"""Module implementing the Ganeti locking code."""
+# pylint: disable-msg=W0212
+
+# W0212 since e.g. LockSet methods use (a lot) the internals of
+# SharedLock
+
+import os
+import select
import threading
+import time
+import errno
from ganeti import errors
from ganeti import utils
return wrap
+class RunningTimeout(object):
+ """Class to calculate remaining timeout when doing several operations.
+
+ """
+ __slots__ = [
+ "_allow_negative",
+ "_start_time",
+ "_time_fn",
+ "_timeout",
+ ]
+
+ def __init__(self, timeout, allow_negative, _time_fn=time.time):
+ """Initializes this class.
+
+ @type timeout: float
+ @param timeout: Timeout duration
+ @type allow_negative: bool
+ @param allow_negative: Whether to return values below zero
+ @param _time_fn: Time function for unittests
+
+ """
+ object.__init__(self)
+
+ if timeout is not None and timeout < 0.0:
+ raise ValueError("Timeout must not be negative")
+
+ self._timeout = timeout
+ self._allow_negative = allow_negative
+ self._time_fn = _time_fn
+
+ self._start_time = None
+
+ def Remaining(self):
+ """Returns the remaining timeout.
+
+ """
+ if self._timeout is None:
+ return None
+
+ # Get start time on first calculation
+ if self._start_time is None:
+ self._start_time = self._time_fn()
+
+ # Calculate remaining time
+ remaining_timeout = self._start_time + self._timeout - self._time_fn()
+
+ if not self._allow_negative:
+ # Ensure timeout is always >= 0
+ return max(0.0, remaining_timeout)
+
+ return remaining_timeout
+
+
+class _SingleNotifyPipeConditionWaiter(object):
+ """Helper class for SingleNotifyPipeCondition
+
+ """
+ __slots__ = [
+ "_fd",
+ "_poller",
+ ]
+
+ def __init__(self, poller, fd):
+ """Constructor for _SingleNotifyPipeConditionWaiter
+
+ @type poller: select.poll
+ @param poller: Poller object
+ @type fd: int
+ @param fd: File descriptor to wait for
+
+ """
+ object.__init__(self)
+ self._poller = poller
+ self._fd = fd
+
+ def __call__(self, timeout):
+ """Wait for something to happen on the pipe.
+
+ @type timeout: float or None
+ @param timeout: Timeout for waiting (can be None)
+
+ """
+ running_timeout = RunningTimeout(timeout, True)
+
+ while True:
+ remaining_time = running_timeout.Remaining()
+
+ if remaining_time is not None:
+ if remaining_time < 0.0:
+ break
+
+ # Our calculation uses seconds, poll() wants milliseconds
+ remaining_time *= 1000
+
+ try:
+ result = self._poller.poll(remaining_time)
+ except EnvironmentError, err:
+ if err.errno != errno.EINTR:
+ raise
+ result = None
+
+ # Check whether we were notified
+ if result and result[0][0] == self._fd:
+ break
+
+
+class _BaseCondition(object):
+ """Base class containing common code for conditions.
+
+ Some of this code is taken from python's threading module.
+
+ """
+ __slots__ = [
+ "_lock",
+ "acquire",
+ "release",
+ ]
+
+ def __init__(self, lock):
+ """Constructor for _BaseCondition.
+
+ @type lock: threading.Lock
+ @param lock: condition base lock
+
+ """
+ object.__init__(self)
+
+ # Recursive locks are not supported
+ assert not hasattr(lock, "_acquire_restore")
+ assert not hasattr(lock, "_release_save")
+
+ self._lock = lock
+
+ # Export the lock's acquire() and release() methods
+ self.acquire = lock.acquire
+ self.release = lock.release
+
+ def _is_owned(self):
+ """Check whether lock is owned by current thread.
+
+ """
+ if self._lock.acquire(0):
+ self._lock.release()
+ return False
+
+ return True
+
+ def _check_owned(self):
+ """Raise an exception if the current thread doesn't own the lock.
+
+ """
+ if not self._is_owned():
+ raise RuntimeError("cannot work with un-aquired lock")
+
+
+class SingleNotifyPipeCondition(_BaseCondition):
+ """Condition which can only be notified once.
