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# Copyright (C) 2006, 2007 Google Inc.
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful, but
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# WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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# 02110-1301, USA.
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"""Module implementing the Ganeti locking code."""
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# pylint: disable-msg=W0613,W0201
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import threading |
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# Wouldn't it be better to define LockingError in the locking module?
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# Well, for now that's how the rest of the code does it...
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from ganeti import errors |
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from ganeti import utils |
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class SharedLock: |
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"""Implements a shared lock.
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Multiple threads can acquire the lock in a shared way, calling
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acquire_shared(). In order to acquire the lock in an exclusive way threads
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can call acquire_exclusive().
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The lock prevents starvation but does not guarantee that threads will acquire
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the shared lock in the order they queued for it, just that they will
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eventually do so.
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"""
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def __init__(self): |
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"""Construct a new SharedLock"""
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# we have two conditions, c_shr and c_exc, sharing the same lock.
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self.__lock = threading.Lock()
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self.__turn_shr = threading.Condition(self.__lock) |
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self.__turn_exc = threading.Condition(self.__lock) |
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# current lock holders
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self.__shr = set() |
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self.__exc = None |
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# lock waiters
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self.__nwait_exc = 0 |
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self.__nwait_shr = 0 |
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# is this lock in the deleted state?
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self.__deleted = False |
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def __is_sharer(self): |
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"""Is the current thread sharing the lock at this time?"""
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return threading.currentThread() in self.__shr |
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def __is_exclusive(self): |
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"""Is the current thread holding the lock exclusively at this time?"""
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return threading.currentThread() == self.__exc |
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def __is_owned(self, shared=-1): |
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"""Is the current thread somehow owning the lock at this time?
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This is a private version of the function, which presumes you're holding
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the internal lock.
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"""
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if shared < 0: |
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return self.__is_sharer() or self.__is_exclusive() |
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elif shared:
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return self.__is_sharer() |
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else:
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return self.__is_exclusive() |
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def _is_owned(self, shared=-1): |
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"""Is the current thread somehow owning the lock at this time?
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Args:
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shared:
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< 0: check for any type of ownership (default)
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0: check for exclusive ownership
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> 0: check for shared ownership
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"""
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self.__lock.acquire()
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try:
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result = self.__is_owned(shared=shared)
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finally:
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self.__lock.release()
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return result
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def __wait(self, c): |
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"""Wait on the given condition, and raise an exception if the current lock
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is declared deleted in the meantime.
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Args:
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c: condition to wait on
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"""
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c.wait() |
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if self.__deleted: |
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raise errors.LockError('deleted lock') |
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def __exclusive_acquire(self): |
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"""Acquire the lock exclusively.
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This is a private function that presumes you are already holding the
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internal lock. It's defined separately to avoid code duplication between
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acquire() and delete()
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"""
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self.__nwait_exc += 1 |
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try:
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# This is to save ourselves from a nasty race condition that could
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# theoretically make the sharers starve.
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if self.__nwait_shr > 0 or self.__nwait_exc > 1: |
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self.__wait(self.__turn_exc) |
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while len(self.__shr) > 0 or self.__exc is not None: |
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self.__wait(self.__turn_exc) |
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self.__exc = threading.currentThread()
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finally:
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self.__nwait_exc -= 1 |
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def acquire(self, blocking=1, shared=0): |
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"""Acquire a shared lock.
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Args:
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shared: whether to acquire in shared mode. By default an exclusive lock
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will be acquired.
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blocking: whether to block while trying to acquire or to operate in try-lock mode.
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this locking mode is not supported yet.
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"""
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if not blocking: |
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# We don't have non-blocking mode for now
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raise NotImplementedError |
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self.__lock.acquire()
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try:
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if self.__deleted: |
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raise errors.LockError('deleted lock') |
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# We cannot acquire the lock if we already have it
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assert not self.__is_owned(), "double acquire() on a non-recursive lock" |
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if shared:
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self.__nwait_shr += 1 |
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try:
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# If there is an exclusive holder waiting we have to wait. We'll
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# only do this once, though, when we start waiting for the lock. Then
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# we'll just wait while there are no exclusive holders.
