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'
# how long to wait for autoserv to write a pidfile
PIDFILE_TIMEOUT = 5 * 60 # 5 min

_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

		import MySQLdb.converters
		self.convert_dict = MySQLdb.converters.conversions
		self.convert_dict.setdefault(bool, self.convert_boolean)

		self.connect()


	@staticmethod
	def convert_boolean(boolean, conversion_dict):
		'Convert booleans to integer strings'
		return str(int(boolean))


	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, conv=self.convert_dict)

				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:
	autoserv_procs_cache = None

	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):
		Dispatcher.autoserv_procs_cache = None
		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)


	@classmethod
	def find_autoservs(cls, orphans_only=False):
		"""\
		Returns a dict mapping pids to command lines for root autoserv
		processes.  If orphans_only=True, return only processes that
		have been orphaned (i.e. parent pid = 1).
		"""
		if cls.autoserv_procs_cache is not None:
			return cls.autoserv_procs_cache

		proc = subprocess.Popen(
		    ['/bin/ps', 'x', '-o', 'pid,pgid,ppid,comm,args'],
		    stdout=subprocess.PIPE)
		# split each line into the four columns output by ps
		procs = [line.split(None, 4) for line in
			 proc.communicate()[0].splitlines()]
		autoserv_procs = {}
		for proc in procs:
			# check ppid == 1 for orphans
			if orphans_only and proc[2] != 1:
				continue
			# only root autoserv processes have pgid == pid
			if (proc[3] == 'autoserv' and   # comm
			    proc[1] == proc[0]):        # pgid == pid
				# map pid to args
				autoserv_procs[int(proc[0])] = proc[4]
		cls.autoserv_procs_cache = autoserv_procs
		return 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_autoservs(orphans_only=True)

		# 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(dont_delete_files=True)
			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
		rebooting_host_ids = set()
		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:
			print 'Recovering aborting QE %d' % queue_entry.id
			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')
			rebooting_host_ids.add(queue_host.id)

		# reverify hosts that were in the middle of verify, repair or
		# reboot
		self._reverify_hosts_where("""(status = 'Repairing' OR
		                               status = 'Verifying' OR
					       status = 'Rebooting')""",
					   exclude_ids=rebooting_host_ids)

		# finally, recover "Running" hosts with no active queue entries,
		# although this should never happen
		message = ('Recovering running host %s - this probably '
			   'indicates a scheduler bug')
		self._reverify_hosts_where("""status = 'Running' AND
		                              id NOT IN (SELECT host_id
					                 FROM host_queue_entries
							 WHERE active)""",
					   print_message=message)


	def _reverify_hosts_where(self, where,
				  print_message='Reverifying host %s',
				  exclude_ids=set()):
		rows = _db.execute('SELECT * FROM hosts WHERE locked = 0 AND ' +
				   where)
		hosts = [Host(row=i) for i in rows]
		for host in hosts:
			if host.id in exclude_ids:
				continue
			if print_message is not None:
				print print_message % host.hostname
			verify_task = VerifyTask(host = host)
			self.add_agent(Agent(tasks = [verify_task]))


	def _recover_hosts(self):
		# recover "Repair Failed" hosts
		message = 'Reverifying dead host %s'
		self._reverify_hosts_where("status = 'Repair Failed'",
					   print_message=message)


	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
		self.start_time = time.time()
		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_command_line(self, command_line, spacer=' ',
				print_error=False):
		results_dir_arg = spacer.join(('', '-r', self.results_dir, ''))
		match = results_dir_arg in command_line
		if print_error and not match:
			print '%s not found in %s' % (repr(results_dir_arg),
						      repr(command_line))
		return match


	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
		return self._check_command_line(cmdline, spacer='\x00',
						print_error=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 _find_autoserv_proc(self):
		autoserv_procs = Dispatcher.find_autoservs()
		for pid, args in autoserv_procs.iteritems():
			if self._check_command_line(args):
				return pid, args
		return None, None


	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()

		if pid is None:
			return self._handle_no_pid()

		if exit_status is None:
			# double check whether or not autoserv is running
			proc_running = self._check_proc_fs(pid)
			if proc_running:
				return pid, exit_status

			# pid but no process - maybe process *just* exited
			pid, exit_status = self.read_pidfile()
			if exit_status is None:
				# 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.on_lost_process(pid)
				return self.pid, self.exit_status

		return pid, exit_status


	def _handle_no_pid(self):
		"""\
		Called when no pidfile is found or no pid is in the pidfile.
		"""
		# is autoserv running?
		pid, args = self._find_autoserv_proc()
		if pid is None:
			# no autoserv process running
			message = 'No pid found at ' + self.pid_file
		else:
			message = ("Process %d (%s) hasn't written pidfile %s" %
				   (pid, args, self.pid_file))

		print message
		if time.time() - self.start_time > PIDFILE_TIMEOUT:
			send_notify_email('Process has failed to write pidfile',
					  message)
			if pid is not None:
				kill_autoserv(pid)
			else:
				pid = 0
			self.on_lost_process(pid)
			return self.pid, self.exit_status

		return None, None


	def on_lost_process(self, pid):
		"""\
		Called when autoserv has exited without writing an exit status,
		or we've timed out waiting for autoserv to write a pid to the
		pidfile.  In either case, we just return failure and the caller
		should signal some kind of warning.

		pid is unimportant here, as it shouldn't be used by anyone.
		"""
		self.lost_process = True
		self.pid = pid
		self.exit_status = 1


	def exit_code(self):
		pid, exit_code = self.get_pidfile_info()
		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, '-n')
			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 -n')
				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, dont_delete_files=False):
		results_dir = results_dir or self.results_dir()
		if not os.path.exists(results_dir):
			return
		if dont_delete_files:
			temp_dir = tempfile.mkdtemp(suffix='.clear_results')
			print 'Moving results from %s to %s' % (results_dir,
								temp_dir)
		for filename in os.listdir(results_dir):
			path = os.path.join(results_dir, filename)
			if dont_delete_files:
				shutil.move(path,
					    os.path.join(temp_dir, filename))
			else:
				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()