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
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)

_connection = None
_cursor = None
_shutdown = False
_notify_email = None


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

	parser = optparse.OptionParser(usage)
	parser.add_option('--no-recover', help='Skip machine/job recovery ' +
	                  'step [for multiple monitors/rolling upgrades]',
	                  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')
	(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

	init(options.logfile)
	dispatcher = Dispatcher(do_recover = not options.no_recover)

	try:
		while not _shutdown:
			dispatcher.tick()
			time.sleep(20)
		dispatcher.shut_down()
	except:
		log_stacktrace("Uncaught exception; terminating monitor_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']
	connect()

	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():
	_cursor.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 _cursor.fetchall()]
	return hosts


def connect():
	path = os.path.dirname(os.path.abspath(sys.argv[0]))
	# get global config and parse for info
	c = global_config.global_config
	dbase = "AUTOTEST_WEB"
	DB_HOST = c.get_config_value(dbase, "host", "localhost")
	DB_SCHEMA = c.get_config_value(dbase, "database", "autotest_web")

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

	global _connection, _cursor
	_connection = MySQLdb.connect(
		host=DB_HOST,
		user=DB_USER,
		passwd=DB_PASS,
		db=DB_SCHEMA
	)
	_connection.autocommit(True)
	_cursor = _connection.cursor()


def disconnect():
	global _connection, _cursor
	_connection.close()
	_connection = None
	_cursor = None


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


def log_stacktrace(reason):
	(type, value, tb) = sys.exc_info()
	str = "EXCEPTION: %s\n" % reason
	str += "%s / %s / %s\n" % (socket.gethostname(), os.getpid(),
	                           time.strftime("%X %x"))
	str += ''.join(traceback.format_exception(type, value, tb))

	sys.stderr.write("\n%s\n" % str)

	if _notify_email:
		sender = "monitor_db"
		subject = "monitor_db exception"
		msg = "From: %s\nTo: %s\nSubject: %s\n\n%s" % (
		         sender, _notify_email, subject, str)
		mailer = smtplib.SMTP('localhost')
		mailer.sendmail(sender, _notify_email, msg)
		mailer.quit()


class Dispatcher:
	def __init__(self, do_recover=True):
		self._agents = []
		self.shutting_down = False

		if do_recover:
			self._recover_lost()
		

	def shut_down(self):
		print "Shutting down!"
		self.shutting_down = True
		while self._agents:
			self.tick()
			time.sleep(40)


	def tick(self):
		if not self.shutting_down:
			self._find_more_work()
		self._handle_agents()


	def add_agent(self, agent):
		self._agents.append(agent)
		agent.dispatcher = self


	def _recover_lost(self):
		_cursor.execute("""SELECT * FROM host_queue_entries WHERE active AND NOT complete""")
		if _cursor.rowcount:
			queue_entries = [HostQueueEntry(row=i) for i in _cursor.fetchall()]
			for queue_entry in queue_entries:
				job = queue_entry.job
				if job.is_synchronous():
					for child_entry in job.get_host_queue_entries():
						child_entry.requeue()
				else:
					queue_entry.requeue()
				queue_entry.clear_results_dir()
			
		_cursor.execute("""SELECT * FROM hosts
		                   WHERE status != 'Ready' AND NOT locked""")
		if _cursor.rowcount:
			hosts = [Host(row=i) for i in _cursor.fetchall()]
			for host in hosts:
				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 _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:
				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 kill(self):
		self.proc.kill()


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


class Agent(object):
	def __init__(self, tasks):
		self.active_task = None
		self.queue = Queue.Queue(0)
		self.dispatcher = None
		
		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 and self.active_task.failure_tasks:
				self.queue = Queue.Queue(0)
				for task in self.active_task.failure_tasks:
					self.add_task(task)
		
		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 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 = None):
		self.done = False
		self.failure_tasks = failure_tasks
		self.started = False
		self.cmd = cmd
		self.agent = None


	def poll(self):
		print "poll"
		if hasattr(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):
		self.monitor.kill()


	def run(self):
		if self.cmd:
			print "agent starting monitor"

			log_file = None
			if hasattr(self, 'host'):
				log_file = os.path.join(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):
		cmd = ['autoserv', '-n', '-R', '-m', host.hostname]
		self.host = host
		AgentTask.__init__(self, cmd)

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


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

		self.host.set_status(status)


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', '-n', '-v', '-m', self.host.hostname,
		       '-r', self.temp_results_dir]

		AgentTask.__init__(self, cmd, failure_tasks = [RepairTask(self.host)])


	def prolog(self):
		print "starting verify on %s" % (self.host.hostname)
		if self.queue_entry:
			self.queue_entry.set_status('Verifying')
		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()
		else:
			shutil.rmtree(self.temp_results_dir)

		if self.success:
			status = 'Ready'
		else:
			status = 'Failed Verify'
			if self.queue_entry:
				if self.queue_entry.meta_host:
					self.host.yield_work()
				else:
					self.queue_entry.set_status('Failed')

		self.host.set_status(status)


	def move_results(self):
		assert self.queue_entry is not None
		target_dir = self.queue_entry.results_dir()
		if self.queue_entry.job.is_synchronous():
			target_dir = os.path.join(target_dir,
						 self.queue_entry.host.hostname)
		if not os.path.exists(target_dir):
			os.makedirs(target_dir)
		files = os.listdir(self.temp_results_dir)
		for filename in files:
			shutil.move(os.path.join(self.temp_results_dir,
						 filename),
				    os.path.join(target_dir, filename))