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if self.__nwait_exc > 0: |
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# TODO: if !blocking...
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self.__wait(self.__turn_shr) |
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while self.__exc is not None: |
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# TODO: if !blocking...
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self.__wait(self.__turn_shr) |
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self.__shr.add(threading.currentThread())
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finally:
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self.__nwait_shr -= 1 |
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else:
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# TODO: if !blocking...
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# (or modify __exclusive_acquire for non-blocking mode)
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self.__exclusive_acquire()
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finally:
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self.__lock.release()
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return True |
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def release(self): |
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"""Release a Shared Lock.
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You must have acquired the lock, either in shared or in exclusive mode,
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before calling this function.
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"""
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self.__lock.acquire()
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try:
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# Autodetect release type
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if self.__is_exclusive(): |
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self.__exc = None |
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# An exclusive holder has just had the lock, time to put it in shared
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# mode if there are shared holders waiting. Otherwise wake up the next
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# exclusive holder.
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if self.__nwait_shr > 0: |
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self.__turn_shr.notifyAll()
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elif self.__nwait_exc > 0: |
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self.__turn_exc.notify()
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elif self.__is_sharer(): |
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self.__shr.remove(threading.currentThread())
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# If there are no more shared holders and some exclusive holders are
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# waiting let's wake one up.
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if len(self.__shr) == 0 and self.__nwait_exc > 0: |
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self.__turn_exc.notify()
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else:
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assert False, "Cannot release non-owned lock" |
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finally:
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self.__lock.release()
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def delete(self, blocking=1): |
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"""Delete a Shared Lock.
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This operation will declare the lock for removal. First the lock will be
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acquired in exclusive mode if you don't already own it, then the lock
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will be put in a state where any future and pending acquire() fail.
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Args:
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blocking: whether to block while trying to acquire or to operate in
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try-lock mode. this locking mode is not supported yet unless
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you are already holding exclusively the lock.
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"""
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self.__lock.acquire()
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try:
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assert not self.__is_sharer(), "cannot delete() a lock while sharing it" |
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if self.__deleted: |
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raise errors.LockError('deleted lock') |
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if not self.__is_exclusive(): |
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if not blocking: |
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# We don't have non-blocking mode for now
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raise NotImplementedError |
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self.__exclusive_acquire()
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self.__deleted = True |
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self.__exc = None |
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# Wake up everybody, they will fail acquiring the lock and
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# raise an exception instead.
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self.__turn_exc.notifyAll()
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self.__turn_shr.notifyAll()
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finally:
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self.__lock.release()
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class LockSet: |
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"""Implements a set of locks.
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This abstraction implements a set of shared locks for the same resource type,
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distinguished by name. The user can lock a subset of the resources and the
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LockSet will take care of acquiring the locks always in the same order, thus
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preventing deadlock.
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All the locks needed in the same set must be acquired together, though.
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"""
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def __init__(self, members=None): |
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"""Constructs a new LockSet.
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Args:
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members: initial members of the set
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"""
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# Used internally to guarantee coherency.
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self.__lock = SharedLock()
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# The lockdict indexes the relationship name -> lock
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# The order-of-locking is implied by the alphabetical order of names
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self.__lockdict = {}
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if members is not None: |
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for name in members: |
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self.__lockdict[name] = SharedLock()
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# The owner dict contains the set of locks each thread owns. For
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# performance each thread can access its own key without a global lock on
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# this structure. It is paramount though that *no* other type of access is
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# done to this structure (eg. no looping over its keys). *_owner helper
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# function are defined to guarantee access is correct, but in general never
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# do anything different than __owners[threading.currentThread()], or there
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# will be trouble.
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self.__owners = {}
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def _is_owned(self): |
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"""Is the current thread a current level owner?"""
