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77 lines
2.7 KiB
Python
77 lines
2.7 KiB
Python
#------------------------------------------------------------------------
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#
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# Copyright (C) 2000 Autonomous Zone Industries
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#
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# License: This is free software. You may use this software for any
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# purpose including modification/redistribution, so long as
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# this header remains intact and that you do not claim any
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# rights of ownership or authorship of this software. This
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# software has been tested, but no warranty is expressed or
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# implied.
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#
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# Author: Gregory P. Smith <greg@krypto.org>
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#
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# Note: I don't know how useful this is in reality since when a
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# DBLockDeadlockError happens the current transaction is supposed to be
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# aborted. If it doesn't then when the operation is attempted again
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# the deadlock is still happening...
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# --Robin
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#
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#------------------------------------------------------------------------
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#
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# import the time.sleep function in a namespace safe way to allow
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# "from bsddb.dbutils import *"
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#
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from time import sleep as _sleep
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import db
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# always sleep at least N seconds between retrys
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_deadlock_MinSleepTime = 1.0/128
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# never sleep more than N seconds between retrys
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_deadlock_MaxSleepTime = 3.14159
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# Assign a file object to this for a "sleeping" message to be written to it
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# each retry
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_deadlock_VerboseFile = None
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def DeadlockWrap(function, *_args, **_kwargs):
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"""DeadlockWrap(function, *_args, **_kwargs) - automatically retries
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function in case of a database deadlock.
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This is a function intended to be used to wrap database calls such
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that they perform retrys with exponentially backing off sleeps in
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between when a DBLockDeadlockError exception is raised.
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A 'max_retries' parameter may optionally be passed to prevent it
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from retrying forever (in which case the exception will be reraised).
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d = DB(...)
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d.open(...)
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DeadlockWrap(d.put, "foo", data="bar") # set key "foo" to "bar"
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"""
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sleeptime = _deadlock_MinSleepTime
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max_retries = _kwargs.get('max_retries', -1)
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if _kwargs.has_key('max_retries'):
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del _kwargs['max_retries']
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while True:
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try:
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return function(*_args, **_kwargs)
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except db.DBLockDeadlockError:
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if _deadlock_VerboseFile:
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_deadlock_VerboseFile.write(
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'dbutils.DeadlockWrap: sleeping %1.3f\n' % sleeptime)
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_sleep(sleeptime)
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# exponential backoff in the sleep time
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sleeptime *= 2
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if sleeptime > _deadlock_MaxSleepTime:
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sleeptime = _deadlock_MaxSleepTime
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max_retries -= 1
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if max_retries == -1:
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raise
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#------------------------------------------------------------------------
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