rrd-sensors-logger

#!/usr/bin/env python

import os, sys

def Adafruit_DHT_read_func(st, pin):
	# XXX: untested leftover code from old python2 version, likely needs to be updated
	import Adafruit_DHT.common as c
	driver = c.get_platform().driver
	dht_err_names = dict((v,k[4:]) for k,v in vars(c).items() if k.startswith('DHT_'))
	def read_func():
		res, rh, t = driver.read(st, pin)
		if res == c.DHT_SUCCESS: read_err = None
		else:
			read_err = dht_err_names.get(res) or f'Unknown [{res}]'
			rh = t = None
		return read_err, rh, t
	return read_func

def Adafruit_DHT_read_proc(args):
	# XXX: untested leftover code from old python2 version, likely needs to be updated
	import Adafruit_DHT, json, select
	poller_timeout, = args
	poller_timeout = float(poller_timeout)
	poller = select.epoll()
	poller.register(sys.stdin, select.EPOLLIN)
	sys.stdout.write('!')
	sys.stdout.flush()

	read_funcs = dict()
	while True:
		try:
			if not poller.poll(poller_timeout): msg = ''
			else:
				msg = sys.stdin.read(3)
				if msg: msg = json.loads(sys.stdin.read(int(msg)))
				if not msg: raise IOError
		except KeyboardInterrupt: continue
		except OSError: return
		res = None
		if msg['cmd'] == 'read':
			st, pin = k = msg['st'], msg['pin']
			if k not in read_funcs:
				st = getattr(Adafruit_DHT, st or 'DHT22')
				read_funcs[k] = Adafruit_DHT_read_func(st, pin)
			res = read_funcs[k]()
		else: raise ValueError(msg)
		msg = json.dumps(res)
		sys.stdout.write(f'{len(msg):03d}{msg}')
		sys.stdout.flush()

# Special case for Adafruit_DHT module,
#  which fails in the main pid for some reason.
if __name__ == '__main__' and sys.argv[1] == '--dht-read-subproc':
	sys.exit(Adafruit_DHT_read_proc(sys.argv[2:]))


import collections as cs, pathlib as pl, datetime as dt, operator as op, functools as ft
import io, re, string, base64, time, math, json, stat, errno, tempfile
import glob, subprocess, signal, struct, contextlib, hashlib, logging

import rrdtool # should be installed with rrdtool binary/package


import yaml # https://pyyaml.org/

class LayeredAttrDict(cs.ChainMap):
	def __init__(self, *maps, **map0):
		super().__init__(*filter(None, [map0] + list(maps)))
	def __getitem__(self, k, _err=KeyError):
		k_maps = list()
		for m in self.maps:
			if k in m: k_maps.append(m[k])
		if not k_maps: raise _err(k)
		if not isinstance(k_maps[0], dict): return k_maps[0]
		return LayeredAttrDict(*(m for m in k_maps if isinstance(m, dict)))
	def __getattr__(self, k): return self.__getitem__(k, _err=AttributeError)
	def __setattr__(self, k, v):
		if k in ['maps']: return super().__setattr__(k, v)
		self[k] = v

yaml_load = yaml.safe_load
yaml_dump = lambda data, dst:\
	yaml.safe_dump(data, dst, allow_unicode=True, default_flow_style=False)
yaml.SafeDumper.add_representer(LayeredAttrDict, yaml.SafeDumper.represent_dict)


### systemd unit file:
#
# [Unit]
# After=time-sync.target
#
# [Service]
# Type=notify
# WatchdogSec=30
# Restart=always
# RestartSec=30
# StartLimitInterval=10min
# StartLimitBurst=10
# ExecStart=/usr/local/bin/rrd-sensors-logger --systemd daemon --http-listen
#
# [Install]
# WantedBy=multi-user.target

conf_base_str = '''
### rrd-sensors-logger configuration file (format: YAML)
### Place this file into ~/.rrd-sensors-logger.yaml or specify explicitly with --conf option.

rrd:
	# Parameters for the created rrd databases
	# Most are translated directly to values for "rrdtool create":
	#  http://oss.oetiker.ch/rrdtool/doc/rrdcreate.en.html

	storage_dir: /var/lib/rrd_logger
	name: rrd_logger.0 # can be used to encode schema version
	cleanup_after: 14d # remove unused rrd files older than that

	# Symlink that gets updated to point to a currently-used rrd file
	current_symlink: rrd_logger.current.rrd

	# See http://oss.oetiker.ch/rrdtool/doc/rrdcreate.en.html#IThe_HEARTBEAT_and_the_STEP
	step: 30s # finest granularity of stored data
	heartbeat: 60s # used for all DS'es, must be at least 20% greater than measurement interval

	aggregate:
		# RRA parameters for rrdtool
		cf: average
		xff: 0.8
		keep: 30d
		# "aggregate.step" gets converted to a number
		#  of datapoints, so it must be a multiple of "step" above
		step: 5min

	# "timesync_file" will contain current posix timestamp and uptime values
	# It should be checked on system boot to make sure clock doesn't get reset to
	#  some insanely-backwards value, as it will make datapoints completely meaningless
	# Best way to use the file would be to start some script with root privileges
	#  that would detect uptime wrap-arounds (abort if it wasn't),
	#  then check if time has been synced via NTP (abort if it was),
	#  then set the time to timestamp to this value + new uptime + update_interval
	# File will be created under "storage_dir" (can be set above)
	timesync_file:
		enabled: true
		offset: 5s # roughly the time for RPi to boot
		path: last_write.timestamps
		check: true
		check_fatal: true

meas:
	interval: 20
	sensors:
		## Common keys for all sensors:
		##  type: type_name # used to pick the code to query the sensor, mandatory
		##  disabled: false # do no actually read stuff from sensor (only return errors), optional
		## Below are examples for implemented sensors.

		# rpi_soc: # sensor name (will correspond to rrd DS name)
		#   type: rpi_soc
		#   # path: /sys/class/thermal/thermal_zoneX/temp
		# mb:
		#   type: lm
		#   chip: atk0110-acpi-0 # see "sensors -u" output
		#   feature: temp1 # either this or "feature_type" can be specified to remove ambiguity
		#   # feature_type: t # v, rpm, t
		# cpu:
		#   type: lm
		#   chip: k10temp-pci-00c3
		#   # only one feature here, so no need for other specs
		# dht22_indoors:
		#   type: adafruit_dht # requires github.com/adafruit/Adafruit_Python_DHT
		#   sysfs_gpio_pin: 9 # must be specified
		#   # sensor_type: DHT22 # as defined in Adafruit_DHT module, DHT22 is the default
		#   # gpio_init: false # null/false, { in | high | low }[-{ up | down | off }]
		#   # retry: [6, 0.2, 1.5] # [attempts, initial_delay, delay_factor], optional
		#   # subprocess: true # query each sensor in its own subprocess, seem to be Adafruit_DHT issue
		# sht75_outside:
		#   type: sht # requires github.com/mk-fg/sht-sensor
		#   sysfs_gpio_pin_sck: 30 # must be specified
		#   sysfs_gpio_pin_data: 60 # must be specified
		#   # sensor_voltage_spec: 3.5V # either 3.5V or 5V, 3.5V (recommended) is the default

graph:
	opts:
		full-size-mode: true
		width: 1000
		height: 500
		start: -5h
		end:
		left-axis-format: '%0.1lf'

'''.replace('\t', '  ')
conf_base = yaml_load(conf_base_str)