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return threading.currentThread() in self.__owners |
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def _add_owned(self, name): |
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"""Note the current thread owns the given lock"""
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if self._is_owned(): |
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self.__owners[threading.currentThread()].add(name)
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else:
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self.__owners[threading.currentThread()] = set([name]) |
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def _del_owned(self, name): |
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"""Note the current thread owns the given lock"""
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self.__owners[threading.currentThread()].remove(name)
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if not self.__owners[threading.currentThread()]: |
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del self.__owners[threading.currentThread()] |
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def _list_owned(self): |
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"""Get the set of resource names owned by the current thread"""
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if self._is_owned(): |
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return self.__owners[threading.currentThread()].copy() |
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else:
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return set() |
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def __names(self): |
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"""Return the current set of names.
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Only call this function while holding __lock and don't iterate on the
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result after releasing the lock.
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"""
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return self.__lockdict.keys() |
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def _names(self): |
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"""Return a copy of the current set of elements.
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Used only for debugging purposes.
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"""
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self.__lock.acquire(shared=1) |
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try:
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result = self.__names()
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finally:
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self.__lock.release()
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return set(result) |
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def acquire(self, names, blocking=1, shared=0): |
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"""Acquire a set of resource locks.
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Args:
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names: the names of the locks which shall be acquired.
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(special lock names, or instance/node names)
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shared: whether to acquire in shared mode. By default an exclusive lock
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will be acquired.
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blocking: whether to block while trying to acquire or to operate in try-lock mode.
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this locking mode is not supported yet.
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Returns:
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True: when all the locks are successfully acquired
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Raises:
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errors.LockError: when any lock we try to acquire has been deleted
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before we succeed. In this case none of the locks requested will be
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acquired.
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"""
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if not blocking: |
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# We don't have non-blocking mode for now
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raise NotImplementedError |
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# Check we don't already own locks at this level
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assert not self._is_owned(), "Cannot acquire locks in the same set twice" |
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if names is None: |
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# If no names are given acquire the whole set by not letting new names
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# being added before we release, and getting the current list of names.
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# Some of them may then be deleted later, but we'll cope with this.
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#
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# We'd like to acquire this lock in a shared way, as it's nice if
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# everybody else can use the instances at the same time. If are acquiring
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# them exclusively though they won't be able to do this anyway, though,
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# so we'll get the list lock exclusively as well in order to be able to
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# do add() on the set while owning it.
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self.__lock.acquire(shared=shared)
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try:
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# Support passing in a single resource to acquire rather than many
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if isinstance(names, basestring): |
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names = [names] |
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else:
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if names is None: |
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names = self.__names()
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names.sort() |
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acquire_list = [] |
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# First we look the locks up on __lockdict. We have no way of being sure
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# they will still be there after, but this makes it a lot faster should
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# just one of them be the already wrong
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for lname in names: |
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try:
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lock = self.__lockdict[lname] # raises KeyError if the lock is not there |
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acquire_list.append((lname, lock)) |
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except (KeyError): |
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if self.__lock._is_owned(): |
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# We are acquiring all the set, it doesn't matter if this particular
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# element is not there anymore.
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continue
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else:
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raise errors.LockError('non-existing lock in set (%s)' % lname) |
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# This will hold the locknames we effectively acquired.
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acquired = set()
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# Now acquire_list contains a sorted list of resources and locks we want.
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# In order to get them we loop on this (private) list and acquire() them.
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# We gave no real guarantee they will still exist till this is done but
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# .acquire() itself is safe and will alert us if the lock gets deleted.
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for (lname, lock) in acquire_list: |
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try:
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lock.acquire(shared=shared) # raises LockError if the lock is deleted
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# now the lock cannot be deleted, we have it!
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self._add_owned(lname)
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acquired.add(lname) |
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except (errors.LockError):
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if self.__lock._is_owned(): |
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# We are acquiring all the set, it doesn't matter if this particular
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# element is not there anymore.
