oncall-engine/engine/apps/schedules/ical_utils.py
Matias Bordese bba6eb333e
Add db indexes to user table (#3067)
Add composite indexes based on existing queries/usage, ensuring partial
index prefixes are useful too.

- `is_active` filtering is set in the default `User` manager
- most of our user queries are per `organization`
- multiple cases filter by `username` or `email` (most notably schedule
related queries, given the low-level backend ical representation)

Also rework how users are fetched from DB when getting users from
schedules ical representation (which was particularly slow when regex
filtering by required permission).

Related to https://github.com/grafana/oncall-private/issues/2163
2023-09-27 12:35:52 +00:00

842 lines
33 KiB
Python

from __future__ import annotations
import datetime
import logging
import re
import typing
from collections import namedtuple
from typing import TYPE_CHECKING
import pytz
import requests
from django.db.models import Q
from django.utils import timezone
from icalendar import Calendar
from icalendar import Event as IcalEvent
from apps.api.permissions import RBACPermission
from apps.schedules.constants import (
CALENDAR_TYPE_FINAL,
ICAL_ATTENDEE,
ICAL_DATETIME_END,
ICAL_DATETIME_START,
ICAL_DESCRIPTION,
ICAL_LOCATION,
ICAL_PRIORITY,
ICAL_RECURRENCE_ID,
ICAL_SEQUENCE,
ICAL_STATUS,
ICAL_STATUS_CANCELLED,
ICAL_SUMMARY,
ICAL_UID,
RE_EVENT_UID_EXPORT,
RE_EVENT_UID_V1,
RE_EVENT_UID_V2,
RE_PRIORITY,
)
from apps.schedules.ical_events import ical_events
from common.timezones import is_valid_timezone
from common.utils import timed_lru_cache
"""
This is a hack to allow us to load models for type checking without circular dependencies.
This module likely needs to refactored to be part of the OnCallSchedule module.
"""
if TYPE_CHECKING:
from apps.schedules.models import OnCallSchedule
from apps.schedules.models.on_call_schedule import OnCallScheduleQuerySet
from apps.user_management.models import Organization, User
from apps.user_management.models.user import UserQuerySet
logger = logging.getLogger(__name__)
logger.setLevel(logging.DEBUG)
EmptyShift = namedtuple(
"EmptyShift",
["start", "end", "summary", "description", "attendee", "all_day", "calendar_type", "calendar_tz", "shift_pk"],
)
EmptyShifts = typing.List[EmptyShift]
DatetimeInterval = namedtuple("DatetimeInterval", ["start", "end"])
DatetimeIntervals = typing.List[DatetimeInterval]
IcalEvents = typing.List[IcalEvent]
def users_in_ical(
usernames_from_ical: typing.List[str],
organization: "Organization",
) -> typing.List["User"]:
"""
This method returns a sequence of `User` objects, filtered by users whose username, or case-insensitive e-mail,
is present in `usernames_from_ical`.
Parameters
----------
usernames_from_ical : typing.List[str]
A list of usernames present in the ical feed
organization : apps.user_management.models.organization.Organization
The organization in question
"""
required_permission = RBACPermission.Permissions.SCHEDULES_WRITE
emails_from_ical = [username.lower() for username in usernames_from_ical]
users_found_in_ical = organization.users.filter(
(Q(username__in=usernames_from_ical) | Q(email__lower__in=emails_from_ical))
).distinct()
if organization.is_rbac_permissions_enabled:
# it is more efficient to check permissions on the subset of users filtered above
# than performing a regex query for the required permission
users_found_in_ical = [u for u in users_found_in_ical if {"action": required_permission.value} in u.permissions]
else:
users_found_in_ical = users_found_in_ical.filter(role__lte=required_permission.fallback_role.value)
return list(users_found_in_ical)
@timed_lru_cache(timeout=100)
def memoized_users_in_ical(usernames_from_ical: typing.List[str], organization: "Organization") -> typing.List["User"]:
# using in-memory cache instead of redis to avoid pickling python objects
return users_in_ical(usernames_from_ical, organization)
# used for display schedule events on web
def list_of_oncall_shifts_from_ical(
schedule: "OnCallSchedule",
datetime_start: datetime.datetime,
datetime_end: datetime.datetime,
with_empty_shifts: bool = False,
with_gaps: bool = False,
filter_by: str | None = None,
from_cached_final: bool = False,
):
"""
Parse the ical file and return list of events with users
This function is used in serializer for api schedules/events/ endpoint
Example output:
[
{
"start": datetime.datetime(2021, 7, 8, 5, 30, tzinfo=<UTC>,
"end": datetime.datetime(2021, 7, 8, 13, 15, tzinfo=<UTC>),
"users": <QuerySet [<User: User object (1)>]>,
"priority": 0,
"source": None,
"calendar_type": 0
}
]
"""
from apps.schedules.models import OnCallSchedule
# get list of iCalendars from current iCal files. If there is more than one calendar, primary calendar will always
# be the first
calendars: typing.Tuple[typing.Optional[Calendar], ...]
