def get_recent(self, site_id: int, unit: MetricUnit,
time: datetime.datetime, limit: int,
**kwargs) -> List[Measurement]:
metric_key = self.key_schema.timeseries_key(site_id, unit)
time_ms = unix_milliseconds(time)
initial_timestamp = time_ms - (limit * 60) * 1000
values = self.redis.range(metric_key, initial_timestamp,
time_ms) # type: ignore
return [
Measurement(site_id=site_id,
metric_unit=unit,
timestamp=value[0] / 1000,
value=value[1]) for value in islice(values, limit)
]
def _get_measurements_for_date(self, site_id: int, date: datetime.datetime,
unit: MetricUnit,
count: int) -> List[Measurement]:
"""
Return up to `count` elements from the sorted set corresponding to
the site_id, date, and metric unit specified here.
"""
measurements = []
# Get the metric key for the day implied by the date.
# metric:[unit-name]:[year-month-day]:[site-id]
# e.g.: metrics:whU:2020-01-01:1
key = self.key_schema.day_metric_key(site_id, unit, date)
# Get `count` number of items from the end of the sorted set.
metrics = self.redis.zrevrange(key, 0, count - 1, withscores=True)
for metric in metrics:
# `zrevrange()` returns (member, score) tuples, and within these
# tuples, "member" is a string of the form [measurement]:[minute].
# The MeasurementMinute class abstracts this for us.
mm = MeasurementMinute.from_zset_value(metric[0])
# Derive the datetime for the measurement using the date and
# the minute of the day. Note that this always returns datetime
# objects whose seconds value is zero.
date = self._get_date_from_day_minute(date, mm.minute_of_day)
# Add a new measurement to the list of measurements.
measurements.append(
Measurement(site_id=site_id,
metric_unit=unit,
timestamp=date,
value=mm.measurement))
return measurements