scheduler/monitor_db

#!/usr/bin/python -u

"""
Autotest scheduler
"""
__author__ = "Paul Turner <pjt@google.com>"

import os, sys, tempfile, shutil, MySQLdb, time, traceback, subprocess, Queue
import optparse, signal, smtplib, socket, datetime, stat, pwd
from common import global_config

RESULTS_DIR = '.'
AUTOSERV_NICE_LEVEL = 10

AUTOTEST_PATH = os.path.join(os.path.dirname(__file__), '..')

if os.environ.has_key('AUTOTEST_DIR'):
	AUTOTEST_PATH = os.environ['AUTOTEST_DIR']
AUTOTEST_SERVER_DIR = os.path.join(AUTOTEST_PATH, 'server')
AUTOTEST_TKO_DIR = os.path.join(AUTOTEST_PATH, 'tko')

if AUTOTEST_SERVER_DIR not in sys.path:
        sys.path.insert(0, AUTOTEST_SERVER_DIR)

AUTOSERV_PID_FILE = '.autoserv_execute'

_db = None
_shutdown = False
_notify_email = None
_autoserv_path = 'autoserv'
_testing_mode = False


def main():
	usage = 'usage: %prog [options] results_dir'

	parser = optparse.OptionParser(usage)
	parser.add_option('--recover-hosts', help='Try to recover dead hosts',
	                  action='store_true')
	parser.add_option('--logfile', help='Set a log file that all stdout ' +
 	                  'should be redirected to.  Stderr will go to this ' +
	                  'file + ".err"')
	parser.add_option('--notify', help='Set an email address to be ' +
	                  'notified of exceptions')
	parser.add_option('--test', help='Indicate that scheduler is under ' +
			  'test and should use dummy autoserv and no parsing',
			  action='store_true')
	(options, args) = parser.parse_args()
	if len(args) != 1:
		parser.print_usage()
		return
	
	global RESULTS_DIR
	RESULTS_DIR = args[0]

	global _notify_email
	_notify_email = options.notify
	
	if options.test:
		global _autoserv_path
		_autoserv_path = 'autoserv_dummy'
		global _testing_mode
		_testing_mode = True

	init(options.logfile)
	dispatcher = Dispatcher()
	dispatcher.do_initial_recovery(recover_hosts=options.recover_hosts)

	try:
		while not _shutdown:
			dispatcher.tick()
			time.sleep(20)
	except:
		log_stacktrace("Uncaught exception; terminating monitor_db")

	_db.disconnect()


def handle_sigint(signum, frame):
	global _shutdown
	_shutdown = True
	print "Shutdown request received."


def init(logfile):
	if logfile:
		enable_logging(logfile)
	print "%s> dispatcher starting" % time.strftime("%X %x")
	print "My PID is %d" % os.getpid()

	os.environ['PATH'] = AUTOTEST_SERVER_DIR + ':' + os.environ['PATH']
	global _db
	_db = DatabaseConn()

	print "Setting signal handler"
	signal.signal(signal.SIGINT, handle_sigint)
	
	print "Connected! Running..."


def enable_logging(logfile):
	out_file = logfile
	err_file = "%s.err" % logfile
	print "Enabling logging to %s (%s)" % (out_file, err_file)
	out_fd = open(out_file, "a", buffering=0)
	err_fd = open(err_file, "a", buffering=0)

	os.dup2(out_fd.fileno(), sys.stdout.fileno())
	os.dup2(err_fd.fileno(), sys.stderr.fileno())

	sys.stdout = out_fd
	sys.stderr = err_fd


def idle_hosts():
	rows = _db.execute("""
		SELECT * FROM hosts h WHERE 
		id NOT IN (SELECT host_id FROM host_queue_entries WHERE active) AND (
				(id IN (SELECT host_id FROM host_queue_entries WHERE not complete AND not active)) 
			OR
				(id IN (SELECT DISTINCT hl.host_id FROM host_queue_entries hqe 
				INNER JOIN hosts_labels hl ON hqe.meta_host=hl.label_id WHERE not hqe.complete AND not hqe.active))
		)
		AND locked=false AND (h.status IS null OR h.status='Ready')	""")
	hosts = [Host(row=i) for i in rows]
	return hosts

def queue_entries_to_abort():
	rows = _db.execute("""
		SELECT * FROM host_queue_entries WHERE status='Abort';
			""")
	qe = [HostQueueEntry(row=i) for i in rows]
	return qe

def remove_file_or_dir(path):
	if stat.S_ISDIR(os.stat(path).st_mode):
		# directory
		shutil.rmtree(path)
	else:
		# file
		os.remove(path)


class DatabaseConn:
	def __init__(self):
		self.reconnect_wait = 20
		self.conn = None
		self.cur = None

		self.connect()


	def connect(self):
		self.disconnect()

		# get global config and parse for info
		c = global_config.global_config
		dbase = "AUTOTEST_WEB"
		DB_HOST = c.get_config_value(dbase, "host")
		DB_SCHEMA = c.get_config_value(dbase, "database")
		
		global _testing_mode
		if _testing_mode:
			DB_SCHEMA = 'stresstest_autotest_web'