### For bencode-like bits below
# Based on old python2 module by Petru Paler, it's not an actual bencode format
# Different from vanilla bencode - encodes none/bool types
# Used only for data_hash below, which itself is only used to generate rrd names from schema

def _ns_class(cls_name, cls_parents, cls_attrs):
	func_type = type(lambda: None)
	for k, v in cls_attrs.items():
		if isinstance(v, func_type): cls_attrs[k] = classmethod(v)
	return type(cls_name, cls_parents, cls_attrs)

class BTEError(Exception): pass

class Bencached:
	__slots__ = 'bencoded',
	def __init__(self, s): self.bencoded = s

class BTE(metaclass=_ns_class):

	def decode_int(cls, x, f):
		f += 1
		newf = x.index(b'e', f)
		n = int(x[f:newf])
		if x[f] == b'-':
			if x[f + 1] == b'0': raise ValueError
		elif x[f] == b'0' and newf != f+1: raise ValueError
		return n, newf+1
	def decode_str(cls, x, f):
		colon = x.index(b':', f)
		n = int(x[f:colon])
		if x[f] == b'0' and colon != f+1: raise ValueError
		colon += 1
		return (x[colon:colon+n], colon+n)
	def decode_list(cls, x, f):
		r, f = [], f+1
		while x[f] != b'e':
			v, f = cls.decode_func[x[f]](cls, x, f)
			r.append(v)
		return r, f + 1
	def decode_dict(cls, x, f):
		r, f = {}, f+1
		while x[f] != b'e':
			k, f = cls.decode_str(x, f)
			r[k], f = cls.decode_func[x[f]](cls, x, f)
		return r, f + 1
	def decode_none(cls, x, f): return None, f+1
	decode_func = dict(l=decode_list, d=decode_dict, i=decode_int, n=decode_none)
	for n in range(10): decode_func[str(n)] = decode_str
	decode_func = dict((k.encode(), v) for k,v in decode_func.items())

	def encode_bencached(cls, x, r): r.append(x.bencoded)
	def encode_int(cls, x, r): r.extend((b'i', str(x), b'e'))
	def encode_float(cls, x, r): r.extend((b'f', struct.pack('!d', x), b'e'))
	def encode_bool(cls, x, r):
		if x: cls.encode_int(1, r)
		else: cls.encode_int(0, r)
	def encode_str(cls, x, r):
		if isinstance(x, str): x = x.encode()
		r.extend((str(len(x)), b':', x))
	def encode_list(cls, x, r):
		r.append(b'l')
		for i in x: cls.encode_func[type(i)](cls, i, r)
		r.append(b'e')
	def encode_dict(cls, x, r):
		r.append(b'd')
		for k, v in sorted(x.items()):
			r.extend((str(len(k)), b':', k))
			cls.encode_func[type(v)](cls, v, r)
		r.append(b'e')
	def encode_none(cls, x, r): r.append(b'n')
	encode_func = {
		Bencached: encode_bencached,
		str: encode_str,
		bytes: encode_str,
		int: encode_int,
		float: encode_float,
		list: encode_list,
		tuple: encode_list,
		dict: encode_dict,
		bool: encode_bool,
		type(None): encode_none }

	def bdecode(cls, x):
		try: r, l = cls.decode_func[x[0]](cls, x, 0)
		except (IndexError, KeyError, ValueError) as err:
			raise BTEError(f'Not a valid bencoded string: {err}')
		if l != len(x):
			raise BTEError('Invalid bencoded value (data after valid prefix)')
		return r

	def bencode(cls, x):
		r = list()
		cls.encode_func[type(x)](cls, x, r)
		return b''.join((v.encode() if isinstance(v, str) else v) for v in r)

def b64(data):
	return base64.urlsafe_b64encode(data).rstrip(b'=').decode()

def get_uid_token(chars=4):
	assert chars * 6 % 8 == 0, chars
	return b64(os.urandom(chars * 6 // 8))

def data_hash(data, n=20, **kws):
	data = _data_hash(data, **kws)
	if not n or n <= 0: return data
	assert n <= len(data), [n, len(data)]
	return data[:n]

def _data_hash(data, as_bencode=False, as_hex=False):
	data = BTE.bencode(data)
	if as_bencode: return data
	data = hashlib.sha256(data)
	if as_hex: return data.hexdigest()
	return b64(data.digest())


class TSValueError(Exception): pass

_short_ts_days = dict(y=365.2422, yr=365.2422, mo=30.5, w=7, d=1)
_short_ts_s = dict(h=3600, hr=3600, m=60, min=60, s=1, sec=1)

def _short_ts_regexp():
	rex = list('^-?')
	for k in [*_short_ts_days, *_short_ts_s]:
		rex.append(fr'(?P<{k}>\d+{k}\s*)?')
	return re.compile(''.join(rex), re.I | re.U)
_short_ts_regexp = _short_ts_regexp()

def ts_diff_parse(spec, t=float, as_td_obj=False):
	try: spec = float(spec)
	except ValueError: pass
	else: return t(spec)
	spec = spec.strip()
	if re.search(r'^[\d.]+$', spec): spec = f'{spec}s'
	m = _short_ts_regexp.search(spec)
	if not m: raise ValueError(spec)
	delta, delta_any = list(), False
	parse_int = lambda v: int(''.join(c for c in v if c.isdigit()))
	for units in [_short_ts_days, _short_ts_s]:
		val = 0
		for k, v in units.items():
			try:
				if not m.group(k): continue
				n = parse_int(m.group(k))
			except IndexError: continue
			delta_any, val = True, val + n * v
		delta.append(val)
	if not delta_any:
		raise ValueError(f'Invalid time delta specification: {spec!r}')
	td = dt.timedelta(*delta)
	return td if as_td_obj else t(td.total_seconds())

def ts_diff_repr( ts_or_delta, ts0=None, ext=None, absolute_diff=False,
		_units=dict( h=3600, m=60, s=1,
			y=365.2422*86400, mo=30.5*86400, w=7*86400, d=1*86400 ) ):
	if isinstance(ts0, (int, float)): ts0 = dt.datetime.fromtimestamp(ts_or_delta)
	assert ts0 is None or isinstance(ts0, (int, float, dt.datetime)), ts0
	if isinstance(ts_or_delta, (int, float)):
		ts_or_delta = dt.timedelta(seconds=ts_or_delta)\
			if not ts0 else dt.datetime.fromtimestamp(ts_or_delta)
	delta = (ts_or_delta - (ts0 or dt.datetime.now()))\
		if not isinstance(ts_or_delta, dt.timedelta) else ts_or_delta
	if absolute_diff: delta = abs(delta)
	res, s = list(), delta.total_seconds()
	for unit, unit_s in sorted(_units.items(), key=op.itemgetter(1), reverse=True):
		val = math.floor(s / unit_s)
		if not val: continue
		res.append(f'{val:.0f}{unit}')
		if len(res) >= 2: break
		s -= val * unit_s
	if not res: return 'now'
	else:
		if ext: res.append(ext)
		return ' '.join(res)

def get_uptime():
	with open('/proc/uptime', 'rb') as src: return float(src.readline().split()[0])


@contextlib.contextmanager
def safe_replacement(path):
	kws = dict( delete=False,
		dir=os.path.dirname(path), prefix=os.path.basename(path)+'.' )
	with tempfile.NamedTemporaryFile(**kws) as tmp:
		try: mode = stat.S_IMODE(os.stat(path).st_mode)
		except (OSError, IOError): mode = None
		try:
			yield tmp
			tmp.flush()
			if mode is not None: os.fchmod(tmp.fileno(), mode)
			os.rename(tmp.name, path)
		except safe_replacement.cancel: pass
		finally:
			try: os.unlink(tmp.name)
			except (OSError, IOError): pass

class CancelFileReplacement(Exception): pass
safe_replacement.cancel = CancelFileReplacement



class RRD:

