Open julj opened 3 years ago
Hello @julj
the dt
says when the actual measurement has been taken on the OWM API side.
This means that if that measurement is the only available one during your for
loop, the value of obs.weather.reference_time())
will never change.
This of course depends on how frequently the measurements change for the place you're asking for
So, in conclusion: PyOWM always returns the dt
that is embedded in the actual OWM API response, if that dt
doesn't change over time this means that either the datapoint hasn't changed since or the OWM API is not updating it correctly
Hi,
there seems to be 2 different issues.
A difference between the dt from a call with your module VS directly to the API:
In [35]: for i in range(5):
...: obs = owm_mgr.weather_at_id(city_id)
...: print(f"{'pyowm reference_time':<25}: {obs.weather.reference_time()}")
...: r = requests.get(f'https://api.openweathermap.org/data/2.5/weather?id={city_id}&appid={OWM_KEY}')
...: print(f"{'owm dt':<25}: {json.loads(r.content.decode('utf-8'))['dt']}")
...:
pyowm reference_time : 1608734979
owm dt : 1608734675
pyowm reference_time : 1608734979
owm dt : 1608734675
pyowm reference_time : 1608734979
owm dt : 1608734675
pyowm reference_time : 1608734979
owm dt : 1608734675
pyowm reference_time : 1608734979
owm dt : 1608734675
And, when called from within a Docker container, some weird dt variations from both (I'll investigate that):
In [24]: for _ in range(5):
...: obs = owm_mgr.weather_at_id(city_id)
...: print(f"{'pyowm reference_time':<25}: {obs.weather.reference_time()}")
...: r = requests.get(f"https://api.openweathermap.org/data/2.5/weather?id={city_id}&appid={os.getenv('OWM_API_KEY')}")
...: print(f"{'own dt':<25}: {json.loads(r.content.decode('utf-8'))['dt']}")
...:
pyowm reference_time : 1608734913
own dt : 1608734675
pyowm reference_time : 1608734979
own dt : 1608734974
pyowm reference_time : 1608734913
own dt : 1608734675
pyowm reference_time : 1608734979
own dt : 1608734974
pyowm reference_time : 1608734913
own dt : 1608734675
Ok this deserves further investigation
@julj Long answer, take time to read
This is very likely tied to how Docker containers time systems work - they were known to have jitters with respect to the host machine's timeframe
Spoiler: I don't have an explanation for that. But I've been able to come up with some further evidence.
I've modified your original code so that the call you make with requests
to the OWM API is exactly equal to the one made by PyOWM (in the example, on city 3143244):
r = requests.get(f'https://api.openweathermap.org/data/2.5/weather',
verify=True, stream=True,
params={'APPID': OWM_KEY, 'lang': 'en', 'id': 3143244})
pyowm reference_time : 1609250868
owm dt : 1609250868
pyowm reference_time : 1609250868
owm dt : 1609250868
pyowm reference_time : 1609250868
owm dt : 1609250868
pyowm reference_time : 1609250868
owm dt : 1609250868
pyowm reference_time : 1609250868
owm dt : 1609250868
It basically seems like that the dt
returned by the server depends on the parameters in the request.
Provided that PyOWM provides the timestamp value as provided by the API (no rounding is performed), I have NO IDEA why this happens.
It is worth to note that the params for the PyOWM GET request depend on PyOWM configuration (eg. proxies, language, etc.)
Any thoughts?
@julj Long answer, take time to read
ISSUE N.2 (DOCKER)
This is very likely tied to how Docker containers time systems work - they were known to have jitters with respect to the host machine's timeframe
But those timestamps are from the API, not from the system clock, right ?
ISSUE N.1 (PYOWM vs OWM API TIME DRIFT)
Spoiler: I don't have an explanation for that. But I've been able to come up with some further evidence.
I've modified your original code so that the call you make with
requests
to the OWM API is exactly equal to the one made by PyOWM (in the example, on city 3143244):r = requests.get(f'https://api.openweathermap.org/data/2.5/weather', verify=True, stream=True, params={'APPID': OWM_KEY, 'lang': 'en', 'id': 3143244}) pyowm reference_time : 1609250868 owm dt : 1609250868 pyowm reference_time : 1609250868 owm dt : 1609250868 pyowm reference_time : 1609250868 owm dt : 1609250868 pyowm reference_time : 1609250868 owm dt : 1609250868 pyowm reference_time : 1609250868 owm dt : 1609250868
It basically seems like that the
dt
returned by the server depends on the parameters in the request.Provided that PyOWM provides the timestamp value as provided by the API (no rounding is performed), I have NO IDEA why this happens.
It is worth to note that the params for the PyOWM GET request depend on PyOWM configuration (eg. proxies, language, etc.)
Any thoughts?
Not really, I don't see why the parameters you set in the request, verify or stream, would change the response. I don't have much time to investigate, but if I come up with any idea I will let you know here. Thank you for your help !
When running successive call to mgr.weather_at_id (and other requests) I get inconsistent results (see below). Using directly the OWM API, the 'dt' value changes only every few minutes...