		DB_USER = c.get_config_value(dbase, "user")
		DB_PASS = c.get_config_value(dbase, "password")

		while not self.conn:
			try:
				self.conn = MySQLdb.connect(host=DB_HOST,
				                            user=DB_USER,
				                            passwd=DB_PASS,
				                            db=DB_SCHEMA)

				self.conn.autocommit(True)
				self.cur = self.conn.cursor()
			except MySQLdb.OperationalError:
				traceback.print_exc()
				print "Can't connect to MYSQL; reconnecting"
				time.sleep(self.reconnect_wait)
				self.disconnect()


	def disconnect(self):
		if self.conn:
			self.conn.close()
		self.conn = None
		self.cur = None


	def execute(self, *args, **dargs):
		while (True):
			try:
				self.cur.execute(*args, **dargs)
				return self.cur.fetchall()
			except MySQLdb.OperationalError:
				traceback.print_exc()
				print "MYSQL connection died; reconnecting"
				time.sleep(self.reconnect_wait)
				self.connect()


def generate_parse_command(results_dir, flags=""):
	parse = os.path.abspath(os.path.join(AUTOTEST_TKO_DIR, 'parse'))
	output = os.path.abspath(os.path.join(results_dir, '.parse.log'))
	cmd = "%s %s -r -o %s > %s 2>&1 &"
	return cmd % (parse, flags, results_dir, output)


def parse_results(results_dir, flags=""):
	if _testing_mode:
		return
	os.system(generate_parse_command(results_dir, flags))


def send_notify_email(subject, message):
	if not _notify_email:
		return

	message = "%s / %s / %s\n%s" % (socket.gethostname(), os.getpid(),
					time.strftime("%X %x"), message)
	sender = pwd.getpwuid(os.getuid())[0] # see os.getlogin() online docs
	msg = "From: %s\nTo: %s\nSubject: %s\n\n%s" % (
		 sender, _notify_email, subject, message)
	mailer = smtplib.SMTP('localhost')
	mailer.sendmail(sender, _notify_email, msg)
	mailer.quit()


def log_stacktrace(reason):
	(type, value, tb) = sys.exc_info()
	str = "EXCEPTION: %s\n" % reason
	str += ''.join(traceback.format_exception(type, value, tb))

	sys.stderr.write("\n%s\n" % str)
	send_notify_email("monitor_db exception", str)


def get_proc_poll_fn(pid):
	proc_path = os.path.join('/proc', str(pid))
	def poll_fn():
		if os.path.exists(proc_path):
			return None
		return 0 # we can't get a real exit code
	return poll_fn


def kill_autoserv(pid, poll_fn=None):
	print 'killing', pid
	if poll_fn is None:
		poll_fn = get_proc_poll_fn(pid)
	if poll_fn() == None:
		os.kill(pid, signal.SIGCONT)
		os.kill(pid, signal.SIGTERM)


class Dispatcher:
	def __init__(self):
		self._agents = []


	def do_initial_recovery(self, recover_hosts=True):
		# always recover processes
		self._recover_processes()

		if recover_hosts:
			self._recover_hosts()


	def tick(self):
		self._find_aborting()
		self._find_more_work()
		self._handle_agents()


	def add_agent(self, agent):
		self._agents.append(agent)
		agent.dispatcher = self
	
	# Find agent corresponding to the specified queue_entry
	def get_agents(self, queue_entry):
		res_agents = []
		for agent in self._agents:
			if queue_entry.id in agent.queue_entry_ids:
				res_agents.append(agent)
		return res_agents
	

	def remove_agent(self, agent):
		self._agents.remove(agent)


	def find_orphaned_autoservs(self):
		"""\
		Returns a dict mapping pids to command lines for root autoserv
		processes that have been orphaned.
		"""
		proc = subprocess.Popen(
		    ['/bin/ps', 'x', '-o', 'pid,ppid,comm,args'],
		    stdout=subprocess.PIPE)
		# split each line into the four columns output by ps
		procs = [line.split(None, 3) for line in
			 proc.communicate()[0].splitlines()]
		autoserv_procs = [(int(proc[0]), proc[3]) # pid, args
				  for proc in procs
				  if proc[2] == 'autoserv' # comm
				  and proc[1] == '1'] # ppid
		return dict(autoserv_procs)


	def recover_queue_entry(self, queue_entry, run_monitor):
		job = queue_entry.job
		if job.is_synchronous():
			all_queue_entries = job.get_host_queue_entries()
		else:
			all_queue_entries = [queue_entry]
		all_queue_entry_ids = [queue_entry.id for queue_entry
				       in all_queue_entries]
		queue_task = RecoveryQueueTask(
		    job=queue_entry.job,
		    queue_entries=all_queue_entries,
		    run_monitor=run_monitor)
		self.add_agent(Agent(tasks=[queue_task],
				     queue_entry_ids=all_queue_entry_ids))


	def _recover_processes(self):
		orphans = self.find_orphaned_autoservs()