+
+ This condition class uses pipes and poll, internally, to be able to wait for
+ notification with a timeout, without resorting to polling. It is almost
+ compatible with Python's threading.Condition, with the following differences:
+ - notifyAll can only be called once, and no wait can happen after that
+ - notify is not supported, only notifyAll
+
+ """
+
+ __slots__ = [
+ "_poller",
+ "_read_fd",
+ "_write_fd",
+ "_nwaiters",
+ "_notified",
+ ]
+
+ _waiter_class = _SingleNotifyPipeConditionWaiter
+
+ def __init__(self, lock):
+ """Constructor for SingleNotifyPipeCondition
+
+ """
+ _BaseCondition.__init__(self, lock)
+ self._nwaiters = 0
+ self._notified = False
+ self._read_fd = None
+ self._write_fd = None
+ self._poller = None
+
+ def _check_unnotified(self):
+ """Throws an exception if already notified.
+
+ """
+ if self._notified:
+ raise RuntimeError("cannot use already notified condition")
+
+ def _Cleanup(self):
+ """Cleanup open file descriptors, if any.
+
+ """
+ if self._read_fd is not None:
+ os.close(self._read_fd)
+ self._read_fd = None
+
+ if self._write_fd is not None:
+ os.close(self._write_fd)
+ self._write_fd = None
+ self._poller = None
+
+ def wait(self, timeout=None):
+ """Wait for a notification.
+
+ @type timeout: float or None
+ @param timeout: Waiting timeout (can be None)
+
+ """
+ self._check_owned()
+ self._check_unnotified()
+
+ self._nwaiters += 1
+ try:
+ if self._poller is None:
+ (self._read_fd, self._write_fd) = os.pipe()
+ self._poller = select.poll()
+ self._poller.register(self._read_fd, select.POLLHUP)
+
+ wait_fn = self._waiter_class(self._poller, self._read_fd)
+ self.release()
+ try:
+ # Wait for notification
+ wait_fn(timeout)
+ finally:
+ # Re-acquire lock
+ self.acquire()
+ finally:
+ self._nwaiters -= 1
+ if self._nwaiters == 0:
+ self._Cleanup()
+
+ def notifyAll(self): # pylint: disable-msg=C0103
+ """Close the writing side of the pipe to notify all waiters.
+
+ """
+ self._check_owned()
+ self._check_unnotified()
+ self._notified = True
+ if self._write_fd is not None:
+ os.close(self._write_fd)
+ self._write_fd = None
+
+
+class PipeCondition(_BaseCondition):
+ """Group-only non-polling condition with counters.
+
+ This condition class uses pipes and poll, internally, to be able to wait for
+ notification with a timeout, without resorting to polling. It is almost
+ compatible with Python's threading.Condition, but only supports notifyAll and
+ non-recursive locks. As an additional features it's able to report whether
+ there are any waiting threads.
+
+ """
+ __slots__ = [
+ "_nwaiters",
+ "_single_condition",
+ ]
+
+ _single_condition_class = SingleNotifyPipeCondition
+
+ def __init__(self, lock):
+ """Initializes this class.
+
+ """
+ _BaseCondition.__init__(self, lock)
+ self._nwaiters = 0
+ self._single_condition = self._single_condition_class(self._lock)
+
+ def wait(self, timeout=None):
+ """Wait for a notification.
+
+ @type timeout: float or None
+ @param timeout: Waiting timeout (can be None)
+
+ """
+ self._check_owned()
+
+ # Keep local reference to the pipe. It could be replaced by another thread
+ # notifying while we're waiting.
+ my_condition = self._single_condition
+
+ assert self._nwaiters >= 0
+ self._nwaiters += 1
+ try:
+ my_condition.wait(timeout)
+ finally:
+ assert self._nwaiters > 0
+ self._nwaiters -= 1
+
+ def notifyAll(self): # pylint: disable-msg=C0103
+ """Notify all currently waiting threads.
+
+ """
+ self._check_owned()
+ self._single_condition.notifyAll()
+ self._single_condition = self._single_condition_class(self._lock)
+
+ def has_waiting(self):
+ """Returns whether there are active waiters.
