backend.py 84.8 KB
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#
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#

# 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.


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"""Functions used by the node daemon

@var _ALLOWED_UPLOAD_FILES: denotes which files are accepted in
     the L{UploadFile} function

"""
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import os
import os.path
import shutil
import time
import stat
import errno
import re
import subprocess
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import random
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import logging
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import tempfile
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import zlib
import base64
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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
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from ganeti import ssconf
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_BOOT_ID_PATH = "/proc/sys/kernel/random/boot_id"


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class RPCFail(Exception):
  """Class denoting RPC failure.

  Its argument is the error message.

  """

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def _Fail(msg, *args, **kwargs):
  """Log an error and the raise an RPCFail exception.

  This exception is then handled specially in the ganeti daemon and
  turned into a 'failed' return type. As such, this function is a
  useful shortcut for logging the error and returning it to the master
  daemon.

  @type msg: string
  @param msg: the text of the exception
  @raise RPCFail

  """
  if args:
    msg = msg % args
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  if "log" not in kwargs or kwargs["log"]: # if we should log this error
    if "exc" in kwargs and kwargs["exc"]:
      logging.exception(msg)
    else:
      logging.error(msg)
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  raise RPCFail(msg)


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def _GetConfig():
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  """Simple wrapper to return a SimpleStore.
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  @rtype: L{ssconf.SimpleStore}
  @return: a SimpleStore instance
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  """
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  return ssconf.SimpleStore()
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def _GetSshRunner(cluster_name):
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  """Simple wrapper to return an SshRunner.

  @type cluster_name: str
  @param cluster_name: the cluster name, which is needed
      by the SshRunner constructor
  @rtype: L{ssh.SshRunner}
  @return: an SshRunner instance

  """
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  return ssh.SshRunner(cluster_name)
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def _Decompress(data):
  """Unpacks data compressed by the RPC client.

  @type data: list or tuple
  @param data: Data sent by RPC client
  @rtype: str
  @return: Decompressed data

  """
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  assert isinstance(data, (list, tuple))
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  assert len(data) == 2
  (encoding, content) = data
  if encoding == constants.RPC_ENCODING_NONE:
    return content
  elif encoding == constants.RPC_ENCODING_ZLIB_BASE64:
    return zlib.decompress(base64.b64decode(content))
  else:
    raise AssertionError("Unknown data encoding")


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def _CleanDirectory(path, exclude=None):
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  """Removes all regular files in a directory.

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  @type path: str
  @param path: the directory to clean
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  @type exclude: list
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  @param exclude: list of files to be excluded, defaults
      to the empty list
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  """
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  if not os.path.isdir(path):
    return
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  if exclude is None:
    exclude = []
  else:
    # Normalize excluded paths
    exclude = [os.path.normpath(i) for i in exclude]
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  for rel_name in utils.ListVisibleFiles(path):
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    full_name = os.path.normpath(os.path.join(path, rel_name))
    if full_name in exclude:
      continue
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    if os.path.isfile(full_name) and not os.path.islink(full_name):
      utils.RemoveFile(full_name)


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def _BuildUploadFileList():
  """Build the list of allowed upload files.

  This is abstracted so that it's built only once at module import time.

  """
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  allowed_files = set([
    constants.CLUSTER_CONF_FILE,
    constants.ETC_HOSTS,
    constants.SSH_KNOWN_HOSTS_FILE,
    constants.VNC_PASSWORD_FILE,
    constants.RAPI_CERT_FILE,
    constants.RAPI_USERS_FILE,
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    constants.HMAC_CLUSTER_KEY,
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    ])

  for hv_name in constants.HYPER_TYPES:
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    hv_class = hypervisor.GetHypervisorClass(hv_name)
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    allowed_files.update(hv_class.GetAncillaryFiles())

  return frozenset(allowed_files)
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_ALLOWED_UPLOAD_FILES = _BuildUploadFileList()


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

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  @rtype: tuple
  @return: True, None
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  """
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  _CleanDirectory(constants.QUEUE_DIR, exclude=[constants.JOB_QUEUE_LOCK_FILE])
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  _CleanDirectory(constants.JOB_QUEUE_ARCHIVE_DIR)


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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
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  @return: master_netdev, master_ip, master_name
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  @raise RPCFail: in case of errors
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  """
  try:
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    cfg = _GetConfig()
    master_netdev = cfg.GetMasterNetdev()
    master_ip = cfg.GetMasterIP()
    master_node = cfg.GetMasterNode()
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  except errors.ConfigurationError, err:
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    _Fail("Cluster configuration incomplete: %s", err, exc=True)
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  return (master_netdev, master_ip, master_node)
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def StartMaster(start_daemons, no_voting):
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  """Activate local node as master node.