		# first, recover running queue entries
		rows = _db.execute("""SELECT * FROM host_queue_entries
		                      WHERE status = 'Running'""")
		queue_entries = [HostQueueEntry(row=i) for i in rows]
		requeue_entries = []
		recovered_entry_ids = set()
		for queue_entry in queue_entries:
			run_monitor = PidfileRunMonitor(
			    queue_entry.results_dir())
			pid, exit_code = run_monitor.get_pidfile_info()
			if pid is None:
				# autoserv apparently never got run, so requeue
				requeue_entries.append(queue_entry)
				continue
			if queue_entry.id in recovered_entry_ids:
				# synchronous job we've already recovered
				continue
			print 'Recovering queue entry %d (pid %d)' % (
			    queue_entry.id, pid)
			job = queue_entry.job
			if job.is_synchronous():
				for entry in job.get_host_queue_entries():
					assert entry.active
					recovered_entry_ids.add(entry.id)
			self.recover_queue_entry(queue_entry,
						 run_monitor)
			orphans.pop(pid, None)

		# and requeue other active queue entries
		rows = _db.execute("""SELECT * FROM host_queue_entries
		                      WHERE active AND NOT complete
				      AND status != 'Running'
				      AND status != 'Pending'
				      AND status != 'Abort'
				      AND status != 'Aborting'""")
		queue_entries = [HostQueueEntry(row=i) for i in rows]
		for queue_entry in queue_entries + requeue_entries:
			print 'Requeuing running QE %d' % queue_entry.id
			queue_entry.clear_results_dir()
			queue_entry.requeue()


		# now kill any remaining autoserv processes
		for pid in orphans.keys():
			print 'Killing orphan %d (%s)' % (pid, orphans[pid])
			kill_autoserv(pid)

		# recover aborting tasks
		rows = _db.execute("""SELECT * FROM host_queue_entries
				   WHERE status='Abort' or status='Aborting'""")
		queue_entries = [HostQueueEntry(row=i) for i in rows]
		for queue_entry in queue_entries:
			queue_host = queue_entry.get_host()
			reboot_task = RebootTask(queue_host)
			verify_task = VerifyTask(host = queue_host)
			self.add_agent(Agent(tasks=[reboot_task,
						    verify_task],
				       queue_entry_ids=[queue_entry.id]))
			queue_entry.set_status('Aborted')
			# Secure the host from being picked up
			queue_host.set_status('Rebooting')

		# reverify hosts that were in the middle of verify, repair or
		# reboot
		rows = _db.execute("""SELECT * FROM hosts
				      WHERE locked = 0 AND
				      (status = 'Repairing'
				       OR status = 'Verifying'
				       OR status = 'Rebooting')""")
		hosts = [Host(row=i) for i in rows]
		for host in hosts:
			self.add_agent(Agent(tasks=[VerifyTask(host=host)]))


	def _recover_hosts(self):
		# look for both "Repair Failed" hosts, which we expect, and
		# "Running" hosts with no active queue entries, which should
		# never happen
		rows = _db.execute(
		    """SELECT * FROM hosts WHERE locked = 0 AND
		       (status = 'Repair Failed'
		        OR (status = 'Running' AND
			    id NOT IN (SELECT host_id FROM host_queue_entries
			               WHERE active)))""")
		hosts = [Host(row=i) for i in rows]
		for host in hosts:
			if host.status == 'Running':
				print ('Recovering running host %s - this '
				       'probably indicates a scheduler bug' %
				       host.hostname)
			verify_task = VerifyTask(host = host)
			self.add_agent(Agent(tasks = [verify_task]))


	def _find_more_work(self):
		print "finding work"

		num_started = 0
		for host in idle_hosts():
			tasks = host.next_queue_entries()
			if tasks:
				for next in tasks:
					try:
						agent = next.run(assigned_host=host)
						if agent:							
							self.add_agent(agent)

							num_started += 1
							if num_started>=100:
								return
							break
					except:
						next.set_status('Failed')
						
#						if next.host:
#							next.host.set_status('Ready')

						log_stacktrace("task_id = %d" % next.id)


	def _find_aborting(self):	
		num_aborted = 0
		# Find jobs that are aborting
		for entry in queue_entries_to_abort():
			agents_to_abort = self.get_agents(entry)
			entry_host = entry.get_host()
			reboot_task = RebootTask(entry_host)
			verify_task = VerifyTask(host = entry_host)
			tasks = [reboot_task, verify_task]
			if agents_to_abort:
				abort_task = AbortTask(entry, agents_to_abort)
				tasks.insert(0, abort_task)
			else:
				entry.set_status('Aborted')
				# just to make sure this host does not get
				# taken away
				entry_host.set_status('Rebooting')
			self.add_agent(Agent(tasks=tasks,
					     queue_entry_ids = [entry.id]))
			num_aborted += 1
			if num_aborted >= 50:
				break


	def _handle_agents(self):
		still_running = []
		for agent in self._agents:
			agent.tick()
			if not agent.is_done():
				still_running.append(agent)
			else:
				print "agent finished"
		self._agents = still_running


class RunMonitor(object):
	def __init__(self, cmd, nice_level = None, log_file = None):
		self.nice_level = nice_level
		self.log_file = log_file
		self.proc = self.run(cmd)

        def run(self, cmd):
		if self.nice_level:
			nice_cmd = ['nice','-n', str(self.nice_level)]
			nice_cmd.extend(cmd)
			cmd = nice_cmd

