#
#
-# Copyright (C) 2006, 2007 Google Inc.
+# Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 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
"""Module implementing the Ganeti locking code."""
+# pylint: disable=W0212
+
+# W0212 since e.g. LockSet methods use (a lot) the internals of
+# SharedLock
+
+import os
+import select
import threading
+import errno
+import weakref
+import logging
+import heapq
+import itertools
+import time
from ganeti import errors
from ganeti import utils
+from ganeti import compat
+from ganeti import query
+
+_EXCLUSIVE_TEXT = "exclusive"
+_SHARED_TEXT = "shared"
+_DELETED_TEXT = "deleted"
-def ssynchronized(lock, shared=0):
+_DEFAULT_PRIORITY = 0
+
+
+def ssynchronized(mylock, shared=0):
"""Shared Synchronization decorator.
Calls the function holding the given lock, either in exclusive or shared
mode. It requires the passed lock to be a SharedLock (or support its
semantics).
+ @type mylock: lockable object or string
+ @param mylock: lock to acquire or class member name of the lock to acquire
+
"""
def wrap(fn):
def sync_function(*args, **kwargs):
+ if isinstance(mylock, basestring):
+ assert args, "cannot ssynchronize on non-class method: self not found"
+ # args[0] is "self"
+ lock = getattr(args[0], mylock)
+ else:
+ lock = mylock
lock.acquire(shared=shared)
try:
return fn(*args, **kwargs)
return wrap
-class _CountingCondition(object):
- """Wrapper for Python's built-in threading.Condition class.
+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 = utils.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
- This wrapper keeps a count of active waiters. We can't access the internal
- "__waiters" attribute of threading.Condition because it's not thread-safe.
+ # 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__ = [
- "_cond",
- "_nwaiters",
+ "_lock",
+ "acquire",
+ "release",
+ "_is_owned",
+ "_acquire_restore",
+ "_release_save",
]
def __init__(self, lock):
- """Initializes this class.
+ """Constructor for _BaseCondition.
+
+ @type lock: threading.Lock
+ @param lock: condition base lock
"""
object.__init__(self)
- self._cond = threading.Condition(lock=lock)
+
+ try:
+ self._release_save = lock._release_save
+ except AttributeError:
+ self._release_save = self._base_release_save
+ try:
+ self._acquire_restore = lock._acquire_restore
+ except AttributeError:
+ self._acquire_restore = self._base_acquire_restore
+ try:
+ self._is_owned = lock.is_owned
+ except AttributeError:
+ self._is_owned = self._base_is_owned
+
+ self._lock = lock
+
+ # Export the lock's acquire() and release() methods
+ self.acquire = lock.acquire
+ self.release = lock.release
+
+ def _base_is_owned(self):
+ """Check whether lock is owned by current thread.
+
+ """
+ if self._lock.acquire(0):
+ self._lock.release()
+ return False
+ return True
+
+ def _base_release_save(self):
+ self._lock.release()
+
+ def _base_acquire_restore(self, _):
+ self._lock.acquire()
+
+ 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 notifyAll(self):
- """Notifies the condition.
+ def _Cleanup(self):
+ """Cleanup open file descriptors, if any.
"""
- return self._cond.notifyAll()
+ if self._read_fd is not None:
+ os.close(self._read_fd)
+ self._read_fd = None
- def wait(self, timeout=None):
- """Waits for the condition to be notified.
+ if self._write_fd is not None:
+ os.close(self._write_fd)
+ self._write_fd = None
+ self._poller = None
+
+ def wait(self, timeout):
+ """Wait for a notification.
@type timeout: float or None
- @param timeout: Timeout in seconds
+ @param timeout: Waiting timeout (can be None)
"""
- assert self._nwaiters >= 0
+ self._check_owned()
+ self._check_unnotified()
self._nwaiters += 1
try:
- return self._cond.wait(timeout=timeout)
+ 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)
+ state = self._release_save()
+ try:
+ # Wait for notification
+ wait_fn(timeout)
+ finally:
+ # Re-acquire lock
+ self._acquire_restore(state)
finally:
self._nwaiters -= 1
+ if self._nwaiters == 0:
+ self._Cleanup()
+
+ def notifyAll(self): # pylint: disable=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__ = [
+ "_waiters",
+ "_single_condition",
+ ]
+
+ _single_condition_class = SingleNotifyPipeCondition
+
+ def __init__(self, lock):
+ """Initializes this class.
+
+ """
+ _BaseCondition.__init__(self, lock)
+ self._waiters = set()
+ self._single_condition = self._single_condition_class(self._lock)
+
+ def wait(self, timeout):
+ """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.
+ cond = self._single_condition
+
+ self._waiters.add(threading.currentThread())
+ try:
+ cond.wait(timeout)
+ finally:
+ self._check_owned()
+ self._waiters.remove(threading.currentThread())
+
+ def notifyAll(self): # pylint: disable=C0103
+ """Notify all currently waiting threads.
