backend.py

#
#

# Copyright (C) 2006, 2007 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.


"""Functions used by the node daemon"""


import os
import os.path
import shutil
import time
import stat
import errno
import re
import subprocess
import random
import logging
import tempfile

from ganeti import errors
from ganeti import utils
from ganeti import ssh
from ganeti import hypervisor
from ganeti import constants
from ganeti import bdev
from ganeti import objects
from ganeti import ssconf


def _GetConfig():
  return ssconf.SimpleConfigReader()


def _GetSshRunner(cluster_name):
  return ssh.SshRunner(cluster_name)


def _CleanDirectory(path, exclude=[]):
  """Removes all regular files in a directory.

  @param exclude: List of files to be excluded.
  @type exclude: list

  """
  if not os.path.isdir(path):
    return

  # Normalize excluded paths
  exclude = [os.path.normpath(i) for i in exclude]

  for rel_name in utils.ListVisibleFiles(path):
    full_name = os.path.normpath(os.path.join(path, rel_name))
    if full_name in exclude:
      continue
    if os.path.isfile(full_name) and not os.path.islink(full_name):
      utils.RemoveFile(full_name)


def JobQueuePurge():
  """Removes job queue files and archived jobs

  """
  _CleanDirectory(constants.QUEUE_DIR, exclude=[constants.JOB_QUEUE_LOCK_FILE])
  _CleanDirectory(constants.JOB_QUEUE_ARCHIVE_DIR)


def GetMasterInfo():
  """Returns master information.

  This is an utility function to compute master information, either
  for consumption here or from the node daemon.

  @rtype: tuple
  @return: (master_netdev, master_ip, master_name)

  """
  try:
    cfg = _GetConfig()
    master_netdev = cfg.GetMasterNetdev()
    master_ip = cfg.GetMasterIP()
    master_node = cfg.GetMasterNode()
  except errors.ConfigurationError, err:
    logging.exception("Cluster configuration incomplete")
    return (None, None)
  return (master_netdev, master_ip, master_node)


def StartMaster(start_daemons):
  """Activate local node as master node.

  The function will always try activate the IP address of the master
  (if someone else has it, then it won't). Then, if the start_daemons
  parameter is True, it will also start the master daemons
  (ganet-masterd and ganeti-rapi).

  """
  ok = True
  master_netdev, master_ip, _ = GetMasterInfo()
  if not master_netdev:
    return False

  if utils.TcpPing(master_ip, constants.DEFAULT_NODED_PORT):
    if utils.OwnIpAddress(master_ip):
      # we already have the ip:
      logging.debug("Already started")
    else:
      logging.error("Someone else has the master ip, not activating")
      ok = False
  else:
    result = utils.RunCmd(["ip", "address", "add", "%s/32" % master_ip,
                           "dev", master_netdev, "label",
                           "%s:0" % master_netdev])
    if result.failed:
      logging.error("Can't activate master IP: %s", result.output)
      ok = False

    result = utils.RunCmd(["arping", "-q", "-U", "-c 3", "-I", master_netdev,
                           "-s", master_ip, master_ip])
    # we'll ignore the exit code of arping

  # and now start the master and rapi daemons
  if start_daemons:
    for daemon in 'ganeti-masterd', 'ganeti-rapi':
      result = utils.RunCmd([daemon])
      if result.failed:
        logging.error("Can't start daemon %s: %s", daemon, result.output)
        ok = False
  return ok


def StopMaster(stop_daemons):
  """Deactivate this node as master.

  The function will always try to deactivate the IP address of the
  master. Then, if the stop_daemons parameter is True, it will also
  stop the master daemons (ganet-masterd and ganeti-rapi).

  """
  master_netdev, master_ip, _ = GetMasterInfo()
  if not master_netdev:
    return False

  result = utils.RunCmd(["ip", "address", "del", "%s/32" % master_ip,
                         "dev", master_netdev])
  if result.failed:
    logging.error("Can't remove the master IP, error: %s", result.output)
    # but otherwise ignore the failure

  if stop_daemons:
    # stop/kill the rapi and the master daemon
    for daemon in constants.RAPI_PID, constants.MASTERD_PID:
      utils.KillProcess(utils.ReadPidFile(utils.DaemonPidFileName(daemon)))

  return True


def AddNode(dsa, dsapub, rsa, rsapub, sshkey, sshpub):
  """Joins this node to the cluster.

