97 lines
2.7 KiB
Python
97 lines
2.7 KiB
Python
from __future__ import unicode_literals
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import logging
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import json
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import threading
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import time
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import uuid
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from django.core.files import locks
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from common.utils import mkstemp
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from ..exceptions import LockError
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lock = threading.Lock()
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logger = logging.getLogger(__name__)
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temporary_file = mkstemp()[1]
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logger.debug('temporary_file: %s', temporary_file)
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class FileLock(object):
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@classmethod
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def acquire_lock(cls, name, timeout=None):
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instance = FileLock(name=name, timeout=timeout)
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return instance
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def _get_lock_dictionary(self):
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if self.timeout:
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result = {
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'expiration': time.time() + self.timeout,
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'uuid': self.uuid
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}
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else:
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result = {
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'expiration': 0,
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'uuid': self.uuid
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}
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return result
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def __init__(self, name, timeout):
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self.name = name
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self.timeout = timeout or 0
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self.uuid = uuid.uuid4().get_hex()
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lock.acquire()
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with open(temporary_file, 'r+') as file_object:
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locks.lock(f=file_object, flags=locks.LOCK_EX)
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data = file_object.read()
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if data:
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file_locks = json.loads(data)
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else:
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file_locks = {}
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if name in file_locks:
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# Someone already got this lock, check to see if it is expired
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if file_locks[name]['expiration'] and time.time() > file_locks[name]['expiration']:
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# It expires and has expired, we re-acquired it
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file_locks[name] = self._get_lock_dictionary()
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else:
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lock.release()
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raise LockError
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else:
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file_locks[name] = self._get_lock_dictionary()
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file_object.seek(0)
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file_object.truncate()
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file_object.write(json.dumps(file_locks))
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lock.release()
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def release(self):
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lock.acquire()
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with open(temporary_file, 'r+') as file_object:
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locks.lock(f=file_object, flags=locks.LOCK_EX)
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try:
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file_locks = json.loads(file_object.read())
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except EOFError:
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file_locks = {}
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if self.name in file_locks:
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if file_locks[self.name]['uuid'] == self.uuid:
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file_locks.pop(self.name)
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else:
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# Lock expired and someone else acquired it
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pass
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else:
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# Lock expired and someone else released it
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pass
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file_object.seek(0)
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file_object.truncate()
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file_object.write(json.dumps(file_locks))
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lock.release()
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