| 1 | #------------------------------------------------------------------------
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| 2 | #
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| 3 | # Copyright (C) 2000 Autonomous Zone Industries
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| 4 | #
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| 5 | # License: This is free software. You may use this software for any
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| 6 | # purpose including modification/redistribution, so long as
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| 7 | # this header remains intact and that you do not claim any
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| 8 | # rights of ownership or authorship of this software. This
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| 9 | # software has been tested, but no warranty is expressed or
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| 10 | # implied.
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| 11 | #
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| 12 | # Author: Gregory P. Smith <greg@krypto.org>
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| 13 | #
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| 14 | # Note: I don't know how useful this is in reality since when a
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| 15 | # DBLockDeadlockError happens the current transaction is supposed to be
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| 16 | # aborted. If it doesn't then when the operation is attempted again
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| 17 | # the deadlock is still happening...
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| 18 | # --Robin
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| 19 | #
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| 20 | #------------------------------------------------------------------------
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| 21 |
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| 22 |
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| 23 | #
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| 24 | # import the time.sleep function in a namespace safe way to allow
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| 25 | # "from bsddb.dbutils import *"
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| 26 | #
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| 27 | from time import sleep as _sleep
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| 28 |
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| 29 | import sys
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| 30 | absolute_import = (sys.version_info[0] >= 3)
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| 31 | if absolute_import :
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| 32 | # Because this syntaxis is not valid before Python 2.5
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| 33 | exec("from . import db")
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| 34 | else :
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| 35 | import db
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| 36 |
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| 37 | # always sleep at least N seconds between retrys
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| 38 | _deadlock_MinSleepTime = 1.0/128
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| 39 | # never sleep more than N seconds between retrys
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| 40 | _deadlock_MaxSleepTime = 3.14159
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| 41 |
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| 42 | # Assign a file object to this for a "sleeping" message to be written to it
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| 43 | # each retry
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| 44 | _deadlock_VerboseFile = None
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| 45 |
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| 46 |
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| 47 | def DeadlockWrap(function, *_args, **_kwargs):
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| 48 | """DeadlockWrap(function, *_args, **_kwargs) - automatically retries
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| 49 | function in case of a database deadlock.
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| 50 |
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| 51 | This is a function intended to be used to wrap database calls such
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| 52 | that they perform retrys with exponentially backing off sleeps in
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| 53 | between when a DBLockDeadlockError exception is raised.
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| 54 |
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| 55 | A 'max_retries' parameter may optionally be passed to prevent it
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| 56 | from retrying forever (in which case the exception will be reraised).
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| 57 |
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| 58 | d = DB(...)
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| 59 | d.open(...)
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| 60 | DeadlockWrap(d.put, "foo", data="bar") # set key "foo" to "bar"
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| 61 | """
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| 62 | sleeptime = _deadlock_MinSleepTime
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| 63 | max_retries = _kwargs.get('max_retries', -1)
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| 64 | if 'max_retries' in _kwargs:
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| 65 | del _kwargs['max_retries']
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| 66 | while True:
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| 67 | try:
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| 68 | return function(*_args, **_kwargs)
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| 69 | except db.DBLockDeadlockError:
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| 70 | if _deadlock_VerboseFile:
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| 71 | _deadlock_VerboseFile.write(
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| 72 | 'dbutils.DeadlockWrap: sleeping %1.3f\n' % sleeptime)
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| 73 | _sleep(sleeptime)
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| 74 | # exponential backoff in the sleep time
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| 75 | sleeptime *= 2
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| 76 | if sleeptime > _deadlock_MaxSleepTime:
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| 77 | sleeptime = _deadlock_MaxSleepTime
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| 78 | max_retries -= 1
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| 79 | if max_retries == -1:
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| 80 | raise
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| 81 |
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| 82 |
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| 83 | #------------------------------------------------------------------------
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