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continue
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else:
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name_fail = lname |
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for lname in self._list_owned(): |
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self.__lockdict[lname].release()
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self._del_owned(lname)
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raise errors.LockError('non-existing lock in set (%s)' % name_fail) |
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except:
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# We shouldn't have problems adding the lock to the owners list, but
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# if we did we'll try to release this lock and re-raise exception.
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# Of course something is going to be really wrong, after this.
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if lock._is_owned():
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lock.release() |
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raise
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except:
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# If something went wrong and we had the set-lock let's release it...
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if self.__lock._is_owned(): |
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self.__lock.release()
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raise
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return acquired
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def release(self, names=None): |
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"""Release a set of resource locks, at the same level.
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You must have acquired the locks, either in shared or in exclusive mode,
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before releasing them.
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Args:
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names: the names of the locks which shall be released.
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(defaults to all the locks acquired at that level).
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"""
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assert self._is_owned(), "release() on lock set while not owner" |
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# Support passing in a single resource to release rather than many
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if isinstance(names, basestring): |
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names = [names] |
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if names is None: |
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names = self._list_owned()
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else:
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names = set(names)
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assert self._list_owned().issuperset(names), ( |
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"release() on unheld resources %s" %
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names.difference(self._list_owned()))
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# First of all let's release the "all elements" lock, if set.
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# After this 'add' can work again
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if self.__lock._is_owned(): |
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self.__lock.release()
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for lockname in names: |
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# If we are sure the lock doesn't leave __lockdict without being
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# exclusively held we can do this...
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self.__lockdict[lockname].release()
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self._del_owned(lockname)
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def add(self, names, acquired=0, shared=0): |
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"""Add a new set of elements to the set
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Args:
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names: names of the new elements to add
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acquired: pre-acquire the new resource?
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shared: is the pre-acquisition shared?
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"""
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assert not self.__lock._is_owned(shared=1), ( |
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"Cannot add new elements while sharing the set-lock")
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# Support passing in a single resource to add rather than many
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if isinstance(names, basestring): |
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names = [names] |
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# If we don't already own the set-level lock acquire it in an exclusive way
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# we'll get it and note we need to release it later.
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release_lock = False
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if not self.__lock._is_owned(): |
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release_lock = True
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self.__lock.acquire()
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try:
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invalid_names = set(self.__names()).intersection(names) |
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if invalid_names:
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# This must be an explicit raise, not an assert, because assert is
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# turned off when using optimization, and this can happen because of
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# concurrency even if the user doesn't want it.
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raise errors.LockError("duplicate add() (%s)" % invalid_names) |
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for lockname in names: |
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lock = SharedLock() |
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|
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if acquired:
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lock.acquire(shared=shared) |
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# now the lock cannot be deleted, we have it!
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try:
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self._add_owned(lockname)
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except:
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# We shouldn't have problems adding the lock to the owners list,
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# but if we did we'll try to release this lock and re-raise
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# exception. Of course something is going to be really wrong,
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# after this. On the other hand the lock hasn't been added to the
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# __lockdict yet so no other threads should be pending on it. This
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# release is just a safety measure.
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lock.release() |
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raise
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self.__lockdict[lockname] = lock
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|
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finally:
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# Only release __lock if we were not holding it previously.
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if release_lock:
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self.__lock.release()
|
538 |
|
539 |
return True |
540 |
|
541 |
def remove(self, names, blocking=1): |
542 |
"""Remove elements from the lock set.
|
543 |
|
544 |
You can either not hold anything in the lockset or already hold a superset
|
545 |
of the elements you want to delete, exclusively.
|
546 |
|
547 |
Args:
|
548 |
names: names of the resource to remove.
|
549 |
blocking: whether to block while trying to acquire or to operate in
|
550 |
try-lock mode. this locking mode is not supported yet unless
|
551 |
you are already holding exclusively the locks.
|
552 |
|
553 |
Returns:
|
554 |
A list of lock which we removed. The list is always equal to the names
|
555 |
list if we were holding all the locks exclusively.