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  The function will always try activate the IP address of the master
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  (unless someone else has it). It will also start the master daemons,
  based on the start_daemons parameter.

  @type start_daemons: boolean
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  @param start_daemons: whether to also start the master
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      daemons (ganeti-masterd and ganeti-rapi)
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  @type no_voting: boolean
  @param no_voting: whether to start ganeti-masterd without a node vote
      (if start_daemons is True), but still non-interactively
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  @rtype: None
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  """
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  # GetMasterInfo will raise an exception if not able to return data
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  master_netdev, master_ip, _ = GetMasterInfo()
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  err_msgs = []
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  if utils.TcpPing(master_ip, constants.DEFAULT_NODED_PORT):
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    if utils.OwnIpAddress(master_ip):
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      # we already have the ip:
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      logging.debug("Master IP already configured, doing nothing")
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    else:
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      msg = "Someone else has the master ip, not activating"
      logging.error(msg)
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      err_msgs.append(msg)
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  else:
    result = utils.RunCmd(["ip", "address", "add", "%s/32" % master_ip,
                           "dev", master_netdev, "label",
                           "%s:0" % master_netdev])
    if result.failed:
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      msg = "Can't activate master IP: %s" % result.output
      logging.error(msg)
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      err_msgs.append(msg)
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    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:
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    daemons_params = {
        'ganeti-masterd': [],
        'ganeti-rapi': [],
        }
    if no_voting:
      daemons_params['ganeti-masterd'].append('--no-voting')
      daemons_params['ganeti-masterd'].append('--yes-do-it')
    for daemon in daemons_params:
      cmd = [daemon]
      cmd.extend(daemons_params[daemon])
      result = utils.RunCmd(cmd)
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      if result.failed:
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        msg = "Can't start daemon %s: %s" % (daemon, result.output)
        logging.error(msg)
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        err_msgs.append(msg)
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  if err_msgs:
    _Fail("; ".join(err_msgs))
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def StopMaster(stop_daemons):
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  """Deactivate this node as master.

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  The function will always try to deactivate the IP address of the
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  master. It will also stop the master daemons depending on the
  stop_daemons parameter.

  @type stop_daemons: boolean
  @param stop_daemons: whether to also stop the master daemons
      (ganeti-masterd and ganeti-rapi)
  @rtype: None
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  """
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  # TODO: log and report back to the caller the error failures; we
  # need to decide in which case we fail the RPC for this
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  # GetMasterInfo will raise an exception if not able to return data
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  master_netdev, master_ip, _ = GetMasterInfo()
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  result = utils.RunCmd(["ip", "address", "del", "%s/32" % master_ip,
                         "dev", master_netdev])
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  if result.failed:
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    logging.error("Can't remove the master IP, error: %s", result.output)
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    # but otherwise ignore the failure

  if stop_daemons:
    # stop/kill the rapi and the master daemon
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    for daemon in constants.RAPI, constants.MASTERD:
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      utils.KillProcess(utils.ReadPidFile(utils.DaemonPidFileName(daemon)))
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def AddNode(dsa, dsapub, rsa, rsapub, sshkey, sshpub):
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  """Joins this node to the cluster.
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  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
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  @type dsa: str
  @param dsa: the DSA private key to write
  @type dsapub: str
  @param dsapub: the DSA public key to write
  @type rsa: str
  @param rsa: the RSA private key to write
  @type rsapub: str
  @param rsapub: the RSA public key to write
  @type sshkey: str
  @param sshkey: the SSH private key to write
  @type sshpub: str
  @param sshpub: the SSH public key to write
  @rtype: boolean
  @return: the success of the operation

