Script to trigger a Subsonic media rescan with locking

rescan_subsonic_media.py

#!/bin/env python

import sys
import requests
import os
import os.path
import time
import logging
import subprocess
import json


def trigger_scan(subsonic, squeeze):
    result = []
    s = requests.Session()
    if subsonic:
        logging.debug("Logging in to subsonic")
        r = s.post('%s/j_acegi_security_check' % config['base_subsonic_url'],
                   {'j_username': config['subsonic_username'],
                    'j_password': config['subsonic_password'],
                    'submit': 'Log+in'})
        logging.debug("Telling subsonic to rescan")
        r = s.get('%s/musicFolderSettings.view?scanNow' % config['base_subsonic_url'])
        result.append(r.status_code)
    if squeeze:
        logging.debug("Telling squeeze to rescan")
        r = s.get('%s:9000/settings/index.html?p0=rescan' % config['base_squeeze_url'])
        result.append(r.status_code)
    return result


def touch(fname, times=None):
    try:
        with open(fname, 'a'):
            os.utime(fname, times)
    except:
        open(fname, 'a').close()


logging.basicConfig(
    filename='/var/log/rescan_subsonic_media.log',
    level=logging.DEBUG,
    format='%(asctime)s %(message)s')

with open('/etc/rescan_subsonic_media_config.json') as f:
    config = json.load(f)

LAST_SCAN_FILENAME = '/var/local/rescan_subsonic_media'
SCAN_LOCK = '/var/local/rescan_subsonic_media.lock'
QUEUED_SCAN_TRIGGERED_DIRNAME = '/var/local/rescan_subsonic_media.trigger_queued'
TIME_DELTA = 60 * 5  # 5 minutes
DRY_RUN = False
TRIGGERED_KEYWORD = 'triggered'

try:
    last_scan = os.path.getmtime(LAST_SCAN_FILENAME)
    # We could instead look for the LastScanned entry in /var/subsonic/subsonic.properties
    # which contains epoch milliseconds
except:
    logging.error("Unexpected error: %s" % sys.exc_info()[0])
    last_scan = 0

time_since_last_scan = time.time() - last_scan
logging.debug("Time since last scan at %s is %s"
              % (last_scan, time_since_last_scan))

triggered = False
if len(sys.argv) > 1 and sys.argv[1] == TRIGGERED_KEYWORD:
    logging.debug("This is a triggered run called by a scheduled at task")
    os.rmdir(QUEUED_SCAN_TRIGGERED_DIRNAME)
    triggered = True

if (time_since_last_scan > TIME_DELTA) or triggered:
    # Over TIME_DELTA has elapsed
    # or this is a triggered call
    # Rescan
    try:
        os.mkdir(SCAN_LOCK)
        touch(LAST_SCAN_FILENAME)
        result = "dryrun" if DRY_RUN else trigger_scan(True, False)
        logging.info("Scanning %s" % result)
        os.rmdir(SCAN_LOCK)
    except:
        logging.debug("Skipping rescan as %s exists implying a rescan is "
                      "already running" % SCAN_LOCK)
        pass
else:
    # Not enough time has elapsed since the last scan
    try:
        os.mkdir(QUEUED_SCAN_TRIGGERED_DIRNAME)
        queue_run = True
    except:
        queue_run = False

    if queue_run:
        # Though a rescan has already been started, since another filesystem
        # change has occured, we'll queue up a run for 4 minutes from now
        process = subprocess.Popen(
            'at now + 4 minute'.split(),
            stdout=subprocess.PIPE, stdin=subprocess.PIPE,
            stderr=subprocess.PIPE)
        stdout_data = process.communicate(
            input='/usr/bin/python %s %s'
                  % (os.path.abspath(__file__), TRIGGERED_KEYWORD))[0]
        logging.debug("Skipping scan but queuing one for 4 minutes")
    else:
        logging.debug("Skipping scan. One's already queued")