JezK
Edit File: dbutils.py
#------------------------------------------------------------------------ # # Copyright (C) 2000 Autonomous Zone Industries # # License: This is free software. You may use this software for any # purpose including modification/redistribution, so long as # this header remains intact and that you do not claim any # rights of ownership or authorship of this software. This # software has been tested, but no warranty is expressed or # implied. # # Author: Gregory P. Smith <greg@krypto.org> # # Note: I don't know how useful this is in reality since when a # DBLockDeadlockError happens the current transaction is supposed to be # aborted. If it doesn't then when the operation is attempted again # the deadlock is still happening... # --Robin # #------------------------------------------------------------------------ # # import the time.sleep function in a namespace safe way to allow # "from bsddb.dbutils import *" # from time import sleep as _sleep import sys absolute_import = (sys.version_info[0] >= 3) if absolute_import : # Because this syntaxis is not valid before Python 2.5 exec("from . import db") else : import db # always sleep at least N seconds between retrys _deadlock_MinSleepTime = 1.0/128 # never sleep more than N seconds between retrys _deadlock_MaxSleepTime = 3.14159 # Assign a file object to this for a "sleeping" message to be written to it # each retry _deadlock_VerboseFile = None def DeadlockWrap(function, *_args, **_kwargs): """DeadlockWrap(function, *_args, **_kwargs) - automatically retries function in case of a database deadlock. This is a function intended to be used to wrap database calls such that they perform retrys with exponentially backing off sleeps in between when a DBLockDeadlockError exception is raised. A 'max_retries' parameter may optionally be passed to prevent it from retrying forever (in which case the exception will be reraised). d = DB(...) d.open(...) DeadlockWrap(d.put, "foo", data="bar") # set key "foo" to "bar" """ sleeptime = _deadlock_MinSleepTime max_retries = _kwargs.get('max_retries', -1) if 'max_retries' in _kwargs: del _kwargs['max_retries'] while True: try: return function(*_args, **_kwargs) except db.DBLockDeadlockError: if _deadlock_VerboseFile: _deadlock_VerboseFile.write( 'dbutils.DeadlockWrap: sleeping %1.3f\n' % sleeptime) _sleep(sleeptime) # exponential backoff in the sleep time sleeptime *= 2 if sleeptime > _deadlock_MaxSleepTime: sleeptime = _deadlock_MaxSleepTime max_retries -= 1 if max_retries == -1: raise #------------------------------------------------------------------------