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  """
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  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)]
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  for name, content, mode in sshd_keys:
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    utils.WriteFile(name, data=content, mode=mode)
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  try:
    priv_key, pub_key, auth_keys = ssh.GetUserFiles(constants.GANETI_RUNAS,
                                                    mkdir=True)
  except errors.OpExecError, err:
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    _Fail("Error while processing user ssh files: %s", err, exc=True)
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  for name, content in [(priv_key, sshkey), (pub_key, sshpub)]:
    utils.WriteFile(name, data=content, mode=0600)
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  utils.AddAuthorizedKey(auth_keys, sshpub)
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  utils.RunCmd([constants.SSH_INITD_SCRIPT, "restart"])
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def LeaveCluster():
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  """Cleans up and remove the current node.

  This function cleans up and prepares the current node to be removed
  from the cluster.

  If processing is successful, then it raises an
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  L{errors.QuitGanetiException} which is used as a special case to
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  shutdown the node daemon.
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  """
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  _CleanDirectory(constants.DATA_DIR)
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  JobQueuePurge()
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  try:
    priv_key, pub_key, auth_keys = ssh.GetUserFiles(constants.GANETI_RUNAS)
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    utils.RemoveAuthorizedKey(auth_keys, utils.ReadFile(pub_key))
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    utils.RemoveFile(priv_key)
    utils.RemoveFile(pub_key)
  except errors.OpExecError:
    logging.exception("Error while processing ssh files")
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  try:
    utils.RemoveFile(constants.HMAC_CLUSTER_KEY)
    utils.RemoveFile(constants.RAPI_CERT_FILE)
    utils.RemoveFile(constants.SSL_CERT_FILE)
  except:
    logging.exception("Error while removing cluster secrets")

  confd_pid = utils.ReadPidFile(utils.DaemonPidFileName(constants.CONFD))

  if confd_pid:
    utils.KillProcess(confd_pid, timeout=2)

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  # Raise a custom exception (handled in ganeti-noded)
  raise errors.QuitGanetiException(True, 'Shutdown scheduled')
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def GetNodeInfo(vgname, hypervisor_type):
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  """Gives back a hash with different information about the node.
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  @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
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  """
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  outputarray = {}
  vginfo = _GetVGInfo(vgname)
  outputarray['vg_size'] = vginfo['vg_size']
  outputarray['vg_free'] = vginfo['vg_free']

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

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  outputarray["bootid"] = utils.ReadFile(_BOOT_ID_PATH, size=128).rstrip("\n")
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  return outputarray
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def VerifyNode(what, cluster_name):
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  """Verify the status of the local node.

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  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).
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  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
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  @rtype: dict
  @return: a dictionary with the same keys as the input dict, and
      values representing the result of the checks
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  """
  result = {}

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  if constants.NV_HYPERVISOR in what:
    result[constants.NV_HYPERVISOR] = tmp = {}
    for hv_name in what[constants.NV_HYPERVISOR]:
      tmp[hv_name] = hypervisor.GetHypervisor(hv_name).Verify()

  if constants.NV_FILELIST in what:
    result[constants.NV_FILELIST] = utils.FingerprintFiles(
      what[constants.NV_FILELIST])

  if constants.NV_NODELIST in what:
    result[constants.NV_NODELIST] = tmp = {}
    random.shuffle(what[constants.NV_NODELIST])
    for node in what[constants.NV_NODELIST]:
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      success, message = _GetSshRunner(cluster_name).VerifyNodeHostname(node)
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      if not success:
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        tmp[node] = message

  if constants.NV_NODENETTEST in what:
    result[constants.NV_NODENETTEST] = tmp = {}
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    my_name = utils.HostInfo().name
    my_pip = my_sip = None
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    for name, pip, sip in what[constants.NV_NODENETTEST]:
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      if name == my_name:
        my_pip = pip
        my_sip = sip
        break
    if not my_pip:
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      tmp[my_name] = ("Can't find my own primary/secondary IP"
                      " in the node list")
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    else:
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      port = utils.GetDaemonPort(constants.NODED)
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      for name, pip, sip in what[constants.NV_NODENETTEST]:
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        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:
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          tmp[name] = ("failure using the %s interface(s)" %
                       " and ".join(fail))