  This does the following:
      - updates the hostkeys of the machine (rsa and dsa)
      - adds the ssh private key to the user
      - adds the ssh public key to the users' authorized_keys file

  """
  sshd_keys =  [(constants.SSH_HOST_RSA_PRIV, rsa, 0600),
                (constants.SSH_HOST_RSA_PUB, rsapub, 0644),
                (constants.SSH_HOST_DSA_PRIV, dsa, 0600),
                (constants.SSH_HOST_DSA_PUB, dsapub, 0644)]
  for name, content, mode in sshd_keys:
    utils.WriteFile(name, data=content, mode=mode)

  try:
    priv_key, pub_key, auth_keys = ssh.GetUserFiles(constants.GANETI_RUNAS,
                                                    mkdir=True)
  except errors.OpExecError, err:
    logging.exception("Error while processing user ssh files")
    return False

  for name, content in [(priv_key, sshkey), (pub_key, sshpub)]:
    utils.WriteFile(name, data=content, mode=0600)

  utils.AddAuthorizedKey(auth_keys, sshpub)

  utils.RunCmd([constants.SSH_INITD_SCRIPT, "restart"])

  return True


def LeaveCluster():
  """Cleans up the current node and prepares it to be removed from the cluster.

  """
  _CleanDirectory(constants.DATA_DIR)
  JobQueuePurge()

  try:
    priv_key, pub_key, auth_keys = ssh.GetUserFiles(constants.GANETI_RUNAS)
  except errors.OpExecError:
    logging.exception("Error while processing ssh files")
    return

  f = open(pub_key, 'r')
  try:
    utils.RemoveAuthorizedKey(auth_keys, f.read(8192))
  finally:
    f.close()

  utils.RemoveFile(priv_key)
  utils.RemoveFile(pub_key)

  # Return a reassuring string to the caller, and quit
  raise errors.QuitGanetiException(False, 'Shutdown scheduled')


def GetNodeInfo(vgname, hypervisor_type):
  """Gives back a hash with different informations about the node.

  @type vgname: C{string}
  @param vgname: the name of the volume group to ask for disk space information
  @type hypervisor_type: C{str}
  @param hypervisor_type: the name of the hypervisor to ask for
      memory information
  @rtype: C{dict}
  @return: dictionary with the following keys:
      - vg_size is the size of the configured volume group in MiB
      - vg_free is the free size of the volume group in MiB
      - memory_dom0 is the memory allocated for domain0 in MiB
      - memory_free is the currently available (free) ram in MiB
      - memory_total is the total number of ram in MiB

  """
  outputarray = {}
  vginfo = _GetVGInfo(vgname)
  outputarray['vg_size'] = vginfo['vg_size']
  outputarray['vg_free'] = vginfo['vg_free']

  hyper = hypervisor.GetHypervisor(hypervisor_type)
  hyp_info = hyper.GetNodeInfo()
  if hyp_info is not None:
    outputarray.update(hyp_info)

  f = open("/proc/sys/kernel/random/boot_id", 'r')
  try:
    outputarray["bootid"] = f.read(128).rstrip("\n")
  finally:
    f.close()

  return outputarray


def VerifyNode(what, cluster_name):
  """Verify the status of the local node.

  Based on the input L{what} parameter, various checks are done on the
  local node.

  If the I{filelist} key is present, this list of
  files is checksummed and the file/checksum pairs are returned.

  If the I{nodelist} key is present, we check that we have
  connectivity via ssh with the target nodes (and check the hostname
  report).

  If the I{node-net-test} key is present, we check that we have
  connectivity to the given nodes via both primary IP and, if
  applicable, secondary IPs.

  @type what: C{dict}
  @param what: a dictionary of things to check:
      - filelist: list of files for which to compute checksums
      - nodelist: list of nodes we should check ssh communication with
      - node-net-test: list of nodes we should check node daemon port
        connectivity with
      - hypervisor: list with hypervisors to run the verify for