	# DS:ds-name:GAUGE | COUNTER | DERIVE | ABSOLUTE:heartbeat:min:max
	# RRA:AVERAGE | MIN | MAX | LAST:xff:steps:rows

	ds_types = 'gauge', 'counter', 'derive', 'absolute' # "compute" is different
	rra_cfs = 'average', 'min', 'max', 'last'

	def __init__(self, storage_dir, name, timesync=None, log=None):
		self.storage_dir, self.name = pl.Path(storage_dir), name
		self._path = self._dss = None
		self.log = log or logging.getLogger(f'rrd.{id(self):x}')

		self.timesync = timesync
		if timesync:
			timesync.path = self.storage_dir / timesync.path
			if timesync.offset: timesync.offset = ts_diff_parse(timesync.offset)
			self.timesync_file_check()


	def ds_for_sensor_metric(self, sensor_name, metric):
		assert '__' not in sensor_name + metric, [sensor_name, metric]
		return f'{sensor_name}__{metric}'
	def sensor_metric_for_ds(self, ds): return tuple(ds.split('__'))

	def timesync_file_write(self):
		if not self.timesync: return
		uptime, ts = get_uptime(), time.time()
		if self.timesync.offset: ts += self.timesync.offset
		with safe_replacement(self.timesync.path) as dst:
			dst.write(f'{uptime!r} {ts!r}\n'.encode())

	def timesync_file_check(self):
		if not self.timesync or not self.timesync.check: return
		try:
			with open(self.timesync.path, 'rb') as src:
				src_uptime, src_ts = map(float, src.read().split())
		except IOError as err:
			if err.errno != errno.ENOENT: raise
		except Exception as err:
			self.log.warn( 'Failed to process/check timestamp/uptime'
				' values from timesync file %r: %s', self.timesync.path, err )
		else:
			uptime, ts = get_uptime(), time.time()
			if src_uptime > uptime and src_ts > ts:
				err_msg = ( f'Detected uptime roll-over ({src_uptime:.1f} -> {uptime:.1f}) with'
					f' backwards time (delta: {abs(src_ts - ts):.1f}), this will cause a lot of issues' )
				if self.timesync.check_fatal: raise RuntimeError(err_msg)
				else: log.error(err_msg)


	@property
	def path(self):
		assert self._path, ( '"ensure_schema" method must'
			' be called before any kind of access/manipulation methods' )
		return self._path

	@staticmethod
	def _path_meta(path):
		return f'{path}.meta'
	@property
	def path_meta(self):
		return self._path_meta(self.path)

	def ensure_schema(self, step, dss, rras, symlink_to=None, cleanup_td=None):
		assert dss and rras, [dss, rras]
		for ds in dss:
			if 'name' not in ds: ds['name'] = self.ds_for_sensor_metric(*ds['src'])
			assert ds['t'] in self.ds_types, ds['t']

		schema = dict(step=step, dss=dss, rras=rras)
		self._path = self.storage_dir / f'{self.name}.{data_hash(schema, n=10)}.rrd'
		self._dss = list(ds['name'] for ds in dss)
		assert len(set(self._dss)) == len(self._dss), dss

		if not self.path.exists():
			self.log.debug('Creating new rrd database: %r', self.path)
			self.storage_dir.mkdir(parents=True, exist_ok=True)
			rrd_clause = lambda t, *a: opts.append(':'.join(map(str, [t.upper()] + list(a))))
			opts = [str(self.path), '--step', str(step)]
			for ds in dss:
				rrd_clause( 'ds', ds['name'], ds['t'].upper(),
					int(ds['hb']), ds.get('min') or 'U', ds.get('max') or 'U' )
			for rra in rras:
				rrd_clause( 'rra', rra['cf'].upper(),
					f'{rra["xff"]:.2f}', rra['steps'], rra['rows'] )
			rrdtool.create(opts)
			with open(self.path_meta, 'w') as dst:
				dst.write('### Auto-generated on database creation\n'
					'### Only some timestamps are used for dir cleanup purposes\n')
				yaml_dump(dict(schema=schema, ts=dict(created=time.time())), dst)

		if symlink_to:
			symlink_to = self.storage_dir / symlink_to
			try: dst = pl.Path(os.readlink(symlink_to))
			except OSError: dst = None
			if not dst or self.path.resolve() != dst.resolve():
				if symlink_to.exists(): os.unlink(symlink_to)
				os.symlink(self.path.resolve(), symlink_to)

		if cleanup_td is not None:
			ts = time.time()
			for p in self.storage_dir.glob(f'{self.name}.*.rrd'):
				if p.resolve() == self.path.resolve(): continue
				p_meta = self._path_meta(p)
				try:
					ts_p = os.stat(p).st_mtime
					try: ts_p = max(ts_p, os.stat(p_meta).st_mtime)
					except (OSError, IOError): pass
				except (OSError, IOError): continue
				if ts_p < ts - cleanup_td:
					self.log.debug('Removing old rrd file: %r', p)
					for p in p, p_meta:
						try: os.unlink(p)
						except (OSError, IOError): pass

	def load_schema(self, path):
		self._path = (self.storage_dir / path).resolve()
		paths = self.path, self.path_meta
		assert all(p.exists() for p in paths), paths


	def update(self, vals_dict, ts=None):
		'vals_dict should be {(sensor_name, metric): value, ...}.'
		if not vals_dict: return
		if ts is None: ts = time.time()
		entry = dict((self.ds_for_sensor_metric(*k), v) for k, v in vals_dict.items())
		entry_str = ':'.join([str(ts), *(str(entry.pop(k, 'U')) for k in self._dss)])
		assert not entry, entry # some unknown keys left-over
		self.timesync_file_write()
		rrdtool.update(str(self.path), entry_str)

	def fetch_last_update(self):
		'Returns ts and dict with values stored on last db update.'
		# There is no way to do it through API atm, sadly
		lines = subprocess.check_output(
			['rrdtool', 'lastupdate', self.path], close_fds=True ).splitlines()
		ts, keys = None, list(self.sensor_metric_for_ds(k) for k in lines[0].split())
		vals = dict.fromkeys(keys)
		for line in lines[1:]:
			if not line.strip(): continue
			ts, line = line.split(':', 1)
			line = line.split()
			assert len(line) == len(keys), [keys, line]
			for k, v in zip(keys, line):
				try: vals[k] = float(v)
				except ValueError: pass # assuming unknown
		if ts: ts = float(ts)
		return ts, vals

	def fetch_last_values(self, time_delta, cf='average'):
		'''Returns a dict with average value for each metric for specified time delta.
			"cf" argument specifies consolidation function to pass to rrdtool, used for
				picking appropriate RRAs, but values returned from rrdtool will still be averaged.'''
		assert cf in self.rra_cfs, cf
		td = int(round(ts_diff_parse(time_delta)))
		(rra_ts0, rra_ts1, rra_step), keys, vals = rrdtool.fetch(
			self.path, cf.upper(), '--resolution', str(td), '--start', f'-{td}' )
		vals = dict(( self.sensor_metric_for_ds(k),
			list(v[n] for v in vals if v[n] is not None) ) for n,k in enumerate(keys))
		for k, vs in vals.items(): # average what's left there
			vals[k] = (sum(vs) / len(vs)) if vs else None
		return vals

