X-Git-Url: https://code.grnet.gr/git/ganeti-local/blobdiff_plain/819ca990bb172529b863350eb4b511a97148759d..4a78c361a6de3bcbf98f02abfe41ae3b11de2b00:/lib/locking.py?ds=inline diff --git a/lib/locking.py b/lib/locking.py index e44546a..ea044d5 100644 --- a/lib/locking.py +++ b/lib/locking.py @@ -1,7 +1,7 @@ # # -# Copyright (C) 2006, 2007, 2008, 2009, 2010 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 @@ -20,7 +20,7 @@ """Module implementing the Ganeti locking code.""" -# pylint: disable-msg=W0212 +# pylint: disable=W0212 # W0212 since e.g. LockSet methods use (a lot) the internals of # SharedLock @@ -32,14 +32,18 @@ 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" _DEFAULT_PRIORITY = 0 @@ -158,7 +162,7 @@ class _BaseCondition(object): except AttributeError: self._acquire_restore = self._base_acquire_restore try: - self._is_owned = lock._is_owned + self._is_owned = lock.is_owned except AttributeError: self._is_owned = self._base_is_owned @@ -243,7 +247,7 @@ class SingleNotifyPipeCondition(_BaseCondition): self._write_fd = None self._poller = None - def wait(self, timeout=None): + def wait(self, timeout): """Wait for a notification. @type timeout: float or None @@ -273,7 +277,7 @@ class SingleNotifyPipeCondition(_BaseCondition): if self._nwaiters == 0: self._Cleanup() - def notifyAll(self): # pylint: disable-msg=C0103 + def notifyAll(self): # pylint: disable=C0103 """Close the writing side of the pipe to notify all waiters. """ @@ -310,7 +314,7 @@ class PipeCondition(_BaseCondition): self._waiters = set() self._single_condition = self._single_condition_class(self._lock) - def wait(self, timeout=None): + def wait(self, timeout): """Wait for a notification. @type timeout: float or None @@ -330,7 +334,7 @@ class PipeCondition(_BaseCondition): self._check_owned() self._waiters.remove(threading.currentThread()) - def notifyAll(self): # pylint: disable-msg=C0103 + def notifyAll(self): # pylint: disable=C0103 """Notify all currently waiting threads. """ @@ -354,6 +358,11 @@ class PipeCondition(_BaseCondition): 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__ = [ @@ -396,12 +405,13 @@ class SharedLock(object): "__pending_by_prio", "__pending_shared", "__shr", + "__time_fn", "name", ] __condition_class = _PipeConditionWithMode - def __init__(self, name, monitor=None): + def __init__(self, name, monitor=None, _time_fn=time.time): """Construct a new SharedLock. @param name: the name of the lock @@ -413,6 +423,9 @@ class SharedLock(object): self.name = name + # Used for unittesting + self.__time_fn = _time_fn + # Internal lock self.__lock = threading.Lock() @@ -430,67 +443,68 @@ class SharedLock(object): # Register with lock monitor if monitor: + logging.debug("Adding lock %s to monitor", name) monitor.RegisterLock(self) - def GetInfo(self, fields): + 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 fields: list of strings - @param fields: List of fields to return + @type requested: set + @param requested: Requested information, see C{query.LQ_*} """ self.__lock.acquire() try: - info = [] - # Note: to avoid unintentional race conditions, no references to # modifiable objects should be returned unless they were created in this # function. - for fname in fields: - if fname == "name": - info.append(self.name) - elif fname == "mode": - if self.__deleted: - info.append("deleted") - assert not (self.__exc or self.__shr) - elif self.__exc: - info.append(_EXCLUSIVE_TEXT) - elif self.__shr: - info.append(_SHARED_TEXT) - else: - info.append(None) - elif fname == "owner": - if self.__exc: - owner = [self.__exc] - else: - owner = self.__shr - - if owner: - assert not self.__deleted - info.append([i.getName() for i in owner]) - else: - info.append(None) - elif fname == "pending": - data = [] - - # Sorting instead of copying and using heaq functions for simplicity - for (_, prioqueue) in sorted(self.__pending): - for cond in prioqueue: - if cond.shared: - mode = _SHARED_TEXT - else: - mode = _EXCLUSIVE_TEXT - - # This function should be fast as it runs with the lock held. - # Hence not using utils.NiceSort. - data.append((mode, sorted(i.getName() - for i in cond.get_waiting()))) - - info.append(data) + 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: - raise errors.OpExecError("Invalid query field '%s'" % fname) + 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 info + return [(self.name, mode, owner_names, pending)] finally: self.