		out_file = None
		if self.log_file:
			try:
				os.makedirs(os.path.dirname(self.log_file))
				out_file = open(self.log_file, 'a')
				out_file.write("\n%s\n" % ('*'*80))
				out_file.write("%s> %s\n" % (time.strftime("%X %x"), cmd))
				out_file.write("%s\n" % ('*'*80))
			except:
				pass
				
		if not out_file:
			out_file = open('/dev/null', 'w')
			
		in_devnull = open('/dev/null', 'r')
		print "cmd = %s" % cmd
		print "path = %s" % os.getcwd()

		proc = subprocess.Popen(cmd, stdout=out_file,
					stderr=subprocess.STDOUT, stdin=in_devnull)
		out_file.close()
		in_devnull.close()
                return proc


	def get_pid(self):
		return self.proc.pid


	def kill(self):
		kill_autoserv(self.get_pid(), self.exit_code)


	def exit_code(self):
		return self.proc.poll()


class PidfileException(Exception):
	"""\
	Raised when there's some unexpected behavior with the pid file.
	"""


class PidfileRunMonitor(RunMonitor):
	def __init__(self, results_dir, cmd=None, nice_level=None,
		     log_file=None):
		self.results_dir = os.path.abspath(results_dir)
		self.pid_file = os.path.join(results_dir, AUTOSERV_PID_FILE)
		self.lost_process = False
		if cmd is None:
			# we're reattaching to an existing pid, so don't call
			# the superconstructor (we don't want to kick off a new
			# process)
			pass
		else:
			RunMonitor.__init__(self, cmd, nice_level, log_file)


	def get_pid(self):
		pid, exit_status = self.get_pidfile_info()
		assert pid is not None
		return pid


	def check_proc_fs(self, pid):
		cmdline_path = os.path.join('/proc', str(pid), 'cmdline')
		try:
			cmdline_file = open(cmdline_path, 'r')
			cmdline = cmdline_file.read().strip()
			cmdline_file.close()
		except IOError:
			return False
		# /proc/.../cmdline has \x00 separating args
		results_dir_arg = '\x00-r\x00%s\x00' % self.results_dir
		if results_dir_arg not in cmdline:
			print '%s not found in %s' % (repr(results_dir_arg),
						      repr(cmdline))
			return False
		return True


	def read_pidfile(self):
		if not os.path.exists(self.pid_file):
			return None, None
		file_obj = open(self.pid_file, 'r')
		lines = file_obj.readlines()
		file_obj.close()
		assert 1 <= len(lines) <= 2
		try:
			pid = int(lines[0])
			exit_status = None
			if len(lines) == 2:
				exit_status = int(lines[1])
		except ValueError, exc:
			raise Exception('Corrupt pid file: ' + str(exc.args))

		return pid, exit_status


	def get_pidfile_info(self):
		"""\
		Returns:
		 None, None if autoserv has not yet run
		 pid,  None if autoserv is running
		 pid, exit_status if autoserv has completed
		"""
		if self.lost_process:
			return self.pid, self.exit_status

		pid, exit_status = self.read_pidfile()

		# double check autoserv is really running if it says it is
		if (pid is not None and exit_status is None
		    and not self.check_proc_fs(pid)):
			# maybe process *just* exited
			pid, exit_status = self.read_pidfile()
			if not exit_status:
				# autoserv exited without writing an exit code
				# to the pidfile
				error = ('autoserv died without writing exit '
					 'code')
				message = error + '\nPid: %s\nPidfile: %s' % (
				    pid, self.pid_file)
				print message
				send_notify_email(error, message)
				self.lost_process = True
				self.pid = pid
				self.exit_status = 1
				return self.pid, self.exit_status

		return pid, exit_status


	def exit_code(self):
		pid, exit_code = self.get_pidfile_info()
		assert pid is not None
		return exit_code


class Agent(object):
	def __init__(self, tasks, queue_entry_ids=[]):
		self.active_task = None
		self.queue = Queue.Queue(0)
		self.dispatcher = None
		self.queue_entry_ids = queue_entry_ids
		
		for task in tasks:
			self.add_task(task)


	def add_task(self, task):
		self.queue.put_nowait(task)
		task.agent = self


	def tick(self):
		print "agent tick"
		if self.active_task and not self.active_task.is_done():
			self.active_task.poll()
		else:
			self._next_task();


	def _next_task(self):
		print "agent picking task"
		if self.active_task:
			assert self.active_task.is_done()

			if not self.active_task.success:
				self.on_task_failure()

		self.active_task = None
		if not self.is_done():
			self.active_task = self.queue.get_nowait()
			if self.active_task:
				self.active_task.start()


	def on_task_failure(self):
		self.queue = Queue.Queue(0)
		for task in self.active_task.failure_tasks:
			self.add_task(task)


	def is_done(self):
		return self.active_task == None and self.queue.empty()


	def start(self):
		assert self.dispatcher

		self._next_task()

	
class AgentTask(object):
	def __init__(self, cmd, failure_tasks = []):
		self.done = False
		self.failure_tasks = failure_tasks
		self.started = False
		self.cmd = cmd
		self.task = None
		self.agent = None
		self.monitor = None


	def poll(self):
		print "poll"
		if self.monitor:
			self.tick(self.monitor.exit_code())
		else:
			self.finished(False)


	def tick(self, exit_code):
		if exit_code==None:
			return
#		print "exit_code was %d" % exit_code
		if exit_code == 0:
			success = True
		else:
			success = False