	def get_meta(self):
		return LayeredAttrDict(yaml_load(self.path_meta))

	def get_info(self):
		info_tree = LayeredAttrDict()
		for k, v in rrdtool.info(self.path).items():
			# Parse stuff like "rra[1].cdp_prep[0].value" and "ds[speed].minimal_heartbeat"
			br, keys = info_tree, cs.deque(k.split('.'))
			while keys:
				kk = keys.popleft()
				m = re.search(r'^(?P<n>[\w\d_]+)(?:\[(?P<k>[\w\d_]+)\])?', kk)
				if not m: raise KeyError(k)
				mn, mk = m.group('n'), m.group('k')
				br_prev, br = br, br.setdefault(mn, dict())
				if mk:
					assert mk not in br, [k, mk, br]
					keys.append(mk)
				elif not keys: br_prev[mn] = v
		return info_tree


	color_scale_c10 = ( '#1f77b4 #ff7f0e #2ca02c' # d3.scale.category10
		' #d62728 #9467bd #8c564b #e377c2 #7f7f7f #bcbd22 #17becf' ).split()

	def graph( self, metrics, sensors, image_path=None,
			legend_style='stats-table',
			hrules=None, colors=None, units=None, alt_axis=None,
			perc=None, perc_direction='+-', defs_table_len=100, **cli_opts ):
		# http://oss.oetiker.ch/rrdtool/gallery/index.en.html
		# http://oss.oetiker.ch/rrdtool/doc/rrdgraph.en.html#IOPTIONS
		# http://oss.oetiker.ch/rrdtool/doc/rrdgraph_graph.en.html
		# http://oss.oetiker.ch/rrdtool/doc/rrdgraph_data.en.html
		# http://oss.oetiker.ch/rrdtool/doc/rrdgraph_rpn.en.html
		# http://oss.oetiker.ch/rrdtool/doc/rrdgraph_examples.en.html

		if isinstance(metrics, str): metrics = [metrics]
		if image_path is None:
			image_path = tempfile.NamedTemporaryFile(
				prefix='rrd.chart.', suffix='.png', delete=False ).name
		assert legend_style == 'stats-table', legend_style

		opts = dict( # sane-ish defaults
			width=1000, height=500,
			start='-24h', end=None, imgformat='PNG',
			pango_markup=True, font='LEGEND:7:monospace' )
		if alt_axis:
			m = alt_axis['metric']
			opts.update(
				right_axis_label=f'{m}, {sensors[m][0]}',
				right_axis_format=alt_axis.get('format'),
				right_axis_formatter=alt_axis.get('formatter'),
				right_axis=f'{alt_axis.get("scale", 1)}:{alt_axis.get("shift", 0)}' )
		opts.update(cli_opts or dict())

		colors = iter(colors or self.color_scale_c10)
		assert not set(perc_direction).difference('+-'), perc_direction

		defs = ['TEXTALIGN:left']
		def def_label(sn, cf=None, length=3, _src=list()):
			if not _src: _src.extend([iter(range(2**30)), string.ascii_lowercase])
			u, un, us, ul = '', next(_src[0]), _src[1], len(_src[1])
			for n in range(length): u, un = us[un % ul] + u, un // ul
			return f'{sn}_{cf or ""}_{u}'
		def defs_add(sn, cfs, fmt=None, def_t=None):
			if isinstance(cfs, str): cfs = [cfs]
			if not def_t: def_t = 'cdef' if len(cfs) > 1 else 'vdef'
			gprint, sn_base = None, sn
			for cf in cfs:
				if isinstance(cf, str): cf = [def_t, cf]
				(cf_t, cf), k = cf, def_label(sn_base)
				if '{sn}' not in cf: cf = '{{sn}},{}'.format(cf.replace('{', '{{').replace('}', '}}'))
				defs.append(f'{cf_t.upper()}:{k}={cf}'.format(sn=sn))
				if fmt: gprint = 'GPRINT:{k}:{fmt}'.format(k=k, fmt=fmt.replace(':', r'\:'))
				sn, k = k, None
			if gprint: defs.append(gprint)

		defs.append(r'COMMENT:{}\n'.format('-'*defs_table_len))

		msusn = list()
		for m in metrics:
			units, ss = sensors[m]
			if 'vertical_label' not in opts: opts['vertical_label'] = f'{m}, {units}'
			sns = list(f'{s}_{m}' for s in ss)
			for s, sn in zip(ss, sns): msusn.append((m, s, units, sn))
		sn_len, u_len = (max(len(v[n]) for v in msusn) for n in [3, 2])

		for m, s, units, sn in msusn:
			# Line
			defs.append(f'DEF:{sn}={self.path}:{s}__{m}:AVERAGE')
			defs.append(f'LINE1:{sn}{next(colors)}:{sn}')

			# Legend
			sn_pad, u_pad = sn_len - len(sn), u_len - len(units)
			defs.append('COMMENT:{}{}{}'.format(' '*sn_pad, units, ' '*u_pad))

			for label, cf in [
					('last', 'LAST'), ('avg', 'AVERAGE'),
					('min', 'MINIMUM'), ('max', 'MAXIMUM') ]:
				vdef = f'{sn}_{label}'
				defs_add(sn, cf, f'<small>{label.title()}:</small> %4.1lf')
			for p in perc or list():
				if p.endswith('σ'): pn, p = p, {'1σ': 68.2, '2σ': 95.4, '3σ': 99.7}[p]
				else: pn = f'{p}%'
				if len(perc_direction) == 1:
					pd = perc_direction[0]
					pn += pd
					if pd == '+':
						defs_add( sn,
							f'{p},PERCENTNAN',
							f'<small>{pn}:</small> %4.1lf' )
					else:
						defs_add( sn,
							['-1,*', ['vdef', f'{p},PERCENTNAN']],
							f'<small>{pn}:</small> %5.1lf' )
				else:
					defs_add( sn,
						['-1,*', ['vdef', f'{p},PERCENTNAN']],
						f'<small>{pn}:</small> %5.1lf' )
					defs_add(sn, f'{p},PERCENTNAN', '%4.1lf')
			defs.append(r'COMMENT:\n')

		defs.append(r'COMMENT:{}\n'.format('-'*defs_table_len))

		for hrule in hrules or list():
			if not isinstance(hrule, dict): hrule = dict(v=hrule)
			hrule = LayeredAttrDict(hrule)
			if not hrule.get('c'): hrule['c'] = next(colors)
			d = f'HRULE:{hrule["v"]}{hrule["c"]}'
			if hrule.get('legend'): d += f':{hrule["legend"]}'
			if hrule.get('dashes'):
				d += ':dashes{}'.format(
					'' if hrule['dashes'] is True else f'={hrule["dashes"]}' )
				if hrule.get('dash_offset'): d += f':dash-offset={hrule["dash_offset"]}'
			defs.append(d)

		args = [str(image_path)]
		for k, v in opts.items():
			if v in [None, False]: continue
			if len(k) != 1:
				args.append(''.join(['--', k.replace('_', '-'), '' if v is True else f'={v}']))
			else:
				args.append(f'-{k}')
				if v is not True: args.append(str(v))
		rrdtool.graph(*map(str, args + defs))

		return image_path


def init_rrd(sensors_interval, sensors, conf):
	rrdb_timesync = conf.timesync_file.enabled and conf.timesync_file
	rrdb = RRD(conf.storage_dir, conf.name, rrdb_timesync)
	ds_step = ts_diff_parse(conf.step, t=int)
	ds_hb = ts_diff_parse(conf.heartbeat, t=int)

