Synnefo » snf-ganeti » ganeti-local

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# Copyright (C) 2010 Google Inc.

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"""LXC hypervisor

"""

import os

import os.path

import time

import logging

from ganeti import constants

from ganeti import errors # pylint: disable-msg=W0611

from ganeti import utils

from ganeti.hypervisor import hv_base

from ganeti.errors import HypervisorError

class LXCHypervisor(hv_base.BaseHypervisor):

  """LXC-based virtualization.

  Since current (Spring 2010) distributions are not yet ready for

  running under a container, the following changes must be done

  manually:

    - remove udev

    - disable the kernel log component of sysklogd/rsyslog/etc.,

      otherwise they will fail to read the log, and at least rsyslog

      will fill the filesystem with error messages

  TODO:

    - move hardcoded parameters into hypervisor parameters, once we

      have the container-parameter support

    - implement memory limits, but only optionally, depending on host

      kernel support

  Problems/issues:

    - LXC is very temperamental; in daemon mode, it succeeds or fails

      in launching the instance silently, without any error

      indication, and when failing it can leave network interfaces

      around, and future successful startups will list the instance

      twice

    - shutdown sequence of containers leaves the init 'dead', and the

      container effectively stopped, but LXC still believes the

      container to be running; need to investigate using the

      notify_on_release and release_agent feature of cgroups

  """

  _ROOT_DIR = constants.RUN_GANETI_DIR + "/lxc"

  _LOG_FILE = constants.LOG_DIR + "hv_lxc.log"

  _DEVS = [

    "c 1:3",   # /dev/null

    "c 1:5",   # /dev/zero

    "c 1:7",   # /dev/full

    "c 1:8",   # /dev/random

    "c 1:9",   # /dev/urandom

    "c 1:10",  # /dev/aio

    "c 5:0",   # /dev/tty

    "c 5:1",   # /dev/console

    "c 5:2",   # /dev/ptmx

    "c 136:*", # first block of Unix98 PTY slaves

    ]

  _DENIED_CAPABILITIES = [

    "mac_override",    # Allow MAC configuration or state changes

    # TODO: remove sys_admin too, for safety

    #"sys_admin",       # Perform  a range of system administration operations

    "sys_boot",        # Use reboot(2) and kexec_load(2)

    "sys_module",      # Load  and  unload kernel modules

    "sys_time",        # Set  system  clock, set real-time (hardware) clock

    ]

  _DIR_MODE = 0755

  PARAMETERS = {

    }

  def __init__(self):

    hv_base.BaseHypervisor.__init__(self)

    utils.EnsureDirs([(self._ROOT_DIR, self._DIR_MODE)])

  @staticmethod

  def _GetMountSubdirs(path):

    """Return the list of mountpoints under a given path.

    This function is Linux-specific.

    """

    #TODO(iustin): investigate and document non-linux options

    #(e.g. via mount output)

    data = []

    fh = open("/proc/mounts", "r")

    try:

      for line in fh:

        _, mountpoint, _ = line.split(" ", 2)

        if (mountpoint.startswith(path) and

            mountpoint != path):

          data.append(mountpoint)

    finally:

      fh.close()

    data.sort(key=lambda x: x.count("/"), reverse=True)

    return data

  @classmethod

  def _InstanceDir(cls, instance_name):

    """Return the root directory for an instance.

    """

    return utils.PathJoin(cls._ROOT_DIR, instance_name)

  @classmethod

  def _InstanceConfFile(cls, instance_name):

    """Return the configuration file for an instance.

    """

    return utils.PathJoin(cls._ROOT_DIR, instance_name + ".conf")

  def ListInstances(self):

    """Get the list of running instances.

    """

    result = utils.RunCmd(["lxc-ls"])

    if result.failed:

      raise errors.HypervisorError("Can't run lxc-ls: %s" % result.output)

    return result.stdout.splitlines()

  def GetInstanceInfo(self, instance_name):

    """Get instance properties.

    @type instance_name: string

    @param instance_name: the instance name

    @return: (name, id, memory, vcpus, stat, times)

    """

    # TODO: read container info from the cgroup mountpoint

    return (instance_name, 0, 0, 0, 0, 0)

  def GetAllInstancesInfo(self):

    """Get properties of all instances.

    @return: [(name, id, memory, vcpus, stat, times),...]

    """

    # TODO: read container info from the cgroup mountpoint

    data = []

    for name in self.ListInstances():

      data.append((name, 0, 0, 0, 0, 0))

    return data

  def _CreateConfigFile(self, instance, root_dir):

    """Create an lxc.conf file for an instance"""

    out = []

    # hostname

    out.append("lxc.utsname = %s" % instance.name)

    # separate pseudo-TTY instances

    out.append("lxc.pts = 255")

    # standard TTYs/console

    out.append("lxc.tty = 6")

    # root FS

    out.append("lxc.rootfs = %s" % root_dir)

    # TODO: additional mounts, if we disable CAP_SYS_ADMIN

    # Device control

    # deny direct device access

    out.append("lxc.cgroup.devices.deny = a")

    for devinfo in self._DEVS:

      out.append("lxc.cgroup.devices.allow = %s rw" % devinfo)