  if constants.NV_LVLIST in what:
    result[constants.NV_LVLIST] = GetVolumeList(what[constants.NV_LVLIST])

  if constants.NV_INSTANCELIST in what:
    result[constants.NV_INSTANCELIST] = GetInstanceList(
      what[constants.NV_INSTANCELIST])

  if constants.NV_VGLIST in what:
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    result[constants.NV_VGLIST] = utils.ListVolumeGroups()
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  if constants.NV_VERSION in what:
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    result[constants.NV_VERSION] = (constants.PROTOCOL_VERSION,
                                    constants.RELEASE_VERSION)
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  if constants.NV_HVINFO in what:
    hyper = hypervisor.GetHypervisor(what[constants.NV_HVINFO])
    result[constants.NV_HVINFO] = hyper.GetNodeInfo()
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  if constants.NV_DRBDLIST in what:
    try:
      used_minors = bdev.DRBD8.GetUsedDevs().keys()
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    except errors.BlockDeviceError, err:
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      logging.warning("Can't get used minors list", exc_info=True)
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      used_minors = str(err)
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    result[constants.NV_DRBDLIST] = used_minors

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

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  @type vg_name: str
  @param vg_name: the volume group whose LVs we should list
  @rtype: dict
  @return:
      dictionary of all partions (key) with value being a tuple of
      their size (in MiB), inactive and online status::

        {'test1': ('20.06', True, True)}

      in case of errors, a string is returned with the error
      details.
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  """
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  lvs = {}
  sep = '|'
  result = utils.RunCmd(["lvs", "--noheadings", "--units=m", "--nosuffix",
                         "--separator=%s" % sep,
                         "-olv_name,lv_size,lv_attr", vg_name])
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  if result.failed:
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    _Fail("Failed to list logical volumes, lvs output: %s", result.output)
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  valid_line_re = re.compile("^ *([^|]+)\|([0-9.]+)\|([^|]{6})\|?$")
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  for line in result.stdout.splitlines():
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    line = line.strip()
    match = valid_line_re.match(line)
    if not match:
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      logging.error("Invalid line returned from lvs output: '%s'", line)
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      continue
    name, size, attr = match.groups()
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    inactive = attr[4] == '-'
    online = attr[5] == 'o'
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    virtual = attr[0] == 'v'
    if virtual:
      # we don't want to report such volumes as existing, since they
      # don't really hold data
      continue
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    lvs[name] = (size, inactive, online)

  return lvs
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def ListVolumeGroups():
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  """List the volume groups and their size.
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  @rtype: dict
  @return: dictionary with keys volume name and values the
      size of the volume
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  """
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  return utils.ListVolumeGroups()
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def NodeVolumes():
  """List all volumes on this node.

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  @rtype: list
  @return:
    A list of dictionaries, each having four keys:
      - name: the logical volume name,
      - size: the size of the logical volume
      - dev: the physical device on which the LV lives
      - vg: the volume group to which it belongs

    In case of errors, we return an empty list and log the
    error.

    Note that since a logical volume can live on multiple physical
    volumes, the resulting list might include a logical volume
    multiple times.

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

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  return [map_line(line.split('|')) for line in result.stdout.splitlines()
          if line.count('|') >= 3]
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def BridgesExist(bridges_list):
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  """Check if a list of bridges exist on the current node.
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  @rtype: boolean
  @return: C{True} if all of them exist, C{False} otherwise
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  """
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  missing = []
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  for bridge in bridges_list:
    if not utils.BridgeExists(bridge):
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      missing.append(bridge)
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  if missing:
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    _Fail("Missing bridges %s", ", ".join(missing))
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def GetInstanceList(hypervisor_list):
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  """Provides a list of instances.
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  @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
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    - instance1.example.com
    - instance2.example.com
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  """
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  results = []
  for hname in hypervisor_list:
    try:
      names = hypervisor.GetHypervisor(hname).ListInstances()
      results.extend(names)
    except errors.HypervisorError, err:
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      _Fail("Error enumerating instances (hypervisor %s): %s",
            hname, err, exc=True)
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  return results
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def GetInstanceInfo(instance, hname):
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  """Gives back the information about an instance as a dictionary.
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  @type instance: string
  @param instance: the instance name
  @type hname: string
  @param hname: the hypervisor type of the instance
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  @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)
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  """
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  output = {}

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

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  return output
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def GetInstanceMigratable(instance):
  """Gives whether an instance can be migrated.