	if ds_hb < sensors_interval * 1.2:
		raise AssertionError(
			f'rrd.heartbeat ({conf.heartbeat:.2f}s) must be at least 20%'
			f' greater than interval between measurements ({sensors_interval:.2f}s)' )

	dss = list()
	for k,s in sensors.items():
		assert re.search(r'^[a-zA-Z0-9_]+$', k), k
		for sk,sv in s.values.items():
			dss.append(dict(
				min=sv.get('min'), max=sv.get('max'),
				src=(k, sk), t=sv.t, hb=ts_diff_parse(conf.heartbeat, t=int) ))

	rra_step = ts_diff_parse(conf.aggregate.step, t=int)
	if rra_step % ds_step != 0:
		raise AssertionError(
			f'Aggregation (RRA) step ({conf.aggregate.step!r})'
			f' must be a multiple of data source (DS) step ({conf.step!r})' )
	rras =[dict(
		xff=conf.aggregate.xff, cf='average',
		steps=int(round(rra_step / ds_step)),
		rows=ts_diff_parse(conf.aggregate.keep, t=int) // rra_step + 1 )]

	rrdb.ensure_schema( step=ds_step,
		dss=dss, rras=rras, symlink_to=conf.current_symlink,
		cleanup_td=conf.cleanup_after and ts_diff_parse(conf.cleanup_after) )
	return rrdb


def rrd_conf_graph( conf, rrdb,
		metrics=None, ss=None, opts=None, threshold=None, path=None ):
	if not metrics: metrics = sensors.metric_default
	if isinstance(metrics, str): metrics = [metrics]
	ss = dict( (m, (sensors.units[m], ss)) for m, ss in
		sensors.filter_by_metrics(metrics, ss or conf.meas.sensors).items() )
	alt_axis = dict(metric=metrics[1], scale=1, shift=1)\
		if len(metrics) > 1 and metrics[1] in ss else None

	graph_opts = conf.graph.opts.copy()
	graph_opts.update( perc=['1σ', '2σ'],
		title='{} history'.format(' / '.join(sensors.metrics[m].title() for m in metrics)) )
	for d in opts or list():
		if not d.strip().startswith('{'): d = f'{{{d}}}'
		graph_opts.update(yaml_load(d))

	hrules = list()
	for spec in threshold or list():
		desc, v = spec.split(':', 1)
		v = float(v)
		hrules.append(dict( v=v, dashes=True,
			legend=f'{desc} threshold ({sensors.value_repr(v, metrics[0])})' ))

	image_path = rrdb.graph( metrics, ss,
		image_path=path, hrules=hrules, alt_axis=alt_axis, **graph_opts )
	return image_path


class HTTPPollExit(Exception): pass

def httpd_poller(conf, rrdb, bind, http_opts=None, http_opts_allow=False):
	import http.server, urllib.parse, socketserver, select, mimetypes, base64

	httpd_log = log or logging.getLogger('httpd')

	@contextlib.contextmanager
	def rrd_graph(*args, **kws):
		image_path = rrd_conf_graph(conf, rrdb, *args, **kws)
		try: yield image_path
		finally:
			try: os.unlink(image_path)
			except (OSError, IOError): pass

	class HTTPReqHandler(http.server.BaseHTTPRequestHandler):

		req_id = None

		def setup(self):
			self.req_id = get_uid_token(4)
			super().setup()

		def log_message(self, fmt, *args):
			httpd_log.debug( 'http-req[%s] :: %s - - [%s] %s', self.req_id,
				self.client_address[0], self.log_date_time_string(), fmt % args )

		def do_GET(self):
			params = self.path.split('/', 3)[1:3]
			if self.path == '/favicon.ico': return ''
			try: metrics, opts_ext = list(urllib.parse.unquote_plus(p) for p in params)
			except ValueError:
				try: (metrics,), opts_ext = params, None
				except ValueError: metrics = opts_ext = None
			opts = list(http_opts or list())
			if http_opts_allow and opts_ext: opts.append(opts_ext)
			if metrics:
				if not re.search(r'^[-a-zA-Z0-9_ ]+$', metrics):
					return self.send_error( 400,
						f'Bad request - invalid metric name spec: {metrics!r}' )
				metrics = metrics.replace('-', ' ').split(' ')

			with rrd_graph(metrics=metrics, opts=opts) as image_path:
				ct, enc = mimetypes.guess_type(image_path)
				if not ct: ct = 'image/png'
				with open(image_path, 'rb') as src:
					src.seek(0, os.SEEK_END)
					self.send_response(200)
					self.send_header('Content-Type', ct)
					self.send_header('Content-Length', src.tell())
					self.end_headers()
					src.seek(0)
					for chunk in iter(ft.partial(src.read, 2**20), b''): self.wfile.write(chunk)

	class ReusePortTCPServer(socketserver.TCPServer): allow_reuse_address = True
	httpd, poller = ReusePortTCPServer(bind, HTTPReqHandler), select.epoll()
	poller.register(httpd.fileno(), select.EPOLLIN)

	def httpd_poller(delay):
		ts = time.time()
		ts1 = ts + delay
		while True:
			delay = ts1 - ts
			if delay <= 0: break
			try: events = poller.poll(delay)
			except KeyboardInterrupt: raise HTTPPollExit
			for fd, ev in events:
				req, addr = httpd.get_request()
				httpd.verify_request(req, addr)
				try: httpd.process_request(req, addr)
				except Exception as err:
					httpd_log.exception( 'Error when processing request'
						' from %s: [%s] %s', addr, err.__class__.__name__, err )
					httpd.shutdown_request(req)
			ts = time.time()

	return httpd_poller


class RawMemSlice:
	# XXX: untested leftover code from old python2 version, likely needs to be updated

	# Read/write always normalize-to/expect LE bytes
	# All units are bytes too, not words or pages

	wf = 'I'
	w = struct.calcsize(wf) # size of a word that will be used for reading/writing
	wm = ~(w - 1)

	def __init__(self, addr, n):
		import mmap
		self.addr_base = addr & ~(mmap.PAGESIZE - 1)
		self.addr_offset = addr - self.addr_base
		self.mem_len = mmap.PAGESIZE * int(math.ceil(
			(n + self.addr_offset) / mmap.PAGESIZE ))
		self.fd = os.open('/dev/mem', os.O_RDWR | os.O_SYNC)
		self.mem = mmap.mmap( self.fd, self.mem_len,
			mmap.MAP_SHARED, mmap.PROT_READ | mmap.PROT_WRITE, offset=self.addr_base )

	def __del__(self):
		try: os.close(self.fd)
		except: pass

	def read(self, n=None, offset=0, unpack=False):
		if n is None: n = self.w
		seek = self.addr_offset & self.wm
		offset += self.addr_offset - seek
		self.mem.seek(seek)
		buff = list()
		for i in range(int(math.ceil((offset + n) / self.w))):
			word, = struct.unpack(self.wf, self.mem.read(self.w))
			buff.append(struct.pack('<I', word))
		buff = ''.join(buff)[offset:offset+n+1]
		if unpack:
			assert n == self.w, [n, self.w]
			buff, = struct.unpack(self.wf, buff)
		return buff

	def write(self, buff, offset=0):
		if isinstance(buff, int): buff = struct.pack(self.wf, buff)
		self.mem.seek(self.addr_offset + offset)
		self.mem.write(buff)