if from_cached_final:
calendars = (Calendar.from_ical(schedule.cached_ical_final_schedule),)
else:
calendars = schedule.get_icalendars()
result_datetime = []
result_date = []
for idx, calendar in enumerate(calendars):
if calendar is not None:
calendar_type: str | int
if from_cached_final:
calendar_type = CALENDAR_TYPE_FINAL
elif idx == 0:
calendar_type = OnCallSchedule.PRIMARY
else:
calendar_type = OnCallSchedule.OVERRIDES
if filter_by is not None and filter_by != calendar_type:
continue
tmp_result_datetime, tmp_result_date = get_shifts_dict(
calendar, calendar_type, schedule, datetime_start, datetime_end, with_empty_shifts
)
result_datetime.extend(tmp_result_datetime)
result_date.extend(tmp_result_date)
if with_gaps and len(result_date) == 0:
as_intervals = [DatetimeInterval(shift["start"], shift["end"]) for shift in result_datetime]
gaps = detect_gaps(as_intervals, datetime_start, datetime_end)
for g in gaps:
result_datetime.append(
{
"start": g.start if g.start else datetime_start,
"end": g.end if g.end else datetime_end,
"users": [],
"missing_users": [],
"priority": None,
"source": None,
"calendar_type": None,
"is_gap": True,
"shift_pk": None,
}
)
def event_start_cmp_key(e):
pytz_tz = pytz.timezone("UTC")
return (
datetime.datetime.combine(e["start"], datetime.datetime.min.time(), tzinfo=pytz_tz)
if type(e["start"]) == datetime.date
else e["start"]
)
result = sorted(result_datetime + result_date, key=event_start_cmp_key)
# if there is no events, return None
return result or None
def get_shifts_dict(
calendar: Calendar,
calendar_type: str | int,
schedule: "OnCallSchedule",
datetime_start: datetime.datetime,
datetime_end: datetime.datetime,
with_empty_shifts: bool = False,
):
events = ical_events.get_events_from_ical_between(calendar, datetime_start, datetime_end)
result_datetime = []
result_date = []
for event in events:
status = event.get(ICAL_STATUS)
if status == ICAL_STATUS_CANCELLED:
# ignore cancelled events
continue
sequence = event.get(ICAL_SEQUENCE)
recurrence_id = event.get(ICAL_RECURRENCE_ID)
if recurrence_id:
recurrence_id = recurrence_id.dt.isoformat()
priority = parse_priority_from_string(event.get(ICAL_SUMMARY, "[L0]"))
pk, source = parse_event_uid(event.get(ICAL_UID), sequence=sequence, recurrence_id=recurrence_id)
users = get_users_from_ical_event(event, schedule.organization)
missing_users = get_missing_users_from_ical_event(event, schedule.organization)
event_calendar_type = calendar_type
if calendar_type == CALENDAR_TYPE_FINAL:
event_calendar_type = (
schedule.OVERRIDES
if (
event.get(ICAL_PRIORITY, "") == schedule.OVERRIDES
or
# keep for backwards compatibility (to be removed later once schedules are refreshed)
event.get(ICAL_LOCATION, "") == schedule.CALENDAR_TYPE_VERBAL[schedule.OVERRIDES]
)
else schedule.PRIMARY
)
# Define on-call shift out of ical event that has the actual user
if len(users) > 0 or with_empty_shifts:
if type(event[ICAL_DATETIME_START].dt) == datetime.date:
start = event[ICAL_DATETIME_START].dt
end = event[ICAL_DATETIME_END].dt
result_date.append(
{
"start": start,
"end": end,
"users": users,
"missing_users": missing_users,