  @type instance: L{objects.Instance}
  @param instance: object representing the instance to be checked.

  @rtype: tuple
  @return: tuple of (result, description) where:
      - result: whether the instance can be migrated or not
      - description: a description of the issue, if relevant

  """
  hyper = hypervisor.GetHypervisor(instance.hypervisor)
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  iname = instance.name
  if iname not in hyper.ListInstances():
    _Fail("Instance %s is not running", iname)
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  for idx in range(len(instance.disks)):
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    link_name = _GetBlockDevSymlinkPath(iname, idx)
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    if not os.path.islink(link_name):
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      _Fail("Instance %s was not restarted since ganeti 1.2.5", iname)
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def GetAllInstancesInfo(hypervisor_list):
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  """Gather data about all instances.

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

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

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  @rtype: dict
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  @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)
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      - vcpus: the number of vcpus
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  """
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  output = {}

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  for hname in hypervisor_list:
    iinfo = hypervisor.GetHypervisor(hname).GetAllInstancesInfo()
    if iinfo:
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      for name, _, memory, vcpus, state, times in iinfo:
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        value = {
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          'memory': memory,
          'vcpus': vcpus,
          'state': state,
          'time': times,
          }
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        if name in output:
          # we only check static parameters, like memory and vcpus,
          # and not state and time which can change between the
          # invocations of the different hypervisors
          for key in 'memory', 'vcpus':
            if value[key] != output[name][key]:
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              _Fail("Instance %s is running twice"
                    " with different parameters", name)
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        output[name] = value
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  return output
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def InstanceOsAdd(instance, reinstall):
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  """Add an OS to an instance.
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  @type instance: L{objects.Instance}
  @param instance: Instance whose OS is to be installed
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  @type reinstall: boolean
  @param reinstall: whether this is an instance reinstall
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  @rtype: None
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  """
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  inst_os = OSFromDisk(instance.os)

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  create_env = OSEnvironment(instance, inst_os)
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  if reinstall:
    create_env['INSTANCE_REINSTALL'] = "1"
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  logfile = "%s/add-%s-%s-%d.log" % (constants.LOG_OS_DIR, instance.os,
                                     instance.name, int(time.time()))
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  result = utils.RunCmd([inst_os.create_script], env=create_env,
                        cwd=inst_os.path, output=logfile,)
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  if result.failed:
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    logging.error("os create command '%s' returned error: %s, logfile: %s,"
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                  " output: %s", result.cmd, result.fail_reason, logfile,
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                  result.output)
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    lines = [utils.SafeEncode(val)
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             for val in utils.TailFile(logfile, lines=20)]
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    _Fail("OS create script failed (%s), last lines in the"
          " log file:\n%s", result.fail_reason, "\n".join(lines), log=False)
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def RunRenameInstance(instance, old_name):
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  """Run the OS rename script for an instance.

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  @type instance: L{objects.Instance}
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  @param instance: Instance whose OS is to be installed
  @type old_name: string
  @param old_name: previous instance name
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  @rtype: boolean
  @return: the success of the operation
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  """
  inst_os = OSFromDisk(instance.os)

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  rename_env = OSEnvironment(instance, inst_os)
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  rename_env['OLD_INSTANCE_NAME'] = old_name
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  logfile = "%s/rename-%s-%s-%s-%d.log" % (constants.LOG_OS_DIR, instance.os,
                                           old_name,
                                           instance.name, int(time.time()))
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  result = utils.RunCmd([inst_os.rename_script], env=rename_env,
                        cwd=inst_os.path, output=logfile)
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  if result.failed:
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    logging.error("os create command '%s' returned error: %s output: %s",
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                  result.cmd, result.fail_reason, result.output)
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    lines = [utils.SafeEncode(val)
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             for val in utils.TailFile(logfile, lines=20)]
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    _Fail("OS rename script failed (%s), last lines in the"
          " log file:\n%s", result.fail_reason, "\n".join(lines), log=False)
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def _GetVGInfo(vg_name):
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  """Get information about the volume group.
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  @type vg_name: str
  @param vg_name: the volume group which we query
  @rtype: dict
  @return:
    A dictionary with the following keys:
      - C{vg_size} is the total size of the volume group in MiB
      - C{vg_free} is the free size of the volume group in MiB
      - C{pv_count} are the number of physical disks in that VG
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    If an error occurs during gathering of data, we return the same dict
    with keys all set to None.
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  """
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  retdic = dict.fromkeys(["vg_size", "vg_free", "pv_count"])