+
+ """
+ self._check_owned()
+
+ return bool(self._nwaiters)
+
+
class _CountingCondition(object):
"""Wrapper for Python's built-in threading.Condition class.
self._cond = threading.Condition(lock=lock)
self._nwaiters = 0
- def notifyAll(self):
+ def notifyAll(self): # pylint: disable-msg=C0103
"""Notifies the condition.
"""
"""Waits for the condition to be notified.
@type timeout: float or None
- @param timeout: Timeout in seconds
+ @param timeout: Waiting timeout (can be None)
"""
assert self._nwaiters >= 0
"__shr",
]
- __condition_class = _CountingCondition
+ __condition_class = PipeCondition
def __init__(self):
"""Construct a new SharedLock.
"""
return self.__pending[0] == cond
- def __acquire_unlocked(self, shared=0, timeout=None):
+ def __acquire_unlocked(self, shared, timeout):
"""Acquire a shared lock.
@param shared: whether to acquire in shared mode; by default an
return False
- def acquire(self, shared=0, timeout=None):
+ def acquire(self, shared=0, timeout=None, test_notify=None):
"""Acquire a shared lock.
- @type shared: int
+ @type shared: integer (0/1) used as a boolean
@param shared: whether to acquire in shared mode; by default an
exclusive lock will be acquired
@type timeout: float
@param timeout: maximum waiting time before giving up
+ @type test_notify: callable or None
+ @param test_notify: Special callback function for unittesting
"""
self.__lock.acquire()
try:
+ # We already got the lock, notify now
+ if __debug__ and callable(test_notify):
+ test_notify()
+
return self.__acquire_unlocked(shared, timeout)
finally:
self.__lock.release()
acquired = self.__is_exclusive()
if not acquired:
- acquired = self.__acquire_unlocked(timeout)
+ acquired = self.__acquire_unlocked(0, timeout)
+
+ assert self.__is_exclusive() and not self.__is_sharer(), \
+ "Lock wasn't acquired in exclusive mode"
if acquired:
self.__deleted = True
ALL_SET = None
+class _AcquireTimeout(Exception):
+ """Internal exception to abort an acquire on a timeout.
+
+ """
+
+
class LockSet:
"""Implements a set of locks.
def __init__(self, members=None):
"""Constructs a new LockSet.
+ @type members: list of strings
@param members: initial members of the set
"""
def _del_owned(self, name=None):
"""Note the current thread owns the given lock"""
+ assert not (name is None and self.__lock._is_owned()), \
+ "Cannot hold internal lock when deleting owner status"
+
if name is not None:
self.__owners[threading.currentThread()].remove(name)
else:
return set()
+ def _release_and_delete_owned(self):
+ """Release and delete all resources owned by the current thread"""
+ for lname in self._list_owned():
+ lock = self.__lockdict[lname]
+ if lock._is_owned():
+ lock.release()
+ self._del_owned(name=lname)
+
def __names(self):
"""Return the current set of names.
self.__lock.release()
return set(result)
- def acquire(self, names, blocking=1, shared=0):
+ def acquire(self, names, timeout=None, shared=0, test_notify=None):
"""Acquire a set of resource locks.
+ @type names: list of strings (or string)
@param names: the names of the locks which shall be acquired
(special lock names, or instance/node names)
+ @type shared: integer (0/1) used as a boolean
@param shared: whether to acquire in shared mode; by default an
exclusive lock will be acquired
- @param blocking: whether to block while trying to acquire or to
- operate in try-lock mode (this locking mode is not supported yet)
+ @type timeout: float or None
+ @param timeout: Maximum time to acquire all locks
+ @type test_notify: callable or None
+ @param test_notify: Special callback function for unittesting
- @return: True when all the locks are successfully acquired
+ @return: Set of all locks successfully acquired or None in case of timeout
@raise errors.LockError: when any lock we try to acquire has
been deleted before we succeed. In this case none of the
locks requested will be acquired.