  """
  result = {}

  if 'hypervisor' in what:
    result['hypervisor'] = my_dict = {}
    for hv_name in what['hypervisor']:
      my_dict[hv_name] = hypervisor.GetHypervisor(hv_name).Verify()

  if 'filelist' in what:
    result['filelist'] = utils.FingerprintFiles(what['filelist'])

  if 'nodelist' in what:
    result['nodelist'] = {}
    random.shuffle(what['nodelist'])
    for node in what['nodelist']:
      success, message = _GetSshRunner(cluster_name).VerifyNodeHostname(node)
      if not success:
        result['nodelist'][node] = message
  if 'node-net-test' in what:
    result['node-net-test'] = {}
    my_name = utils.HostInfo().name
    my_pip = my_sip = None
    for name, pip, sip in what['node-net-test']:
      if name == my_name:
        my_pip = pip
        my_sip = sip
        break
    if not my_pip:
      result['node-net-test'][my_name] = ("Can't find my own"
                                          " primary/secondary IP"
                                          " in the node list")
    else:
      port = utils.GetNodeDaemonPort()
      for name, pip, sip in what['node-net-test']:
        fail = []
        if not utils.TcpPing(pip, port, source=my_pip):
          fail.append("primary")
        if sip != pip:
          if not utils.TcpPing(sip, port, source=my_sip):
            fail.append("secondary")
        if fail:
          result['node-net-test'][name] = ("failure using the %s"
                                           " interface(s)" %
                                           " and ".join(fail))

  return result


def GetVolumeList(vg_name):
  """Compute list of logical volumes and their size.

  Returns:
    dictionary of all partions (key) with their size (in MiB), inactive
    and online status:
    {'test1': ('20.06', True, True)}

  """
  lvs = {}
  sep = '|'
  result = utils.RunCmd(["lvs", "--noheadings", "--units=m", "--nosuffix",
                         "--separator=%s" % sep,
                         "-olv_name,lv_size,lv_attr", vg_name])
  if result.failed:
    logging.error("Failed to list logical volumes, lvs output: %s",
                  result.output)
    return result.output

  valid_line_re = re.compile("^ *([^|]+)\|([0-9.]+)\|([^|]{6})\|?$")
  for line in result.stdout.splitlines():
    line = line.strip()
    match = valid_line_re.match(line)
    if not match:
      logging.error("Invalid line returned from lvs output: '%s'", line)
      continue
    name, size, attr = match.groups()
    inactive = attr[4] == '-'
    online = attr[5] == 'o'
    lvs[name] = (size, inactive, online)

  return lvs


def ListVolumeGroups():
  """List the volume groups and their size.

  Returns:
    Dictionary with keys volume name and values the size of the volume

  """
  return utils.ListVolumeGroups()


def NodeVolumes():
  """List all volumes on this node.

  """
  result = utils.RunCmd(["lvs", "--noheadings", "--units=m", "--nosuffix",
                         "--separator=|",
                         "--options=lv_name,lv_size,devices,vg_name"])
  if result.failed:
    logging.error("Failed to list logical volumes, lvs output: %s",
                  result.output)
    return {}

  def parse_dev(dev):
    if '(' in dev:
      return dev.split('(')[0]
    else:
      return dev

  def map_line(line):
    return {
      'name': line[0].strip(),
      'size': line[1].strip(),
      'dev': parse_dev(line[2].strip()),
      'vg': line[3].strip(),
    }

  return [map_line(line.split('|')) for line in result.stdout.splitlines()
          if line.count('|') >= 3]


def BridgesExist(bridges_list):
  """Check if a list of bridges exist on the current node.

  Returns:
    True if all of them exist, false otherwise

  """
  for bridge in bridges_list:
    if not utils.BridgeExists(bridge):
      return False

  return True


def GetInstanceList(hypervisor_list):
  """Provides a list of instances.

  @type hypervisor_list: list
  @param hypervisor_list: the list of hypervisors to query information

  @rtype: list
  @return: a list of all running instances on the current node
             - instance1.example.com
             - instance2.example.com

  """
  results = []
  for hname in hypervisor_list:
    try:
      names = hypervisor.GetHypervisor(hname).ListInstances()
      results.extend(names)
    except errors.HypervisorError, err:
      logging.exception("Error enumerating instances for hypevisor %s", hname)
      # FIXME: should we somehow not propagate this to the master?
      raise

  return results


def GetInstanceInfo(instance, hname):
  """Gives back the informations about an instance as a dictionary.

  @type instance: string
  @param instance: the instance name
  @type hname: string
  @param hname: the hypervisor type of the instance

  @rtype: dict
  @return: dictionary with the following keys:
      - memory: memory size of instance (int)
      - state: xen state of instance (string)
      - time: cpu time of instance (float)

  """
  output = {}

  iinfo = hypervisor.GetHypervisor(hname).GetInstanceInfo(instance)
  if iinfo is not None:
    output['memory'] = iinfo[2]
    output['state'] = iinfo[4]
    output['time'] = iinfo[5]

  return output


def GetAllInstancesInfo(hypervisor_list):
  """Gather data about all instances.

