lvm2/daemons/lvmdbusd/main.py

# Copyright (C) 2015-2016 Red Hat, Inc. All rights reserved.
#
# This copyrighted material is made available to anyone wishing to use,
# modify, copy, or redistribute it subject to the terms and conditions
# of the GNU General Public License v.2.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.

from . import cfg
from . import objectmanager
from . import utils
from .cfg import BUS_NAME, BASE_INTERFACE, BASE_OBJ_PATH, MANAGER_OBJ_PATH
import threading
from . import cmdhandler
import time
import signal
import dbus
import dbus.mainloop.glib
from . import lvmdb
# noinspection PyUnresolvedReferences
from gi.repository import GLib
from .fetch import load
from .manager import Manager
import traceback
import queue
from . import udevwatch
from .utils import log_debug, log_error
import argparse
import os
import sys
from .refresh import handle_external_event, event_complete


class Lvm(objectmanager.ObjectManager):
	def __init__(self, object_path):
		super(Lvm, self).__init__(object_path, BASE_INTERFACE)


def _discard_pending_refreshes():
	# We just handled a refresh, if we have any in the queue they can be
	# removed because by definition they are older than the refresh we just did.
	# As we limit the number of refreshes getting into the queue
	# we should only ever have one to remove.
	requests = []
	while not cfg.worker_q.empty():
		try:
			r = cfg.worker_q.get(block=False)
			if r.method != handle_external_event:
				requests.append(r)
			else:
				# Make sure we make this event complete even though it didn't
				# run, otherwise no other events will get processed
				event_complete()
				break
		except queue.Empty:
			break

	# Any requests we removed, but did not discard need to be re-queued
	for r in requests:
		cfg.worker_q.put(r)


def process_request():
	while cfg.run.value != 0:
		# noinspection PyBroadException
		try:
			req = cfg.worker_q.get(True, 5)

			start = cfg.db.num_refreshes

			log_debug(
				"Running method: %s with args %s" %
				(str(req.method), str(req.arguments)))
			req.run_cmd()

			end = cfg.db.num_refreshes

			num_refreshes = end - start

			if num_refreshes > 0:
				_discard_pending_refreshes()

				if num_refreshes > 1:
					log_debug(
						"Inspect method %s for too many refreshes" %
						(str(req.method)))
			log_debug("Method complete ")
		except queue.Empty:
			pass
		except Exception:
			st = traceback.format_exc()
			utils.log_error("process_request exception: \n%s" % st)


def main():
	start = time.time()
	# Add simple command line handling
	parser = argparse.ArgumentParser()
	parser.add_argument(
		"--udev", action='store_true',
		help="Use udev for updating state",
		default=False,
		dest='use_udev')
	parser.add_argument(
		"--debug", action='store_true',
		help="Dump debug messages", default=False,
		dest='debug')
	parser.add_argument(
		"--nojson", action='store_false',
		help="Do not use LVM JSON output (disables lvmshell)", default=True,
		dest='use_json')
	parser.add_argument(
		"--lvmshell", action='store_true',
		help="Use the lvm shell, not fork & exec lvm",
		default=False,
		dest='use_lvm_shell')

	use_session = os.getenv('LVMDBUSD_USE_SESSION', False)

	# Ensure that we get consistent output for parsing stdout/stderr
	os.environ["LC_ALL"] = "C"

	cfg.args = parser.parse_args()

	if cfg.args.use_lvm_shell and not cfg.args.use_json:
		log_error("You cannot specify --lvmshell and --nojson")
		sys.exit(1)

	cmdhandler.set_execution(cfg.args.use_lvm_shell)

	# List of threads that we start up
	thread_list = []

	# Install signal handlers
	for s in [signal.SIGHUP, signal.SIGINT]:
		try:
			signal.signal(s, utils.handler)
		except RuntimeError:
			pass

	dbus.mainloop.glib.DBusGMainLoop(set_as_default=True)
	dbus.mainloop.glib.threads_init()

	if use_session:
		cfg.bus = dbus.SessionBus()
	else:
		cfg.bus = dbus.SystemBus()
	# The base name variable needs to exist for things to work.
	# noinspection PyUnusedLocal
	base_name = dbus.service.BusName(BUS_NAME, cfg.bus)
	cfg.om = Lvm(BASE_OBJ_PATH)
	cfg.om.register_object(Manager(MANAGER_OBJ_PATH))

	cfg.load = load

	cfg.db = lvmdb.DataStore(cfg.args.use_json)

	# Using a thread to process requests, we cannot hang the dbus library
	# thread that is handling the dbus interface
	thread_list.append(threading.Thread(target=process_request))

	cfg.load(refresh=False, emit_signal=False, need_main_thread=False)
	cfg.loop = GLib.MainLoop()

	for process in thread_list:
		process.damon = True
		process.start()

	# Add udev watching
	if cfg.args.use_udev:
		log_debug('Utilizing udev to trigger updates')

	# In all cases we are going to monitor for udev until we get an
	# ExternalEvent.  In the case where we get an external event and the user
	# didn't specify --udev we will stop monitoring udev
	udevwatch.add()

	end = time.time()
	log_debug(
		'Service ready! total time= %.4f, lvm time= %.4f count= %d' %
		(end - start, cmdhandler.total_time, cmdhandler.total_count),
		'bg_black', 'fg_light_green')

	try:
		if cfg.run.value != 0:
			cfg.loop.run()
			udevwatch.remove()

			for process in thread_list:
				process.join()
	except KeyboardInterrupt:
		utils.handler(signal.SIGINT, None)
	return 0