"priority": priority,
"source": source,
"calendar_type": event_calendar_type,
"shift_pk": pk,
}
)
else:
start, end = ical_events.get_start_and_end_with_respect_to_event_type(event)
if start < end:
result_datetime.append(
{
"start": start.astimezone(pytz.UTC),
"end": end.astimezone(pytz.UTC),
"users": users,
"missing_users": missing_users,
"priority": priority,
"source": source,
"calendar_type": event_calendar_type,
"shift_pk": pk,
}
)
return result_datetime, result_date
def list_of_empty_shifts_in_schedule(
schedule: "OnCallSchedule", start_date: datetime.date, end_date: datetime.date
) -> EmptyShifts:
# Calculate lookup window in schedule's tz
# If we can't get tz from ical use UTC
from apps.schedules.models import OnCallSchedule
calendars = schedule.get_icalendars()
empty_shifts: EmptyShifts = []
for idx, calendar in enumerate(calendars):
if calendar is not None:
if idx == 0:
calendar_type = OnCallSchedule.PRIMARY
else:
calendar_type = OnCallSchedule.OVERRIDES
calendar_tz = get_icalendar_tz_or_utc(calendar)
# utcoffset can technically return None, but we're confident it is a timedelta here
schedule_timezone_offset: datetime.timedelta = datetime.datetime.now().astimezone(calendar_tz).utcoffset() # type: ignore[assignment]
start_datetime = datetime.datetime.combine(start_date, datetime.time.min) + datetime.timedelta(
milliseconds=1
)
start_datetime_with_offset = (start_datetime - schedule_timezone_offset).astimezone(pytz.UTC)
end_datetime = datetime.datetime.combine(end_date, datetime.time.max)
end_datetime_with_offset = (end_datetime - schedule_timezone_offset).astimezone(pytz.UTC)
events = ical_events.get_events_from_ical_between(
calendar, start_datetime_with_offset, end_datetime_with_offset
)
# Keep hashes of checked events to include only first recurrent event into result
checked_events = set()
empty_shifts_per_calendar = []
for event in events:
users = get_users_from_ical_event(event, schedule.organization)
if len(users) == 0:
summary = event.get(ICAL_SUMMARY, "")
description = event.get(ICAL_DESCRIPTION, "")
attendee = event.get(ICAL_ATTENDEE, "")
pk, _ = parse_event_uid(event.get(ICAL_UID))
event_hash = hash(f"{event[ICAL_UID]}{summary}{description}{attendee}")
if event_hash in checked_events:
continue
checked_events.add(event_hash)
start, end, all_day = event_start_end_all_day_with_respect_to_type(event, calendar_tz)
if not all_day:
start = start.astimezone(pytz.UTC)
end = end.astimezone(pytz.UTC)
empty_shifts_per_calendar.append(
EmptyShift(
start=start,
end=end,
summary=summary,
description=description,
attendee=attendee,
all_day=all_day,
calendar_type=calendar_type,
calendar_tz=calendar_tz,
shift_pk=pk,
)
)
empty_shifts.extend(empty_shifts_per_calendar)
return sorted(empty_shifts, key=lambda dt: dt.start)
def list_users_to_notify_from_ical(
schedule: "OnCallSchedule",
events_datetime: typing.Optional[datetime.datetime] = None,
) -> typing.Sequence["User"]:
"""
Retrieve on-call users for the current time
"""
events_datetime = events_datetime if events_datetime else datetime.datetime.now(timezone.utc)
return list_users_to_notify_from_ical_for_period(
