collect.py

#!/usr/bin/env python3

# Copyright 2020 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Forwards data from a serial device to an InfluxDB database."""

import argparse
import importlib
import logging
import sys
import threading
import time
from typing import BinaryIO, Callable, FrozenSet, Generator, Optional

from retrying import retry
import serial

import influxdb
import persistent_queue
import serial_samples

import sched
import subprocess
import time
import os

def restart_script():
    logging.info("Restarting script...")
    os._exit(1)  # Force immediate exit

def RetryOnIOError(exception):
    """Returns True if 'exception' is an IOError."""
    return isinstance(exception, IOError)


@retry(wait_exponential_multiplier=1000,
       wait_exponential_max=60000,
       retry_on_exception=RetryOnIOError)
def ReadLoop(args, queue: persistent_queue.Queue):
    """Reads samples and stores them in a queue. Retries on IO errors."""
    serial_fn: Optional[Callable[[BinaryIO], Generator[bytes, None,
                                                       None]]] = None
    if args.serial_function:
        module, fn_name = args.serial_function.rsplit(".", 1)
        serial_fn = getattr(importlib.import_module(module), fn_name)
    try:
        logging.debug("Read loop started")
        with serial.serial_for_url(args.device,
                                   baudrate=args.baud_rate,
                                   timeout=args.read_timeout) as handle:
            if serial_fn:
                lines = serial_fn(handle)
            else:
                lines = serial_samples.SerialLines(handle, args.max_line_length, 10.0)
            start_time = time.time()
            for line in lines:
                # If line does not start with start string
                if not line.startswith(b'FTX'):
                   continue
                try:
                    line = str(line, encoding="UTF-8")
                except TypeError:
                    pass
                # Parse 'line', either with or without timestamp.
                words = line.strip().split(" ")
                if len(words) == 2:
                    (tags, values) = words
                    timestamp = int(time.time() * 1000000000)
                elif len(words) == 3:
                    (tags, values, timestamp) = words
                    float(timestamp)
                else:
                    raise ValueError("Unable to parse line {0!r}".format(line))
                tags: str = ",".join(t for t in (tags, args.tags) if t)
                queue.put("{0} {1} {2:d}".format(tags, values, timestamp))
    except:
        logging.exception("Error, retrying with backoff")
        raise
        

@retry(wait_exponential_multiplier=1000,
       wait_exponential_max=60000,
       retry_on_exception=RetryOnIOError)
def WriteLoop(args, queue: persistent_queue.Queue):
    """Reads samples and stores them in a queue. Retries on IO errors."""
    logging.debug("Write loop started")
    warn_on_status: FrozenSet[int] = frozenset(
        int(status) for status in args.warn_on_status)
    try:
        influxdb_line: str
        for influxdb_line in queue.get_blocking(tick=60):
            influxdb.PostLines(args.database,
                               args.host,
                               [influxdb_line.encode(encoding='UTF-8')],
                               warn_on_status=warn_on_status)
    except:
        logging.exception("Error, retrying with backoff")
        raise


def RunAndDie(fun, *args):
    """Runs 'fn' on 'args'. If 'fn' exists, exit the whole program."""
    try:
        fun(*args)
    finally:
        sys.exit(1)

def main():
    """Parses the command line arguments and invokes the main loop."""
    parser = argparse.ArgumentParser(
        formatter_class=argparse.ArgumentDefaultsHelpFormatter,
        description="""
          Collects values from a serial port and sends them to InfluxDB.

          Note that the first received line is discarded to prevent recording
          incomplete data.

          Make sure to set READ_TIMEOUT higher than the longest expected
          period of inactivity of your device. For example, if your device
          sends data every 60 seconds, set --read-timeout=70 (or any similar
          value >60s).
        """,
        epilog="""See
          https://pyserial.readthedocs.io/en/latest/url_handlers.html#urls
          for URL types accepted by -d/--device.
          Run `python -m serial.tools.list_ports` to list of all available
          COM ports.
        """)
    parser.add_argument('-d',
                        '--device',
                        required=True,
                        help='serial device to read from, or a URL accepted '
                        'by serial_for_url()')
    parser.add_argument('-r',
                         '--baud-rate',
                        type=int,
                        default=9600,
                        help='baud rate of the serial device')
    parser.add_argument('-t',
                        '--read-timeout',
                        type=int,
                        required=True,
                        help='read timeout on the serial device; this should '
                        'be longer that the longest expected period of '
                        'inactivity of the serial device')
    parser.add_argument('--max-line-length',
                        type=int,
                        default=1024,
                        help='maximum line length')
    parser.add_argument('--serial-function',
                        help='custom function that reads from a serial device '
                        'passed as its argument and yields InfluxDB '
                        'lines; specified as module.functionname')

    parser.add_argument('-H',
                        '--host',
                        default='localhost:8086',
                        help='host and port with InfluxDB to send data to')
    parser.add_argument('-D',
                        '--database',
                        required=True,
                        help='database to save data to')
    parser.add_argument('-T',
                        '--tags',
                        default='',
                        help='additional static tags for measurements'
                        ' separated by comma, for example foo=x,bar=y')
    parser.add_argument('--warn_on_status',
                        nargs='*',
                        default=[400],
                        help='when one of these HTTP statuses is received from'
                        ' InfluxDB, a warning is printed and the'
                        ' datapoint is skipped; allows to continue on'
                        ' invalid datapoints')

    parser.add_argument('-q',
                        '--queue',
                        default=':memory:',
                        help='path for a persistent queue database file; this '
                        'file will be automatically created and managed '
                        'by the program; it ensures that no datapoints '
                        'are ever lost, even if the database is '
                        'temporarily unreachable; NOTE that at the '
                        'moment old lines are not garbage collected '
                        'from the file, so it grows forever!')
    parser.add_argument('-w',
                        '--wal_autocheckpoint',
                        type=int,
                        default=10,
                        help='switches the queue SQLite database to use the '
                        'WAL mode and sets this parameter in the database')

    parser.add_argument('--debug',
                        action='store_true',
                        help='enable debug level')
    args = parser.parse_args()

    if args.debug:
        logging.basicConfig(level=logging.DEBUG)

    # Create a scheduler and schedule the script to restart in 24 hours
    scheduler = sched.scheduler(time.time, time.sleep)
    restart_delay = 24 * 60 * 60  # 24 hours in seconds
    scheduler.enter(restart_delay, 1, restart_script)

    # Start the scheduler in a separate thread
    scheduler_thread = threading.Thread(target=scheduler.run)
    scheduler_thread.start()

    while True:
        try:
            with persistent_queue.Queue(
                    args.queue, wal_autocheckpoint=args.wal_autocheckpoint) as queue:
                reader = threading.Thread(name="read",
                                          target=ReadLoop,
                                          args=(args, queue))
                writer = threading.Thread(name="write",
                                          target=WriteLoop,
                                          args=(args, queue))
                reader.start()
                writer.start()
                reader.join()
                writer.join()
        except Exception:
            logging.exception("Unhandled exception occurred, restarting script...")
            time.sleep(5)  # Wait a bit before restarting
            continue
        break  # Exit the loop if no exceptions occurred

if __name__ == "__main__":
    while True:
        try:
            main()
        except Exception:
            logging.exception("Unhandled exception occurred in main(), restarting script...")
            time.sleep(5)  # Wait a bit before restarting