+
+ """
+ self._check_owned()
+ self._single_condition.notifyAll()
+ self._single_condition = self._single_condition_class(self._lock)
+
+ def get_waiting(self):
+ """Returns a list of all waiting threads.
+
+ """
+ self._check_owned()
+
+ return self._waiters
def has_waiting(self):
"""Returns whether there are active waiters.
"""
- return bool(self._nwaiters)
+ self._check_owned()
+
+ return bool(self._waiters)
+
+ def __repr__(self):
+ return ("<%s.%s waiters=%s at %#x>" %
+ (self.__class__.__module__, self.__class__.__name__,
+ self._waiters, id(self)))
+
+
+class _PipeConditionWithMode(PipeCondition):
+ __slots__ = [
+ "shared",
+ ]
+
+ def __init__(self, lock, shared):
+ """Initializes this class.
+
+ """
+ self.shared = shared
+ PipeCondition.__init__(self, lock)
class SharedLock(object):
"""Implements a shared lock.
- Multiple threads can acquire the lock in a shared way, calling
- acquire_shared(). In order to acquire the lock in an exclusive way threads
- can call acquire_exclusive().
+ Multiple threads can acquire the lock in a shared way by calling
+ C{acquire(shared=1)}. In order to acquire the lock in an exclusive way
+ threads can call C{acquire(shared=0)}.
+
+ Notes on data structures: C{__pending} contains a priority queue (heapq) of
+ all pending acquires: C{[(priority1: prioqueue1), (priority2: prioqueue2),
+ ...]}. Each per-priority queue contains a normal in-order list of conditions
+ to be notified when the lock can be acquired. Shared locks are grouped
+ together by priority and the condition for them is stored in
+ C{__pending_shared} if it already exists. C{__pending_by_prio} keeps
+ references for the per-priority queues indexed by priority for faster access.
- The lock prevents starvation but does not guarantee that threads will acquire
- the shared lock in the order they queued for it, just that they will
- eventually do so.
+ @type name: string
+ @ivar name: the name of the lock
"""
__slots__ = [
- "__active_shr_c",
- "__inactive_shr_c",
+ "__weakref__",
"__deleted",
"__exc",
"__lock",
"__pending",
+ "__pending_by_prio",
+ "__pending_shared",
"__shr",
+ "__time_fn",
+ "name",
]
- __condition_class = _CountingCondition
+ __condition_class = _PipeConditionWithMode
- def __init__(self):
+ def __init__(self, name, monitor=None, _time_fn=time.time):
"""Construct a new SharedLock.
+ @param name: the name of the lock
+ @type monitor: L{LockMonitor}
+ @param monitor: Lock monitor with which to register
+
"""
object.__init__(self)
+ self.name = name
+
+ # Used for unittesting
+ self.__time_fn = _time_fn
+
# Internal lock
self.__lock = threading.Lock()
# Queue containing waiting acquires
self.__pending = []
-
- # Active and inactive conditions for shared locks
- self.__active_shr_c = self.__condition_class(self.__lock)
- self.__inactive_shr_c = self.__condition_class(self.__lock)
+ self.__pending_by_prio = {}
+ self.__pending_shared = {}
# Current lock holders
self.__shr = set()
# is this lock in the deleted state?
self.__deleted = False
+ # Register with lock monitor
+ if monitor:
+ logging.debug("Adding lock %s to monitor", name)
+ monitor.RegisterLock(self)
+
+ def __repr__(self):
+ return ("<%s.%s name=%s at %#x>" %
+ (self.__class__.__module__, self.__class__.__name__,
+ self.name, id(self)))
+
+ def GetLockInfo(self, requested):
+ """Retrieves information for querying locks.
+
+ @type requested: set
+ @param requested: Requested information, see C{query.LQ_*}
+
+ """
+ self.__lock.acquire()
+ try:
+ # Note: to avoid unintentional race conditions, no references to
+ # modifiable objects should be returned unless they were created in this
+ # function.
+ mode = None
+ owner_names = None
+
+ if query.LQ_MODE in requested:
+ if self.__deleted:
+ mode = _DELETED_TEXT
+ assert not (self.__exc or self.__shr)
+ elif self.__exc:
+ mode = _EXCLUSIVE_TEXT
+ elif self.__shr:
+ mode = _SHARED_TEXT
+
+ # Current owner(s) are wanted
+ if query.LQ_OWNER in requested:
+ if self.__exc:
+ owner = [self.__exc]
+ else:
+ owner = self.__shr
+
+ if owner:
+ assert not self.__deleted
+ owner_names = [i.getName() for i in owner]
+
+ # Pending acquires are wanted
+ if query.LQ_PENDING in requested:
+ pending = []
+
+ # Sorting instead of copying and using heaq functions for simplicity
+ for (_, prioqueue) in sorted(self.__pending):
+ for cond in prioqueue:
+ if cond.shared:
+ pendmode = _SHARED_TEXT
+ else:
+ pendmode = _EXCLUSIVE_TEXT
+
+ # List of names will be sorted in L{query._GetLockPending}
+ pending.append((pendmode, [i.getName()
+ for i in cond.get_waiting()]))
+ else:
+ pending = None
+
+ return [(self.name, mode, owner_names, pending)]
+ finally:
+ self.__lock.release()
+
def __check_deleted(self):
"""Raises an exception if the lock has been deleted.