  This is the equivalent of `GetInstanceInfo()`, except that it
  computes data for all instances at once, thus being faster if one
  needs data about more than one instance.

  @type hypervisor_list: list
  @param hypervisor_list: list of hypervisors to query for instance data

  @rtype: dict of dicts
  @return: dictionary of instance: data, with data having the following keys:
      - memory: memory size of instance (int)
      - state: xen state of instance (string)
      - time: cpu time of instance (float)
      - vcpuus: the number of vcpus

  """
  output = {}

  for hname in hypervisor_list:
    iinfo = hypervisor.GetHypervisor(hname).GetAllInstancesInfo()
    if iinfo:
      for name, inst_id, memory, vcpus, state, times in iinfo:
        value = {
          'memory': memory,
          'vcpus': vcpus,
          'state': state,
          'time': times,
          }
        if name in output and output[name] != value:
          raise errors.HypervisorError("Instance %s running duplicate"
                                       " with different parameters" % name)
        output[name] = value

  return output


def AddOSToInstance(instance, os_disk, swap_disk):
  """Add an OS to an instance.

  Args:
    instance: the instance object
    os_disk: the instance-visible name of the os device
    swap_disk: the instance-visible name of the swap device

  """
  inst_os = OSFromDisk(instance.os)

  create_script = inst_os.create_script

  os_device = instance.FindDisk(os_disk)
  if os_device is None:
    logging.error("Can't find this device-visible name '%s'", os_disk)
    return False

  swap_device = instance.FindDisk(swap_disk)
  if swap_device is None:
    logging.error("Can't find this device-visible name '%s'", swap_disk)
    return False

  real_os_dev = _RecursiveFindBD(os_device)
  if real_os_dev is None:
    raise errors.BlockDeviceError("Block device '%s' is not set up" %
                                  str(os_device))
  real_os_dev.Open()

  real_swap_dev = _RecursiveFindBD(swap_device)
  if real_swap_dev is None:
    raise errors.BlockDeviceError("Block device '%s' is not set up" %
                                  str(swap_device))
  real_swap_dev.Open()

  logfile = "%s/add-%s-%s-%d.log" % (constants.LOG_OS_DIR, instance.os,
                                     instance.name, int(time.time()))
  if not os.path.exists(constants.LOG_OS_DIR):
    os.mkdir(constants.LOG_OS_DIR, 0750)

  command = utils.BuildShellCmd("cd %s && %s -i %s -b %s -s %s &>%s",
                                inst_os.path, create_script, instance.name,
                                real_os_dev.dev_path, real_swap_dev.dev_path,
                                logfile)
  env = {'HYPERVISOR': instance.hypervisor}

  result = utils.RunCmd(command, env=env)
  if result.failed:
    logging.error("os create command '%s' returned error: %s, logfile: %s,"
                  " output: %s", command, result.fail_reason, logfile,
                  result.output)
    return False

  return True


def RunRenameInstance(instance, old_name, os_disk, swap_disk):
  """Run the OS rename script for an instance.

  Args:
    instance: the instance object
    old_name: the old name of the instance
    os_disk: the instance-visible name of the os device
    swap_disk: the instance-visible name of the swap device

  """
  inst_os = OSFromDisk(instance.os)

  script = inst_os.rename_script

  os_device = instance.FindDisk(os_disk)
  if os_device is None:
    logging.error("Can't find this device-visible name '%s'", os_disk)
    return False

  swap_device = instance.FindDisk(swap_disk)
  if swap_device is None:
    logging.error("Can't find this device-visible name '%s'", swap_disk)
    return False

  real_os_dev = _RecursiveFindBD(os_device)
  if real_os_dev is None:
    raise errors.BlockDeviceError("Block device '%s' is not set up" %
                                  str(os_device))
  real_os_dev.Open()

  real_swap_dev = _RecursiveFindBD(swap_device)
  if real_swap_dev is None:
    raise errors.BlockDeviceError("Block device '%s' is not set up" %
                                  str(swap_device))
  real_swap_dev.Open()

  logfile = "%s/rename-%s-%s-%s-%d.log" % (constants.LOG_OS_DIR, instance.os,
                                           old_name,
                                           instance.name, int(time.time()))
  if not os.path.exists(constants.LOG_OS_DIR):
    os.mkdir(constants.LOG_OS_DIR, 0750)

  command = utils.BuildShellCmd("cd %s && %s -o %s -n %s -b %s -s %s &>%s",
                                inst_os.path, script, old_name, instance.name,
                                real_os_dev.dev_path, real_swap_dev.dev_path,
                                logfile)

  result = utils.RunCmd(command)

  if result.failed:
    logging.error("os create command '%s' returned error: %s output: %s",
                  command, result.fail_reason, result.output)
    return False

  return True


def _GetVGInfo(vg_name):
  """Get informations about the volume group.

