Una historia de exceso y tiempo perdido. De acuerdo con py3

Hace unas semanas, en nuestra infraestructura, descubrí un pequeño error de configuración en la variable de entorno TZ. La corrección de este error alteró el frágil equilibrio de errores en el universo y los gráficos RPS para uno de los proyectos en nuestro grafito literalmente se volvieron locos. Te diré cómo perseguí unas horas durante varios días.

Cómo todo empezó

El script, que se lanzó a mano y funcionó perfectamente, arrojó un error al comenzar desde cron.d. Un estudio superficial de los registros en texto sin formato indicó lo que estaba mal.

#   
$ TZ='' clickhouse-client; echo exit=$?
ClickHouse client version 20.3.2.1.
Connecting to localhost:9000 as user default.
Connected to ClickHouse server version 20.3.2 revision 54433.
Poco::Exception. Code: 1000, e.code() = 0, e.displayText() = Exception: Could not determine time zone from TZ variable value: '': filesystem error: in file_size: Is a directory [/usr/share/zoneinfo] (version 20.3.2.1)
exit=232

¿Error con nosotros o en el programa?

¿Es correcto el comportamiento del programa o es un error?

La documentación de GNU indica que hay 3 formatos posibles para una variable de entorno TZ:

• Formato sin DST (horario de verano) std offset. Ejemplos EST+5,GMT+0
• Formatear con el horario de verano: std offset dst [offset],start[/time],end[/time]. Ejemplo EST+5EDT,M3.2.0/2,M11.1.0/2.
• El nombre del archivo de descripción de zona horaria. Puede comenzar con un colon :. Si el primer carácter (o después de los dos puntos) es una barra oblicua /, esta debe ser la ruta absoluta al archivo. Si no, entonces /usr/share/zoneinfo/${TZ}.

¿Por qué un cliente ClickHouse necesita conocimiento de la hora local?

Date DateTime DBMS timestamp, toDateTime('2020-02-02 20:20:20') (, , ) UInt32. , . TZ , , 98% .

, ClickHouse ( Poco) , . .

, . cron.d TZ, . . , 2020-04-15 2020-04-20 .

2020-04-22 ( ): " RPS "

, -, . .

self.now = int(datetime.datetime.utcnow().timestamp())
...
dt = datetime.datetime.strptime(time_str, time_format).utctimetuple()
timestamp = time.mktime(dt)

datetime.utcnow()?

Return the current UTC date and time, with tzinfo=None.
This is like now(), but returns the current UTC date and time, as a naive datetime object. An aware current UTC datetime can be obtained by calling datetime.now(timezone.utc). See also now().
Warning: Because naive datetime objects are treated by many datetime methods as local times, it is preferred to use aware datetimes to represent times in UTC. As such, the recommended way to create an object representing the current time in UTC is by calling datetime.now(timezone.utc).

, UTC, tzinfo=None datetime. .timestamp() UNIX time , UTC. : TZ=UTC

datetime.now().timestamp(). , .timestamp(), datetime.now(timezone.utc)

datetime.utctimetuple()?

datetime.timetuple():
Return time.struct_time such as returned by time.localtime().
datetime.utctimetuple():
If datetime instance d is naive, this is the same as d.timetuple() except that tm_isdst is forced to 0 regardless of what d.dst() returns. DST is never in effect for a UTC time.
If d is aware, d is normalized to UTC time, by subtracting d.utcoffset(), and a time.struct_time for the normalized time is returned. tm_isdst is forced to 0.
Warning: Because naive datetime objects are treated by many datetime methods as local times, it is preferred to use aware datetimes to represent times in UTC; as a result, using utcfromtimetuple may give misleading results. If you have a naive datetime representing UTC, use datetime.replace(tzinfo=timezone.utc) to make it aware, at which point you can use datetime.timetuple().

. time.struct_time, time.mktime(). , python2. , . , UNIX timestamp .

