#!/usr/bin/python
#

# Copyright (C) 2006, 2007, 2008 Google Inc.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301, USA.


"""Tool to restart erronously downed virtual machines.

This program and set of classes implement a watchdog to restart
virtual machines in a Ganeti cluster that have crashed or been killed
by a node reboot.  Run from cron or similar.

"""

import os
import sys
import time
import logging
from optparse import OptionParser

from ganeti import utils
from ganeti import constants
from ganeti import serializer
from ganeti import errors
from ganeti import opcodes
from ganeti import cli
from ganeti import luxi


MAXTRIES = 5
BAD_STATES = ['ERROR_down']
HELPLESS_STATES = ['ERROR_nodedown', 'ERROR_nodeoffline']
NOTICE = 'NOTICE'
ERROR = 'ERROR'
KEY_RESTART_COUNT = "restart_count"
KEY_RESTART_WHEN = "restart_when"
KEY_BOOT_ID = "bootid"


# Global client object
client = None


class NotMasterError(errors.GenericError):
  """Exception raised when this host is not the master."""


def Indent(s, prefix='| '):
  """Indent a piece of text with a given prefix before each line.

  @param s: the string to indent
  @param prefix: the string to prepend each line

  """
  return "%s%s\n" % (prefix, ('\n' + prefix).join(s.splitlines()))


def StartMaster():
  """Try to start the master daemon.

  """
  result = utils.RunCmd(['ganeti-masterd'])
  if result.failed:
    logging.error("Can't start the master daemon: output '%s'", result.output)
  return not result.failed


def EnsureDaemon(daemon):
  """Check for and start daemon if not alive.

  """
  pidfile = utils.DaemonPidFileName(daemon)
  pid = utils.ReadPidFile(pidfile)
  if pid == 0 or not utils.IsProcessAlive(pid): # no file or dead pid
    logging.debug("Daemon '%s' not alive, trying to restart", daemon)
    result = utils.RunCmd([daemon])
    if not result:
      logging.error("Can't start daemon '%s', failure %s, output: %s",
                    daemon, result.fail_reason, result.output)


class WatcherState(object):
  """Interface to a state file recording restart attempts.

  """
  def __init__(self):
    """Open, lock, read and parse the file.

    Raises exception on lock contention.

    """
    # The two-step dance below is necessary to allow both opening existing
    # file read/write and creating if not existing.  Vanilla open will truncate
    # an existing file -or- allow creating if not existing.
    fd = os.open(constants.WATCHER_STATEFILE, os.O_RDWR | os.O_CREAT)
    self.statefile = os.fdopen(fd, 'w+')

    utils.LockFile(self.statefile.fileno())

    try:
      state_data = self.statefile.read()
      if not state_data:
        self._data = {}
      else:
        self._data = serializer.Load(state_data)
    except Exception, msg:
      # Ignore errors while loading the file and treat it as empty
      self._data = {}
      logging.warning(("Invalid state file. Using defaults."
                       " Error message: %s"), msg)

    if "instance" not in self._data:
      self._data["instance"] = {}
    if "node" not in self._data:
      self._data["node"] = {}

    self._orig_data = serializer.Dump(self._data)

  def Save(self):
    """Save state to file, then unlock and close it.

    """
    assert self.statefile

    serialized_form = serializer.Dump(self._data)
    if self._orig_data == serialized_form:
      logging.debug("Data didn't change, just touching status file")
      os.utime(constants.WATCHER_STATEFILE, None)
      return

    # We need to make sure the file is locked before renaming it, otherwise
    # starting ganeti-watcher again at the same time will create a conflict.
    fd = utils.WriteFile(constants.WATCHER_STATEFILE,
                         data=serialized_form,
                         prewrite=utils.LockFile, close=False)
    self.statefile = os.fdopen(fd, 'w+')

  def Close(self):
    """Unlock configuration file and close it.

    """
    assert self.statefile

    # Files are automatically unlocked when closing them
    self.statefile.close()
    self.statefile = None

  def GetNodeBootID(self, name):
    """Returns the last boot ID of a node or None.

    """
    ndata = self._data["node"]

    if name in ndata and KEY_BOOT_ID in ndata[name]:
      return ndata[name][KEY_BOOT_ID]
    return None

  def SetNodeBootID(self, name, bootid):
    """Sets the boot ID of a node.

    """
    assert bootid

    ndata = self._data["node"]

    if name not in ndata:
      ndata[name] = {}

    ndata[name][KEY_BOOT_ID] = bootid

  def NumberOfRestartAttempts(self, instance):
    """Returns number of previous restart attempts.

    @type instance: L{Instance}
    @param instance: the instance to look up

    """
    idata = self._data["instance"]

    if instance.name in idata:
      return idata[instance.name][KEY_RESTART_COUNT]

    return 0

  def RecordRestartAttempt(self, instance):
    """Record a restart attempt.