		self.finished(success)


	def is_done(self):
		return self.done


	def finished(self, success):
		self.done = True
		self.success = success
		self.epilog()


	def prolog(self):
		pass


	def epilog(self):
		pass


	def start(self):
		assert self.agent

		if not self.started:
			self.prolog()
			self.run()

		self.started = True


	def abort(self):
		if self.monitor:
			self.monitor.kill()
		self.done = True


	def run(self):
		if self.cmd:
			print "agent starting monitor"
			log_file = None
			if hasattr(self, 'host'):
				log_file = os.path.join(RESULTS_DIR, 'hosts',
							self.host.hostname)
			self.monitor = RunMonitor(
			    self.cmd, nice_level = AUTOSERV_NICE_LEVEL,
			    log_file = log_file)


class RepairTask(AgentTask):
	def __init__(self, host, fail_queue_entry=None):
		"""\
		fail_queue_entry: queue entry to mark failed if this repair
		fails.
		"""
		cmd = [_autoserv_path , '-R', '-m', host.hostname]
		self.host = host
		self.fail_queue_entry = fail_queue_entry
		AgentTask.__init__(self, cmd)


	def prolog(self):
		print "repair_task starting"
		self.host.set_status('Repairing')


	def epilog(self):
		if self.success:
			self.host.set_status('Ready')
		else:
			self.host.set_status('Repair Failed')
			if self.fail_queue_entry:
				self.fail_queue_entry.handle_host_failure()


class VerifyTask(AgentTask):
	def __init__(self, queue_entry=None, host=None):
		assert bool(queue_entry) != bool(host)

		self.host = host or queue_entry.host
		self.queue_entry = queue_entry

		self.temp_results_dir = tempfile.mkdtemp(suffix='.verify')
		cmd = [_autoserv_path,'-v','-m',self.host.hostname,
		       '-r', self.temp_results_dir]

		fail_queue_entry = None
		if queue_entry and not queue_entry.meta_host:
			fail_queue_entry = queue_entry
		failure_tasks = [RepairTask(self.host, fail_queue_entry)]

		AgentTask.__init__(self, cmd, failure_tasks=failure_tasks)


	def prolog(self):
		print "starting verify on %s" % (self.host.hostname)
		if self.queue_entry:
			self.queue_entry.set_status('Verifying')
			self.queue_entry.clear_results_dir(
			    self.queue_entry.verify_results_dir())
		self.host.set_status('Verifying')


	def epilog(self):
		if self.queue_entry and (self.success or
					 not self.queue_entry.meta_host):
			self.move_results()
		shutil.rmtree(self.temp_results_dir)

		if self.success:
			self.host.set_status('Ready')
		elif self.queue_entry:
			self.queue_entry.requeue()


	def move_results(self):
		assert self.queue_entry is not None
		target_dir = self.queue_entry.verify_results_dir()
		if not os.path.exists(target_dir):
			os.makedirs(target_dir)
		files = os.listdir(self.temp_results_dir)
		for filename in files:
			if filename == AUTOSERV_PID_FILE:
				continue
			self.force_move(os.path.join(self.temp_results_dir,
						     filename),
					os.path.join(target_dir, filename))


	@staticmethod
	def force_move(source, dest):
		"""\
		Replacement for shutil.move() that will delete the destination
		if it exists, even if it's a directory.
		"""
		if os.path.exists(dest):
			print ('Warning: removing existing destination file ' +
			       dest)
			remove_file_or_dir(dest)
		shutil.move(source, dest)


class VerifySynchronousTask(VerifyTask):
	def __init__(self, queue_entry):
		VerifyTask.__init__(self, queue_entry = queue_entry)


	def epilog(self):
		VerifyTask.epilog(self)
		if self.success:
			if self.queue_entry.job.num_complete() > 0:
				# some other entry failed verify, and we've
				# already been marked as stopped
				return

			self.queue_entry.set_status('Pending')
			job = self.queue_entry.job
			if job.is_ready():
				agent = job.run(self.queue_entry)
				self.agent.dispatcher.add_agent(agent)

class QueueTask(AgentTask):
	def __init__(self, job, queue_entries, cmd):
		AgentTask.__init__(self, cmd)
		self.job = job
		self.queue_entries = queue_entries


	@staticmethod
	def _write_keyval(results_dir, field, value):
		key_path = os.path.join(results_dir, 'keyval')
		keyval_file = open(key_path, 'a')
		print >> keyval_file, '%s=%d' % (field, value)
		keyval_file.close()


	def results_dir(self):
		return self.queue_entries[0].results_dir()


	def run(self):
		"""\
		Override AgentTask.run() so we can use a PidfileRunMonitor.
		"""
		self.monitor = PidfileRunMonitor(self.results_dir(),
						 cmd=self.cmd,
						 nice_level=AUTOSERV_NICE_LEVEL)


	def prolog(self):
		# write the parser commands into the results directories
		if self.job.is_synchronous() or self.job.num_machines()==1:
			results_dir = self.job.results_dir()
			cmdfile = os.path.join(results_dir, '.parse.cmd')
			cmd = generate_parse_command(results_dir)
			print >> open(cmdfile, 'w'), cmd
		else:
			for queue_entry in self.queue_entries:
				results_dir = queue_entry.results_dir()
				cmdfile = os.path.join(results_dir,
						       '.parse.cmd')
				cmd = generate_parse_command(results_dir,
							     '-l 2')
				print >> open(cmdfile, 'w'), cmd