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

  if retval.failed:
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    logging.error("volume group %s not present", vg_name)
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    return retdic
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  valarr = retval.stdout.strip().rstrip(':').split(':')
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  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:
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      logging.exception("Fail to parse vgs output: %s", err)
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  else:
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    logging.error("vgs output has the wrong number of fields (expected"
                  " three): %s", str(valarr))
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  return retdic


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def _GetBlockDevSymlinkPath(instance_name, idx):
  return os.path.join(constants.DISK_LINKS_DIR,
                      "%s:%d" % (instance_name, idx))


def _SymlinkBlockDev(instance_name, device_path, idx):
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  """Set up symlinks to a instance's block device.

  This is an auxiliary function run when an instance is start (on the primary
  node) or when an instance is migrated (on the target node).


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  @param instance_name: the name of the target instance
  @param device_path: path of the physical block device, on the node
  @param idx: the disk index
  @return: absolute path to the disk's symlink
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  """
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  link_name = _GetBlockDevSymlinkPath(instance_name, idx)
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  try:
    os.symlink(device_path, link_name)
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  except OSError, err:
    if err.errno == errno.EEXIST:
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      if (not os.path.islink(link_name) or
          os.readlink(link_name) != device_path):
        os.remove(link_name)
        os.symlink(device_path, link_name)
    else:
      raise

  return link_name


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def _RemoveBlockDevLinks(instance_name, disks):
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  """Remove the block device symlinks belonging to the given instance.

  """
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  for idx, _ in enumerate(disks):
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    link_name = _GetBlockDevSymlinkPath(instance_name, idx)
    if os.path.islink(link_name):
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      try:
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        os.remove(link_name)
      except OSError:
        logging.exception("Can't remove symlink '%s'", link_name)
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def _GatherAndLinkBlockDevs(instance):
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  """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.

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  @type instance: L{objects.Instance}
  @param instance: the instance whose disks we shoul assemble
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  @rtype: list
  @return: list of (disk_object, device_path)
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  """
  block_devices = []
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  for idx, disk in enumerate(instance.disks):
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    device = _RecursiveFindBD(disk)
    if device is None:
      raise errors.BlockDeviceError("Block device '%s' is not set up." %
                                    str(disk))
    device.Open()
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    try:
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      link_name = _SymlinkBlockDev(instance.name, device.dev_path, idx)
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    except OSError, e:
      raise errors.BlockDeviceError("Cannot create block device symlink: %s" %
                                    e.strerror)

    block_devices.append((disk, link_name))

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  return block_devices


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

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  @type instance: L{objects.Instance}
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  @param instance: the instance object
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  @rtype: None
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  """
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  running_instances = GetInstanceList([instance.hypervisor])
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  if instance.name in running_instances:
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    logging.info("Instance %s already running, not starting", instance.name)
    return
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  try:
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    block_devices = _GatherAndLinkBlockDevs(instance)
    hyper = hypervisor.GetHypervisor(instance.hypervisor)
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    hyper.StartInstance(instance, block_devices)
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  except errors.BlockDeviceError, err:
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    _Fail("Block device error: %s", err, exc=True)
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  except errors.HypervisorError, err:
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    _RemoveBlockDevLinks(instance.name, instance.disks)
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    _Fail("Hypervisor error: %s", err, exc=True)
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def InstanceShutdown(instance, timeout):
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  """Shut an instance down.

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  @note: this functions uses polling with a hardcoded timeout.