schedule,
events_datetime,
events_datetime,
)
def list_users_to_notify_from_ical_for_period(
schedule: "OnCallSchedule",
start_datetime: datetime.datetime,
end_datetime: datetime.datetime,
) -> typing.List["User"]:
users_found_in_ical: typing.Sequence["User"] = []
events = schedule.final_events(start_datetime, end_datetime)
usernames = []
for event in events:
usernames += [u["email"] for u in event.get("users", [])]
users_found_in_ical = users_in_ical(usernames, schedule.organization)
return users_found_in_ical
def get_oncall_users_for_multiple_schedules(
schedules: typing.List["OnCallSchedule"], events_datetime=None
) -> typing.Dict["OnCallSchedule", UserQuerySet]:
if events_datetime is None:
events_datetime = datetime.datetime.now(timezone.utc)
# Exit early if there are no schedules
if not schedules:
return {}
# Get on-call users
oncall_users = {}
for schedule in schedules:
# pass user list to list_users_to_notify_from_ical
schedule_oncall_users = list_users_to_notify_from_ical(schedule, events_datetime=events_datetime)
oncall_users.update({schedule.pk: schedule_oncall_users})
return oncall_users
def parse_username_from_string(string: str) -> str:
"""
Parse on-call shift user from the given string
Example input:
[L1] bob@company.com
Example output:
bob@company.com
"""
return re.sub(RE_PRIORITY, "", string.strip(), 1).strip()
def parse_priority_from_string(string: str) -> int:
"""
Parse on-call shift priority from the given string
Example input:
[L1] @alex @bob
Example output:
1
"""
priority = 0
priority_matches = re.findall(RE_PRIORITY, string.strip())
if len(priority_matches) > 0:
priority = int(priority_matches[0])
if priority < 1:
priority = 0
return priority
def parse_event_uid(string: str, sequence: str = None, recurrence_id: str = None):
pk = None
source = None
source_verbal = None
match = RE_EVENT_UID_V2.match(string)
if match:
_, pk, _, _, source = match.groups()
else:
match = RE_EVENT_UID_EXPORT.match(string)
if match:
pk, _, _ = match.groups()
else:
# eventually this path would be automatically deprecated
# once all ical representations are refreshed
match = RE_EVENT_UID_V1.match(string)
if match:
_, _, _, source = match.groups()
else:
# fallback to use the UID string as the rotation ID
pk = string
# in ical imported calendars, sequence and/or recurrence_id
# distinguish main recurring event vs instance modification
# (see https://icalendar.org/iCalendar-RFC-5545/3-8-4-4-recurrence-id.html)
if sequence:
pk = f"{pk}_{sequence}"
if recurrence_id:
pk = f"{pk}_{recurrence_id}"
if source is not None:
source = int(source)
from apps.schedules.models import CustomOnCallShift
source_verbal = CustomOnCallShift.SOURCE_CHOICES[source][1]
return pk, source_verbal
def get_usernames_from_ical_event(event):
usernames_found = []
priority = parse_priority_from_string(event.get(ICAL_SUMMARY, "[L0]"))
if ICAL_SUMMARY in event:
usernames_found.append(parse_username_from_string(event[ICAL_SUMMARY]))
if ICAL_DESCRIPTION in event:
usernames_found.append(parse_username_from_string(event[ICAL_DESCRIPTION]))
if ICAL_ATTENDEE in event:
if isinstance(event[ICAL_ATTENDEE], str):
