Synnefo » snf-ganeti

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# Copyright (C) 2006, 2007, 2011 Google Inc.

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# This program is free software; you can redistribute it and/or modify

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# General Public License for more details.

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# You should have received a copy of the GNU General Public License

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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

# 02110-1301, USA.

"""Module implementing the logic behind the cluster operations

This module implements the logic for doing operations in the cluster. There

are two kinds of classes defined:

  - logical units, which know how to deal with their specific opcode only

  - the processor, which dispatches the opcodes to their logical units

"""

import logging

import random

import time

from ganeti import opcodes

from ganeti import constants

from ganeti import errors

from ganeti import rpc

from ganeti import cmdlib

from ganeti import locking

from ganeti import utils

_OP_PREFIX = "Op"

_LU_PREFIX = "LU"

class LockAcquireTimeout(Exception):

  """Exception to report timeouts on acquiring locks.

  """

def _CalculateLockAttemptTimeouts():

  """Calculate timeouts for lock attempts.

  """

  result = [constants.LOCK_ATTEMPTS_MINWAIT]

  running_sum = result[0]

  # Wait for a total of at least LOCK_ATTEMPTS_TIMEOUT before doing a

  # blocking acquire

  while running_sum < constants.LOCK_ATTEMPTS_TIMEOUT:

    timeout = (result[-1] * 1.05) ** 1.25

    # Cap max timeout. This gives other jobs a chance to run even if

    # we're still trying to get our locks, before finally moving to a

    # blocking acquire.

    timeout = min(timeout, constants.LOCK_ATTEMPTS_MAXWAIT)

    # And also cap the lower boundary for safety

    timeout = max(timeout, constants.LOCK_ATTEMPTS_MINWAIT)

    result.append(timeout)

    running_sum += timeout

  return result

class LockAttemptTimeoutStrategy(object):

  """Class with lock acquire timeout strategy.

  """

  __slots__ = [

    "_timeouts",

    "_random_fn",

    "_time_fn",

    ]

  _TIMEOUT_PER_ATTEMPT = _CalculateLockAttemptTimeouts()

  def __init__(self, _time_fn=time.time, _random_fn=random.random):

    """Initializes this class.

    @param _time_fn: Time function for unittests

    @param _random_fn: Random number generator for unittests

    """

    object.__init__(self)

    self._timeouts = iter(self._TIMEOUT_PER_ATTEMPT)

    self._time_fn = _time_fn

    self._random_fn = _random_fn

  def NextAttempt(self):

    """Returns the timeout for the next attempt.

    """

    try:

      timeout = self._timeouts.next()

    except StopIteration:

      # No more timeouts, do blocking acquire

      timeout = None

    if timeout is not None:

      # Add a small variation (-/+ 5%) to timeout. This helps in situations

      # where two or more jobs are fighting for the same lock(s).

      variation_range = timeout * 0.1

      timeout += ((self._random_fn() * variation_range) -

                  (variation_range * 0.5))

    return timeout

class OpExecCbBase: # pylint: disable-msg=W0232

  """Base class for OpCode execution callbacks.

  """

  def NotifyStart(self):

    """Called when we are about to execute the LU.

    This function is called when we're about to start the lu's Exec() method,

    that is, after we have acquired all locks.

    """

  def Feedback(self, *args):

    """Sends feedback from the LU code to the end-user.

    """

  def CheckCancel(self):

    """Check whether job has been cancelled.

    """

def _LUNameForOpName(opname):

  """Computes the LU name for a given OpCode name.

  """

  assert opname.startswith(_OP_PREFIX), \

      "Invalid OpCode name, doesn't start with %s: %s" % (_OP_PREFIX, opname)

  return _LU_PREFIX + opname[len(_OP_PREFIX):]

def _ComputeDispatchTable():

  """Computes the opcode-to-lu dispatch table.