  @type instance: L{objects.Instance}
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  @param instance: the instance object
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  @type timeout: integer
  @param timeout: maximum timeout for soft shutdown
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  @rtype: None
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  """
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  hv_name = instance.hypervisor
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  hyper = hypervisor.GetHypervisor(hv_name)
  running_instances = hyper.ListInstances()
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  iname = instance.name
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  if iname not in running_instances:
    logging.info("Instance %s not running, doing nothing", iname)
    return
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  start = time.time()
  end = start + timeout
  sleep_time = 1
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  tried_once = False
  while not tried_once and time.time() < end:
    try:
      hyper.StopInstance(instance, retry=tried_once)
    except errors.HypervisorError, err:
      _Fail("Failed to stop instance %s: %s", iname, err)
    tried_once = True
    time.sleep(sleep_time)
    if instance.name not in hyper.ListInstances():
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      break
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    if sleep_time < 5:
      # 1.2 behaves particularly good for our case:
      # it gives us 10 increasing steps and caps just slightly above 5 seconds
      sleep_time *= 1.2
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  else:
    # the shutdown did not succeed
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    logging.error("Shutdown of '%s' unsuccessful, forcing", iname)
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    try:
      hyper.StopInstance(instance, force=True)
    except errors.HypervisorError, err:
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      _Fail("Failed to force stop instance %s: %s", iname, err)
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    time.sleep(1)
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    if instance.name in GetInstanceList([hv_name]):
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      _Fail("Could not shutdown instance %s even by destroy", iname)
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  _RemoveBlockDevLinks(iname, instance.disks)
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def InstanceReboot(instance, reboot_type):
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  """Reboot an instance.

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  @type instance: L{objects.Instance}
  @param instance: the instance object to reboot
  @type reboot_type: str
  @param reboot_type: the type of reboot, one the following
    constants:
      - L{constants.INSTANCE_REBOOT_SOFT}: only reboot the
        instance OS, do not recreate the VM
      - L{constants.INSTANCE_REBOOT_HARD}: tear down and
        restart the VM (at the hypervisor level)
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      - the other reboot type (L{constants.INSTANCE_REBOOT_FULL}) is
        not accepted here, since that mode is handled differently, in
        cmdlib, and translates into full stop and start of the
        instance (instead of a call_instance_reboot RPC)
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  @rtype: None
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  """
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  running_instances = GetInstanceList([instance.hypervisor])
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  if instance.name not in running_instances:
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    _Fail("Cannot reboot instance %s that is not running", instance.name)
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  hyper = hypervisor.GetHypervisor(instance.hypervisor)
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  if reboot_type == constants.INSTANCE_REBOOT_SOFT:
    try:
      hyper.RebootInstance(instance)
    except errors.HypervisorError, err:
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      _Fail("Failed to soft reboot instance %s: %s", instance.name, err)
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  elif reboot_type == constants.INSTANCE_REBOOT_HARD:
    try:
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      InstanceShutdown(instance)
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      return StartInstance(instance)
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    except errors.HypervisorError, err:
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      _Fail("Failed to hard reboot instance %s: %s", instance.name, err)
1054
  else:
1055
    _Fail("Invalid reboot_type received: %s", reboot_type)
1056
1057


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def MigrationInfo(instance):
  """Gather information about an instance to be migrated.

  @type instance: L{objects.Instance}
  @param instance: the instance definition

  """
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  hyper = hypervisor.GetHypervisor(instance.hypervisor)
  try:
    info = hyper.MigrationInfo(instance)
  except errors.HypervisorError, err:
1069
    _Fail("Failed to fetch migration information: %s", err, exc=True)
1070
  return info
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1080
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def AcceptInstance(instance, info, target):
  """Prepare the node to accept an instance.

  @type instance: L{objects.Instance}
  @param instance: the instance definition
  @type info: string/data (opaque)
  @param info: migration information, from the source node
  @type target: string
  @param target: target host (usually ip), on this node

  """
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  hyper = hypervisor.GetHypervisor(instance.hypervisor)
  try:
    hyper.AcceptInstance(instance, info, target)
  except errors.HypervisorError, err:
1088
    _Fail("Failed to accept instance: %s", err, exc=True)
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def FinalizeMigration(instance, info, success):
  """Finalize any preparation to accept an instance.

  @type instance: L{objects.Instance}
  @param instance: the instance definition
  @type info: string/data (opaque)
  @param info: migration information, from the source node
  @type success: boolean
  @param success: whether the migration was a success or a failure

  """