"""
if self.__deleted:
- raise errors.LockError("Deleted lock")
+ raise errors.LockError("Deleted lock %s" % self.name)
def __is_sharer(self):
"""Is the current thread sharing the lock at this time?
else:
return self.__is_exclusive()
- def _is_owned(self, shared=-1):
+ def is_owned(self, shared=-1):
"""Is the current thread somehow owning the lock at this time?
@param shared:
finally:
self.__lock.release()
+ #: Necessary to remain compatible with threading.Condition, which tries to
+ #: retrieve a locks' "_is_owned" attribute
+ _is_owned = is_owned
+
def _count_pending(self):
"""Returns the number of pending acquires.
"""
self.__lock.acquire()
try:
- return len(self.__pending)
+ return sum(len(prioqueue) for (_, prioqueue) in self.__pending)
+ finally:
+ self.__lock.release()
+
+ def _check_empty(self):
+ """Checks whether there are any pending acquires.
+
+ @rtype: bool
+
+ """
+ self.__lock.acquire()
+ try:
+ # Order is important: __find_first_pending_queue modifies __pending
+ (_, prioqueue) = self.__find_first_pending_queue()
+
+ return not (prioqueue or
+ self.__pending or
+ self.__pending_by_prio or
+ self.__pending_shared)
finally:
self.__lock.release()
else:
return len(self.__shr) == 0 and self.__exc is None
+ def __find_first_pending_queue(self):
+ """Tries to find the topmost queued entry with pending acquires.
+
+ Removes empty entries while going through the list.
+
+ """
+ while self.__pending:
+ (priority, prioqueue) = self.__pending[0]
+
+ if prioqueue:
+ return (priority, prioqueue)
+
+ # Remove empty queue
+ heapq.heappop(self.__pending)
+ del self.__pending_by_prio[priority]
+ assert priority not in self.__pending_shared
+
+ return (None, None)
+
def __is_on_top(self, cond):
"""Checks whether the passed condition is on top of the queue.
The caller must make sure the queue isn't empty.
"""
- return self.__pending[0] == cond
+ (_, prioqueue) = self.__find_first_pending_queue()
- def __acquire_unlocked(self, shared=0, timeout=None):
+ return cond == prioqueue[0]
+
+ def __acquire_unlocked(self, shared, timeout, priority):
"""Acquire a shared lock.
@param shared: whether to acquire in shared mode; by default an
exclusive lock will be acquired
@param timeout: maximum waiting time before giving up
+ @type priority: integer
+ @param priority: Priority for acquiring lock
"""
self.__check_deleted()
# We cannot acquire the lock if we already have it
- assert not self.__is_owned(), "double acquire() on a non-recursive lock"
+ assert not self.__is_owned(), ("double acquire() on a non-recursive lock"
+ " %s" % self.name)
+
+ # Remove empty entries from queue
+ self.__find_first_pending_queue()
# Check whether someone else holds the lock or there are pending acquires.
if not self.__pending and self.__can_acquire(shared):
self.__do_acquire(shared)
return True
- if shared:
- wait_condition = self.__active_shr_c
+ prioqueue = self.__pending_by_prio.get(priority, None)
- # Check if we're not yet in the queue
- if wait_condition not in self.__pending:
- self.__pending.append(wait_condition)
+ if shared:
+ # Try to re-use condition for shared acquire
+ wait_condition = self.__pending_shared.get(priority, None)
+ assert (wait_condition is None or
+ (wait_condition.shared and wait_condition in prioqueue))
else:
- wait_condition = self.__condition_class(self.__lock)
- # Always add to queue
- self.__pending.append(wait_condition)
+ wait_condition = None
+
+ if wait_condition is None:
+ if prioqueue is None:
+ assert priority not in self.__pending_by_prio
+
+ prioqueue = []
+ heapq.heappush(self.__pending, (priority, prioqueue))
+ self.__pending_by_prio[priority] = prioqueue
+
+ wait_condition = self.__condition_class(self.__lock, shared)
+ prioqueue.append(wait_condition)
+
+ if shared:
+ # Keep reference for further shared acquires on same priority. This is
+ # better than trying to find it in the list of pending acquires.
