# -*- coding: utf-8 -*- # # Copyright © 2014 eNovance # # Licensed under the Apache License, Version 2.0 (the "License"); you may # not use this file except in compliance with the License. You may obtain # a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, WITHOUT # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the # License for the specific language governing permissions and limitations # under the License. import hashlib import struct import time from concurrent import futures import msgpack from oslo_utils import encodeutils import six import sysv_ipc import tooz from tooz import coordination from tooz import locking from tooz import utils if sysv_ipc.KEY_MIN <= 0: _KEY_RANGE = abs(sysv_ipc.KEY_MIN) + sysv_ipc.KEY_MAX else: _KEY_RANGE = sysv_ipc.KEY_MAX - sysv_ipc.KEY_MIN def ftok(name, project): # Similar to ftok & http://semanchuk.com/philip/sysv_ipc/#ftok_weakness # but hopefully without as many weaknesses... h = hashlib.md5() if not isinstance(project, six.binary_type): project = project.encode('ascii') h.update(project) if not isinstance(name, six.binary_type): name = name.encode('ascii') h.update(name) return (int(h.hexdigest(), 16) % _KEY_RANGE) + sysv_ipc.KEY_MIN class IPCLock(locking.Lock): """A sysv IPC based lock. Please ensure you have read over (and understand) the limitations of sysv IPC locks, and especially have tried and used $ ipcs -l (note the maximum number of semaphores system wide field that command outputs). To ensure that you do not reach that limit it is recommended to use destroy() at the correct program exit/entry points. """ _LOCK_PROJECT = b'__TOOZ_LOCK_' def __init__(self, name): super(IPCLock, self).__init__(name) self.key = ftok(name, self._LOCK_PROJECT) self._lock = None def break_(self): try: lock = sysv_ipc.Semaphore(key=self.key) lock.remove() except sysv_ipc.ExistentialError: return False else: return True def acquire(self, blocking=True): if (blocking is not True and sysv_ipc.SEMAPHORE_TIMEOUT_SUPPORTED is False): raise tooz.NotImplemented("This system does not support" " semaphore timeouts") blocking, timeout = utils.convert_blocking(blocking) start_time = None if not blocking: timeout = 0 elif blocking and timeout is not None: start_time = time.time() while True: tmplock = None try: tmplock = sysv_ipc.Semaphore(self.key, flags=sysv_ipc.IPC_CREX, initial_value=1) tmplock.undo = True except sysv_ipc.ExistentialError: # We failed to create it because it already exists, then try to # grab the existing one. try: tmplock = sysv_ipc.Semaphore(self.key) tmplock.undo = True except sysv_ipc.ExistentialError: # Semaphore has been deleted in the mean time, retry from # the beginning! continue if start_time is not None: elapsed = max(0.0, time.time() - start_time) if elapsed >= timeout: # Ran out of time... return False adjusted_timeout = timeout - elapsed else: adjusted_timeout = timeout try: tmplock.acquire(timeout=adjusted_timeout) except sysv_ipc.BusyError: tmplock = None return False except sysv_ipc.ExistentialError: # Likely the lock has been deleted in the meantime, retry continue else: self._lock = tmplock return True def release(self): if self._lock is not None: try: self._lock.remove() self._lock = None except sysv_ipc.ExistentialError: return False return True return False class IPCDriver(coordination.CoordinationDriver): """A `IPC`_ based driver. This driver uses `IPC`_ concepts to provide the coordination driver semantics and required API(s). It **is** missing some functionality but in the future these not implemented API(s) will be filled in. General recommendations/usage considerations: - It is **not** distributed (or recommended to be used in those situations, so the developer using this should really take that into account when applying this driver in there app). .. _IPC: http://en.wikipedia.org/wiki/Inter-process_communication """ CHARACTERISTICS = ( coordination.Characteristics.NON_TIMEOUT_BASED, coordination.Characteristics.DISTRIBUTED_ACROSS_THREADS, coordination.Characteristics.DISTRIBUTED_ACROSS_PROCESSES, ) """ Tuple of :py:class:`~tooz.coordination.Characteristics` introspectable enum member(s) that can be used to interogate how this driver works. """ _SEGMENT_SIZE = 1024 _GROUP_LIST_KEY = "GROUP_LIST" _GROUP_PROJECT = "_TOOZ_INTERNAL" _INTERNAL_LOCK_NAME = "TOOZ_INTERNAL_LOCK" def __init__(self, member_id, parsed_url, options): """Initialize the IPC driver.""" super(IPCDriver, self).__init__(member_id) self._executor = utils.ProxyExecutor.build("IPC", options) def _start(self): self._group_list = sysv_ipc.SharedMemory( ftok(self._GROUP_LIST_KEY, self._GROUP_PROJECT), sysv_ipc.IPC_CREAT, size=self._SEGMENT_SIZE) self._lock = self.get_lock(self._INTERNAL_LOCK_NAME) self._executor.start() def _stop(self): self._executor.stop() try: self._group_list.detach() self._group_list.remove() except sysv_ipc.ExistentialError: pass def _read_group_list(self): data = self._group_list.read(byte_count=2) length = struct.unpack("H", data)[0] if length == 0: return set() data = self._group_list.read(byte_count=length, offset=2) return set(msgpack.loads(data)) def _write_group_list(self, group_list): data = msgpack.dumps(list(group_list)) if len(data) >= self._SEGMENT_SIZE - 2: raise tooz.ToozError("Group list is too big") self._group_list.write(struct.pack('H', len(data))) self._group_list.write(data, offset=2) def create_group(self, group_id): def _create_group(): with self._lock: group_list = self._read_group_list() if group_id in group_list: raise coordination.GroupAlreadyExist(group_id) group_list.add(group_id) self._write_group_list(group_list) return IPCFutureResult(self._executor.submit(_create_group)) def delete_group(self, group_id): def _delete_group(): with self._lock: group_list = self._read_group_list() if group_id not in group_list: raise coordination.GroupNotCreated(group_id) group_list.remove(group_id) self._write_group_list(group_list) return IPCFutureResult(self._executor.submit(_delete_group)) def watch_join_group(self, group_id, callback): # Check the group exist self.get_members(group_id).get() super(IPCDriver, self).watch_join_group(group_id, callback) def watch_leave_group(self, group_id, callback): # Check the group exist self.get_members(group_id).get() super(IPCDriver, self).watch_leave_group(group_id, callback) def _get_groups_handler(self): with self._lock: return self._read_group_list() def get_groups(self): return IPCFutureResult(self._executor.submit( self._get_groups_handler)) @staticmethod def get_lock(name): return IPCLock(name) class IPCFutureResult(coordination.CoordAsyncResult): """IPC asynchronous result that references a future.""" def __init__(self, fut): self._fut = fut def get(self, timeout=10): try: return self._fut.result(timeout=timeout) except futures.TimeoutError as e: coordination.raise_with_cause(coordination.OperationTimedOut, encodeutils.exception_to_unicode(e), cause=e) def done(self): return self._fut.done()