    @type instance: L{Instance}
    @param instance: the instance being restarted

    """
    idata = self._data["instance"]

    if instance.name not in idata:
      inst = idata[instance.name] = {}
    else:
      inst = idata[instance.name]

    inst[KEY_RESTART_WHEN] = time.time()
    inst[KEY_RESTART_COUNT] = inst.get(KEY_RESTART_COUNT, 0) + 1

  def RemoveInstance(self, instance):
    """Update state to reflect that a machine is running.

    This method removes the record for a named instance (as we only
    track down instances).

    @type instance: L{Instance}
    @param instance: the instance to remove from books

    """
    idata = self._data["instance"]

    if instance.name in idata:
      del idata[instance.name]


class Instance(object):
  """Abstraction for a Virtual Machine instance.

  """
  def __init__(self, name, state, autostart):
    self.name = name
    self.state = state
    self.autostart = autostart

  def Restart(self):
    """Encapsulates the start of an instance.

    """
    op = opcodes.OpStartupInstance(instance_name=self.name, force=False)
    cli.SubmitOpCode(op, cl=client)

  def ActivateDisks(self):
    """Encapsulates the activation of all disks of an instance.

    """
    op = opcodes.OpActivateInstanceDisks(instance_name=self.name)
    cli.SubmitOpCode(op, cl=client)


def GetClusterData():
  """Get a list of instances on this cluster.

  """
  op1_fields = ["name", "status", "admin_state", "snodes"]
  op1 = opcodes.OpQueryInstances(output_fields=op1_fields, names=[],
                                 use_locking=True)
  op2_fields = ["name", "bootid", "offline"]
  op2 = opcodes.OpQueryNodes(output_fields=op2_fields, names=[],
                             use_locking=True)

  job_id = client.SubmitJob([op1, op2])

  all_results = cli.PollJob(job_id, cl=client, feedback_fn=logging.debug)

  logging.debug("Got data from cluster, writing instance status file")

  result = all_results[0]
  smap = {}

  instances = {}

  # write the upfile
  up_data = "".join(["%s %s\n" % (fields[0], fields[1]) for fields in result])
  utils.WriteFile(file_name=constants.INSTANCE_UPFILE, data=up_data)

  for fields in result:
    (name, status, autostart, snodes) = fields

    # update the secondary node map
    for node in snodes:
      if node not in smap:
        smap[node] = []
      smap[node].append(name)

    instances[name] = Instance(name, status, autostart)

  nodes =  dict([(name, (bootid, offline))
                 for name, bootid, offline in all_results[1]])

  client.ArchiveJob(job_id)

  return instances, nodes, smap


class Watcher(object):
  """Encapsulate the logic for restarting erronously halted virtual machines.

  The calling program should periodically instantiate me and call Run().
  This will traverse the list of instances, and make up to MAXTRIES attempts
  to restart machines that are down.

  """
  def __init__(self, opts, notepad):
    self.notepad = notepad
    master = client.QueryConfigValues(["master_node"])[0]
    if master != utils.HostInfo().name:
      raise NotMasterError("This is not the master node")
    # first archive old jobs
    self.ArchiveJobs(opts.job_age)
    # and only then submit new ones
    self.instances, self.bootids, self.smap = GetClusterData()
    self.started_instances = set()
    self.opts = opts

  def Run(self):
    """Watcher run sequence.

    """
    notepad = self.notepad
    self.CheckInstances(notepad)
    self.CheckDisks(notepad)
    self.VerifyDisks()

  @staticmethod
  def ArchiveJobs(age):
    """Archive old jobs.

    """
    arch_count, left_count = client.AutoArchiveJobs(age)
    logging.debug("Archived %s jobs, left %s" % (arch_count, left_count))

  def CheckDisks(self, notepad):
    """Check all nodes for restarted ones.

    """
    check_nodes = []
    for name, (new_id, offline) in self.bootids.iteritems():
      old = notepad.GetNodeBootID(name)
      if new_id is None:
        # Bad node, not returning a boot id
        if not offline:
          logging.debug("Node %s missing boot id, skipping secondary checks",
                        name)
        continue
      if old != new_id:
        # Node's boot ID has changed, proably through a reboot.
        check_nodes.append(name)

    if check_nodes:
      # Activate disks for all instances with any of the checked nodes as a
      # secondary node.
      for node in check_nodes:
        if node not in self.smap:
          continue
        for instance_name in self.smap[node]:
          instance = self.instances[instance_name]
          if not instance.autostart:
            logging.info(("Skipping disk activation for non-autostart"
                          " instance %s"), instance.name)
            continue
          if instance.name in self.started_instances:
            # we already tried to start the instance, which should have
            # activated its drives (if they can be at all)
            continue
          try:
            logging.info("Activating disks for instance %s", instance.name)
            instance.ActivateDisks()
          except Exception:
            logging.exception("Error while activating disks for instance %s",
                              instance.name)

      # Keep changed boot IDs
      for name in check_nodes:
        notepad.SetNodeBootID(name, self.bootids[name][0])

  def CheckInstances(self, notepad):
    """Make a pass over the list of instances, restarting downed ones.