"""
- if not blocking:
- # We don't have non-blocking mode for now
- raise NotImplementedError
+ assert timeout is None or timeout >= 0.0
# Check we don't already own locks at this level
assert not self._is_owned(), "Cannot acquire locks in the same set twice"
- if names is None:
- # If no names are given acquire the whole set by not letting new names
- # being added before we release, and getting the current list of names.
- # Some of them may then be deleted later, but we'll cope with this.
- #
- # We'd like to acquire this lock in a shared way, as it's nice if
- # everybody else can use the instances at the same time. If are acquiring
- # them exclusively though they won't be able to do this anyway, though,
- # so we'll get the list lock exclusively as well in order to be able to
- # do add() on the set while owning it.
- self.__lock.acquire(shared=shared)
- try:
- # note we own the set-lock
- self._add_owned()
- names = self.__names()
- except:
- # We shouldn't have problems adding the lock to the owners list, but
- # if we did we'll try to release this lock and re-raise exception.
- # Of course something is going to be really wrong, after this.
- self.__lock.release()
- raise
+ # We need to keep track of how long we spent waiting for a lock. The
+ # timeout passed to this function is over all lock acquires.
+ running_timeout = RunningTimeout(timeout, False)
try:
- # Support passing in a single resource to acquire rather than many
- if isinstance(names, basestring):
- names = [names]
+ if names is not None:
+ # Support passing in a single resource to acquire rather than many
+ if isinstance(names, basestring):
+ names = [names]
+
+ return self.__acquire_inner(names, False, shared,
+ running_timeout.Remaining, test_notify)
+
else:
- names = sorted(names)
+ # If no names are given acquire the whole set by not letting new names
+ # being added before we release, and getting the current list of names.
+ # Some of them may then be deleted later, but we'll cope with this.
+ #
+ # We'd like to acquire this lock in a shared way, as it's nice if
+ # everybody else can use the instances at the same time. If are
+ # acquiring them exclusively though they won't be able to do this
+ # anyway, though, so we'll get the list lock exclusively as well in
+ # order to be able to do add() on the set while owning it.
+ if not self.__lock.acquire(shared=shared,
+ timeout=running_timeout.Remaining()):
+ raise _AcquireTimeout()
+ try:
+ # note we own the set-lock
+ self._add_owned()
+
+ return self.__acquire_inner(self.__names(), True, shared,
+ running_timeout.Remaining, test_notify)
+ except:
+ # We shouldn't have problems adding the lock to the owners list, but
+ # if we did we'll try to release this lock and re-raise exception.
+ # Of course something is going to be really wrong, after this.
+ self.__lock.release()
+ self._del_owned()
+ raise
+
+ except _AcquireTimeout:
+ return None
+
+ def __acquire_inner(self, names, want_all, shared, timeout_fn, test_notify):
+ """Inner logic for acquiring a number of locks.
+
+ @param names: Names of the locks to be acquired
+ @param want_all: Whether all locks in the set should be acquired
+ @param shared: Whether to acquire in shared mode
+ @param timeout_fn: Function returning remaining timeout
+ @param test_notify: Special callback function for unittesting
+
+ """
+ acquire_list = []
+
+ # First we look the locks up on __lockdict. We have no way of being sure
+ # they will still be there after, but this makes it a lot faster should
+ # just one of them be the already wrong. Using a sorted sequence to prevent
+ # deadlocks.
+ for lname in sorted(utils.UniqueSequence(names)):
+ try:
+ lock = self.__lockdict[lname] # raises KeyError if lock is not there
+ except KeyError:
+ if want_all:
+ # We are acquiring all the set, it doesn't matter if this particular
+ # element is not there anymore.
+ continue
+
+ raise errors.LockError("Non-existing lock in set (%s)" % lname)
+
+ acquire_list.append((lname, lock))
+
+ # This will hold the locknames we effectively acquired.
+ acquired = set()
+
+ try:
+ # Now acquire_list contains a sorted list of resources and locks we
+ # want. In order to get them we loop on this (private) list and
+ # acquire() them. We gave no real guarantee they will still exist till
+ # this is done but .acquire() itself is safe and will alert us if the
+ # lock gets deleted.