class InvalidPlatform(Exception): pass

def detect_rpi():
	if not hasattr(detect_rpi, 'cache'):
		import re
		with open('/proc/cpuinfo', 'r') as src: cpuinfo = src.read()
		m = re.search(r'^Revision\s*:\s*([\da-f]{4})$', cpuinfo, re.MULTILINE | re.I)
		if not m: raise OSError(cpuinfo)
		# https://elinux.org/RPi_HardwareHistory
		rev, rev_int = m.group(1).lower(), int(m.group(1), 16)
		if rev_int <= 0x15 or rev in '900021 900032'.split(): hw = 'rpi1'
		elif rev in 'a01040 a01041 a21041 a22042'.split(): hw = 'rpi2'
		elif rev in '900092 900093 920093 9000c1'.split(): hw = 'rpi0'
		elif rev in 'a02082 a020a0 a22082 a32082 a020d3'.split(): hw = 'rpi3'
		else: raise OSError(rev, cpuinfo)
		detect_rpi.cache = hw
	return detect_rpi.cache

def rpi_set_internal_resistor_state(bcm_gpio_n, state, platform=False):
	'Resistor state can be "up", "down" or "off".'
	state_val = dict(off=0, down=1, up=2)[state]
	addr_bcm_peri_base = dict(rpi1=0x20000000, rpi2=0x3f000000)
	if not platform: platform = detect_rpi()
	if not platform or platform not in addr_bcm_peri_base:
		raise InvalidPlatform( 'Internal pull-up control for'
			f' anything but RPi/RPi2 is not supported, platform: {platform!r}' )
	addr_gpio_base = addr_bcm_peri_base[platform] + 0x200000
	addr_gpio_pull = addr_gpio_base + 37 * RawMemSlice.w
	# addr_gpio_pull_clk = addr_gpio_pull + 1 * RawMemSlice.w

	mem = RawMemSlice(addr_gpio_pull, RawMemSlice.w * 2)
	# print(mem.read(unpack=True))
	# print(' '.join(hex(ord(c)) for c in mem.read(4)))

	if not isinstance(bcm_gpio_n, (tuple, list)):
		bcm_gpio_n = [bcm_gpio_n]
	pin_bitmask = ft.reduce( op.or_,
		map(lambda n: 1<<n, bcm_gpio_n), 0 )

	mem.write(state_val)
	time.sleep(2e-6)
	mem.write(pin_bitmask, RawMemSlice.w)
	time.sleep(2e-6)
	mem.write(0)
	mem.write(0, RawMemSlice.w)

def gpio_init(sysfs_gpio_n, state, path_gpio=pl.Path('/sys/class/gpio')):
	if not state: return
	pin_str = str(int(sysfs_gpio_n))
	m = re.search(r'^(in|high|low)(?:-(up|down|off))?$', state)
	assert m, state
	d, pull = m.groups()
	log.debug('Initializing gpio pin %s into state: %s (pull: %s)', pin_str, d, pull)
	d_path = path_gpio / f'gpio{pin_str}/direction'
	if not d_path.exists():
		with (path_gpio / 'export').open('wb') as dst: dst.write(pin_str.encode())
	with d_path.open('wb') as dst: dst.write(d.encode())
	if pull: rpi_set_internal_resistor_state(sysfs_gpio_n, pull)

class SensorDisabled(Exception): pass

class Sensor:

	values = LayeredAttrDict() # must be overidden
	disabled = True

	def __init__(self, conf, log=None):
		self.conf, self.log = conf, log
		if not self.log:
			log = self.__class__.__name__
			if log.startswith('Sensor'): log = log[6:]
			self.log = logging.getLogger(f'sensor.{log}.{id(self):x}')
		disabled = self.conf.get('disabled')
		if disabled is not None: self.disabled = bool(disabled)

	def __repr__(self):
		return ( '<{1.__class__.__name__} {0:x},'
			' disabled: {1.disabled}, values: {1.values}>' ).format(id(self), self)

	def read_keys(self, *ks):
		return op.itemgetter(ks)(self.read())

	def read(self):
		if self.disabled: raise SensorDisabled()
		data = self.read_raw() or dict()
		# self.log.debug('Raw data: %r', data)
		for k, v in data.items():
			ka = self.values[k]
			if not isinstance(v, (int, float)):
				del data[k]
				continue
			v_min, v_max = (ka.get(k) for k in ['min', 'max'])
			if v_min is not None: v = max(v_min, v)
			if v_max is not None: v = min(v_max, v)
			data[k] = v
		return data

	def read_raw(self):
		raise NotImplementedError

class SensorRPiSoC(Sensor):
	# XXX: untested leftover code from old python2 version, likely needs to be updated

	disabled = False
	values = LayeredAttrDict(t=dict(min=0, max=100, t='gauge'))
	path = '/sys/class/thermal/thermal_zone0/temp'

	def __init__(self, conf, log=None):
		super(SensorRPiSoC, self).__init__(conf, log=log)
		self.path = conf.get('path') or self.path

	def read_raw(self):
		try:
			with open(self.path, 'rb') as src: src = src.read().strip().split()[0]
		except Exception as err:
			self.log.error('Failed to get SoC temperature value: %s %s', type(err), err)
		else: return dict(t=int(src[:3]) / 10)

class SensorLM(Sensor):

	disabled = False
	values = LayeredAttrDict(t=dict(min=0, max=200, t='gauge'))
	types = {'in': 'v', 'fan': 'rpm', 'temp': 't'} # see FEATURE_* constants for more keys
	lib = lib_err = lib_ss = None

	def lib_init(self):
		if not self.lib:
			import atexit, sensors # https://bastienleonard.github.io/pysensors/
			type_map = dict((getattr(sensors, f'feature_{k}'.upper()), v) for k,v in self.types.items())
			atexit.register(sensors.cleanup)
			cls = self.__class__
			cls.lib, cls.lib_err = sensors, sensors.SensorsException
			cls.lib_ss = dict()
			for chip in sensors.get_detected_chips():
				chip_name = str(chip)
				chip_ss, chip_st = cls.lib_ss[chip_name] = dict(), cs.defaultdict(list)
				for feat in chip.get_features():
					try:
						st = type_map[feat.type]
						for sf in chip.get_all_subfeatures(feat):
							if sf.name.endswith('_input'): break
						else: raise KeyError
					except KeyError:
						self.log.debug( 'Skipping sensor with unknown'
							' type or subfeature types (chip=%s): %s', chip, feat )
						continue
					chip_ss[feat.name] = chip, sf.number, st
					chip_st[st].append(feat.name)

	def __init__(self, conf, log=None):
		super(SensorLM, self).__init__(conf, log=log)
		self.lib_init()
		chip_ss, chip_st = self.lib_ss[conf.chip]
		feat, ft = conf.get('feature'), conf.get('feature_type')
		if feat:
			try: self.s, self.sfn, self.st = chip_ss[feat]
			except KeyError:
				feats = chip_ss.keys()
				self.log.error( 'Failed to find feature: %r'
					' (all available: %s, conf: %s)', feat, feats, conf )
				raise
			if ft: assert self.st == ft, [self.s.name, self.st, ft, chip_st[ft]]
		else:
			if ft: ss = chip_st[ft]
			else: ss = list(chip_ss.values())
			assert len(ss) == 1, ss
			self.s, self.sfn, self.st = ss[0]

	def read_raw(self):
		try: val = self.s.get_value(self.sfn)
		except Exception as err:
			self.log.error( 'Failed to get value (type: %s, chip: %s,'
				' sensor: %s): %s %s', self.st, self.conf.chip, self.s.name, type(err), err )
		else: return {self.st: val}

