#------------------------------------------------------------------------

[0] Fix | Delete

#

[1] Fix | Delete

# Copyright (C) 2000 Autonomous Zone Industries

[2] Fix | Delete

#

[3] Fix | Delete

# License: This is free software. You may use this software for any

[4] Fix | Delete

# purpose including modification/redistribution, so long as

[5] Fix | Delete

# this header remains intact and that you do not claim any

[6] Fix | Delete

# rights of ownership or authorship of this software. This

[7] Fix | Delete

# software has been tested, but no warranty is expressed or

[8] Fix | Delete

# implied.

[9] Fix | Delete

#

[10] Fix | Delete

# Author: Gregory P. Smith <greg@krypto.org>

[11] Fix | Delete

#

[12] Fix | Delete

# Note: I don't know how useful this is in reality since when a

[13] Fix | Delete

# DBLockDeadlockError happens the current transaction is supposed to be

[14] Fix | Delete

# aborted. If it doesn't then when the operation is attempted again

[15] Fix | Delete

# the deadlock is still happening...

[16] Fix | Delete

# --Robin

[17] Fix | Delete

#

[18] Fix | Delete

#------------------------------------------------------------------------

[19] Fix | Delete

[20] Fix | Delete

[21] Fix | Delete

#

[22] Fix | Delete

# import the time.sleep function in a namespace safe way to allow

[23] Fix | Delete

# "from bsddb.dbutils import *"

[24] Fix | Delete

#

[25] Fix | Delete

from time import sleep as _sleep

[26] Fix | Delete

[27] Fix | Delete

import sys

[28] Fix | Delete

absolute_import = (sys.version_info[0] >= 3)

[29] Fix | Delete

if absolute_import :

[30] Fix | Delete

# Because this syntaxis is not valid before Python 2.5

[31] Fix | Delete

exec("from . import db")

[32] Fix | Delete

else :

[33] Fix | Delete

import db

[34] Fix | Delete

[35] Fix | Delete

# always sleep at least N seconds between retrys

[36] Fix | Delete

_deadlock_MinSleepTime = 1.0/128

[37] Fix | Delete

# never sleep more than N seconds between retrys

[38] Fix | Delete

_deadlock_MaxSleepTime = 3.14159

[39] Fix | Delete

[40] Fix | Delete

# Assign a file object to this for a "sleeping" message to be written to it

[41] Fix | Delete

# each retry

[42] Fix | Delete

_deadlock_VerboseFile = None

[43] Fix | Delete

[44] Fix | Delete

[45] Fix | Delete

def DeadlockWrap(function, *_args, **_kwargs):

[46] Fix | Delete

"""DeadlockWrap(function, *_args, **_kwargs) - automatically retries

[47] Fix | Delete

function in case of a database deadlock.

[48] Fix | Delete

[49] Fix | Delete

This is a function intended to be used to wrap database calls such

[50] Fix | Delete

that they perform retrys with exponentially backing off sleeps in

[51] Fix | Delete

between when a DBLockDeadlockError exception is raised.

[52] Fix | Delete

[53] Fix | Delete

A 'max_retries' parameter may optionally be passed to prevent it

[54] Fix | Delete

from retrying forever (in which case the exception will be reraised).

[55] Fix | Delete

[56] Fix | Delete

d = DB(...)

[57] Fix | Delete

d.open(...)

[58] Fix | Delete

DeadlockWrap(d.put, "foo", data="bar") # set key "foo" to "bar"

[59] Fix | Delete

"""

[60] Fix | Delete

sleeptime = _deadlock_MinSleepTime

[61] Fix | Delete

max_retries = _kwargs.get('max_retries', -1)

[62] Fix | Delete

if 'max_retries' in _kwargs:

[63] Fix | Delete

del _kwargs['max_retries']

[64] Fix | Delete

while True:

[65] Fix | Delete

try:

[66] Fix | Delete

return function(*_args, **_kwargs)

[67] Fix | Delete

except db.DBLockDeadlockError:

[68] Fix | Delete

if _deadlock_VerboseFile:

[69] Fix | Delete

_deadlock_VerboseFile.write(

[70] Fix | Delete

'dbutils.DeadlockWrap: sleeping %1.3f\n' % sleeptime)

[71] Fix | Delete

_sleep(sleeptime)

[72] Fix | Delete

# exponential backoff in the sleep time

[73] Fix | Delete

sleeptime *= 2

[74] Fix | Delete

if sleeptime > _deadlock_MaxSleepTime:

[75] Fix | Delete

sleeptime = _deadlock_MaxSleepTime

[76] Fix | Delete

max_retries -= 1

[77] Fix | Delete

if max_retries == -1:

[78] Fix | Delete

raise

[79] Fix | Delete

[80] Fix | Delete

[81] Fix | Delete

#------------------------------------------------------------------------

[82] Fix | Delete

[83] Fix | Delete