Uma história de excesso e perda de tempo. De acordo com py3

Algumas semanas atrás, em nossa infraestrutura, descobri um pequeno erro de configuração na variável de ambiente TZ. A correção desse erro perturbou o frágil equilíbrio de bugs no universo e os gráficos RPS para um dos projetos em nosso grafite literalmente enlouqueceram. Vou lhe contar como persegui algumas horas por vários dias.

Como tudo começou

O script, que foi iniciado manualmente e funcionou perfeitamente, gerou um erro ao iniciar no cron.d. Um estudo superficial dos logs em texto simples indicava o que estava errado.

#   
$ 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

Erro conosco ou no programa?

O comportamento do programa está correto ou é um bug?

A documentação do GNU indica que existem 3 formatos possíveis para uma variável de ambiente TZ:

• Formate sem DST (horário de verão) std offset. Exemplos EST+5,GMT+0
• Formatar com o horário de verão: std offset dst [offset],start[/time],end[/time]. Exemplo EST+5EDT,M3.2.0/2,M11.1.0/2.
• O nome do arquivo de descrição do fuso horário. Pode começar com dois pontos :. Se o primeiro caractere (ou após os dois pontos) for uma barra /, esse deve ser o caminho absoluto para o arquivo. Se não, então /usr/share/zoneinfo/${TZ}.

Por que um cliente ClickHouse precisa de conhecimento da 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++

O maravilhoso Tikki Schellen aconselha razoavelmente : "Não se demore com as próprias mãos". Para mim, no ranking de perigo, caiu em uma linha com o DNS. Tente evitá-lo sempre que possível.

E neste momento interessante, desejo me manter saudável. Tente ficar em casa e, de repente, você está muito entediado e não tem nada para fazer, pode jogar na InnoGames . By the way, temos vagas abertas