  """

  return dict((op, getattr(cmdlib, _LUNameForOpName(op.__name__)))

              for op in opcodes.OP_MAPPING.values()

              if op.WITH_LU)

class Processor(object):

  """Object which runs OpCodes"""

  DISPATCH_TABLE = _ComputeDispatchTable()

  def __init__(self, context, ec_id):

    """Constructor for Processor

    @type context: GanetiContext

    @param context: global Ganeti context

    @type ec_id: string

    @param ec_id: execution context identifier

    """

    self.context = context

    self._ec_id = ec_id

    self._cbs = None

    self.rpc = rpc.RpcRunner(context.cfg)

    self.hmclass = HooksMaster

  def _AcquireLocks(self, level, names, shared, timeout, priority):

    """Acquires locks via the Ganeti lock manager.

    @type level: int

    @param level: Lock level

    @type names: list or string

    @param names: Lock names

    @type shared: bool

    @param shared: Whether the locks should be acquired in shared mode

    @type timeout: None or float

    @param timeout: Timeout for acquiring the locks

    @raise LockAcquireTimeout: In case locks couldn't be acquired in specified

        amount of time

    """

    if self._cbs:

      self._cbs.CheckCancel()

    acquired = self.context.glm.acquire(level, names, shared=shared,

                                        timeout=timeout, priority=priority)

    if acquired is None:

      raise LockAcquireTimeout()

    return acquired

  def _ExecLU(self, lu):

    """Logical Unit execution sequence.

    """

    write_count = self.context.cfg.write_count

    lu.CheckPrereq()

    hm = HooksMaster(self.rpc.call_hooks_runner, lu)

    h_results = hm.RunPhase(constants.HOOKS_PHASE_PRE)

    lu.HooksCallBack(constants.HOOKS_PHASE_PRE, h_results,

                     self.Log, None)

    if getattr(lu.op, "dry_run", False):

      # in this mode, no post-hooks are run, and the config is not

      # written (as it might have been modified by another LU, and we

      # shouldn't do writeout on behalf of other threads

      self.LogInfo("dry-run mode requested, not actually executing"

                   " the operation")

      return lu.dry_run_result

    try:

      result = lu.Exec(self.Log)

      h_results = hm.RunPhase(constants.HOOKS_PHASE_POST)

      result = lu.HooksCallBack(constants.HOOKS_PHASE_POST, h_results,

                                self.Log, result)

    finally:

      # FIXME: This needs locks if not lu_class.REQ_BGL

      if write_count != self.context.cfg.write_count:

        hm.RunConfigUpdate()

    return result

  def _LockAndExecLU(self, lu, level, calc_timeout, priority):

    """Execute a Logical Unit, with the needed locks.

    This is a recursive function that starts locking the given level, and

    proceeds up, till there are no more locks to acquire. Then it executes the

    given LU and its opcodes.

    """

    adding_locks = level in lu.add_locks

    acquiring_locks = level in lu.needed_locks

    if level not in locking.LEVELS:

      if self._cbs:

        self._cbs.NotifyStart()

      result = self._ExecLU(lu)

    elif adding_locks and acquiring_locks:

      # We could both acquire and add locks at the same level, but for now we

      # don't need this, so we'll avoid the complicated code needed.

      raise NotImplementedError("Can't declare locks to acquire when adding"

                                " others")

    elif adding_locks or acquiring_locks:

      lu.DeclareLocks(level)

      share = lu.share_locks[level]

      try:

        assert adding_locks ^ acquiring_locks, \

          "Locks must be either added or acquired"

        if acquiring_locks:

          # Acquiring locks

          needed_locks = lu.needed_locks[level]

          acquired = self._AcquireLocks(level, needed_locks, share,

                                        calc_timeout(), priority)

        else:

          # Adding locks

          add_locks = lu.add_locks[level]

          lu.remove_locks[level] = add_locks

          try:

            self.context.glm.add(level, add_locks, acquired=1, shared=share)

          except errors.LockError:

            raise errors.OpPrereqError(

              "Couldn't add locks (%s), probably because of a race condition"

              " with another job, who added them first" % add_locks,

              errors.ECODE_FAULT)

          acquired = add_locks

        try:

          lu.acquired_locks[level] = acquired

          result = self._LockAndExecLU(lu, level + 1, calc_timeout, priority)

        finally:

          if level in lu.remove_locks:

            self.context.glm.remove(level, lu.remove_locks[level])

      finally:

        if self.context.glm.is_owned(level):

          self.context.glm.release(level)

    else:

      result = self._LockAndExecLU(lu, level + 1, calc_timeout, priority)

    return result

  def ExecOpCode(self, op, cbs, timeout=None, priority=None):

    """Execute an opcode.