+ assert priority not in self.__pending_shared
+ self.__pending_shared[priority] = wait_condition
+
+ wait_start = self.__time_fn()
+ acquired = False
try:
# Wait until we become the topmost acquire in the queue or the timeout
# expires.
- while not (self.__is_on_top(wait_condition) and
- self.__can_acquire(shared)):
- # Wait for notification
- wait_condition.wait(timeout)
- self.__check_deleted()
+ while True:
+ if self.__is_on_top(wait_condition) and self.__can_acquire(shared):
+ self.__do_acquire(shared)
+ acquired = True
+ break
- # A lot of code assumes blocking acquires always succeed. Loop
- # internally for that case.
- if timeout is not None:
+ # A lot of code assumes blocking acquires always succeed, therefore we
+ # can never return False for a blocking acquire
+ if (timeout is not None and
+ utils.TimeoutExpired(wait_start, timeout, _time_fn=self.__time_fn)):
break
- if self.__is_on_top(wait_condition) and self.__can_acquire(shared):
- self.__do_acquire(shared)
- return True
+ # Wait for notification
+ wait_condition.wait(timeout)
+ self.__check_deleted()
finally:
# Remove condition from queue if there are no more waiters
- if not wait_condition.has_waiting() and not self.__deleted:
- self.__pending.remove(wait_condition)
+ if not wait_condition.has_waiting():
+ prioqueue.remove(wait_condition)
+ if wait_condition.shared:
+ # Remove from list of shared acquires if it wasn't while releasing
+ # (e.g. on lock deletion)
+ self.__pending_shared.pop(priority, None)
- return False
+ return acquired
- def acquire(self, shared=0, timeout=None):
+ def acquire(self, shared=0, timeout=None, priority=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 priority: integer
+ @param priority: Priority for acquiring lock
+ @type test_notify: callable or None
+ @param test_notify: Special callback function for unittesting
"""
+ if priority is None:
+ priority = _DEFAULT_PRIORITY
+
self.__lock.acquire()
try:
- return self.__acquire_unlocked(shared, timeout)
+ # We already got the lock, notify now
+ if __debug__ and callable(test_notify):
+ test_notify()
+
+ return self.__acquire_unlocked(shared, timeout, priority)
+ finally:
+ self.__lock.release()
+
+ def downgrade(self):
+ """Changes the lock mode from exclusive to shared.
+
+ Pending acquires in shared mode on the same priority will go ahead.
+
+ """
+ self.__lock.acquire()
+ try:
+ assert self.__is_owned(), "Lock must be owned"
+
+ if self.__is_exclusive():
+ # Do nothing if the lock is already acquired in shared mode
+ self.__exc = None
+ self.__do_acquire(1)
+
+ # Important: pending shared acquires should only jump ahead if there
+ # was a transition from exclusive to shared, otherwise an owner of a
+ # shared lock can keep calling this function to push incoming shared
+ # acquires
+ (priority, prioqueue) = self.__find_first_pending_queue()
+ if prioqueue:
+ # Is there a pending shared acquire on this priority?
+ cond = self.__pending_shared.pop(priority, None)
+ if cond:
+ assert cond.shared
+ assert cond in prioqueue
+
+ # Ensure shared acquire is on top of queue
+ if len(prioqueue) > 1:
+ prioqueue.remove(cond)
+ prioqueue.insert(0, cond)
+
+ # Notify
+ cond.notifyAll()
+
+ assert not self.__is_exclusive()
+ assert self.__is_sharer()
+
+ return True
finally:
self.__lock.release()
# Autodetect release type
if self.__is_exclusive():
self.__exc = None
+ notify = True
else:
self.__shr.remove(threading.currentThread())
+ notify = not self.__shr
- # Notify topmost condition in queue
- if self.__pending:
- first_condition = self.__pending[0]
- first_condition.notifyAll()
+ # Notify topmost condition in queue if there are no owners left (for
+ # shared locks)
+ if notify:
+ self.__notify_topmost()
+ finally:
+ self.__lock.release()
- if first_condition == self.__active_shr_c:
- self.__active_shr_c = self.__inactive_shr_c
- self.__inactive_shr_c = first_condition
+ def __notify_topmost(self):
+ """Notifies topmost condition in queue of pending acquires.
+ """
+ (priority, prioqueue) = self.__find_first_pending_queue()
+ if prioqueue:
+ cond = prioqueue[0]
+ cond.notifyAll()
+ if cond.shared:
+ # Prevent further shared acquires from sneaking in while waiters are
+ # notified
+ self.__pending_shared.pop(priority, None)
+
+ def _notify_topmost(self):
+ """Exported version of L{__notify_topmost}.
+
+ """
+ self.__lock.acquire()
+ try:
+ return self.__notify_topmost()
finally:
self.__lock.release()
- def delete(self, timeout=None):
+ def delete(self, timeout=None, priority=None):
"""Delete a Shared Lock.
