root / snf-astakos-app / astakos / im / lock.py @ bf46214d
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# Copyright 2012-2013 GRNET S.A. All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or
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# without modification, are permitted provided that the following
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# conditions are met:
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#
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# 1. Redistributions of source code must retain the above
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# copyright notice, this list of conditions and the following
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# disclaimer.
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#
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# 2. Redistributions in binary form must reproduce the above
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# copyright notice, this list of conditions and the following
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# disclaimer in the documentation and/or other materials
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# provided with the distribution.
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#
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# THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS
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# OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR
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# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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# POSSIBILITY OF SUCH DAMAGE.
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#
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# The views and conclusions contained in the software and
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# documentation are those of the authors and should not be
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# interpreted as representing official policies, either expressed
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# or implied, of GRNET S.A.
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from django.db import transaction |
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from django.db import connection |
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from time import sleep |
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import logging |
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logger = logging.getLogger(__name__) |
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def with_lock(retries=3, retry_wait=1.0): |
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def wrap(func): |
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def inner(*args, **kwargs): |
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transaction.commit() |
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_retries = retries |
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cursor = connection.cursor() |
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locked = True
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try:
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while 1: |
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cursor.execute("SELECT pg_try_advisory_lock(1)")
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r = cursor.fetchone() |
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if r is None: |
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m = "Impossible"
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raise AssertionError(m) |
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locked = r[0]
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if locked:
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break
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_retries -= 1
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if _retries <= 0: |
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return False |
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sleep(retry_wait) |
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return func(*args, **kwargs)
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finally:
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if locked:
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try:
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transaction.commit() |
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except Exception as e: |
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logger.exception(e) |
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transaction.rollback() |
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cursor.execute("SELECT pg_advisory_unlock(1)")
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cursor.fetchall() |
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return inner
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return wrap
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