    @type op: an OpCode instance

    @param op: the opcode to be executed

    @type cbs: L{OpExecCbBase}

    @param cbs: Runtime callbacks

    @type timeout: float or None

    @param timeout: Maximum time to acquire all locks, None for no timeout

    @type priority: number or None

    @param priority: Priority for acquiring lock(s)

    @raise LockAcquireTimeout: In case locks couldn't be acquired in specified

        amount of time

    """

    if not isinstance(op, opcodes.OpCode):

      raise errors.ProgrammerError("Non-opcode instance passed"

                                   " to ExecOpcode")

    lu_class = self.DISPATCH_TABLE.get(op.__class__, None)

    if lu_class is None:

      raise errors.OpCodeUnknown("Unknown opcode")

    if timeout is None:

      calc_timeout = lambda: None

    else:

      calc_timeout = utils.RunningTimeout(timeout, False).Remaining

    self._cbs = cbs

    try:

      # Acquire the Big Ganeti Lock exclusively if this LU requires it,

      # and in a shared fashion otherwise (to prevent concurrent run with

      # an exclusive LU.

      self._AcquireLocks(locking.LEVEL_CLUSTER, locking.BGL,

                          not lu_class.REQ_BGL, calc_timeout(),

                          priority)

      try:

        lu = lu_class(self, op, self.context, self.rpc)

        lu.ExpandNames()

        assert lu.needed_locks is not None, "needed_locks not set by LU"

        try:

          return self._LockAndExecLU(lu, locking.LEVEL_INSTANCE, calc_timeout,

                                     priority)

        finally:

          if self._ec_id:

            self.context.cfg.DropECReservations(self._ec_id)

      finally:

        self.context.glm.release(locking.LEVEL_CLUSTER)

    finally:

      self._cbs = None

  def Log(self, *args):

    """Forward call to feedback callback function.

    """

    if self._cbs:

      self._cbs.Feedback(*args)

  def LogStep(self, current, total, message):

    """Log a change in LU execution progress.

    """

    logging.debug("Step %d/%d %s", current, total, message)

    self.Log("STEP %d/%d %s" % (current, total, message))

  def LogWarning(self, message, *args, **kwargs):

    """Log a warning to the logs and the user.

    The optional keyword argument is 'hint' and can be used to show a

    hint to the user (presumably related to the warning). If the

    message is empty, it will not be printed at all, allowing one to

    show only a hint.

    """

    assert not kwargs or (len(kwargs) == 1 and "hint" in kwargs), \

           "Invalid keyword arguments for LogWarning (%s)" % str(kwargs)

    if args:

      message = message % tuple(args)

    if message:

      logging.warning(message)

      self.Log(" - WARNING: %s" % message)

    if "hint" in kwargs:

      self.Log("      Hint: %s" % kwargs["hint"])

  def LogInfo(self, message, *args):

    """Log an informational message to the logs and the user.

    """

    if args:

      message = message % tuple(args)

    logging.info(message)

    self.Log(" - INFO: %s" % message)

  def GetECId(self):

    """Returns the current execution context ID.

    """

    if not self._ec_id:

      raise errors.ProgrammerError("Tried to use execution context id when"

                                   " not set")

    return self._ec_id

class HooksMaster(object):

  """Hooks master.

  This class distributes the run commands to the nodes based on the

  specific LU class.

  In order to remove the direct dependency on the rpc module, the

  constructor needs a function which actually does the remote

  call. This will usually be rpc.call_hooks_runner, but any function

  which behaves the same works.