  Args:
    vg_name: the volume group

  Returns:
    { 'vg_size' : xxx, 'vg_free' : xxx, 'pv_count' : xxx }
    where
    vg_size is the total size of the volume group in MiB
    vg_free is the free size of the volume group in MiB
    pv_count are the number of physical disks in that vg

  If an error occurs during gathering of data, we return the same dict
  with keys all set to None.

  """
  retdic = dict.fromkeys(["vg_size", "vg_free", "pv_count"])

  retval = utils.RunCmd(["vgs", "-ovg_size,vg_free,pv_count", "--noheadings",
                         "--nosuffix", "--units=m", "--separator=:", vg_name])

  if retval.failed:
    logging.error("volume group %s not present", vg_name)
    return retdic
  valarr = retval.stdout.strip().rstrip(':').split(':')
  if len(valarr) == 3:
    try:
      retdic = {
        "vg_size": int(round(float(valarr[0]), 0)),
        "vg_free": int(round(float(valarr[1]), 0)),
        "pv_count": int(valarr[2]),
        }
    except ValueError, err:
      logging.exception("Fail to parse vgs output")
  else:
    logging.error("vgs output has the wrong number of fields (expected"
                  " three): %s", str(valarr))
  return retdic


def _GatherBlockDevs(instance):
  """Set up an instance's block device(s).

  This is run on the primary node at instance startup. The block
  devices must be already assembled.

  """
  block_devices = []
  for disk in instance.disks:
    device = _RecursiveFindBD(disk)
    if device is None:
      raise errors.BlockDeviceError("Block device '%s' is not set up." %
                                    str(disk))
    device.Open()
    block_devices.append((disk, device))
  return block_devices


def StartInstance(instance, extra_args):
  """Start an instance.

  @type instance: instance object
  @param instance: the instance object
  @rtype: boolean
  @return: whether the startup was successful or not

  """
  running_instances = GetInstanceList([instance.hypervisor])

  if instance.name in running_instances:
    return True

  block_devices = _GatherBlockDevs(instance)
  hyper = hypervisor.GetHypervisor(instance.hypervisor)

  try:
    hyper.StartInstance(instance, block_devices, extra_args)
  except errors.HypervisorError, err:
    logging.exception("Failed to start instance")
    return False

  return True


def ShutdownInstance(instance):
  """Shut an instance down.

  @type instance: instance object
  @param instance: the instance object
  @rtype: boolean
  @return: whether the startup was successful or not

  """
  hv_name = instance.hypervisor
  running_instances = GetInstanceList([hv_name])

  if instance.name not in running_instances:
    return True

  hyper = hypervisor.GetHypervisor(hv_name)
  try:
    hyper.StopInstance(instance)
  except errors.HypervisorError, err:
    logging.error("Failed to stop instance")
    return False

  # test every 10secs for 2min
  shutdown_ok = False

  time.sleep(1)
  for dummy in range(11):
    if instance.name not in GetInstanceList([hv_name]):
      break
    time.sleep(10)
  else:
    # the shutdown did not succeed
    logging.error("shutdown of '%s' unsuccessful, using destroy", instance)

    try:
      hyper.StopInstance(instance, force=True)
    except errors.HypervisorError, err:
      logging.exception("Failed to stop instance")
      return False

    time.sleep(1)
    if instance.name in GetInstanceList([hv_name]):
      logging.error("could not shutdown instance '%s' even by destroy",
                    instance.name)
      return False

  return True


def RebootInstance(instance, reboot_type, extra_args):
  """Reboot an instance.

  Args:
    instance    - name of instance to reboot
    reboot_type - how to reboot [soft,hard,full]

  """
  running_instances = GetInstanceList([instance.hypervisor])

  if instance.name not in running_instances:
    logging.error("Cannot reboot instance that is not running")
    return False

  hyper = hypervisor.GetHypervisor(instance.hypervisor)
  if reboot_type == constants.INSTANCE_REBOOT_SOFT:
    try:
      hyper.RebootInstance(instance)
    except errors.HypervisorError, err:
      logging.exception("Failed to soft reboot instance")
      return False
  elif reboot_type == constants.INSTANCE_REBOOT_HARD:
    try:
      ShutdownInstance(instance)
      StartInstance(instance, extra_args)
    except errors.HypervisorError, err:
      logging.exception("Failed to hard reboot instance")
      return False
  else:
    raise errors.ParameterError("reboot_type invalid")

  return True


def MigrateInstance(instance, target, live):
  """Migrates an instance to another node.