This operation will declare the lock for removal. First the lock will be
@type timeout: float
@param timeout: maximum waiting time before giving up
+ @type priority: integer
+ @param priority: Priority for acquiring lock
"""
+ if priority is None:
+ priority = _DEFAULT_PRIORITY
+
self.__lock.acquire()
try:
assert not self.__is_sharer(), "Cannot delete() a lock while sharing it"
acquired = self.__is_exclusive()
if not acquired:
- acquired = self.__acquire_unlocked(timeout)
+ acquired = self.__acquire_unlocked(0, timeout, priority)
if acquired:
+ assert self.__is_exclusive() and not self.__is_sharer(), \
+ "Lock wasn't acquired in exclusive mode"
+
self.__deleted = True
self.__exc = None
+ assert not (self.__exc or self.__shr), "Found owner during deletion"
+
# Notify all acquires. They'll throw an error.
- while self.__pending:
- self.__pending.pop().notifyAll()
+ for (_, prioqueue) in self.__pending:
+ for cond in prioqueue:
+ cond.notifyAll()
+
+ assert self.__deleted
return acquired
finally:
self.__lock.release()
+ def _release_save(self):
+ shared = self.__is_sharer()
+ self.release()
+ return shared
+
+ def _acquire_restore(self, shared):
+ self.acquire(shared=shared)
+
# Whenever we want to acquire a full LockSet we pass None as the value
# to acquire. Hide this behind this nicely named constant.
ALL_SET = None
+class _AcquireTimeout(Exception):
+ """Internal exception to abort an acquire on a timeout.
+
+ """
+
+
class LockSet:
"""Implements a set of locks.
All the locks needed in the same set must be acquired together, though.
+ @type name: string
+ @ivar name: the name of the lockset
+
"""
- def __init__(self, members=None):
+ def __init__(self, members, name, monitor=None):
"""Constructs a new LockSet.
+ @type members: list of strings
@param members: initial members of the set
+ @type monitor: L{LockMonitor}
+ @param monitor: Lock monitor with which to register member locks
"""
- # Used internally to guarantee coherency.
- self.__lock = SharedLock()
+ assert members is not None, "members parameter is not a list"
+ self.name = name
+
+ # Lock monitor
+ self.__monitor = monitor
+
+ # Used internally to guarantee coherency
+ self.__lock = SharedLock(self._GetLockName("[lockset]"), monitor=monitor)
# The lockdict indexes the relationship name -> lock
# The order-of-locking is implied by the alphabetical order of names
self.__lockdict = {}
- if members is not None:
- for name in members:
- self.__lockdict[name] = SharedLock()
+ for mname in members:
+ self.__lockdict[mname] = SharedLock(self._GetLockName(mname),
+ monitor=monitor)
# The owner dict contains the set of locks each thread owns. For
# performance each thread can access its own key without a global lock on
# will be trouble.
self.__owners = {}
- def _is_owned(self):
- """Is the current thread a current level owner?"""
+ def _GetLockName(self, mname):
+ """Returns the name for a member lock.
+
+ """
+ return "%s/%s" % (self.name, mname)
+
+ def _get_lock(self):
+ """Returns the lockset-internal lock.
+
+ """
+ return self.__lock
+
+ def _get_lockdict(self):
+ """Returns the lockset-internal lock dictionary.
+
+ Accessing this structure is only safe in single-thread usage or when the
+ lockset-internal lock is held.
+
+ """
+ return self.__lockdict
+
+ def is_owned(self):
+ """Is the current thread a current level owner?
+
+ @note: Use L{check_owned} to check if a specific lock is held
+
+ """
return threading.currentThread() in self.__owners
+ def check_owned(self, names, shared=-1):
+ """Check if locks are owned in a specific mode.
+
+ @type names: sequence or string
+ @param names: Lock names (or a single lock name)
+ @param shared: See L{SharedLock.is_owned}
+ @rtype: bool
+ @note: Use L{is_owned} to check if the current thread holds I{any} lock and
+ L{list_owned} to get the names of all owned locks
+
+ """
+ if isinstance(names, basestring):
+ names = [names]
+
+ # Avoid check if no locks are owned anyway
+ if names and self.is_owned():
+ candidates = []
+
+ # Gather references to all locks (in case they're deleted in the meantime)
+ for lname in names:
+ try:
+ lock = self.__lockdict[lname]
+ except KeyError:
+ raise errors.LockError("Non-existing lock '%s' in set '%s' (it may"
+ " have been removed)" % (lname, self.name))
+ else:
+ candidates.append(lock)
+
+ return compat.all(lock.is_owned(shared=shared) for lock in candidates)
+ else:
+ return False
+
def _add_owned(self, name=None):
"""Note the current thread owns the given lock"""
if name is None:
- if not self._is_owned():
+ if not self.is_owned():
self.__owners[threading.currentThread()] = set()
else:
- if self._is_owned():
+ if self.is_owned():
self.__owners[threading.currentThread()].add(name)
else:
self.__owners[threading.currentThread()] = set([name])
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)
# Only remove the key if we don't hold the set-lock as well
- if (not self.__lock._is_owned() and
+ if (not self.__lock.is_owned() and
not self.__owners[threading.currentThread()]):
del self.__owners[threading.currentThread()]
- def _list_owned(self):
+ def list_owned(self):
"""Get the set of resource names owned by the current thread"""
- if self._is_owned():
+ if self.is_owned():
return self.__owners[threading.currentThread()].copy()
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.