		# write some job timestamps into the job keyval file
		queued = time.mktime(self.job.created_on.timetuple())
		started = time.time()
		self._write_keyval(self.results_dir(), "job_queued", queued)
		self._write_keyval(self.results_dir(), "job_started", started)
		for queue_entry in self.queue_entries:
			print "starting queue_task on %s/%s" % (queue_entry.host.hostname, queue_entry.id)
			queue_entry.set_status('Running')
			queue_entry.host.set_status('Running')
		if (not self.job.is_synchronous() and
		    self.job.num_machines() > 1):
			assert len(self.queue_entries) == 1
			self.job.write_to_machines_file(self.queue_entries[0])


	def epilog(self):
		if self.success:
			status = 'Completed'
		else:
			status = 'Failed'

		# write another timestamp into the job keyval file
		finished = time.time()
		self._write_keyval(self.results_dir(), "job_finished", finished)
		for queue_entry in self.queue_entries:
			queue_entry.set_status(status)
			queue_entry.host.set_status('Ready')

		if self.job.is_synchronous() or self.job.num_machines()==1:
			if self.job.is_finished():
				parse_results(self.job.results_dir())
		else:
			for queue_entry in self.queue_entries:
				parse_results(queue_entry.results_dir(),
					      flags='-l 2')

		print "queue_task finished with %s/%s" % (status, self.success)


class RecoveryQueueTask(QueueTask):
	def __init__(self, job, queue_entries, run_monitor):
		QueueTask.__init__(self, job, queue_entries, cmd=None)
		self.run_monitor = run_monitor


	def run(self):
		self.monitor = self.run_monitor


	def prolog(self):
		# recovering an existing process - don't do prolog
		pass


class RebootTask(AgentTask):
	def __init__(self, host):
		global _autoserv_path
		
		# Current implementation of autoserv requires control file
		# to be passed on reboot action request. TODO: remove when no
		# longer appropriate.
		self.cmd = [_autoserv_path, '-b', '-m', host.hostname,
			    '/dev/null']
		self.host = host
		AgentTask.__init__(self, self.cmd,
				   failure_tasks=[RepairTask(host)])


	def prolog(self):
		print "starting reboot task for host: %s" % self.host.hostname
		self.host.set_status("Rebooting")


class AbortTask(AgentTask):
	def __init__(self, queue_entry, agents_to_abort):
		self.queue_entry = queue_entry
		self.agents_to_abort = agents_to_abort
		for agent in agents_to_abort:
			agent.dispatcher.remove_agent(agent)
		AgentTask.__init__(self, '')


	def prolog(self):
		print "starting abort on host %s, job %s" % (
			self.queue_entry.host_id, self.queue_entry.job_id)
		self.queue_entry.set_status('Aborting')
		

	def epilog(self):
		self.queue_entry.set_status('Aborted')
		self.success = True

	def run(self):
		for agent in self.agents_to_abort:
			if (agent.active_task):
				agent.active_task.abort()


class DBObject(object):
	def __init__(self, fields, id=None, row=None, new_record=False):
		assert (bool(id) != bool(row)) and fields

		self.__table = self._get_table()
		self.__fields = fields

		self.__new_record = new_record

		if row is None:
			sql = 'SELECT * FROM %s WHERE ID=%%s' % self.__table
			rows = _db.execute(sql, (id,))
			if len(rows) == 0:
				raise "row not found (table=%s, id=%s)" % \
							(self.__table, id)
			row = rows[0]

		assert len(row)==len(fields), (
		    "table = %s, row = %s/%d, fields = %s/%d" % (
		    self.__table, row, len(row), fields, len(fields)))

		self.__valid_fields = {}
		for i,value in enumerate(row):
			self.__dict__[fields[i]] = value
			self.__valid_fields[fields[i]] = True

		del self.__valid_fields['id']


	@classmethod
	def _get_table(cls):
		raise NotImplementedError('Subclasses must override this')


	def count(self, where, table = None):
		if not table:
			table = self.__table
	
		rows = _db.execute("""
			SELECT count(*) FROM %s
			WHERE %s
		""" % (table, where))

		assert len(rows) == 1

		return int(rows[0][0])


	def num_cols(self):
		return len(self.__fields)


	def update_field(self, field, value):
		assert self.__valid_fields[field]
		
		if self.__dict__[field] == value:
			return

		query = "UPDATE %s SET %s = %%s WHERE id = %%s" % \
							(self.__table, field)
		_db.execute(query, (value, self.id))

		self.__dict__[field] = value


	def save(self):
		if self.__new_record:
			keys = self.__fields[1:] # avoid id
			columns = ','.join([str(key) for key in keys])
			values = ['"%s"' % self.__dict__[key] for key in keys]
			values = ','.join(values)
			query = """INSERT INTO %s (%s) VALUES (%s)""" % \
						(self.__table, columns, values)
			_db.execute(query)


	def delete(self):
		query = 'DELETE FROM %s WHERE id=%%s' % self.__table
		_db.execute(query, (self.id,))


