#------------------------------------------------------------------------## 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@electricrain.com>## 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 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 _kwargs.has_key('max_retries'):        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  #------------------------------------------------------------------------