# PagerDuty adds only one attendee and in this case event[ICAL_ATTENDEE] is string.
# If several attendees were added to the event than event[ICAL_ATTENDEE] will be list
# (E.g. several invited in Google cal).
usernames_found.append(parse_username_from_string(event[ICAL_ATTENDEE]))
return usernames_found, priority
def get_missing_users_from_ical_event(event, organization: "Organization"):
all_usernames, _ = get_usernames_from_ical_event(event)
users = list(get_users_from_ical_event(event, organization))
found_usernames = [u.username for u in users]
found_emails = [u.email.lower() for u in users]
return [u for u in all_usernames if u != "" and u not in found_usernames and u.lower() not in found_emails]
def get_users_from_ical_event(event, organization: "Organization") -> typing.Sequence["User"]:
usernames_from_ical, _ = get_usernames_from_ical_event(event)
users = []
if len(usernames_from_ical) != 0:
users = memoized_users_in_ical(tuple(usernames_from_ical), organization)
return users
def is_icals_equal_line_by_line(first, second):
first = first.split("\n")
second = second.split("\n")
if len(first) != len(second):
return False
else:
for idx, first_item in enumerate(first):
if first_item.startswith("DTSTAMP"):
continue
else:
second_item = second[idx]
if first_item != second_item:
return False
return True
def is_icals_equal(first, second):
first_cal = Calendar.from_ical(first)
if first_cal.get("PRODID", None) in ("-//My calendar product//amixr//", "-//web schedule//oncall//"):
# Compare schedules generated by oncall line by line, since they not support SEQUENCE field yet.
# But we are sure that same calendars will have same lines, since we are generating it.
return is_icals_equal_line_by_line(first, second)
else:
# Compare external calendars by events, since sometimes they contain different lines even for equal calendars.
second_cal = Calendar.from_ical(second)
first_subcomponents = first_cal.subcomponents
second_subcomponents = second_cal.subcomponents
# only consider VEVENT components
first_cal_events = {
cmp.get("UID", None): cmp.get("SEQUENCE", None) for cmp in first_subcomponents if cmp.name == "VEVENT"
}
second_cal_events = {
cmp.get("UID", None): cmp.get("SEQUENCE", None) for cmp in second_subcomponents if cmp.name == "VEVENT"
}
# check events and their respective sequences are equal
return first_cal_events == second_cal_events
def ical_date_to_datetime(date, tz, start):
datetime_to_combine = datetime.time.min
all_day = False
if type(date) == datetime.date:
all_day = True
calendar_timezone_offset = datetime.datetime.now().astimezone(tz).utcoffset()
date = datetime.datetime.combine(date, datetime_to_combine).astimezone(tz) - calendar_timezone_offset
if not start:
date -= datetime.timedelta(seconds=1)
return date, all_day
def calculate_shift_diff(shifts: list, prev_shifts: list) -> typing.Tuple[bool, list]:
"""
Get shifts diff comparing with the previous shifts
"""
fields_to_compare = ["users", "end", "start", "all_day", "priority_level", "shift"]
shifts_fields = [{k: v for k, v in shift.items() if k in fields_to_compare} for shift in shifts]
prev_shifts_fields = [{k: v for k, v in shift.items() if k in fields_to_compare} for shift in prev_shifts]
shift_changed = len(shifts) != len(prev_shifts)
diff = []
for idx, shift in enumerate(shifts_fields):
if shift not in prev_shifts_fields:
shift_changed = True
diff.append(shifts[idx])
return shift_changed, diff
def get_icalendar_tz_or_utc(icalendar):
calendar_timezone = icalendar.get("X-WR-TIMEZONE", "UTC")
if pytz_timezone := is_valid_timezone(calendar_timezone):
return pytz_timezone
# try to convert the timezone from windows to iana
if (converted_timezone := convert_windows_timezone_to_iana(calendar_timezone)) is None:
return "UTC"
return pytz.timezone(converted_timezone)
def fetch_ical_file_or_get_error(ical_url: str) -> typing.Tuple[str | None, str | None]:
cached_ical_file: str | None = None
ical_file_error: str | None = None
try:
new_ical_file = fetch_ical_file(ical_url)
Calendar.from_ical(new_ical_file)
cached_ical_file = new_ical_file
except requests.exceptions.RequestException:
ical_file_error = "iCal download failed"
except ValueError:
ical_file_error = "wrong iCal"
# TODO: catch icalendar exceptions
return cached_ical_file, ical_file_error
def fetch_ical_file(ical_url: str) -> str:
# without user-agent header google calendar sometimes returns text/html instead of text/calendar
headers = {"User-Agent": "Grafana OnCall"}
r = requests.get(ical_url, headers=headers, timeout=10)
logger.info(f"fetch_ical_file: content-type={r.headers.get('Content-Type')}")
return r.text
def create_base_icalendar(name: str) -> Calendar:
cal = Calendar()
cal.add("calscale", "GREGORIAN")
cal.add("x-wr-calname", name)
cal.add("x-wr-timezone", "UTC")
cal.add("version", "2.0")
cal.add("prodid", "//Grafana Labs//Grafana On-Call//")
# suggested minimum interval for polling for changes
cal.add("REFRESH-INTERVAL;VALUE=DURATION", "P1H")
return cal
def get_user_events_from_calendars(
ical_obj: Calendar, calendar: Calendar, user: User, name: typing.Optional[str] = None
) -> None:
if calendar:
for component in calendar.walk():
if component.name == "VEVENT":
event_user = get_usernames_from_ical_event(component)
event_user_value = event_user[0][0]
if event_user_value == user.username or event_user_value.lower() == user.email.lower():
if name:
component["SUMMARY"] = "{}: {}".format(name, component["SUMMARY"])
ical_obj.add_component(component)
def _get_ical_data_final_schedule(schedule: "OnCallSchedule") -> str | None:
ical_data = schedule.cached_ical_final_schedule
if ical_data is None:
schedule.refresh_ical_final_schedule()
# casting is safe here. cached_ical_final_schedule is updated inside of refresh_ical_final_schedule
return typing.cast(str, schedule.cached_ical_final_schedule)
return ical_data
def ical_export_from_schedule(schedule: "OnCallSchedule") -> bytes:
ical_data = _get_ical_data_final_schedule(schedule)
return ical_data.encode()
def user_ical_export(user: "User", schedules: "OnCallScheduleQuerySet") -> bytes:
schedule_name = "On-Call Schedule for {0}".format(user.username)
ical_obj = create_base_icalendar(schedule_name)
for schedule in schedules:
name = schedule.name
ical_data = _get_ical_data_final_schedule(schedule)
get_user_events_from_calendars(ical_obj, Calendar.from_ical(ical_data), user, name=name)
return ical_obj.to_ical()
def detect_gaps(intervals: DatetimeIntervals, start: datetime.datetime, end: datetime.datetime) -> DatetimeIntervals:
gaps: DatetimeIntervals = []
intervals = sorted(intervals, key=lambda dt: dt.start)
if len(intervals) > 0:
base_interval = intervals[0]
if base_interval.start > start:
gaps.append(DatetimeInterval(None, base_interval.start))
for interval in intervals[1:]:
overlaps, new_base_interval = merge_if_overlaps(base_interval, interval)
if not overlaps:
gaps.append(DatetimeInterval(base_interval.end, interval.start))
base_interval = new_base_interval
if base_interval.end < end:
gaps.append(DatetimeInterval(base_interval.end, None))
return gaps
def merge_if_overlaps(a: DatetimeInterval, b: DatetimeInterval) -> typing.Tuple[bool, DatetimeInterval]:
if a.end >= b.end:
return True, DatetimeInterval(a.start, a.end)
if b.start - a.end < datetime.timedelta(minutes=1):
return True, DatetimeInterval(a.start, b.end)
else:
return False, DatetimeInterval(b.start, b.end)
def start_end_with_respect_to_all_day(event: IcalEvent, calendar_tz):
start, _ = ical_date_to_datetime(event[ICAL_DATETIME_START].dt, calendar_tz, start=True)
end, _ = ical_date_to_datetime(event[ICAL_DATETIME_END].dt, calendar_tz, start=False)
return start, end
def event_start_end_all_day_with_respect_to_type(event: IcalEvent, calendar_tz):
all_day = False
if type(event[ICAL_DATETIME_START].dt) == datetime.date:
start, end = start_end_with_respect_to_all_day(event, calendar_tz)
all_day = True
else:
start, end = ical_events.get_start_and_end_with_respect_to_event_type(event)
return start, end, all_day
def convert_windows_timezone_to_iana(tz_name: str) -> str | None:
"""
Conversion info taken from https://raw.githubusercontent.com/unicode-org/cldr/main/common/supplemental/windowsZones.xml
Also see https://gist.github.com/mrled/8d29fde758cfc7dd0b52f3bbf2b8f06e
NOTE: This mapping could be updated, and it's technically a guess.
Also, there could probably be issues with DST for some timezones.