    """
    for instance in self.instances.values():
      if instance.state in BAD_STATES:
        n = notepad.NumberOfRestartAttempts(instance)

        if n > MAXTRIES:
          # stay quiet.
          continue
        elif n < MAXTRIES:
          last = " (Attempt #%d)" % (n + 1)
        else:
          notepad.RecordRestartAttempt(instance)
          logging.error("Could not restart %s after %d attempts, giving up",
                        instance.name, MAXTRIES)
          continue
        try:
          logging.info("Restarting %s%s",
                        instance.name, last)
          instance.Restart()
          self.started_instances.add(instance.name)
        except Exception:
          logging.exception("Error while restarting instance %s",
                            instance.name)

        notepad.RecordRestartAttempt(instance)
      elif instance.state in HELPLESS_STATES:
        if notepad.NumberOfRestartAttempts(instance):
          notepad.RemoveInstance(instance)
      else:
        if notepad.NumberOfRestartAttempts(instance):
          notepad.RemoveInstance(instance)
          logging.info("Restart of %s succeeded", instance.name)

  @staticmethod
  def VerifyDisks():
    """Run gnt-cluster verify-disks.

    """
    op = opcodes.OpVerifyDisks()
    job_id = client.SubmitJob([op])
    result = cli.PollJob(job_id, cl=client, feedback_fn=logging.debug)[0]
    client.ArchiveJob(job_id)
    if not isinstance(result, (tuple, list)):
      logging.error("Can't get a valid result from verify-disks")
      return
    offline_disk_instances = result[2]
    if not offline_disk_instances:
      # nothing to do
      return
    logging.debug("Will activate disks for instances %s",
                  ", ".join(offline_disk_instances))
    # we submit only one job, and wait for it. not optimal, but spams
    # less the job queue
    job = [opcodes.OpActivateInstanceDisks(instance_name=name)
           for name in offline_disk_instances]
    job_id = cli.SendJob(job, cl=client)

    cli.PollJob(job_id, cl=client, feedback_fn=logging.debug)


def ParseOptions():
  """Parse the command line options.

  @return: (options, args) as from OptionParser.parse_args()

  """
  parser = OptionParser(description="Ganeti cluster watcher",
                        usage="%prog [-d]",
                        version="%%prog (ganeti) %s" %
                        constants.RELEASE_VERSION)

  parser.add_option("-d", "--debug", dest="debug",
                    help="Write all messages to stderr",
                    default=False, action="store_true")
  parser.add_option("-A", "--job-age", dest="job_age",
                    help="Autoarchive jobs older than this age (default"
                    " 6 hours)", default=6*3600)
  options, args = parser.parse_args()
  options.job_age = cli.ParseTimespec(options.job_age)
  return options, args


def main():
  """Main function.

  """
  global client

  options, args = ParseOptions()

  utils.SetupLogging(constants.LOG_WATCHER, debug=options.debug,
                     stderr_logging=options.debug)

  update_file = False
  try:
    # on master or not, try to start the node dameon (use _PID but is
    # the same as daemon name)
    EnsureDaemon(constants.NODED_PID)

    notepad = WatcherState()
    try:
      try:
        client = cli.GetClient()
      except errors.OpPrereqError:
        # this is, from cli.GetClient, a not-master case
        logging.debug("Not on master, exiting")
        update_file = True
        sys.exit(constants.EXIT_SUCCESS)
      except luxi.NoMasterError, err:
        logging.warning("Master seems to be down (%s), trying to restart",
                        str(err))
        if not StartMaster():
          logging.critical("Can't start the master, exiting")
          sys.exit(constants.EXIT_FAILURE)
        # else retry the connection
        client = cli.GetClient()

      # we are on master now (use _PID but is the same as daemon name)
      EnsureDaemon(constants.RAPI_PID)

      try:
        watcher = Watcher(options, notepad)
      except errors.ConfigurationError:
        # Just exit if there's no configuration
        update_file = True
        sys.exit(constants.EXIT_SUCCESS)

      watcher.Run()
      update_file = True

    finally:
      if update_file:
        notepad.Save()
      else:
        logging.debug("Not updating status file due to failure")
  except SystemExit:
    raise
  except NotMasterError:
    logging.debug("Not master, exiting")
    sys.exit(constants.EXIT_NOTMASTER)
  except errors.ResolverError, err:
    logging.error("Cannot resolve hostname '%s', exiting.", err.args[0])
    sys.exit(constants.EXIT_NODESETUP_ERROR)
  except errors.JobQueueFull:
    logging.error("Job queue is full, can't query cluster state")
  except errors.JobQueueDrainError:
    logging.error("Job queue is drained, can't maintain cluster state")
  except Exception, err:
    logging.error(str(err), exc_info=True)
    sys.exit(constants.EXIT_FAILURE)


if __name__ == '__main__':
  main()