|
556 |
|
557 |
"""
|
558 |
if not blocking and not self._is_owned(): |
559 |
# We don't have non-blocking mode for now
|
560 |
raise NotImplementedError |
561 |
|
562 |
# Support passing in a single resource to remove rather than many
|
563 |
if isinstance(names, basestring): |
564 |
names = [names] |
565 |
|
566 |
# If we own any subset of this lock it must be a superset of what we want
|
567 |
# to delete. The ownership must also be exclusive, but that will be checked
|
568 |
# by the lock itself.
|
569 |
assert not self._is_owned() or self._list_owned().issuperset(names), ( |
570 |
"remove() on acquired lockset while not owning all elements")
|
571 |
|
572 |
removed = [] |
573 |
|
574 |
for lname in names: |
575 |
# Calling delete() acquires the lock exclusively if we don't already own
|
576 |
# it, and causes all pending and subsequent lock acquires to fail. It's
|
577 |
# fine to call it out of order because delete() also implies release(),
|
578 |
# and the assertion above guarantees that if we either already hold
|
579 |
# everything we want to delete, or we hold none.
|
580 |
try:
|
581 |
self.__lockdict[lname].delete()
|
582 |
removed.append(lname) |
583 |
except (KeyError, errors.LockError): |
584 |
# This cannot happen if we were already holding it, verify:
|
585 |
assert not self._is_owned(), "remove failed while holding lockset" |
586 |
else:
|
587 |
# If no LockError was raised we are the ones who deleted the lock.
|
588 |
# This means we can safely remove it from lockdict, as any further or
|
589 |
# pending delete() or acquire() will fail (and nobody can have the lock
|
590 |
# since before our call to delete()).
|
591 |
#
|
592 |
# This is done in an else clause because if the exception was thrown
|
593 |
# it's the job of the one who actually deleted it.
|
594 |
del self.__lockdict[lname] |
595 |
# And let's remove it from our private list if we owned it.
|
596 |
if self._is_owned(): |
597 |
self._del_owned(lname)
|
598 |
|
599 |
return removed
|
600 |
|
601 |
|
602 |
# Locking levels, must be acquired in increasing order.
|
603 |
# Current rules are:
|
604 |
# - at level LEVEL_CLUSTER resides the Big Ganeti Lock (BGL) which must be
|
605 |
# acquired before performing any operation, either in shared or in exclusive
|
606 |
# mode. acquiring the BGL in exclusive mode is discouraged and should be
|
607 |
# avoided.
|
608 |
# - at levels LEVEL_NODE and LEVEL_INSTANCE reside node and instance locks.
|
609 |
# If you need more than one node, or more than one instance, acquire them at
|
610 |
# the same time.
|
611 |
# - level LEVEL_CONFIG contains the configuration lock, which you must acquire
|
612 |
# before reading or changing the config file.
|
613 |
LEVEL_CLUSTER = 0
|
614 |
LEVEL_NODE = 1
|
615 |
LEVEL_INSTANCE = 2
|
616 |
LEVEL_CONFIG = 3
|
617 |
|
618 |
LEVELS = [LEVEL_CLUSTER, |
619 |
LEVEL_NODE, |
620 |
LEVEL_INSTANCE, |
621 |
LEVEL_CONFIG] |
622 |
|
623 |
# Lock levels which are modifiable
|
624 |
LEVELS_MOD = [LEVEL_NODE, LEVEL_INSTANCE] |
625 |
|
626 |
# Constant for the big ganeti lock and config lock
|
627 |
BGL = 'BGL'
|
628 |
CONFIG = 'config'
|
629 |
|
630 |
|
631 |
class GanetiLockManager: |
632 |
"""The Ganeti Locking Library
|
633 |
|
634 |
The purpouse of this small library is to manage locking for ganeti clusters
|
635 |
in a central place, while at the same time doing dynamic checks against
|
636 |
possible deadlocks. It will also make it easier to transition to a different
|
637 |
lock type should we migrate away from python threads.