"""
windows_to_iana_map = {
"AUS Central Standard Time": "Australia/Darwin",
"AUS Eastern Standard Time": "Australia/Sydney",
"Afghanistan Standard Time": "Asia/Kabul",
"Alaskan Standard Time": "America/Anchorage",
"Aleutian Standard Time": "America/Adak",
"Altai Standard Time": "Asia/Barnaul",
"Arab Standard Time": "Asia/Riyadh",
"Arabian Standard Time": "Asia/Dubai",
"Arabic Standard Time": "Asia/Baghdad",
"Argentina Standard Time": "America/Buenos_Aires",
"Astrakhan Standard Time": "Europe/Astrakhan",
"Atlantic Standard Time": "America/Halifax",
"Aus Central W. Standard Time": "Australia/Eucla",
"Azerbaijan Standard Time": "Asia/Baku",
"Azores Standard Time": "Atlantic/Azores",
"Bahia Standard Time": "America/Bahia",
"Bangladesh Standard Time": "Asia/Dhaka",
"Belarus Standard Time": "Europe/Minsk",
"Bougainville Standard Time": "Pacific/Bougainville",
"Canada Central Standard Time": "America/Regina",
"Cape Verde Standard Time": "Atlantic/Cape_Verde",
"Caucasus Standard Time": "Asia/Yerevan",
"Cen. Australia Standard Time": "Australia/Adelaide",
"Central America Standard Time": "America/Guatemala",
"Central Asia Standard Time": "Asia/Almaty",
"Central Brazilian Standard Time": "America/Cuiaba",
"Central Europe Standard Time": "Europe/Budapest",
"Central European Standard Time": "Europe/Warsaw",
"Central Pacific Standard Time": "Pacific/Guadalcanal",
"Central Standard Time": "America/Chicago",
"Central Standard Time (Mexico)": "America/Mexico_City",
"Chatham Islands Standard Time": "Pacific/Chatham",
"China Standard Time": "Asia/Shanghai",
"Cuba Standard Time": "America/Havana",
"Dateline Standard Time": "Etc/GMT+12",
"E. Africa Standard Time": "Africa/Nairobi",
"E. Australia Standard Time": "Australia/Brisbane",
"E. Europe Standard Time": "Europe/Chisinau",
"E. South America Standard Time": "America/Sao_Paulo",
"Easter Island Standard Time": "Pacific/Easter",
"Eastern Standard Time": "America/New_York",
"Eastern Standard Time (Mexico)": "America/Cancun",
"Egypt Standard Time": "Africa/Cairo",
"Ekaterinburg Standard Time": "Asia/Yekaterinburg",
"FLE Standard Time": "Europe/Kiev",
"Fiji Standard Time": "Pacific/Fiji",
"GMT Standard Time": "Europe/London",
"GTB Standard Time": "Europe/Bucharest",
"Georgian Standard Time": "Asia/Tbilisi",
"Greenland Standard Time": "America/Godthab",
"Greenwich Standard Time": "Atlantic/Reykjavik",
"Haiti Standard Time": "America/Port-au-Prince",
"Hawaiian Standard Time": "Pacific/Honolulu",
"India Standard Time": "Asia/Calcutta",
"Iran Standard Time": "Asia/Tehran",
"Israel Standard Time": "Asia/Jerusalem",
"Jordan Standard Time": "Asia/Amman",
"Kaliningrad Standard Time": "Europe/Kaliningrad",
"Korea Standard Time": "Asia/Seoul",
"Libya Standard Time": "Africa/Tripoli",
"Line Islands Standard Time": "Pacific/Kiritimati",
"Lord Howe Standard Time": "Australia/Lord_Howe",
"Magadan Standard Time": "Asia/Magadan",
"Magallanes Standard Time": "America/Punta_Arenas",
"Marquesas Standard Time": "Pacific/Marquesas",
"Mauritius Standard Time": "Indian/Mauritius",
"Middle East Standard Time": "Asia/Beirut",
"Montevideo Standard Time": "America/Montevideo",
"Morocco Standard Time": "Africa/Casablanca",