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


	def epilog(self):
		VerifyTask.epilog(self)
		print "verify_synchronous finished: %s/%s" % (self.queue_entry.host.hostname, self.success)
		if self.success:
			if self.queue_entry.job.num_complete()==0:
				self.queue_entry.set_status('Pending')
	
				job = self.queue_entry.job
				if job.is_ready():
					self.agent.dispatcher.add_agent(job.run(self.queue_entry))
			else:
				self.queue_entry.set_status('Stopped') # some other entry failed verify
		else:		
			if self.queue_entry.meta_host:
				self.queue_entry.set_status('Queued')
			else:
				job = self.queue_entry.job
				for child_entry in job.get_host_queue_entries():
					if child_entry.active:
						child_entry.set_status('Stopped')


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


	def prolog(self):
		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')
			# write some job timestamps into the job keyval file
			queued = time.mktime(self.job.created_on.timetuple())
			started = time.time()
			self._write_keyval(queue_entry, "job_queued", queued)
			self._write_keyval(queue_entry, "job_started", started)


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

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

		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 RebootTask(AgentTask):
	def __init__(self):
		AgentTask.__init__(self, host)
		self.cmd = "autoserv -n -b -m %s /dev/null" % host
		self.host = host


	def tick(self, exit_code):
		raise "not implemented"


	def run(self):
		raise "not implemented"
		


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

		self.__table = table
		self.__fields = fields

		self.__new_record = new_record

		if row is None:
			sql = 'SELECT * FROM %s WHERE ID=%%s' % self.__table
			_cursor.execute(sql, (id,))
			if not _cursor.rowcount:
				raise "row not found (table=%s, id=%s)" % \
							(self.__table, id)
			row = _cursor.fetchone()

		assert len(row)==len(fields), "table = %s, row = %s/%d, fields = %s/%d" % (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']

	def count(self, where, table = None):
		if not table:
			table = self.__table

		_cursor.execute("""
			SELECT count(*) FROM %s
			WHERE %s
		""" % (table, where))
		count = _cursor.fetchall()

		return int(count[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)
		_cursor.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)
			_cursor.execute(query)


	def delete(self):
		_cursor.execute("""DELETE FROM %s WHERE id = %%s""" % \
						self.__table, (self.id,))


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


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


	def current_task(self):
		_cursor.execute("""
			SELECT * FROM host_queue_entries WHERE host_id=%s AND NOT complete AND active
			""", (self.id,))
		
		if not _cursor.rowcount:
			return None
		else:
			assert _cursor.rowcount == 1
			results = _cursor.fetchone();
#			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)
		_cursor.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 not _cursor.rowcount:
			return None
		else:
			return [HostQueueEntry(row=i) for i in _cursor.fetchall()]
	
	def yield_work(self):
		print "%s yielding work" % self.hostname
		if self.current_task():
			self.current_task().requeue()
		
	def set_status(self,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, 'host_queue_entries', 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))


	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)
		else:
			self.queue_log_record('Releasing host')
			self.update_field('host_id', None)

		self.host = host


	def get_host(self):
		if not self.host:
			if self.host_id:
				self.host  = Host(self.host_id)
		if self.host:
			return self.host
		else:
			return None


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


	def results_dir(self):
		if self.job.num_machines()==1 or self.job.is_synchronous():
			results_dir = self.job.job_dir
		else:
			assert self.host
			results_dir = '%s/%s' % (self.job.job_dir,
						 self.host.hostname)

		return results_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']:
			self.update_field('complete', False)
			self.update_field('active', True)

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


	def run(self,assigned_host=None):
		if self.meta_host:
			assert assigned_host
			self.job.create_results_dir()
			self.set_host(assigned_host)
			print "creating block %s/%s" % (self.job.id,
							self.host.id)

			row = [0, self.job.id, self.host.id]
			block = IneligibleHostQueue(row=row, new_record=True)
			block.save()
		
		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 clear_results_dir(self):
		if os.path.exists(self.results_dir()):
			shutil.rmtree(self.results_dir())


class Job(DBObject):
	def __init__(self, id=None, row=None):
		assert id or row
		DBObject.__init__(self,'jobs',['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))


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


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

		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 write_machines_file(self):
		if self.num_machines()>1:
			print "writing machines file"
			mf = open("%s/.machines" % self.job_dir, 'w')
			for queue_entry in self.get_host_queue_entries():
				if queue_entry.get_host():
					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.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():
			if self.num_machines() > 1:
				self.write_machines_file()
			hosts = self.get_host_queue_entries()
			hostnames = ','.join([i.host.hostname for i in hosts])
			queue_entries = self.get_host_queue_entries()
		else:
			assert queue_entry
			hostnames = queue_entry.host.hostname
			queue_entries = [queue_entry]

		params = ['autoserv', '-n', '-r', 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))

		agent = Agent(tasks)

		return agent


if __name__ == '__main__':
	main()