class SensorAdafruitDHT(Sensor):
	# XXX: untested leftover code from old python2 version, likely needs to be updated

	disabled = False
	values = LayeredAttrDict(
		t=dict(min=-40, max=80, t='gauge'),
		rh=dict(min=0, max=100, t='gauge') )

	dht_proc = dht_log = None

	@classmethod
	def _read_proc_start(cls, poll_timeout=-1, restart=False):
		if not cls.dht_log:
			log = cls.__name__
			if log.startswith('Sensor'): log = log[6:]
			cls.dht_log = logging.getLogger(f'sensor.{log}.dht_log')
		if cls.dht_proc:
			if cls.dht_proc.poll() is None:
				if not restart: return
				cls.dht_proc.kill()
			err = cls.dht_proc.wait()
			cls.log.debug('Sensor-poll subprocess exit code: %s', err)
		cls.dht_proc = subprocess.Popen(
			self_exec_cmd('--dht-read-subproc', repr(poll_timeout)),
			stdin=subprocess.PIPE, stdout=subprocess.PIPE, close_fds=True )
		assert cls.dht_proc.stdout.read(1) == '!'

	def _read_proc(self, restart=False):
		self._read_proc_start(self.read_timeout, restart=restart)
		msg = json.dumps(dict(cmd='read', st=self.st, pin=self.pin))
		self.dht_proc.stdin.write(f'{len(msg):03d}{msg}')
		self.dht_proc.stdin.flush()
		msg = self.dht_proc.stdout.read(3)
		if not msg.isdigit(): msg = ''
		if msg: msg = self.dht_proc.stdout.read(int(msg))
		if msg: return json.loads(msg)
		if restart: raise RuntimeError('DHT sensor-poll subprocess failed')
		return self._read_proc(restart=True)

	def __init__(self, conf, log=None):
		super(SensorAdafruitDHT, self).__init__(conf, log=log)
		self.st = self.conf.get('sensor_type') or 'DHT22'
		self.pin = int(self.conf.sysfs_gpio_pin)
		self.read_n, self.read_delay, self.read_delay_k =\
			self.conf.get('retry') or [6, 0.2, 1.5]
		gpio_init(self.pin, self.conf.get('gpio_init'))
		if not self.conf.get('subprocess', True):
			import Adafruit_DHT
			read_st = getattr(Adafruit_DHT, self.st)
			self.read_func = Adafruit_DHT_read_func(read_st, self.pin)
		else:
			self.read_timeout = self.conf.interval * 5
			self._read_proc_start(self.read_timeout)
			self.read_func = self._read_proc

	def read_raw(self):
		delay = self.read_delay
		for n in range(1, self.read_n + 1):
			read_err, rh, t = self.read_func()
			if rh is None or t is None or rh > 100:
				self.log.debug( 'Sensor (pin: %s, type: %s) read retry (n: %s)'
					' in %.1fs, error: %s', self.pin, self.st, n, delay, read_err or 'unknown' )
				time.sleep(delay)
				delay *= self.read_delay_k
				continue
			return dict(t=t, rh=rh)

class SensorSHT(Sensor):
	# XXX: untested leftover code from old python2 version, likely needs to be updated

	disabled = False
	values = LayeredAttrDict(
		t=dict(min=-40, max=100, t='gauge'),
		rh=dict(min=0, max=100, t='gauge') )

	def __init__(self, conf, log=None):
		super(SensorSHT, self).__init__(conf, log=log)
		from sht_sensor import Sht
		pin_sck, pin_data = map( int,
			[self.conf.sysfs_gpio_pin_sck, self.conf.sysfs_gpio_pin_data] )
		voltage = self.conf.get('sensor_voltage_spec') or '3.5V'
		self.sht = Sht(pin_sck, pin_data, voltage=voltage)

	def read_raw(self):
		t = self.sht.read_t()
		rh = self.sht.read_rh(t)
		return dict(t=t, rh=rh)


class SensorMeta:

	units = dict(t='°C', rh='%RH', v='V', rpm='rpm')
	metrics = dict(t='temperature', rh='humidity', v='voltage', rpm='rpm')
	formats = dict(t='.1f', rh='.1f', v='.2f', rpm='.0f')
	types = dict(
		rpi_soc=SensorRPiSoC, lm=SensorLM,
		adafruit_dht=SensorAdafruitDHT, sht=SensorSHT )
	metric_default = 't'

	def value_repr(self, n, metric, units=True):
		if isinstance(n, int): n = str(n)
		else: n = format(n, self.formats[metric])
		if units: n = f'{n} {cls.units[metric]}'
		return n

	def get_sensor(self, t, conf, log=None, **kws):
		return self.types[t](conf, log=log, **kws)

	def filter_by_metrics(self, metrics, sensors):
		ss = dict()
		for m in metrics:
			for sn, sd in sensors.items():
				if m in self.types[sd.type].values:
					if m not in ss: ss[m] = list()
					ss[m].append(sn)
		return ss

sensors = SensorMeta()



def self_exec_cmd(*args):
	args = [__file__] + list(args)
	if os.access(__file__, os.X_OK): return args
	return [sys.executable or 'python2'] + args

def main(args=None):
	import argparse
	parser = argparse.ArgumentParser(
		usage='%(prog)s: [opts]',
		description='Daemon to log sensor data to an rrd database.')

	parser.add_argument('-c', '--conf',
		action='append', metavar='path', default=list(),
		help='YAML configuration files to process.'
			' Can be specified more than once.'
			' Values from the latter ones override values in the former.'
			' Available CLI options override values in any config.'
			' Config with all possible options is embedded in the'
				' code and is always used as a baseline, ~/.rrd-sensors-logger.yaml path'
				' is used (if exists) on top of that, unless this option is specified.'
			' Use "print-conf-example" command to produce example conf file.'
			' Empty values for this option are safely ignored.')
	parser.add_argument('-x', '--conf-data',
		action='append', metavar='yaml-data', default=list(),
		help='YAML data to process and add on top of other configs.'
			' Automatically wrapped into mapping, can be specified more than once.'
			' Values from the latter data override values in the former.'
			' Applied after all --conf arguments (if any).'
			' Available CLI options override values in any config.'
			' Example (quoted): "rrd: {storage_dir: /some/my/path}".')

	parser.add_argument('--systemd', action='store_true',
		help='Use systemd service'
			' notification/watchdog mechanisms in daemon modes, if available.')
	parser.add_argument('-d', '--debug', action='store_true', help='Verbose operation mode.')

	cmds = parser.add_subparsers(
		dest='cmd', title='Actions',
		description='Supported actions (have their own suboptions as well)')


	cmd = cmds.add_parser('print-conf-example',
		help='Print example config to stdout and exit.')
	cmd = cmds.add_parser('print-systemd-unit',
		help='Print example systemd unit file to stdout and exit.')


	cmd = cmds.add_parser('daemon',
		usage='%(prog)s [command-opts]',
		help='Run as daemon and update values in an rrd file.')
	cmd.add_argument('-l', '--http-listen', nargs='?',
		metavar='[address:]port', const='localhost:8123',
		help='Run http server that would render charts, same as "graph" option.'
			' Optional argument is the address:port'
				' or just port to run server on (default: localhost:8123).')
	cmd.add_argument('-o', '--http-opts',
		action='append', metavar='yaml-data', default=list(),
		help='Same as --opts for "graph" command, see description there.')
	cmd.add_argument('--http-opts-allow', action='store_true',
		help='Allow specifying rrdtool options via URL - VERY DANGEROUS.'
			' Only intended for testing or whitelist-restricted access,'
				' as it may allow execution of arbitrary commands,'
				' if and of the rrdtool options allow that or are handled insecurely.')