# If we don't already own the set-level lock acquired
# we'll get it and note we need to release it later.
release_lock = False
- if not self.__lock._is_owned():
+ if not self.__lock.is_owned():
release_lock = True
self.__lock.acquire(shared=1)
try:
self.__lock.release()
return set(result)
- def acquire(self, names, blocking=1, shared=0):
+ def acquire(self, names, timeout=None, shared=0, priority=None,
+ 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 priority: integer
+ @param priority: Priority for acquiring 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"
+ assert not self.is_owned(), ("Cannot acquire locks in the same set twice"
+ " (lockset %s)" % self.name)
- 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
+ if priority is None:
+ priority = _DEFAULT_PRIORITY
+
+ # 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 = utils.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, priority,
+ 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 we 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, priority=priority,
+ timeout=running_timeout.Remaining()):
+ raise _AcquireTimeout()
+ try:
+ # note we own the set-lock
+ self._add_owned()
+
+ return self.__acquire_inner(self.__names(), True, shared, priority,
+ 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, priority,
+ 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 priority: Priority for acquiring locks
+ @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 %s in set %s (it may have"
+ " been removed)" % (lname, self.name))
+
+ 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,
+ priority=priority,
+ 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 %s in set %s (it may"
+ " have been removed)" % (lname, self.name))
+
+ 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 (set %s)" %
+ (lname, self.name))
+
+ 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.
- if lock._is_owned():
+ # 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
+ def downgrade(self, names=None):
+ """Downgrade a set of resource locks from exclusive to shared mode.
+
+ The locks must have been acquired in exclusive mode.
+
+ """
+ assert self.is_owned(), ("downgrade on lockset %s while not owning any"
+ " lock" % self.name)
+
+ # Support passing in a single resource to downgrade rather than many
+ if isinstance(names, basestring):
+ names = [names]
+
+ owned = self.list_owned()
+
+ if names is None:
+ names = owned
+ else:
+ names = set(names)
+ assert owned.issuperset(names), \
+ ("downgrade() on unheld resources %s (set %s)" %
+ (names.difference(owned), self.name))
+
+ for lockname in names:
+ self.__lockdict[lockname].downgrade()
+
+ # Do we own the lockset in exclusive mode?
+ if self.__lock.is_owned(shared=0):
+ # Have all locks been downgraded?
+ if not compat.any(lock.is_owned(shared=0)
+ for lock in self.__lockdict.values()):
+ self.__lock.downgrade()
+ assert self.__lock.is_owned(shared=1)
+
+ return True
+
def release(self, 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.
+ @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 self._is_owned(), "release() on lock set while not owner"
+ assert self.is_owned(), ("release() on lock set %s while not owner" %
+ self.name)
# Support passing in a single resource to release rather than many
if isinstance(names, basestring):
names = [names]
if names is None:
- names = self._list_owned()
+ names = self.list_owned()
else:
names = set(names)
- assert self._list_owned().issuperset(names), (
- "release() on unheld resources %s" %
- names.difference(self._list_owned()))
+ assert self.list_owned().issuperset(names), (
+ "release() on unheld resources %s (set %s)" %
+ (names.difference(self.list_owned()), self.name))
# First of all let's release the "all elements" lock, if set.
# After this 'add' can work again
- if self.__lock._is_owned():
+ if self.__lock.is_owned():
self.__lock.release()
self._del_owned()
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?
"""
# Check we don't already own locks at this level
- assert not self._is_owned() or self.__lock._is_owned(shared=0), \
- "Cannot add locks if the set is only partially owned, or shared"
+ assert not self.is_owned() or self.__lock.is_owned(shared=0), \
+ ("Cannot add locks if the set %s is only partially owned, or shared" %
+ self.name)
# Support passing in a single resource to add rather than many
if isinstance(names, basestring):
# If we don't already own the set-level lock acquired in an exclusive way
# we'll get it and note we need to release it later.
release_lock = False
- if not self.__lock._is_owned():
+ if not self.__lock.is_owned():
release_lock = True
self.__lock.acquire()
# This must be an explicit raise, not an assert, because assert is
# turned off when using optimization, and this can happen because of
# concurrency even if the user doesn't want it.
- raise errors.LockError("duplicate add() (%s)" % invalid_names)
+ raise errors.LockError("duplicate add(%s) on lockset %s" %
+ (invalid_names, self.name))
for lockname in names:
- lock = SharedLock()
+ lock = SharedLock(self._GetLockName(lockname), monitor=self.__monitor)
if acquired:
+ # No need for priority or timeout here as this lock has just been
+ # created
lock.acquire(shared=shared)
# now the lock cannot be deleted, we have it!
try:
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]