  @type instance: C{objects.Instance}
  @param instance: the instance definition
  @type target: string
  @param target: the target node name
  @type live: boolean
  @param live: whether the migration should be done live or not (the
      interpretation of this parameter is left to the hypervisor)
  @rtype: tuple
  @return: a tuple of (success, msg) where:
      - succes is a boolean denoting the success/failure of the operation
      - msg is a string with details in case of failure

  """
  hyper = hypervisor.GetHypervisor(instance.hypervisor_name)

  try:
    hyper.MigrateInstance(instance.name, target, live)
  except errors.HypervisorError, err:
    msg = "Failed to migrate instance: %s" % str(err)
    logging.error(msg)
    return (False, msg)
  return (True, "Migration successfull")


def CreateBlockDevice(disk, size, owner, on_primary, info):
  """Creates a block device for an instance.

  Args:
   disk: a ganeti.objects.Disk object
   size: the size of the physical underlying device
   owner: a string with the name of the instance
   on_primary: a boolean indicating if it is the primary node or not
   info: string that will be sent to the physical device creation

  Returns:
    the new unique_id of the device (this can sometime be
    computed only after creation), or None. On secondary nodes,
    it's not required to return anything.

  """
  clist = []
  if disk.children:
    for child in disk.children:
      crdev = _RecursiveAssembleBD(child, owner, on_primary)
      if on_primary or disk.AssembleOnSecondary():
        # we need the children open in case the device itself has to
        # be assembled
        crdev.Open()
      clist.append(crdev)
  try:
    device = bdev.FindDevice(disk.dev_type, disk.physical_id, clist)
    if device is not None:
      logging.info("removing existing device %s", disk)
      device.Remove()
  except errors.BlockDeviceError, err:
    pass

  device = bdev.Create(disk.dev_type, disk.physical_id,
                       clist, size)
  if device is None:
    raise ValueError("Can't create child device for %s, %s" %
                     (disk, size))
  if on_primary or disk.AssembleOnSecondary():
    if not device.Assemble():
      errorstring = "Can't assemble device after creation"
      logging.error(errorstring)
      raise errors.BlockDeviceError("%s, very unusual event - check the node"
                                    " daemon logs" % errorstring)
    device.SetSyncSpeed(constants.SYNC_SPEED)
    if on_primary or disk.OpenOnSecondary():
      device.Open(force=True)
    DevCacheManager.UpdateCache(device.dev_path, owner,
                                on_primary, disk.iv_name)

  device.SetInfo(info)

  physical_id = device.unique_id
  return physical_id


def RemoveBlockDevice(disk):
  """Remove a block device.

  This is intended to be called recursively.

  """
  try:
    # since we are removing the device, allow a partial match
    # this allows removal of broken mirrors
    rdev = _RecursiveFindBD(disk, allow_partial=True)
  except errors.BlockDeviceError, err:
    # probably can't attach
    logging.info("Can't attach to device %s in remove", disk)
    rdev = None
  if rdev is not None:
    r_path = rdev.dev_path
    result = rdev.Remove()
    if result:
      DevCacheManager.RemoveCache(r_path)
  else:
    result = True
  if disk.children:
    for child in disk.children:
      result = result and RemoveBlockDevice(child)
  return result


def _RecursiveAssembleBD(disk, owner, as_primary):
  """Activate a block device for an instance.

  This is run on the primary and secondary nodes for an instance.

  This function is called recursively.

  Args:
    disk: a objects.Disk object
    as_primary: if we should make the block device read/write

  Returns:
    the assembled device or None (in case no device was assembled)

  If the assembly is not successful, an exception is raised.

