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rrd.py 2.41 KiB
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"""The data model used for the MetObs widgets using tower data.
"""

import os
from datetime import datetime, timedelta

import rrdtool

from metobs import data as d
from aosstower import station


# minimum set of records for the tower
VARS = {'air_temp', 'rh', 'dewpoint',
        'wind_speed', 'winddir_east', 'winddir_north',
        'pressure', 'precip', 'accum_precip',
        'solar_flux', 'altimeter'}


def add_vector_winds(record):
    east, north, spd = d.wind_vector_components(float(record['wind_speed']),
                                                float(record['wind_dir']))

    record['winddir_east'] = '%.3d' % east
    record['winddir_north'] = '%.3d' % north
    record['wind_speed'] = '%.3d' % spd


def add_altimeter(record, elev=station.ELEVATION):
    record['altimeter'] = '%.3d' % d.altimeter(float(record['pressure']), elev)


def add_dewpoint(record):
    record['dewpoint'] = '%.3d' % d.dewpoint(float(record['air_temp']),
                                             float(record['rh']))


def initialize_rrd(filepath, start=None, days=365, data_interval=5):
    """Create a new empty RRD database.
    """
    assert not os.path.exists(filepath), "DB already exists"
    start = start or (datetime.utcnow() - timedelta(days=days))
    # normalize start to data interval
    secs = d.to_unix_timestamp(start)
    secs -= secs % data_interval

    rrdtool.create(filepath,
                   '--start={}'.format(secs),
                   '--step={:d}'.format(data_interval),
                   'DS:air_temp:GAUGE:10:-40:50',
                   'DS:rh:GAUGE:10:0:100',
                   'DS:dewpoint:GAUGE:10:0:100',
                   'DS:wind_speed:GAUGE:10:0:100',
                   'DS:winddir_north:GAUGE:10:-100:100',
                   'DS:winddir_east:GAUGE:10:-100:100',
                   'DS:pressure:GAUGE:10:0:1100',
                   'DS:precip:GAUGE:10:0:100',
                   'DS:accum_precip:GAUGE:10:0:100',
                   'DS:solar_flux:GAUGE:10:0:1000',
                   'DS:altimeter:GAUGE:10:0:100',
                   # native resolution
                   'RRA:AVERAGE:0.5:1:6307200',
                   # 1 minute
                   'RRA:AVERAGE:0.5:{:d}:525600'.format(60/data_interval),
                   # 5 minute
                   'RRA:AVERAGE:0.5:{:d}:105120'.format(300/data_interval),
                   # 30 minute
                   'RRA:AVERAGE:0.5:{:d}:17520'.format(1800/data_interval))