Python, , .

, datetime.strptime().timestamp()

TZ

, . - , - UTC, - , . , .

, RPS :

, , . , .

, :

• , TZ=''
• UTC strptime()
• UTC, strptime()
• strptime()

strptime 2020-04-24T05:31:55+02:00

#!/usr/bin/env python
from datetime import datetime, timezone  # noqa
from time import mktime
def pprint(d: dict):
    for k in d:
        print("{}: {}".format(k, d[k]))
now = {'now': datetime.now(),
       # 'now_tz': datetime.now(timezone.utc), # the same as now for timestamp
       'utcnow': datetime.utcnow()}
now_ts = [int(now[k].timestamp()) for k in now]
now_dict = {k: [now_ts[i], now_ts[i] - now_ts[0]] for i, k in enumerate(now)}
pprint(now_dict)
# pprint(now)
# print('Timestamps in now: {}'.format(set(now_ts)))
print()
ts_c = 1587699115  # the known correct value
time_format = "%Y-%m-%dT%H:%M:%S%z"
time_str = "2020-04-24T05:31:55+02:00"
timetuples = {
    'timetuple': datetime.strptime(time_str, time_format).timetuple(),
    'utctimetuple': datetime.strptime(time_str, time_format).utctimetuple(),
}
ts = {
    'timestamp': [
        int(datetime.strptime(time_str, time_format).timestamp()),
        int(datetime.strptime(time_str, time_format).timestamp()) - ts_c,
    ],
    'timetuple': [
        int(mktime(timetuples['timetuple'])),
        int(mktime(timetuples['timetuple'])) - ts_c,
    ],
    'utctimetuple': [
        int(mktime(timetuples['utctimetuple'])),
        int(mktime(timetuples['utctimetuple'])) - ts_c,
    ],
}
pprint(ts)
# pprint(timetuples)
# print('Timestamps in ts: {}'.format(set(int(v[0]) for v in ts.values())))

#!/usr/bin/env bash
for tz in '' Europe/Moscow UTC Europe/Berlin
do
  date "+==TZ=${tz} %s=="
  TZ=$tz python example.py
  date '+++%s++' -d '2020-04-24T05:31:55+02:00'
done

TZ. , +02:00.

now timestamp . , timetuple + mktime .

==TZ='' 1587914590==
now: [1587914590, 0]
utcnow: [1587914590, 0]
timestamp: [1587699115, 0]
timetuple: [1587706315, 7200] - TZ - UTC
utctimetuple: [1587699115, 0]
++1587699115++

==TZ=Europe/Moscow 1587914590==
now: [1587914590, 0]
utcnow: [1587903790, -10800] - UTC - TZ
timestamp: [1587699115, 0]
timetuple: [1587695515, -3600] - +02:00 - TZ
utctimetuple: [1587688315, -10800] - UTC - TZ
++1587699115++

==TZ=UTC 1587914590==
now: [1587914590, 0]
utcnow: [1587914590, 0]
timestamp: [1587699115, 0]
timetuple: [1587706315, 7200] - +02:00 - UTC
utctimetuple: [1587699115, 0]
++1587699115++

==TZ=Europe/Berlin 1587914590==
now: [1587914590, 0]
utcnow: [1587907390, -7200] - UTC - TZ
timestamp: [1587699115, 0]
timetuple: [1587699115, 0]
utctimetuple: [1587695515, -3600] - UTC - TZ...    DST!
++1587699115++

El maravilloso Tikki Schellen aconseja razonablemente : "No te tomes el tiempo con tus propias manos". Para mí, en el ranking de peligro, cayó en una línea con DNS. Intenta evitarlo en general siempre que sea posible.

Y en este momento interesante deseo mantenerme saludable. Intenta quedarte en casa y si de repente estás muy aburrido y no tienes nada que hacer, puedes jugar juegos de InnoGames . Por cierto, tenemos vacantes abiertas