	cmd = cmds.add_parser('print-last',
		usage='%(prog)s [command-opts]',
		help='Print last stored value for each sensor.')
	cmd.add_argument('-t', '--time-delta',
		metavar='ts-diff-spec', default='20min',
		help='Time delta (from now) to show values for (default: %(default)s).')
	cmd.add_argument('-c', '--cf',
		metavar='{ average | min | max | last }', default='average',
		help='Consolidation function (see rrdtool docs) to use (default: %(default)s).')
	cmd.add_argument('-l', '--last-update', action='store_true',
		help='Do not use --time-delta or --cf,'
			' just print last (raw) stored values (rrdtool lastupdate).')


	cmd = cmds.add_parser('graph',
		usage='%(prog)s [command-opts]',
		help='Build and store graph of last measurements.',
		epilog='Prints path to resulting image to stdout.')
	cmd.add_argument('metric',
		nargs='*', default=sensors.metric_default,
		help='Name of a metric to graph (default: %(default)s).'
			' Can be specified multiple times to graph more than one of these.')
	cmd.add_argument('-s', '--sensor',
		action='append', metavar='sensor-name', default=list(),
		help='Name of a sensor to graph metric for'
			' (default: all of them). Can be used multiple times.')
	cmd.add_argument('-t', '--threshold',
		action='append', metavar='name:value', default=list(),
		help='Named threshold value (horizontal line)'
			' to add to a graph. Can be used multiple times.')
	cmd.add_argument('-p', '--path', metavar='path',
		help='Path to resulting image file. Default is to use random temporary path.')
	cmd.add_argument('-o', '--opts',
		action='append', metavar='yaml-data', default=list(),
		help='YAML data to pass as rrdtool options for a graph.'
			' Automatically wrapped into mapping, can be specified more than once.'
			' See http://oss.oetiker.ch/rrdtool/doc/rrdgraph.en.html#IOPTIONS for a list of these.'
			' Example (quoted): "start: -1h, width: 1280, height: 800, title: last data"')


	opts = parser.parse_args(sys.argv[1:] if args is None else args)

	if opts.cmd == 'print-conf-example':
		return print(conf_base_str)
	if opts.cmd == 'print-systemd-unit':
		with open(__file__) as src:
			echo = False
			for line in iter(src.readline, ''):
				if echo: print(re.sub(r'^#+\s*', '', line.strip()))
				if re.search('^### systemd unit file:', line):
					echo = True
					continue
				elif echo and not line.strip(): return

	global log
	import logging
	log = '%(levelname)s :: %(message)s'
	if not opts.systemd: log = f'%(asctime)s :: {log}'
	logging.basicConfig(
		format=log, datefmt='%Y-%m-%d %H:%M:%S',
		level=logging.DEBUG if opts.debug else logging.WARNING )
	log = logging.getLogger()

	if opts.systemd:
		from systemd import daemon
		def sd_cycle(ts=None):
			if not sd_cycle.ready:
				daemon.notify('READY=1')
				daemon.notify(f'STATUS=Running in {opts.cmd} mode...')
				sd_cycle.ready = True
			if sd_cycle.delay:
				if ts is None: ts = time.time()
				delay = ts - sd_cycle.ts_next
				if delay > 0: time.sleep(delay)
				sd_cycle.ts_next += sd_cycle.delay
			else: sd_cycle.ts_next = None
			if sd_cycle.wdt: daemon.notify('WATCHDOG=1')
		sd_cycle.ts_next = time.time()
		wd_pid, wd_usec = (os.environ.get(k) for k in ['WATCHDOG_PID', 'WATCHDOG_USEC'])
		if wd_pid and wd_pid.isdigit() and int(wd_pid) == os.getpid():
			wd_interval = float(wd_usec) / 2e6 # half of interval in seconds
			assert wd_interval > 0, wd_interval
		else: wd_interval = None
		if wd_interval:
			log.debug('Initializing systemd watchdog pinger with interval: %ss', wd_interval)
			sd_cycle.wdt, sd_cycle.delay = True, wd_interval
		else: sd_cycle.wdt, sd_cycle.delay = False, None
		sd_cycle.ready = False
	else: sd_cycle = None
	signal.signal(signal.SIGTERM, lambda sig,frm: sys.exit(0))

	conf_list = list()
	if not opts.conf:
		opts.conf = [os.path.expanduser('~/.rrd-sensors-logger.yaml')]
		if not os.path.exists(opts.conf[0]): opts.conf = list()
	for p in filter(None, opts.conf):
		with open(p) as src: conf_list.append(yaml_load(src))
	for d in opts.conf_data:
		if not d.strip().startswith('{'): d = f'{{{d}}}'
		with open(d) as src: conf_list.append(yaml_load(src))
	conf = LayeredAttrDict(*conf_list, conf_base)

	ss_interval, ss = ts_diff_parse(conf.meas.interval), LayeredAttrDict()
	for k, spec in (conf.meas.sensors or dict()).items():
		if not spec.get('type'): continue
		spec.interval = ss_interval
		ss[k] = sensors.get_sensor(spec.type, spec)
	rrdb = init_rrd(ss_interval, ss, conf.rrd)


	if opts.cmd == 'daemon':
		delay_func = time.sleep

		if opts.http_listen:
			bind = opts.http_listen.split(':', 1)
			bind = ('', int(bind[0])) if len(bind) == 1 else (bind[0], int(bind[1]))
			log.debug('Starting http server on socket (py bind format): %s', bind)
			delay_func = httpd_poller( conf, rrdb, bind,
				http_opts=opts.http_opts, http_opts_allow=opts.http_opts_allow )

		log.debug('Entering sensor/rrdb read/update loop...')
		ts_read = time.time()
		while True:
			while True:
				if not sd_cycle or not sd_cycle.ts_next: break
				ts_next = min(sd_cycle.ts_next, ts_read)
				if ts_next == sd_cycle.ts_next: sd_cycle()
				else: break
			delay = ts_read - time.time()
			if delay > 0:
				try: delay_func(delay)
				except HTTPPollExit: return
			ts_read += ss_interval

			vals = dict()
			for k, s in ss.items():
				try:
					data = s.read()
					if not data: raise ValueError('No data returned')
				except SensorDisabled:
					log.debug('Skipping disabled sensor: %r', k)
					continue
				except Exception as err:
					log.debug('Failed to read data from sensor %r: %s', k, err)
					continue
				log.debug('Sensor %r data: %s', k, data)
				for m, v in data.items(): vals[k, m] = v
			try: rrdb.update(vals)
			except Exception as err: log.exception('rrd db update failed: %s', err)
		raise RuntimeError # should never get here


	elif opts.cmd == 'print-last':
		vals = dict()
		if opts.last_update: ts, vals_raw = rrdb.fetch_last_update()
		else: vals_raw = rrdb.fetch_last_values(opts.time_delta, cf=opts.cf)
		for (s, k), v in vals_raw.items(): vals[f'{s}.{k}'] = v
		yaml_dump(vals, sys.stdout)


	elif opts.cmd == 'graph':
		image_path = rrd_conf_graph( conf, rrdb, opts.metric,
			ss=opts.sensor, opts=opts.opts, threshold=opts.threshold, path=opts.path )
		print(image_path)


	else: parser.error(f'Unrecognized command: {opts.cmd}')

if __name__ == '__main__': sys.exit(main())