# If we own any subset of this lock it must be a superset of what we want
# to delete. The ownership must also be exclusive, but that will be checked
# by the lock itself.
- assert not self._is_owned() or self._list_owned().issuperset(names), (
- "remove() on acquired lockset while not owning all elements")
+ assert not self.is_owned() or self.list_owned().issuperset(names), (
+ "remove() on acquired lockset %s while not owning all elements" %
+ self.name)
removed = []
removed.append(lname)
except (KeyError, errors.LockError):
# This cannot happen if we were already holding it, verify:
- assert not self._is_owned(), "remove failed while holding lockset"
+ assert not self.is_owned(), ("remove failed while holding lockset %s" %
+ self.name)
else:
# If no LockError was raised we are the ones who deleted the lock.
# This means we can safely remove it from lockdict, as any further or
# it's the job of the one who actually deleted it.
del self.__lockdict[lname]
# And let's remove it from our private list if we owned it.
- if self._is_owned():
+ if self.is_owned():
self._del_owned(name=lname)
return removed
# the same time.
LEVEL_CLUSTER = 0
LEVEL_INSTANCE = 1
-LEVEL_NODE = 2
-
-LEVELS = [LEVEL_CLUSTER,
- LEVEL_INSTANCE,
- LEVEL_NODE]
+LEVEL_NODEGROUP = 2
+LEVEL_NODE = 3
+LEVEL_NODE_RES = 4
+
+LEVELS = [
+ LEVEL_CLUSTER,
+ LEVEL_INSTANCE,
+ LEVEL_NODEGROUP,
+ LEVEL_NODE,
+ LEVEL_NODE_RES,
+ ]
# Lock levels which are modifiable
-LEVELS_MOD = [LEVEL_NODE, LEVEL_INSTANCE]
-
+LEVELS_MOD = frozenset([
+ LEVEL_NODE_RES,
+ LEVEL_NODE,
+ LEVEL_NODEGROUP,
+ LEVEL_INSTANCE,
+ ])
+
+#: Lock level names (make sure to use singular form)
LEVEL_NAMES = {
LEVEL_CLUSTER: "cluster",
LEVEL_INSTANCE: "instance",
+ LEVEL_NODEGROUP: "nodegroup",
LEVEL_NODE: "node",
+ LEVEL_NODE_RES: "node-res",
}
# Constant for the big ganeti lock
-BGL = 'BGL'
+BGL = "BGL"
class GanetiLockManager:
"""
_instance = None
- def __init__(self, nodes=None, instances=None):
+ def __init__(self, nodes, nodegroups, instances):
"""Constructs a new GanetiLockManager object.
There should be only a GanetiLockManager object at any time, so this
function raises an error if this is not the case.
@param nodes: list of node names
+ @param nodegroups: list of nodegroup uuids
@param instances: list of instance names
"""
self.__class__._instance = self
+ self._monitor = LockMonitor()
+
# The keyring contains all the locks, at their level and in the correct
# locking order.
self.__keyring = {
- LEVEL_CLUSTER: LockSet([BGL]),
- LEVEL_NODE: LockSet(nodes),
- LEVEL_INSTANCE: LockSet(instances),
- }
+ LEVEL_CLUSTER: LockSet([BGL], "cluster", monitor=self._monitor),
+ LEVEL_NODE: LockSet(nodes, "node", monitor=self._monitor),
+ LEVEL_NODE_RES: LockSet(nodes, "node-res", monitor=self._monitor),
+ LEVEL_NODEGROUP: LockSet(nodegroups, "nodegroup", monitor=self._monitor),
+ LEVEL_INSTANCE: LockSet(instances, "instance",
+ monitor=self._monitor),
+ }
+
+ assert compat.all(ls.name == LEVEL_NAMES[level]
+ for (level, ls) in self.__keyring.items())
+
+ def AddToLockMonitor(self, provider):
+ """Registers a new lock with the monitor.
+
+ See L{LockMonitor.RegisterLock}.
+
+ """
+ return self._monitor.RegisterLock(provider)
+
+ def QueryLocks(self, fields):
+ """Queries information from all locks.
+
+ See L{LockMonitor.QueryLocks}.
+
+ """
+ return self._monitor.QueryLocks(fields)
def _names(self, level):
"""List the lock names at the given level.
assert level in LEVELS, "Invalid locking level %s" % level
return self.__keyring[level]._names()
- def _is_owned(self, level):
+ def is_owned(self, level):
"""Check whether we are owning locks at the given level
"""
- return self.__keyring[level]._is_owned()
-
- is_owned = _is_owned
+ return self.__keyring[level].is_owned()
- def _list_owned(self, level):
+ def list_owned(self, level):
"""Get the set of owned locks at the given level
"""
- return self.__keyring[level]._list_owned()
+ return self.__keyring[level].list_owned()
+
+ def check_owned(self, level, names, shared=-1):
+ """Check if locks at a certain level are owned in a specific mode.
