root / snf-astakos-app / astakos / im / lock.py @ 09f54ceb
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1 | 57f5ea5c | Giorgos Korfiatis | # Copyright 2012-2013 GRNET S.A. All rights reserved.
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2 | 57f5ea5c | Giorgos Korfiatis | #
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3 | 57f5ea5c | Giorgos Korfiatis | # Redistribution and use in source and binary forms, with or
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4 | 57f5ea5c | Giorgos Korfiatis | # without modification, are permitted provided that the following
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5 | 57f5ea5c | Giorgos Korfiatis | # conditions are met:
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6 | 57f5ea5c | Giorgos Korfiatis | #
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7 | 57f5ea5c | Giorgos Korfiatis | # 1. Redistributions of source code must retain the above
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8 | 57f5ea5c | Giorgos Korfiatis | # copyright notice, this list of conditions and the following
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9 | 57f5ea5c | Giorgos Korfiatis | # disclaimer.
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10 | 57f5ea5c | Giorgos Korfiatis | #
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11 | 57f5ea5c | Giorgos Korfiatis | # 2. Redistributions in binary form must reproduce the above
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12 | 57f5ea5c | Giorgos Korfiatis | # copyright notice, this list of conditions and the following
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13 | 57f5ea5c | Giorgos Korfiatis | # disclaimer in the documentation and/or other materials
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14 | 57f5ea5c | Giorgos Korfiatis | # provided with the distribution.
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15 | 57f5ea5c | Giorgos Korfiatis | #
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16 | 57f5ea5c | Giorgos Korfiatis | # THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS
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17 | 57f5ea5c | Giorgos Korfiatis | # OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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18 | 57f5ea5c | Giorgos Korfiatis | # WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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19 | 57f5ea5c | Giorgos Korfiatis | # PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR
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20 | 57f5ea5c | Giorgos Korfiatis | # CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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21 | 57f5ea5c | Giorgos Korfiatis | # SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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22 | 57f5ea5c | Giorgos Korfiatis | # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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23 | 57f5ea5c | Giorgos Korfiatis | # USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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24 | 57f5ea5c | Giorgos Korfiatis | # AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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25 | 57f5ea5c | Giorgos Korfiatis | # LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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26 | 57f5ea5c | Giorgos Korfiatis | # ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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27 | 57f5ea5c | Giorgos Korfiatis | # POSSIBILITY OF SUCH DAMAGE.
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28 | 57f5ea5c | Giorgos Korfiatis | #
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29 | 57f5ea5c | Giorgos Korfiatis | # The views and conclusions contained in the software and
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30 | 57f5ea5c | Giorgos Korfiatis | # documentation are those of the authors and should not be
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31 | 57f5ea5c | Giorgos Korfiatis | # interpreted as representing official policies, either expressed
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32 | 57f5ea5c | Giorgos Korfiatis | # or implied, of GRNET S.A.
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33 | 57f5ea5c | Giorgos Korfiatis | |
34 | 57f5ea5c | Giorgos Korfiatis | from django.db import transaction |
35 | 57f5ea5c | Giorgos Korfiatis | from django.db import connection |
36 | 57f5ea5c | Giorgos Korfiatis | from time import sleep |
37 | 57f5ea5c | Giorgos Korfiatis | |
38 | 57f5ea5c | Giorgos Korfiatis | def with_lock(retries=3, retry_wait=1.0): |
39 | 57f5ea5c | Giorgos Korfiatis | def wrap(func): |
40 | 57f5ea5c | Giorgos Korfiatis | def inner(*args, **kwargs): |
41 | 57f5ea5c | Giorgos Korfiatis | |
42 | 57f5ea5c | Giorgos Korfiatis | transaction.commit() |
43 | 57f5ea5c | Giorgos Korfiatis | |
44 | 57f5ea5c | Giorgos Korfiatis | cursor = connection.cursor() |
45 | 57f5ea5c | Giorgos Korfiatis | locked = True
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46 | 57f5ea5c | Giorgos Korfiatis | try:
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47 | 57f5ea5c | Giorgos Korfiatis | while 1: |
48 | 57f5ea5c | Giorgos Korfiatis | cursor.execute("SELECT pg_try_advisory_lock(1)")
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49 | 57f5ea5c | Giorgos Korfiatis | r = cursor.fetchone() |
50 | 57f5ea5c | Giorgos Korfiatis | if r is None: |
51 | 57f5ea5c | Giorgos Korfiatis | m = "Impossible"
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52 | 57f5ea5c | Giorgos Korfiatis | raise AssertionError(m) |
53 | 57f5ea5c | Giorgos Korfiatis | locked = r[0]
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54 | 57f5ea5c | Giorgos Korfiatis | if locked:
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55 | 57f5ea5c | Giorgos Korfiatis | break
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56 | 57f5ea5c | Giorgos Korfiatis | |
57 | 57f5ea5c | Giorgos Korfiatis | retries -= 1
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58 | 57f5ea5c | Giorgos Korfiatis | if retries <= 0: |
59 | 57f5ea5c | Giorgos Korfiatis | return False |
60 | 57f5ea5c | Giorgos Korfiatis | sleep(retry_wait) |
61 | 57f5ea5c | Giorgos Korfiatis | |
62 | 57f5ea5c | Giorgos Korfiatis | return func(*args, **kwargs)
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63 | 57f5ea5c | Giorgos Korfiatis | |
64 | 57f5ea5c | Giorgos Korfiatis | finally:
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65 | 57f5ea5c | Giorgos Korfiatis | if locked:
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66 | 57f5ea5c | Giorgos Korfiatis | cursor.execute("SELECT pg_advisory_unlock(1)")
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67 | 57f5ea5c | Giorgos Korfiatis | cursor.fetchall() |
68 | 57f5ea5c | Giorgos Korfiatis | return inner
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69 | 57f5ea5c | Giorgos Korfiatis | return wrap |