	@classmethod
	def fetch(cls, where):
		rows = _db.execute(
		    'SELECT * FROM %s WHERE %s' % (cls._get_table(), where))
		for row in rows:
			yield cls(row=row)


class IneligibleHostQueue(DBObject):
	def __init__(self, id=None, row=None, new_record=None):
		fields = ['id', 'job_id', 'host_id']
		DBObject.__init__(self, fields, id=id, row=row,
				  new_record=new_record)


	@classmethod
	def _get_table(cls):
		return 'ineligible_host_queues'


class Host(DBObject):
	def __init__(self, id=None, row=None):
		fields =  ['id', 'hostname', 'locked', 'synch_id','status']
		DBObject.__init__(self, fields, id=id, row=row)


	@classmethod
	def _get_table(cls):
		return 'hosts'


	def current_task(self):
		rows = _db.execute("""
			SELECT * FROM host_queue_entries WHERE host_id=%s AND NOT complete AND active
			""", (self.id,))
		
		if len(rows) == 0:
			return None
		else:
			assert len(rows) == 1
			results = rows[0];
#			print "current = %s" % results
			return HostQueueEntry(row=results)


	def next_queue_entries(self):
		if self.locked:
			print "%s locked, not queuing" % self.hostname
			return None
#		print "%s/%s looking for work" % (self.hostname, self.platform_id)
		rows = _db.execute("""
			SELECT * FROM host_queue_entries
			WHERE ((host_id=%s) OR (meta_host IS NOT null AND
			(meta_host IN (
				SELECT label_id FROM hosts_labels WHERE host_id=%s
				)
			)
			AND job_id NOT IN ( 
				SELECT job_id FROM ineligible_host_queues
				WHERE host_id=%s
			)))
			AND NOT complete AND NOT active
			ORDER BY priority DESC, meta_host, id
			LIMIT 1
		""", (self.id,self.id, self.id))

		if len(rows) == 0:
			return None
		else:
			return [HostQueueEntry(row=i) for i in rows]
	
	def yield_work(self):
		print "%s yielding work" % self.hostname
		if self.current_task():
			self.current_task().requeue()
		
	def set_status(self,status):
		print '%s -> %s' % (self.hostname, status)
		self.update_field('status',status)


class HostQueueEntry(DBObject):
	def __init__(self, id=None, row=None):
		assert id or row
		fields = ['id', 'job_id', 'host_id', 'priority', 'status',
			  'meta_host', 'active', 'complete']
		DBObject.__init__(self, fields, id=id, row=row)

		self.job = Job(self.job_id)

		if self.host_id:
			self.host = Host(self.host_id)
		else:
			self.host = None

		self.queue_log_path = os.path.join(self.job.results_dir(),
						   'queue.log.' + str(self.id))


	@classmethod
	def _get_table(cls):
		return 'host_queue_entries'


	def set_host(self, host):
		if host:
			self.queue_log_record('Assigning host ' + host.hostname)
			self.update_field('host_id', host.id)
			self.update_field('active', True)
			self.block_host(host.id)
		else:
			self.queue_log_record('Releasing host')
			self.unblock_host(self.host.id)
			self.update_field('host_id', None)

		self.host = host


	def get_host(self):
		return self.host


	def queue_log_record(self, log_line):
		now = str(datetime.datetime.now())
		queue_log = open(self.queue_log_path, 'a', 0)
		queue_log.write(now + ' ' + log_line + '\n')
		queue_log.close()


	def block_host(self, host_id):
		print "creating block %s/%s" % (self.job.id, host_id)
		row = [0, self.job.id, host_id]
		block = IneligibleHostQueue(row=row, new_record=True)
		block.save()


	def unblock_host(self, host_id):
		print "removing block %s/%s" % (self.job.id, host_id)
		blocks = list(IneligibleHostQueue.fetch(
		    'job_id=%d and host_id=%d' % (self.job.id, host_id)))
		assert len(blocks) == 1
		blocks[0].delete()


	def results_dir(self):
		if self.job.is_synchronous() or self.job.num_machines() == 1:
			return self.job.job_dir
		else:
			assert self.host
			return os.path.join(self.job.job_dir,
					    self.host.hostname)


	def verify_results_dir(self):
		if self.job.is_synchronous() or self.job.num_machines() > 1:
			assert self.host
			return os.path.join(self.job.job_dir,
					    self.host.hostname)
		else:
			return self.job.job_dir


	def set_status(self, status):
		self.update_field('status', status)
		if self.host:
			hostname = self.host.hostname
		else:
			hostname = 'no host'
		print "%s/%d status -> %s" % (hostname, self.id, self.status)
		if status in ['Queued']:
			self.update_field('complete', False)
			self.update_field('active', False)

		if status in ['Pending', 'Running', 'Verifying', 'Starting',
			      'Abort', 'Aborting']:
			self.update_field('complete', False)
			self.update_field('active', True)

		if status in ['Failed', 'Completed', 'Stopped', 'Aborted']:
			self.update_field('complete', True)
			self.update_field('active', False)


	def run(self,assigned_host=None):
		if self.meta_host:
			assert assigned_host
			# ensure results dir exists for the queue log
			self.job.create_results_dir()
			self.set_host(assigned_host)