"Mountain Standard Time": "America/Denver",
"Mountain Standard Time (Mexico)": "America/Chihuahua",
"Myanmar Standard Time": "Asia/Rangoon",
"N. Central Asia Standard Time": "Asia/Novosibirsk",
"Namibia Standard Time": "Africa/Windhoek",
"Nepal Standard Time": "Asia/Katmandu",
"New Zealand Standard Time": "Pacific/Auckland",
"Newfoundland Standard Time": "America/St_Johns",
"Norfolk Standard Time": "Pacific/Norfolk",
"North Asia East Standard Time": "Asia/Irkutsk",
"North Asia Standard Time": "Asia/Krasnoyarsk",
"North Korea Standard Time": "Asia/Pyongyang",
"Omsk Standard Time": "Asia/Omsk",
"Pacific SA Standard Time": "America/Santiago",
"Pacific Standard Time": "America/Los_Angeles",
"Pacific Standard Time (Mexico)": "America/Tijuana",
"Pakistan Standard Time": "Asia/Karachi",
"Paraguay Standard Time": "America/Asuncion",
"Qyzylorda Standard Time": "Asia/Qyzylorda",
"Romance Standard Time": "Europe/Paris",
"Russia Time Zone 10": "Asia/Srednekolymsk",
"Russia Time Zone 11": "Asia/Kamchatka",
"Russia Time Zone 3": "Europe/Samara",
"Russian Standard Time": "Europe/Moscow",
"SA Eastern Standard Time": "America/Cayenne",
"SA Pacific Standard Time": "America/Bogota",
"SA Western Standard Time": "America/La_Paz",
"SE Asia Standard Time": "Asia/Bangkok",
"Saint Pierre Standard Time": "America/Miquelon",
"Sakhalin Standard Time": "Asia/Sakhalin",
"Samoa Standard Time": "Pacific/Apia",
"Sao Tome Standard Time": "Africa/Sao_Tome",
"Saratov Standard Time": "Europe/Saratov",
"Singapore Standard Time": "Asia/Singapore",
"South Africa Standard Time": "Africa/Johannesburg",
"South Sudan Standard Time": "Africa/Juba",
"Sri Lanka Standard Time": "Asia/Colombo",
"Sudan Standard Time": "Africa/Khartoum",
"Syria Standard Time": "Asia/Damascus",
"Taipei Standard Time": "Asia/Taipei",
"Tasmania Standard Time": "Australia/Hobart",
"Tocantins Standard Time": "America/Araguaina",
"Tokyo Standard Time": "Asia/Tokyo",
"Tomsk Standard Time": "Asia/Tomsk",
"Tonga Standard Time": "Pacific/Tongatapu",
"Transbaikal Standard Time": "Asia/Chita",
"Turkey Standard Time": "Europe/Istanbul",
"Turks And Caicos Standard Time": "America/Grand_Turk",
"US Eastern Standard Time": "America/Indianapolis",
"US Mountain Standard Time": "America/Phoenix",
"UTC": "Etc/UTC",
"UTC+12": "Etc/GMT-12",
"UTC+13": "Etc/GMT-13",
"UTC-02": "Etc/GMT+2",
"UTC-08": "Etc/GMT+8",
"UTC-09": "Etc/GMT+9",
"UTC-11": "Etc/GMT+11",
"Ulaanbaatar Standard Time": "Asia/Ulaanbaatar",
"Venezuela Standard Time": "America/Caracas",
"Vladivostok Standard Time": "Asia/Vladivostok",
"Volgograd Standard Time": "Europe/Volgograd",
"W. Australia Standard Time": "Australia/Perth",
"W. Central Africa Standard Time": "Africa/Lagos",
"W. Europe Standard Time": "Europe/Berlin",
"W. Mongolia Standard Time": "Asia/Hovd",
"West Asia Standard Time": "Asia/Tashkent",
"West Bank Standard Time": "Asia/Hebron",
"West Pacific Standard Time": "Pacific/Port_Moresby",
"Yakutsk Standard Time": "Asia/Yakutsk",
"Yukon Standard Time": "America/Whitehorse",
}
result = windows_to_iana_map.get(tz_name)
logger.debug("Converting the timezone from Windows to IANA. '{}' -> '{}'".format(tz_name, result))
return result