__lock.release() @@ -527,7 +541,7 @@ class SharedLock(object): 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: @@ -542,6 +556,10 @@ class SharedLock(object): 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. @@ -563,7 +581,9 @@ class SharedLock(object): self.__lock.acquire() try: # Order is important: __find_first_pending_queue modifies __pending - return not (self.__find_first_pending_queue() or + (_, prioqueue) = self.__find_first_pending_queue() + + return not (prioqueue or self.__pending or self.__pending_by_prio or self.__pending_shared) @@ -597,16 +617,15 @@ class SharedLock(object): while self.__pending: (priority, prioqueue) = self.__pending[0] - if not prioqueue: - heapq.heappop(self.__pending) - del self.__pending_by_prio[priority] - assert priority not in self.__pending_shared - continue - if prioqueue: - return 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 + return (None, None) def __is_on_top(self, cond): """Checks whether the passed condition is on top of the queue. @@ -614,7 +633,9 @@ class SharedLock(object): The caller must make sure the queue isn't empty. """ - return cond == self.__find_first_pending_queue()[0] + (_, prioqueue) = self.__find_first_pending_queue() + + return cond == prioqueue[0] def __acquire_unlocked(self, shared, timeout, priority): """Acquire a shared lock. @@ -668,32 +689,37 @@ class SharedLock(object): 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. - # TODO: Decrease timeout with spurious notifications - 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(): prioqueue.remove(wait_condition) if wait_condition.shared: - del self.__pending_shared[priority] + # 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, priority=None, test_notify=None): @@ -723,6 +749,48 @@ class SharedLock(object): 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() + def release(self): """Release a Shared Lock. @@ -738,14 +806,38 @@ class SharedLock(object): # 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 - prioqueue = self.__find_first_pending_queue() - if prioqueue: - prioqueue[0].notifyAll() + # Notify topmost condition in queue if there are no owners left (for + # shared locks) + if notify: + self.__notify_topmost() + finally: + self.__lock.release() + 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() @@ -777,10 +869,10 @@ class SharedLock(object): if not acquired: 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" - if acquired: self.__deleted = True self.__exc = None @@ -846,8 +938,8 @@ class LockSet: # Lock monitor self.__monitor = monitor - # Used internally to guarantee coherency. - self.__lock = SharedLock(name) + # 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 @@ -872,17 +964,68 @@ class LockSet: """ return "%s/%s" % (self.name, mname) - def _is_owned(self): - """Is the current thread a current level owner?""" + 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]) @@ -890,29 +1033,29 @@ class LockSet: def _del_owned(self, name=None): """Note the current thread owns the given lock""" - assert not (name is None and self.__lock._is_owned()), \ + 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(): + for lname in self.list_owned(): lock = self.__lockdict[lname] - if lock._is_owned(): + if lock.is_owned(): lock.release() self._del_owned(name=lname) @@ -934,7 +1077,7 @@ class LockSet: # 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: @@ -971,8 +1114,8 @@ class LockSet: 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" - " (lockset %s)" % self.name) + assert not self.is_owned(), ("Cannot acquire locks in the same set twice" + " (lockset %s)" % self.name) if priority is None: priority = _DEFAULT_PRIORITY @@ -1102,7 +1245,7 @@ class LockSet: # 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(): + if lock.is_owned(): lock.release() raise @@ -1113,6 +1256,42 @@ class LockSet: 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. @@ -1124,24 +1303,24 @@ class LockSet: (defaults to all the locks acquired at that level). """ - assert self._is_owned(), ("release() on lock set %s while not owner" % - self.name) + 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), ( + assert self.list_owned().issuperset(names), ( "release() on unheld resources %s (set %s)" % - (names.difference(self._list_owned()), self.name)) + (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() @@ -1163,7 +1342,7 @@ class LockSet: """ # Check we don't already own locks at this level - assert not self._is_owned() or self.