|
638 |
|
639 |
"""
|
640 |
_instance = None
|
641 |
|
642 |
def __init__(self, nodes=None, instances=None): |
643 |
"""Constructs a new GanetiLockManager object.
|
644 |
|
645 |
There should be only a
|
646 |
GanetiLockManager object at any time, so this function raises an error if this
|
647 |
is not the case.
|
648 |
|
649 |
Args:
|
650 |
nodes: list of node names
|
651 |
instances: list of instance names
|
652 |
|
653 |
"""
|
654 |
assert self.__class__._instance is None, "double GanetiLockManager instance" |
655 |
self.__class__._instance = self |
656 |
|
657 |
# The keyring contains all the locks, at their level and in the correct
|
658 |
# locking order.
|
659 |
self.__keyring = {
|
660 |
LEVEL_CLUSTER: LockSet([BGL]), |
661 |
LEVEL_NODE: LockSet(nodes), |
662 |
LEVEL_INSTANCE: LockSet(instances), |
663 |
LEVEL_CONFIG: LockSet([CONFIG]), |
664 |
} |
665 |
|
666 |
def _names(self, level): |
667 |
"""List the lock names at the given level.
|
668 |
Used for debugging/testing purposes.
|
669 |
|
670 |
Args:
|
671 |
level: the level whose list of locks to get
|
672 |
|
673 |
"""
|
674 |
assert level in LEVELS, "Invalid locking level %s" % level |
675 |
return self.__keyring[level]._names() |
676 |
|
677 |
def _is_owned(self, level): |
678 |
"""Check whether we are owning locks at the given level
|
679 |
|
680 |
"""
|
681 |
return self.__keyring[level]._is_owned() |
682 |
|
683 |
def _list_owned(self, level): |
684 |
"""Get the set of owned locks at the given level
|
685 |
|
686 |
"""
|
687 |
return self.__keyring[level]._list_owned() |
688 |
|
689 |
def _upper_owned(self, level): |
690 |
"""Check that we don't own any lock at a level greater than the given one.
|
691 |
|
692 |
"""
|
693 |
# This way of checking only works if LEVELS[i] = i, which we check for in
|
694 |
# the test cases.
|
695 |
return utils.any((self._is_owned(l) for l in LEVELS[level + 1:])) |
696 |
|
697 |
def _BGL_owned(self): |
698 |
"""Check if the current thread owns the BGL.
|
699 |
|
700 |
Both an exclusive or a shared acquisition work.
|
701 |
|
702 |
"""
|
703 |
return BGL in self.__keyring[LEVEL_CLUSTER]._list_owned() |
704 |
|
705 |
def _contains_BGL(self, level, names): |
706 |
"""Check if acting on the given level and set of names will change the
|
707 |
status of the Big Ganeti Lock.
|
708 |
|
709 |
"""
|
710 |
return level == LEVEL_CLUSTER and (names is None or BGL in names) |
711 |
|
712 |
def acquire(self, level, names, blocking=1, shared=0): |
713 |
"""Acquire a set of resource locks, at the same level.
|
714 |
|
715 |
Args:
|
716 |
level: the level at which the locks shall be acquired.
|
717 |
It must be a memmber of LEVELS.
|
718 |
names: the names of the locks which shall be acquired.
|
719 |
(special lock names, or instance/node names)
|
720 |
shared: whether to acquire in shared mode. By default an exclusive lock
|
721 |
will be acquired.
|
722 |
blocking: whether to block while trying to acquire or to operate in try-lock mode.
|
723 |
this locking mode is not supported yet.