+ for (lname, lock) in acquire_list:
+ if __debug__ and callable(test_notify):
+ test_notify_fn = lambda: test_notify(lname)
+ else:
+ test_notify_fn = None
+
+ timeout = timeout_fn()
- acquire_list = []
- # First we look the locks up on __lockdict. We have no way of being sure
- # they will still be there after, but this makes it a lot faster should
- # just one of them be the already wrong
- for lname in utils.UniqueSequence(names):
try:
- lock = self.__lockdict[lname] # raises KeyError if lock is not there
- acquire_list.append((lname, lock))
- except (KeyError):
- if self.__lock._is_owned():
+ # raises LockError if the lock was deleted
+ acq_success = lock.acquire(shared=shared, timeout=timeout,
+ test_notify=test_notify_fn)
+ except errors.LockError:
+ if want_all:
# We are acquiring all the set, it doesn't matter if this
# particular element is not there anymore.
continue
- else:
- raise errors.LockError('non-existing lock in set (%s)' % lname)
-
- # This will hold the locknames we effectively acquired.
- acquired = set()
- # Now acquire_list contains a sorted list of resources and locks we want.
- # In order to get them we loop on this (private) list and acquire() them.
- # We gave no real guarantee they will still exist till this is done but
- # .acquire() itself is safe and will alert us if the lock gets deleted.
- for (lname, lock) in acquire_list:
+
+ raise errors.LockError("Non-existing lock in set (%s)" % lname)
+
+ if not acq_success:
+ # Couldn't get lock or timeout occurred
+ if timeout is None:
+ # This shouldn't happen as SharedLock.acquire(timeout=None) is
+ # blocking.
+ raise errors.LockError("Failed to get lock %s" % lname)
+
+ raise _AcquireTimeout()
+
try:
- lock.acquire(shared=shared) # raises LockError if the lock is deleted
# now the lock cannot be deleted, we have it!
self._add_owned(name=lname)
acquired.add(lname)
- except (errors.LockError):
- if self.__lock._is_owned():
- # We are acquiring all the set, it doesn't matter if this
- # particular element is not there anymore.
- continue
- else:
- name_fail = lname
- for lname in self._list_owned():
- self.__lockdict[lname].release()
- self._del_owned(name=lname)
- raise errors.LockError('non-existing lock in set (%s)' % name_fail)
+
except:
# We shouldn't have problems adding the lock to the owners list, but
# if we did we'll try to release this lock and re-raise exception.
- # Of course something is going to be really wrong, after this.
+ # Of course something is going to be really wrong after this.
if lock._is_owned():
lock.release()
raise
except:
- # If something went wrong and we had the set-lock let's release it...
- if self.__lock._is_owned():
- self.__lock.release()
+ # Release all owned locks
+ self._release_and_delete_owned()
raise
return acquired
You must have acquired the locks, either in shared or in exclusive mode,
before releasing them.
+ @type names: list of strings, or None
@param names: the names of the locks which shall be released
(defaults to all the locks acquired at that level).
def add(self, names, acquired=0, shared=0):
"""Add a new set of elements to the set
+ @type names: list of strings
@param names: names of the new elements to add
+ @type acquired: integer (0/1) used as a boolean
@param acquired: pre-acquire the new resource?
+ @type shared: integer (0/1) used as a boolean
@param shared: is the pre-acquisition shared?
"""
return True
- def remove(self, names, blocking=1):
+ def remove(self, names):
"""Remove elements from the lock set.
You can either not hold anything in the lockset or already hold a superset
of the elements you want to delete, exclusively.
+ @type names: list of strings
@param names: names of the resource to remove.
- @param blocking: whether to block while trying to acquire or to
- operate in try-lock mode (this locking mode is not supported
- yet unless you are already holding exclusively the locks)
- @return:: a list of locks which we removed; the list is always
+ @return: a list of locks which we removed; the list is always
equal to the names list if we were holding all the locks
exclusively
"""
- if not blocking and not self._is_owned():
- # We don't have non-blocking mode for now
- raise NotImplementedError
-
# Support passing in a single resource to remove rather than many
if isinstance(names, basestring):
names = [names]
# the test cases.
return utils.any((self._is_owned(l) for l in LEVELS[level + 1:]))
- def _BGL_owned(self):
+ def _BGL_owned(self): # pylint: disable-msg=C0103
"""Check if the current thread owns the BGL.
