection.py", line 60, in create_connection
    for res in socket.getaddrinfo(host, port, family, socket.SOCK_STREAM):
  File "/usr/lib/python3.6/socket.py", line 745, in getaddrinfo
    for res in _socket.getaddrinfo(host, port, family, type, proto, flags):
socket.gaierror: [Errno -2] Name or service not known

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/urllib3/connectionpool.py", line 601, in urlopen
    chunked=chunked)
  File "/usr/lib/python3/dist-packages/urllib3/connectionpool.py", line 346, in _make_request
    self._validate_conn(conn)
  File "/usr/lib/python3/dist-packages/urllib3/connectionpool.py", line 852, in _validate_conn
    conn.connect()
  File "/usr/lib/python3/dist-packages/urllib3/connection.py", line 284, in connect
    conn = self._new_conn()
  File "/usr/lib/python3/dist-packages/urllib3/connection.py", line 150, in _new_conn
    self, "Failed to establish a new connection: %s" % e)
urllib3.exceptions.NewConnectionError: <urllib3.connection.VerifiedHTTPSConnection object at 0x7f1cea4779e8>: Failed to establish a new connection: [Errno -2] Name or service not known

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/requests/adapters.py", line 440, in send
    timeout=timeout
  File "/usr/lib/python3/dist-packages/urllib3/connectionpool.py", line 639, in urlopen
    _stacktrace=sys.exc_info()[2])
  File "/usr/lib/python3/dist-packages/urllib3/util/retry.py", line 398, in increment
    raise MaxRetryError(_pool, url, error or ResponseError(cause))
urllib3.exceptions.MaxRetryError: HTTPSConnectionPool(host='api.github.com', port=443): Max retries exceeded with url: / (Caused by NewConnectionError('<urllib3.connection.VerifiedHTTPSConnection object at 0x7f1cea4779e8>: Failed to establish a new connection: [Errno -2] Name or service not known',))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "test.py", line 6, in <module>
    resp = requests.get(url=url, timeout=7)
  File "/usr/lib/python3/dist-packages/requests/api.py", line 72, in get
    return request('get', url, params=params, **kwargs)
  File "/usr/lib/python3/dist-packages/requests/api.py", line 58, in request
    return session.request(method=method, url=url, **kwargs)
  File "/usr/lib/python3/dist-packages/requests/sessions.py", line 520, in request
    resp = self.send(prep, **send_kwargs)
  File "/usr/lib/python3/dist-packages/requests/sessions.py", line 630, in send
    r = adapter.send(request, **kwargs)
  File "/usr/lib/python3/dist-packages/requests/adapters.py", line 508, in send
    raise ConnectionError(e, request=request)
requests.exceptions.ConnectionError: HTTPSConnectionPool(host='api.github.com', port=443): Max retries exceeded with url: / (Caused by NewConnectionError('<urllib3.connection.VerifiedHTTPSConnection object at 0x7f1cea4779e8>: Failed to establish a new connection: [Errno -2] Name or service not known',))

Answer 1

socket.gaierror: [Errno -2] Name or service not known means that the name resolution is failing for the given domain (api.github.com).

Name resolution (DNS in the usual notion) can fail for various reasons. As you have disconnected the internet, the reason is pretty obvious (Name or service not known).

gai (GetAddressInfo) is actually used by glibc to perform the name resolutions, it's part of glibc (and socket is using that as you can imagine). You can also actually configure it in /etc/gai.conf.

Answer 2

An possible solution is capture socket.gaioerror with OSError

Documentation info:

exception socket.gaierror

A subclass of OSError, this exception is raised for address-related errors by getaddrinfo() and getnameinfo(). The accompanying value is a pair (error, string) representing an error returned by a library call. string represents the description of error, as returned by the gai_strerror() C function. The numeric error value will match one of the EAI_* constants defined in this module.

Links: https://docs.python.org/3/library/socket.html#socket.gaierror

https://docs.python.org/3/library/exceptions.html#OSError