|
724 |
|
725 |
"""
|
726 |
assert level in LEVELS, "Invalid locking level %s" % level |
727 |
|
728 |
# Check that we are either acquiring the Big Ganeti Lock or we already own
|
729 |
# it. Some "legacy" opcodes need to be sure they are run non-concurrently
|
730 |
# so even if we've migrated we need to at least share the BGL to be
|
731 |
# compatible with them. Of course if we own the BGL exclusively there's no
|
732 |
# point in acquiring any other lock, unless perhaps we are half way through
|
733 |
# the migration of the current opcode.
|
734 |
assert (self._contains_BGL(level, names) or self._BGL_owned()), ( |
735 |
"You must own the Big Ganeti Lock before acquiring any other")
|
736 |
|
737 |
# Check we don't own locks at the same or upper levels.
|
738 |
assert not self._upper_owned(level), ("Cannot acquire locks at a level" |
739 |
" while owning some at a greater one")
|
740 |
|
741 |
# Acquire the locks in the set.
|
742 |
return self.__keyring[level].acquire(names, shared=shared, |
743 |
blocking=blocking) |
744 |
|
745 |
def release(self, level, names=None): |
746 |
"""Release a set of resource locks, at the same level.
|
747 |
|
748 |
You must have acquired the locks, either in shared or in exclusive mode,
|
749 |
before releasing them.
|
750 |
|
751 |
Args:
|
752 |
level: the level at which the locks shall be released.
|
753 |
It must be a memmber of LEVELS.
|
754 |
names: the names of the locks which shall be released.
|
755 |
(defaults to all the locks acquired at that level).
|
756 |
|
757 |
"""
|
758 |
assert level in LEVELS, "Invalid locking level %s" % level |
759 |
assert (not self._contains_BGL(level, names) or |
760 |
not self._upper_owned(LEVEL_CLUSTER)), ( |
761 |
"Cannot release the Big Ganeti Lock while holding something"
|
762 |
" at upper levels")
|
763 |
|
764 |
# Release will complain if we don't own the locks already
|
765 |
return self.__keyring[level].release(names) |
766 |
|
767 |
def add(self, level, names, acquired=0, shared=0): |
768 |
"""Add locks at the specified level.
|
769 |
|
770 |
Args:
|
771 |
level: the level at which the locks shall be added.
|
772 |
It must be a memmber of LEVELS_MOD.
|
773 |
names: names of the locks to acquire
|
774 |
acquired: whether to acquire the newly added locks
|
775 |
shared: whether the acquisition will be shared
|
776 |
"""
|
777 |
assert level in LEVELS_MOD, "Invalid or immutable level %s" % level |
778 |
assert self._BGL_owned(), ("You must own the BGL before performing other" |
779 |
" operations")
|
780 |
assert not self._upper_owned(level), ("Cannot add locks at a level" |
781 |
" while owning some at a greater one")
|
782 |
return self.__keyring[level].add(names, acquired=acquired, shared=shared) |
783 |
|
784 |
def remove(self, level, names, blocking=1): |
785 |
"""Remove locks from the specified level.
|
786 |
|
787 |
You must either already own the locks you are trying to remove exclusively
|
788 |
or not own any lock at an upper level.
|
789 |
|
790 |
Args:
|
791 |
level: the level at which the locks shall be removed.
|
792 |
It must be a memmber of LEVELS_MOD.
|
793 |
names: the names of the locks which shall be removed.
|
794 |
(special lock names, or instance/node names)
|
795 |
blocking: whether to block while trying to operate in try-lock mode.
|
796 |
this locking mode is not supported yet.
|
797 |
|
798 |
"""
|
799 |
assert level in LEVELS_MOD, "Invalid or immutable level %s" % level |
800 |
assert self._BGL_owned(), ("You must own the BGL before performing other" |
801 |
" operations")
|
802 |
# Check we either own the level or don't own anything from here up.
|
803 |
# LockSet.remove() will check the case in which we don't own all the needed
|
804 |
# resources, or we have a shared ownership.
|
805 |
assert self._is_owned(level) or not self._upper_owned(level), ( |
806 |
"Cannot remove locks at a level while not owning it or"
|
807 |
" owning some at a greater one")
|
808 |
return self.__keyring[level].remove(names, blocking=blocking) |