    # Networking

    for idx, nic in enumerate(instance.nics):

      out.append("# NIC %d" % idx)

      mode = nic.nicparams[constants.NIC_MODE]

      link = nic.nicparams[constants.NIC_LINK]

      if mode == constants.NIC_MODE_BRIDGED:

        out.append("lxc.network.type = veth")

        out.append("lxc.network.link = %s" % link)

      else:

        raise errors.HypervisorError("LXC hypervisor only supports"

                                     " bridged mode (NIC %d has mode %s)" %

                                     (idx, mode))

      out.append("lxc.network.hwaddr = %s" % nic.mac)

      out.append("lxc.network.flags = up")

    # Capabilities

    for cap in self._DENIED_CAPABILITIES:

      out.append("lxc.cap.drop = %s" % cap)

    return "\n".join(out) + "\n"

  def StartInstance(self, instance, block_devices):

    """Start an instance.

    For LCX, we try to mount the block device and execute 'lxc-start

    start' (we use volatile containers).

    """

    root_dir = self._InstanceDir(instance.name)

    try:

      utils.EnsureDirs([(root_dir, self._DIR_MODE)])

    except errors.GenericError, err:

      raise HypervisorError("Cannot create instance directory: %s", str(err))

    conf_file = self._InstanceConfFile(instance.name)

    utils.WriteFile(conf_file, data=self._CreateConfigFile(instance, root_dir))

    if not os.path.ismount(root_dir):

      if not block_devices:

        raise HypervisorError("LXC needs at least one disk")

      sda_dev_path = block_devices[0][1]

      result = utils.RunCmd(["mount", sda_dev_path, root_dir])

      if result.failed:

        raise HypervisorError("Can't mount the chroot dir: %s" % result.output)

    # TODO: replace the global log file with a per-instance log file

    result = utils.RunCmd(["lxc-start", "-n", instance.name,

                           "-o", self._LOG_FILE, "-l", "DEBUG",

                           "-f", conf_file, "-d"])

    if result.failed:

      raise HypervisorError("Running the lxc-start script failed: %s" %

                            result.output)

  def StopInstance(self, instance, force=False, retry=False, name=None):

    """Stop an instance.

    This method has complicated cleanup tests, as we must:

      - try to kill all leftover processes

      - try to unmount any additional sub-mountpoints

      - finally unmount the instance dir

    """

    if name is None:

      name = instance.name

    root_dir = self._InstanceDir(name)

    if not os.path.exists(root_dir):

      return

    if name in self.ListInstances():

      # Signal init to shutdown; this is a hack

      if not retry and not force:

        result = utils.RunCmd(["chroot", root_dir, "poweroff"])

        if result.failed:

          raise HypervisorError("Can't run 'poweroff' for the instance: %s" %

                                result.output)

      time.sleep(2)

      result = utils.RunCmd(["lxc-stop", "-n", name])

      if result.failed:

        logging.warning("Error while doing lxc-stop for %s: %s", name,

                        result.output)

    for mpath in self._GetMountSubdirs(root_dir):

      result = utils.RunCmd(["umount", mpath])

      if result.failed:

        logging.warning("Error while umounting subpath %s for instance %s: %s",

                        mpath, name, result.output)

    result = utils.RunCmd(["umount", root_dir])

    if result.failed and force:

      msg = ("Processes still alive in the chroot: %s" %

             utils.RunCmd("fuser -vm %s" % root_dir).output)

      logging.error(msg)

      raise HypervisorError("Can't umount the chroot dir: %s (%s)" %

                            (result.output, msg))

  def RebootInstance(self, instance):

    """Reboot an instance.

    This is not (yet) implemented (in Ganeti) for the LXC hypervisor.

    """

    # TODO: implement reboot

    raise HypervisorError("The LXC hypervisor doesn't implement the"

                          " reboot functionality")

  def GetNodeInfo(self):

    """Return information about the node.

    This is just a wrapper over the base GetLinuxNodeInfo method.

    @return: a dict with the following keys (values in MiB):

          - memory_total: the total memory size on the node

          - memory_free: the available memory on the node for instances

          - memory_dom0: the memory used by the node itself, if available

    """

    return self.GetLinuxNodeInfo()

  @classmethod

  def GetShellCommandForConsole(cls, instance, hvparams, beparams):

    """Return a command for connecting to the console of an instance.

    """

    return "lxc-console -n %s" % instance.name

  def Verify(self):

    """Verify the hypervisor.

    For the chroot manager, it just checks the existence of the base dir.

    """

    if not os.path.exists(self._ROOT_DIR):

      return "The required directory '%s' does not exist." % self._ROOT_DIR

  @classmethod

  def PowercycleNode(cls):

    """LXC powercycle, just a wrapper over Linux powercycle.

    """

    cls.LinuxPowercycle()

  def MigrateInstance(self, instance, target, live):

    """Migrate an instance.

    @type instance: L{objects.Instance}

    @param instance: the instance to be migrated

    @type target: string

    @param target: hostname (usually ip) of the target node

    @type live: boolean

    @param live: whether to do a live or non-live migration

    """

    raise HypervisorError("Migration not supported by the LXC hypervisor")