		print "%s/%s scheduled on %s, status=%s" % (self.job.name,
				self.meta_host, self.host.hostname, self.status)

		return self.job.run(queue_entry=self)

	def requeue(self):
		self.set_status('Queued')

		if self.meta_host:
			self.set_host(None)


	def handle_host_failure(self):
		"""\
		Called when this queue entry's host has failed verification and
		repair.
		"""
		assert not self.meta_host
		self.set_status('Failed')
		if self.job.is_synchronous():
			self.job.stop_all_entries()


	def clear_results_dir(self, results_dir=None):
		results_dir = results_dir or self.results_dir()
		if not os.path.exists(results_dir):
			return
		for filename in os.listdir(results_dir):
			if 'queue.log' in filename:
				continue
			path = os.path.join(results_dir, filename)
			remove_file_or_dir(path)


class Job(DBObject):
	def __init__(self, id=None, row=None):
		assert id or row
		DBObject.__init__(self,
				  ['id','owner','name','priority',
				   'control_file','control_type','created_on',
				   'synch_type', 'synch_count','synchronizing'],
				  id=id, row=row)

		self.job_dir = os.path.join(RESULTS_DIR, "%s-%s" % (self.id,
								    self.owner))


	@classmethod
	def _get_table(cls):
		return 'jobs'


	def is_server_job(self):
		return self.control_type != 2


	def get_host_queue_entries(self):
		rows = _db.execute("""
			SELECT * FROM host_queue_entries
			WHERE job_id= %s
		""", (self.id,))
		entries = [HostQueueEntry(row=i) for i in rows]

		assert len(entries)>0

		return entries


	def set_status(self, status, update_queues=False):
		self.update_field('status',status)
		
		if update_queues:
			for queue_entry in self.get_host_queue_entries():
				queue_entry.set_status(status)


	def is_synchronous(self):
		return self.synch_type == 2


	def is_ready(self):
		if not self.is_synchronous():
			return True
		sql = "job_id=%s AND status='Pending'" % self.id
		count = self.count(sql, table='host_queue_entries')
		return (count == self.synch_count)


	def ready_to_synchronize(self):
		# heuristic
		queue_entries = self.get_host_queue_entries()
		count = 0
		for queue_entry in queue_entries:
			if queue_entry.status == 'Pending':
				count += 1

		return (count/self.synch_count >= 0.5)


	def start_synchronizing(self):
		self.update_field('synchronizing', True)


	def results_dir(self):
		return self.job_dir

	def num_machines(self, clause = None):
		sql = "job_id=%s" % self.id
		if clause:
			sql += " AND (%s)" % clause
		return self.count(sql, table='host_queue_entries')


	def num_queued(self):
		return self.num_machines('not complete')


	def num_active(self):
		return self.num_machines('active')


	def num_complete(self):
		return self.num_machines('complete')


	def is_finished(self):
		left = self.num_queued()
		print "%s: %s machines left" % (self.name, left)
		return left==0

	def stop_synchronizing(self):
		self.update_field('synchronizing', False)
		self.set_status('Queued', update_queues = False)


	def stop_all_entries(self):
		for child_entry in self.get_host_queue_entries():
			if not child_entry.complete:
				child_entry.set_status('Stopped')


	def write_to_machines_file(self, queue_entry):
		hostname = queue_entry.get_host().hostname
		print "writing %s to job %s machines file" % (hostname, self.id)
		file_path = os.path.join(self.job_dir, '.machines')
		mf = open(file_path, 'a')
		mf.write("%s\n" % queue_entry.get_host().hostname)
		mf.close()


	def create_results_dir(self, queue_entry=None):
		print "create: active: %s complete %s" % (self.num_active(),
							  self.num_complete())

		if not os.path.exists(self.job_dir):
			os.makedirs(self.job_dir)

		if queue_entry:
			return queue_entry.results_dir()
		return self.job_dir


	def run(self, queue_entry):
		results_dir = self.create_results_dir(queue_entry)

		if self.is_synchronous():
			if not self.is_ready():
				return Agent([VerifySynchronousTask(
						queue_entry = queue_entry)],
					     [queue_entry.id])

		queue_entry.set_status('Starting')

		ctrl = open(os.tmpnam(), 'w')
		if self.control_file:
			ctrl.write(self.control_file)
		else:
			ctrl.write("")
		ctrl.flush()

		if self.is_synchronous():
			queue_entries = self.get_host_queue_entries()
		else:
			assert queue_entry
			queue_entries = [queue_entry]
		hostnames = ','.join([entry.get_host().hostname
				      for entry in queue_entries])

		params = [_autoserv_path, '-p', '-n',
			  '-r', os.path.abspath(results_dir),
			  '-b', '-u', self.owner, '-l', self.name,
			  '-m', hostnames, ctrl.name]

		if not self.is_server_job():
			params.append('-c')

		tasks = []
		if not self.is_synchronous():
			tasks.append(VerifyTask(queue_entry))

		tasks.append(QueueTask(job = self,
				       queue_entries = queue_entries,
				       cmd = params))

		ids = []
		for entry in queue_entries:
			ids.append(entry.id)
		
		agent = Agent(tasks, ids)

		return agent


if __name__ == '__main__':
	main()