__lock._is_owned(shared=0), \ + 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) @@ -1174,7 +1353,7 @@ class LockSet: # 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() @@ -1237,7 +1416,7 @@ class LockSet: # 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), ( + assert not self.is_owned() or self.list_owned().issuperset(names), ( "remove() on acquired lockset %s while not owning all elements" % self.name) @@ -1254,8 +1433,8 @@ class LockSet: 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 %s" - % self.name) + 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 @@ -1266,7 +1445,7 @@ class LockSet: # 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 @@ -1285,24 +1464,35 @@ LEVEL_CLUSTER = 0 LEVEL_INSTANCE = 1 LEVEL_NODEGROUP = 2 LEVEL_NODE = 3 +LEVEL_NODE_RES = 4 -LEVELS = [LEVEL_CLUSTER, - LEVEL_INSTANCE, - LEVEL_NODEGROUP, - LEVEL_NODE] +LEVELS = [ + LEVEL_CLUSTER, + LEVEL_INSTANCE, + LEVEL_NODEGROUP, + LEVEL_NODE, + LEVEL_NODE_RES, + ] # Lock levels which are modifiable -LEVELS_MOD = [LEVEL_NODE, LEVEL_NODEGROUP, 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: @@ -1337,20 +1527,32 @@ class GanetiLockManager: # The keyring contains all the locks, at their level and in the correct # locking order. self.__keyring = { - LEVEL_CLUSTER: LockSet([BGL], "BGL", monitor=self._monitor), - LEVEL_NODE: LockSet(nodes, "nodes", monitor=self._monitor), - LEVEL_NODEGROUP: LockSet(nodegroups, "nodegroups", monitor=self._monitor), - LEVEL_INSTANCE: LockSet(instances, "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), } - def QueryLocks(self, fields, sync): + 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, sync) + return self._monitor.QueryLocks(fields) def _names(self, level): """List the lock names at the given level. @@ -1363,19 +1565,25 @@ class GanetiLockManager: 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. @@ -1383,18 +1591,18 @@ class GanetiLockManager: """ # This way of checking only works if LEVELS[i] = i, which we check for in # the test cases. - return compat.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): # pylint: disable-msg=C0103 + 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() @staticmethod - def _contains_BGL(level, names): # pylint: disable-msg=C0103 + 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 @@ -1439,6 +1647,22 @@ class GanetiLockManager: 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. @@ -1457,7 +1681,7 @@ class GanetiLockManager: not self._upper_owned(LEVEL_CLUSTER)), ( "Cannot release the Big Ganeti Lock while holding something" " at upper levels (%r)" % - (utils.CommaJoin(["%s=%r" % (LEVEL_NAMES[i], self._list_owned(i)) + (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 @@ -1502,12 +1726,25 @@ class GanetiLockManager: # 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) +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" @@ -1517,48 +1754,76 @@ class LockMonitor(object): """ 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, lock): + 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} + """ - logging.debug("Registering lock %s", lock.name) - assert lock not in self._locks, "Duplicate lock registration" - assert not compat.any(lock.name == i.name for i in self._locks.keys()), \ - "Found duplicate lock name" - self._locks[lock] = None + assert provider not in self._locks, "Duplicate registration" - @ssynchronized(_LOCK_ATTR) - def _GetLockInfo(self, fields): - """Get information from all locks while the monitor lock is held. + # 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. - """ - result = {} + self._locks[provider] = self._counter.next() + + def _GetLockInfo(self, requested): + """Get information from all locks. - for lock in self._locks.keys(): - assert lock.name not in result, "Found duplicate lock name" - result[lock.name] = lock.GetInfo(fields) + """ + # 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 result + return [(info, idx, num) + for (provider, num) in items + for (idx, info) in enumerate(provider.GetLockInfo(requested))] - def QueryLocks(self, fields, sync): + def _Query(self, fields): """Queries information from all locks. @type fields: list of strings @param fields: List of fields to return - @type sync: boolean - @param sync: Whether to operate in synchronous mode """ - if sync: - raise NotImplementedError("Synchronous queries are not implemented") + qobj = query.Query(query.LOCK_FIELDS, fields) - # Get all data without sorting - result = self._GetLockInfo(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) - # Sort by name - return [result[name] for name in utils.NiceSort(result.keys())] + # Prepare query response + return query.GetQueryResponse(qobj, ctx)