  """
  children = []
  if disk.children:
    mcn = disk.ChildrenNeeded()
    if mcn == -1:
      mcn = 0 # max number of Nones allowed
    else:
      mcn = len(disk.children) - mcn # max number of Nones
    for chld_disk in disk.children:
      try:
        cdev = _RecursiveAssembleBD(chld_disk, owner, as_primary)
      except errors.BlockDeviceError, err:
        if children.count(None) >= mcn:
          raise
        cdev = None
        logging.debug("Error in child activation: %s", str(err))
      children.append(cdev)

  if as_primary or disk.AssembleOnSecondary():
    r_dev = bdev.AttachOrAssemble(disk.dev_type, disk.physical_id, children)
    r_dev.SetSyncSpeed(constants.SYNC_SPEED)
    result = r_dev
    if as_primary or disk.OpenOnSecondary():
      r_dev.Open()
    DevCacheManager.UpdateCache(r_dev.dev_path, owner,
                                as_primary, disk.iv_name)

  else:
    result = True
  return result


def AssembleBlockDevice(disk, owner, as_primary):
  """Activate a block device for an instance.

  This is a wrapper over _RecursiveAssembleBD.

  Returns:
    a /dev path for primary nodes
    True for secondary nodes

  """
  result = _RecursiveAssembleBD(disk, owner, as_primary)
  if isinstance(result, bdev.BlockDev):
    result = result.dev_path
  return result


def ShutdownBlockDevice(disk):
  """Shut down a block device.

  First, if the device is assembled (can `Attach()`), then the device
  is shutdown. Then the children of the device are shutdown.

  This function is called recursively. Note that we don't cache the
  children or such, as oppossed to assemble, shutdown of different
  devices doesn't require that the upper device was active.

  """
  r_dev = _RecursiveFindBD(disk)
  if r_dev is not None:
    r_path = r_dev.dev_path
    result = r_dev.Shutdown()
    if result:
      DevCacheManager.RemoveCache(r_path)
  else:
    result = True
  if disk.children:
    for child in disk.children:
      result = result and ShutdownBlockDevice(child)
  return result


def MirrorAddChildren(parent_cdev, new_cdevs):
  """Extend a mirrored block device.

  """
  parent_bdev = _RecursiveFindBD(parent_cdev, allow_partial=True)
  if parent_bdev is None:
    logging.error("Can't find parent device")
    return False
  new_bdevs = [_RecursiveFindBD(disk) for disk in new_cdevs]
  if new_bdevs.count(None) > 0:
    logging.error("Can't find new device(s) to add: %s:%s",
                  new_bdevs, new_cdevs)
    return False
  parent_bdev.AddChildren(new_bdevs)
  return True


def MirrorRemoveChildren(parent_cdev, new_cdevs):
  """Shrink a mirrored block device.

  """
  parent_bdev = _RecursiveFindBD(parent_cdev)
  if parent_bdev is None:
    logging.error("Can't find parent in remove children: %s", parent_cdev)
    return False
  devs = []
  for disk in new_cdevs:
    rpath = disk.StaticDevPath()
    if rpath is None:
      bd = _RecursiveFindBD(disk)
      if bd is None:
        logging.error("Can't find dynamic device %s while removing children",
                      disk)
        return False
      else:
        devs.append(bd.dev_path)
    else:
      devs.append(rpath)
  parent_bdev.RemoveChildren(devs)
  return True


def GetMirrorStatus(disks):
  """Get the mirroring status of a list of devices.

  Args:
    disks: list of `objects.Disk`

  Returns:
    list of (mirror_done, estimated_time) tuples, which
    are the result of bdev.BlockDevice.CombinedSyncStatus()

  """
  stats = []
  for dsk in disks:
    rbd = _RecursiveFindBD(dsk)
    if rbd is None:
      raise errors.BlockDeviceError("Can't find device %s" % str(dsk))
    stats.append(rbd.CombinedSyncStatus())
  return stats


def _RecursiveFindBD(disk, allow_partial=False):
  """Check if a device is activated.

  If so, return informations about the real device.

  Args:
    disk: the objects.Disk instance
    allow_partial: don't abort the find if a child of the
                   device can't be found; this is intended to be
                   used when repairing mirrors

  Returns:
    None if the device can't be found
    otherwise the device instance

  """
  children = []
  if disk.children:
    for chdisk in disk.children:
      children.append(_RecursiveFindBD(chdisk))

  return bdev.FindDevice(disk.dev_type, disk.physical_id, children)


def FindBlockDevice(disk):
  """Check if a device is activated.

  If so, return informations about the real device.

  Args:
    disk: the objects.Disk instance
  Returns:
    None if the device can't be found
    (device_path, major, minor, sync_percent, estimated_time, is_degraded)

  """
  rbd = _RecursiveFindBD(disk)
  if rbd is None:
    return rbd
  return (rbd.dev_path, rbd.major, rbd.minor) + rbd.GetSyncStatus()


def UploadFile(file_name, data, mode, uid, gid, atime, mtime):
  """Write a file to the filesystem.