+
+ @see: L{LockSet.check_owned}
+
+ """
+ return self.__keyring[level].check_owned(names, shared=shared)
def _upper_owned(self, level):
"""Check that we don't own any lock at a level greater than the given one.
"""
# This way of checking only works if LEVELS[i] = i, which we check for in
# the test cases.
- return utils.any((self._is_owned(l) for l in LEVELS[level + 1:]))
+ return compat.any((self.is_owned(l) for l in LEVELS[level + 1:]))
- def _BGL_owned(self):
+ def _BGL_owned(self): # pylint: disable=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()
+ return BGL in self.__keyring[LEVEL_CLUSTER].list_owned()
- def _contains_BGL(self, level, names):
+ @staticmethod
+ def _contains_BGL(level, names): # pylint: disable=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, priority=None):
"""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
+ @type priority: integer
+ @param priority: Priority for acquiring lock
"""
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,
+ priority=priority)
+
+ def downgrade(self, level, names=None):
+ """Downgrade a set of resource locks from exclusive to shared mode.
+
+ You must have acquired the locks in exclusive mode.
+
+ @type level: member of locking.LEVELS
+ @param level: the level at which the locks shall be downgraded
+ @type names: list of strings, or None
+ @param names: the names of the locks which shall be downgraded
+ (defaults to all the locks acquired at the level)
+
+ """
+ assert level in LEVELS, "Invalid locking level %s" % level
+
+ return self.__keyring[level].downgrade(names=names)
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
# Check we either own the level or don't own anything from here
# up. LockSet.remove() will check the case in which we don't own
# all the needed resources, or we have a shared ownership.
- assert self._is_owned(level) or not self._upper_owned(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)
+
+
+def _MonitorSortKey((item, idx, num)):
+ """Sorting key function.
+
+ Sort by name, registration order and then order of information. This provides
+ a stable sort order over different providers, even if they return the same
+ name.
+
+ """
+ (name, _, _, _) = item
+
+ return (utils.NiceSortKey(name), num, idx)
+
+
+class LockMonitor(object):
+ _LOCK_ATTR = "_lock"
+
+ def __init__(self):
+ """Initializes this class.
+
+ """
+ self._lock = SharedLock("LockMonitor")
+
+ # Counter for stable sorting
+ self._counter = itertools.count(0)
+
+ # Tracked locks. Weak references are used to avoid issues with circular
+ # references and deletion.
+ self._locks = weakref.WeakKeyDictionary()
+
+ @ssynchronized(_LOCK_ATTR)
+ def RegisterLock(self, provider):
+ """Registers a new lock.
+
+ @param provider: Object with a callable method named C{GetLockInfo}, taking
+ a single C{set} containing the requested information items
+ @note: It would be nicer to only receive the function generating the
+ requested information but, as it turns out, weak references to bound
+ methods (e.g. C{self.GetLockInfo}) are tricky; there are several
+ workarounds, but none of the ones I found works properly in combination
+ with a standard C{WeakKeyDictionary}
+
+ """
+ assert provider not in self._locks, "Duplicate registration"
+
+ # There used to be a check for duplicate names here. As it turned out, when
+ # a lock is re-created with the same name in a very short timeframe, the
+ # previous instance might not yet be removed from the weakref dictionary.
+ # By keeping track of the order of incoming registrations, a stable sort
+ # ordering can still be guaranteed.
+
+ self._locks[provider] = self._counter.next()
+
+ def _GetLockInfo(self, requested):
+ """Get information from all locks.
+
+ """
+ # Must hold lock while getting consistent list of tracked items
+ self._lock.acquire(shared=1)
+ try:
+ items = self._locks.items()
+ finally:
+ self._lock.release()
+
+ return [(info, idx, num)
+ for (provider, num) in items
+ for (idx, info) in enumerate(provider.GetLockInfo(requested))]
+
+ def _Query(self, fields):
+ """Queries information from all locks.
+
+ @type fields: list of strings
+ @param fields: List of fields to return
+
+ """
+ qobj = query.Query(query.LOCK_FIELDS, fields)
+
+ # Get all data with internal lock held and then sort by name and incoming
+ # order
+ lockinfo = sorted(self._GetLockInfo(qobj.RequestedData()),
+ key=_MonitorSortKey)
+
+ # Extract lock information and build query data
+ return (qobj, query.LockQueryData(map(compat.fst, lockinfo)))
+
+ def QueryLocks(self, fields):
+ """Queries information from all locks.
+
+ @type fields: list of strings
+ @param fields: List of fields to return
+
+ """
+ (qobj, ctx) = self._Query(fields)
+
+ # Prepare query response
+ return query.GetQueryResponse(qobj, ctx)
projects / ganeti-local / blobdiff