| 1 | n/a | #------------------------------------------------------------------------ |
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| 2 | n/a | # |
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| 3 | n/a | # Copyright (C) 2000 Autonomous Zone Industries |
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| 4 | n/a | # |
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| 5 | n/a | # License: This is free software. You may use this software for any |
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| 6 | n/a | # purpose including modification/redistribution, so long as |
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| 7 | n/a | # this header remains intact and that you do not claim any |
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| 8 | n/a | # rights of ownership or authorship of this software. This |
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| 9 | n/a | # software has been tested, but no warranty is expressed or |
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| 10 | n/a | # implied. |
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| 11 | n/a | # |
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| 12 | n/a | # Author: Gregory P. Smith <greg@krypto.org> |
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| 13 | n/a | # |
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| 14 | n/a | # Note: I don't know how useful this is in reality since when a |
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| 15 | n/a | # DBLockDeadlockError happens the current transaction is supposed to be |
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| 16 | n/a | # aborted. If it doesn't then when the operation is attempted again |
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| 17 | n/a | # the deadlock is still happening... |
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| 18 | n/a | # --Robin |
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| 19 | n/a | # |
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| 20 | n/a | #------------------------------------------------------------------------ |
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| 21 | n/a | |
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| 22 | n/a | |
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| 23 | n/a | # |
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| 24 | n/a | # import the time.sleep function in a namespace safe way to allow |
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| 25 | n/a | # "from bsddb.dbutils import *" |
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| 26 | n/a | # |
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| 27 | 1 | from time import sleep as _sleep |
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| 28 | n/a | |
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| 29 | 1 | import sys |
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| 30 | 1 | absolute_import = (sys.version_info[0] >= 3) |
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| 31 | 1 | if absolute_import : |
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| 32 | n/a | # Because this syntaxis is not valid before Python 2.5 |
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| 33 | 0 | exec("from . import db") |
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| 34 | n/a | else : |
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| 35 | 1 | import db |
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| 36 | n/a | |
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| 37 | n/a | # always sleep at least N seconds between retrys |
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| 38 | 1 | _deadlock_MinSleepTime = 1.0/128 |
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| 39 | n/a | # never sleep more than N seconds between retrys |
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| 40 | 1 | _deadlock_MaxSleepTime = 3.14159 |
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| 41 | n/a | |
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| 42 | n/a | # Assign a file object to this for a "sleeping" message to be written to it |
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| 43 | n/a | # each retry |
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| 44 | 1 | _deadlock_VerboseFile = None |
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| 45 | n/a | |
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| 46 | n/a | |
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| 47 | 1 | def DeadlockWrap(function, *_args, **_kwargs): |
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| 48 | n/a | """DeadlockWrap(function, *_args, **_kwargs) - automatically retries |
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| 49 | n/a | function in case of a database deadlock. |
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| 50 | n/a | |
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| 51 | n/a | This is a function intended to be used to wrap database calls such |
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| 52 | n/a | that they perform retrys with exponentially backing off sleeps in |
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| 53 | n/a | between when a DBLockDeadlockError exception is raised. |
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| 54 | n/a | |
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| 55 | n/a | A 'max_retries' parameter may optionally be passed to prevent it |
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| 56 | n/a | from retrying forever (in which case the exception will be reraised). |
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| 57 | n/a | |
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| 58 | n/a | d = DB(...) |
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| 59 | n/a | d.open(...) |
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| 60 | n/a | DeadlockWrap(d.put, "foo", data="bar") # set key "foo" to "bar" |
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| 61 | n/a | """ |
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| 62 | 4493 | sleeptime = _deadlock_MinSleepTime |
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| 63 | 4493 | max_retries = _kwargs.get('max_retries', -1) |
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| 64 | 4493 | if 'max_retries' in _kwargs: |
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| 65 | 0 | del _kwargs['max_retries'] |
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| 66 | 4493 | while True: |
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| 67 | 4493 | try: |
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| 68 | 4493 | return function(*_args, **_kwargs) |
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| 69 | 329 | except db.DBLockDeadlockError: |
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| 70 | 0 | if _deadlock_VerboseFile: |
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| 71 | 0 | _deadlock_VerboseFile.write( |
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| 72 | 0 | 'dbutils.DeadlockWrap: sleeping %1.3f\n' % sleeptime) |
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| 73 | 0 | _sleep(sleeptime) |
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| 74 | n/a | # exponential backoff in the sleep time |
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| 75 | 0 | sleeptime *= 2 |
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| 76 | 0 | if sleeptime > _deadlock_MaxSleepTime: |
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| 77 | 0 | sleeptime = _deadlock_MaxSleepTime |
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| 78 | 0 | max_retries -= 1 |
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| 79 | 0 | if max_retries == -1: |
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| 80 | 0 | raise |
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| 81 | n/a | |
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| 82 | n/a | |
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| 83 | n/a | #------------------------------------------------------------------------ |
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