  """

  def __init__(self, callfn, lu):

    self.callfn = callfn

    self.lu = lu

    self.op = lu.op

    self.env, node_list_pre, node_list_post = self._BuildEnv()

    self.node_list = {constants.HOOKS_PHASE_PRE: node_list_pre,

                      constants.HOOKS_PHASE_POST: node_list_post}

  def _BuildEnv(self):

    """Compute the environment and the target nodes.

    Based on the opcode and the current node list, this builds the

    environment for the hooks and the target node list for the run.

    """

    env = {

      "PATH": "/sbin:/bin:/usr/sbin:/usr/bin",

      "GANETI_HOOKS_VERSION": constants.HOOKS_VERSION,

      "GANETI_OP_CODE": self.op.OP_ID,

      "GANETI_OBJECT_TYPE": self.lu.HTYPE,

      "GANETI_DATA_DIR": constants.DATA_DIR,

      }

    if self.lu.HPATH is not None:

      lu_env, lu_nodes_pre, lu_nodes_post = self.lu.BuildHooksEnv()

      if lu_env:

        for key in lu_env:

          env["GANETI_" + key] = lu_env[key]

    else:

      lu_nodes_pre = lu_nodes_post = []

    return env, frozenset(lu_nodes_pre), frozenset(lu_nodes_post)

  def _RunWrapper(self, node_list, hpath, phase):

    """Simple wrapper over self.callfn.

    This method fixes the environment before doing the rpc call.

    """

    env = self.env.copy()

    env["GANETI_HOOKS_PHASE"] = phase

    env["GANETI_HOOKS_PATH"] = hpath

    if self.lu.cfg is not None:

      env["GANETI_CLUSTER"] = self.lu.cfg.GetClusterName()

      env["GANETI_MASTER"] = self.lu.cfg.GetMasterNode()

    env = dict([(str(key), str(val)) for key, val in env.iteritems()])

    return self.callfn(node_list, hpath, phase, env)

  def RunPhase(self, phase, nodes=None):

    """Run all the scripts for a phase.

    This is the main function of the HookMaster.

    @param phase: one of L{constants.HOOKS_PHASE_POST} or

        L{constants.HOOKS_PHASE_PRE}; it denotes the hooks phase

    @param nodes: overrides the predefined list of nodes for the given phase

    @return: the processed results of the hooks multi-node rpc call

    @raise errors.HooksFailure: on communication failure to the nodes

    @raise errors.HooksAbort: on failure of one of the hooks

    """

    if not self.node_list[phase] and not nodes:

      # empty node list, we should not attempt to run this as either

      # we're in the cluster init phase and the rpc client part can't

      # even attempt to run, or this LU doesn't do hooks at all

      return

    hpath = self.lu.HPATH

    if nodes is not None:

      results = self._RunWrapper(nodes, hpath, phase)

    else:

      results = self._RunWrapper(self.node_list[phase], hpath, phase)

    errs = []

    if not results:

      msg = "Communication Failure"

      if phase == constants.HOOKS_PHASE_PRE:

        raise errors.HooksFailure(msg)

      else:

        self.lu.LogWarning(msg)

        return results

    for node_name in results:

      res = results[node_name]

      if res.offline:

        continue

      msg = res.fail_msg

      if msg:

        self.lu.LogWarning("Communication failure to node %s: %s",

                           node_name, msg)

        continue

      for script, hkr, output in res.payload:

        if hkr == constants.HKR_FAIL:

          if phase == constants.HOOKS_PHASE_PRE:

            errs.append((node_name, script, output))

          else:

            if not output:

              output = "(no output)"

            self.lu.LogWarning("On %s script %s failed, output: %s" %

                               (node_name, script, output))

    if errs and phase == constants.HOOKS_PHASE_PRE:

      raise errors.HooksAbort(errs)

    return results

  def RunConfigUpdate(self):

    """Run the special configuration update hook

    This is a special hook that runs only on the master after each

    top-level LI if the configuration has been updated.

    """

    phase = constants.HOOKS_PHASE_POST

    hpath = constants.HOOKS_NAME_CFGUPDATE

    nodes = [self.lu.cfg.GetMasterNode()]

    self._RunWrapper(nodes, hpath, phase)