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Add and improve comments about staggering of event listeners (#99058)

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This commit is contained in:
Erik Montnemery
2023-08-25 19:47:13 +02:00
committed by GitHub
parent 8768c39021
commit 3a71e21d6a
2 changed files with 12 additions and 6 deletions
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6
homeassistant/helpers/event.py
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@@ -68,6 +68,10 @@ _ENTITIES_LISTENER = "entities"
_LOGGER = logging.getLogger(__name__)
# Used to spread async_track_utc_time_change listeners and DataUpdateCoordinator
# refresh cycles between RANDOM_MICROSECOND_MIN..RANDOM_MICROSECOND_MAX.
# The values have been determined experimentally in production testing, background
# in PR https://github.com/home-assistant/core/pull/82233
RANDOM_MICROSECOND_MIN = 50000
RANDOM_MICROSECOND_MAX = 500000
@@ -1640,7 +1644,7 @@ def async_track_utc_time_change(
matching_seconds = dt_util.parse_time_expression(second, 0, 59)
matching_minutes = dt_util.parse_time_expression(minute, 0, 59)
matching_hours = dt_util.parse_time_expression(hour, 0, 23)
# Avoid aligning all time trackers to the same second
# Avoid aligning all time trackers to the same fraction of a second
# since it can create a thundering herd problem
# https://github.com/home-assistant/core/issues/82231
microsecond = randint(RANDOM_MICROSECOND_MIN, RANDOM_MICROSECOND_MAX)