  This allows the master to overwrite(!) a file. It will only perform
  the operation if the file belongs to a list of configuration files.

  """
  if not os.path.isabs(file_name):
    logging.error("Filename passed to UploadFile is not absolute: '%s'",
                  file_name)
    return False

  allowed_files = [
    constants.CLUSTER_CONF_FILE,
    constants.ETC_HOSTS,
    constants.SSH_KNOWN_HOSTS_FILE,
    constants.VNC_PASSWORD_FILE,
    ]

  if file_name not in allowed_files:
    logging.error("Filename passed to UploadFile not in allowed"
                 " upload targets: '%s'", file_name)
    return False

  utils.WriteFile(file_name, data=data, mode=mode, uid=uid, gid=gid,
                  atime=atime, mtime=mtime)
  return True


def _ErrnoOrStr(err):
  """Format an EnvironmentError exception.

  If the `err` argument has an errno attribute, it will be looked up
  and converted into a textual EXXXX description. Otherwise the string
  representation of the error will be returned.

  """
  if hasattr(err, 'errno'):
    detail = errno.errorcode[err.errno]
  else:
    detail = str(err)
  return detail


def _OSOndiskVersion(name, os_dir):
  """Compute and return the API version of a given OS.

  This function will try to read the API version of the os given by
  the 'name' parameter and residing in the 'os_dir' directory.

  Return value will be either an integer denoting the version or None in the
  case when this is not a valid OS name.

  """
  api_file = os.path.sep.join([os_dir, "ganeti_api_version"])

  try:
    st = os.stat(api_file)
  except EnvironmentError, err:
    raise errors.InvalidOS(name, os_dir, "'ganeti_api_version' file not"
                           " found (%s)" % _ErrnoOrStr(err))

  if not stat.S_ISREG(stat.S_IFMT(st.st_mode)):
    raise errors.InvalidOS(name, os_dir, "'ganeti_api_version' file is not"
                           " a regular file")

  try:
    f = open(api_file)
    try:
      api_versions = f.readlines()
    finally:
      f.close()
  except EnvironmentError, err:
    raise errors.InvalidOS(name, os_dir, "error while reading the"
                           " API version (%s)" % _ErrnoOrStr(err))

  api_versions = [version.strip() for version in api_versions]
  try:
    api_versions = [int(version) for version in api_versions]
  except (TypeError, ValueError), err:
    raise errors.InvalidOS(name, os_dir,
                           "API version is not integer (%s)" % str(err))

  return api_versions


def DiagnoseOS(top_dirs=None):
  """Compute the validity for all OSes.

  Returns an OS object for each name in all the given top directories
  (if not given defaults to constants.OS_SEARCH_PATH)

  Returns:
    list of OS objects

  """
  if top_dirs is None:
    top_dirs = constants.OS_SEARCH_PATH

  result = []
  for dir_name in top_dirs:
    if os.path.isdir(dir_name):
      try:
        f_names = utils.ListVisibleFiles(dir_name)
      except EnvironmentError, err:
        logging.exception("Can't list the OS directory %s", dir_name)
        break
      for name in f_names:
        try:
          os_inst = OSFromDisk(name, base_dir=dir_name)
          result.append(os_inst)
        except errors.InvalidOS, err:
          result.append(objects.OS.FromInvalidOS(err))

  return result


def OSFromDisk(name, base_dir=None):
  """Create an OS instance from disk.

  This function will return an OS instance if the given name is a
  valid OS name. Otherwise, it will raise an appropriate
  `errors.InvalidOS` exception, detailing why this is not a valid
  OS.

  @type base_dir: string
  @keyword base_dir: Base directory containing OS installations.
                     Defaults to a search in all the OS_SEARCH_PATH dirs.

  """

  if base_dir is None:
    os_dir = utils.FindFile(name, constants.OS_SEARCH_PATH, os.path.isdir)
    if os_dir is None:
      raise errors.InvalidOS(name, None, "OS dir not found in search path")
  else:
    os_dir = os.path.sep.join([base_dir, name])

  api_versions = _OSOndiskVersion(name, os_dir)

  if constants.OS_API_VERSION not in api_versions:
    raise errors.InvalidOS(name, os_dir, "API version mismatch"
                           " (found %s want %s)"
                           % (api_versions, constants.OS_API_VERSION))

  # OS Scripts dictionary, we will populate it with the actual script names
  os_scripts = {'create': '', 'export': '', 'import': '', 'rename': ''}