1#------------------------------------------------------------------------ 2# 3# Copyright (C) 2000 Autonomous Zone Industries 4# 5# License: This is free software. You may use this software for any 6# purpose including modification/redistribution, so long as 7# this header remains intact and that you do not claim any 8# rights of ownership or authorship of this software. This 9# software has been tested, but no warranty is expressed or 10# implied. 11# 12# Author: Gregory P. Smith <greg@krypto.org> 13# 14# Note: I don't know how useful this is in reality since when a 15# DBLockDeadlockError happens the current transaction is supposed to be 16# aborted. If it doesn't then when the operation is attempted again 17# the deadlock is still happening... 18# --Robin 19# 20#------------------------------------------------------------------------ 21 22 23# 24# import the time.sleep function in a namespace safe way to allow 25# "from bsddb.dbutils import *" 26# 27from time import sleep as _sleep 28 29import sys 30absolute_import = (sys.version_info[0] >= 3) 31if absolute_import : 32 # Because this syntaxis is not valid before Python 2.5 33 exec("from . import db") 34else : 35 import db 36 37# always sleep at least N seconds between retrys 38_deadlock_MinSleepTime = 1.0/128 39# never sleep more than N seconds between retrys 40_deadlock_MaxSleepTime = 3.14159 41 42# Assign a file object to this for a "sleeping" message to be written to it 43# each retry 44_deadlock_VerboseFile = None 45 46 47def DeadlockWrap(function, *_args, **_kwargs): 48 """DeadlockWrap(function, *_args, **_kwargs) - automatically retries 49 function in case of a database deadlock. 50 51 This is a function intended to be used to wrap database calls such 52 that they perform retrys with exponentially backing off sleeps in 53 between when a DBLockDeadlockError exception is raised. 54 55 A 'max_retries' parameter may optionally be passed to prevent it 56 from retrying forever (in which case the exception will be reraised). 57 58 d = DB(...) 59 d.open(...) 60 DeadlockWrap(d.put, "foo", data="bar") # set key "foo" to "bar" 61 """ 62 sleeptime = _deadlock_MinSleepTime 63 max_retries = _kwargs.get('max_retries', -1) 64 if 'max_retries' in _kwargs: 65 del _kwargs['max_retries'] 66 while True: 67 try: 68 return function(*_args, **_kwargs) 69 except db.DBLockDeadlockError: 70 if _deadlock_VerboseFile: 71 _deadlock_VerboseFile.write( 72 'dbutils.DeadlockWrap: sleeping %1.3f\n' % sleeptime) 73 _sleep(sleeptime) 74 # exponential backoff in the sleep time 75 sleeptime *= 2 76 if sleeptime > _deadlock_MaxSleepTime: 77 sleeptime = _deadlock_MaxSleepTime 78 max_retries -= 1 79 if max_retries == -1: 80 raise 81 82 83#------------------------------------------------------------------------ 84