Both an exclusive or a shared acquisition work.
"""
return BGL in self.__keyring[LEVEL_CLUSTER]._list_owned()
- def _contains_BGL(self, level, names):
+ @staticmethod
+ def _contains_BGL(level, names): # pylint: disable-msg=C0103
"""Check if the level contains the BGL.
Check if acting on the given level and set of names will change
"""
return level == LEVEL_CLUSTER and (names is None or BGL in names)
- def acquire(self, level, names, blocking=1, shared=0):
+ def acquire(self, level, names, timeout=None, shared=0):
"""Acquire a set of resource locks, at the same level.
- @param level: the level at which the locks shall be acquired;
- it must be a member of LEVELS.
+ @type level: member of locking.LEVELS
+ @param level: the level at which the locks shall be acquired
+ @type names: list of strings (or string)
@param names: the names of the locks which shall be acquired
(special lock names, or instance/node names)
+ @type shared: integer (0/1) used as a boolean
@param shared: whether to acquire in shared mode; by default
an exclusive lock will be acquired
- @param blocking: whether to block while trying to acquire or to
- operate in try-lock mode (this locking mode is not supported yet)
+ @type timeout: float
+ @param timeout: Maximum time to acquire all locks
"""
assert level in LEVELS, "Invalid locking level %s" % level
" while owning some at a greater one")
# Acquire the locks in the set.
- return self.__keyring[level].acquire(names, shared=shared,
- blocking=blocking)
+ return self.__keyring[level].acquire(names, shared=shared, timeout=timeout)
def release(self, level, names=None):
"""Release a set of resource locks, at the same level.
You must have acquired the locks, either in shared or in exclusive
mode, before releasing them.
- @param level: the level at which the locks shall be released;
- it must be a member of LEVELS
+ @type level: member of locking.LEVELS
+ @param level: the level at which the locks shall be released
+ @type names: list of strings, or None
@param names: the names of the locks which shall be released
(defaults to all the locks acquired at that level)
assert (not self._contains_BGL(level, names) or
not self._upper_owned(LEVEL_CLUSTER)), (
"Cannot release the Big Ganeti Lock while holding something"
- " at upper levels")
+ " at upper levels (%r)" %
+ (utils.CommaJoin(["%s=%r" % (LEVEL_NAMES[i], self._list_owned(i))
+ for i in self.__keyring.keys()]), ))
# Release will complain if we don't own the locks already
return self.__keyring[level].release(names)
def add(self, level, names, acquired=0, shared=0):
"""Add locks at the specified level.
- @param level: the level at which the locks shall be added;
- it must be a member of LEVELS_MOD.
+ @type level: member of locking.LEVELS_MOD
+ @param level: the level at which the locks shall be added
+ @type names: list of strings
@param names: names of the locks to acquire
+ @type acquired: integer (0/1) used as a boolean
@param acquired: whether to acquire the newly added locks
+ @type shared: integer (0/1) used as a boolean
@param shared: whether the acquisition will be shared
"""
" while owning some at a greater one")
return self.__keyring[level].add(names, acquired=acquired, shared=shared)
- def remove(self, level, names, blocking=1):
+ def remove(self, level, names):
"""Remove locks from the specified level.
You must either already own the locks you are trying to remove
exclusively or not own any lock at an upper level.
- @param level: the level at which the locks shall be removed;
- it must be a member of LEVELS_MOD
+ @type level: member of locking.LEVELS_MOD
+ @param level: the level at which the locks shall be removed
+ @type names: list of strings
@param names: the names of the locks which shall be removed
(special lock names, or instance/node names)
- @param blocking: whether to block while trying to operate in
- try-lock mode (this locking mode is not supported yet)
"""
assert level in LEVELS_MOD, "Invalid or immutable level %s" % level
assert self._is_owned(level) or not self._upper_owned(level), (
"Cannot remove locks at a level while not owning it or"
" owning some at a greater one")
- return self.__keyring[level].remove(names, blocking=blocking)
+ return self.__keyring[level].remove(names)
projects / ganeti-local / blobdiff