decorator retry

# 2013-03-06 johnpfeiffer

import time
from functools import wraps


def retry( ExceptionToCheck , tries = 4 , delay = 1 , backoff = 2 , logger = None ):
    """Retry calling the decorated function using an exponential backoff.

    http://www.saltycrane.com/blog/2009/11/trying-out-retry-decorator-python/
    original from: http://wiki.python.org/moin/PythonDecoratorLibrary#Retry

    :param ExceptionToCheck: the exception to check. may be a tuple of
        exceptions to check
    :type ExceptionToCheck: Exception or tuple
    :param tries: number of times to try (not retry) before giving up
    :type tries: int
    :param delay: initial delay between retries in seconds
    :type delay: int
    :param backoff: backoff multiplier e.g. value of 2 will double the delay
        each retry
    :type backoff: int
    :param logger: logger to use. If None, print
    :type logger: logging.Logger instance
    """
    def deco_retry( f ):

        @wraps( f )
        def f_retry( *args , **kwargs ):
            mtries, mdelay = tries, delay
            while mtries > 1:
                try:
                    return f( *args , **kwargs )
                except ExceptionToCheck, e:
                    message = "%s, Retrying in %d seconds..." % ( str(e) , mdelay )
                    if logger:
                        logger.warning( message )
                    else:
                        print message
                    time.sleep( mdelay )
                    mtries -= 1
                    mdelay *= backoff
            return f( *args , **kwargs )

        return f_retry  # true decorator

    return deco_retry


"""
class Retry( object ):
    defaultexceptions = (Exception,)
    def init( self , tries , exceptions = None , delay = 0 ):   # todo backoff = 2 (exponential backoff)
    "" "
        Decorator for retrying a function if exception occurs
        tries -- number of tries
        exceptions -- exceptions to catch
        delay -- wait between retries
    "" "

        self.tries = tries
        if exceptions is None:
            exceptions = Retry.defaultexceptions
        self.exceptions =  exceptions
        self.delay = delay

    def _call( self , f ):
        def fn(args, *kwargs):
            exception = None
            for i in range( self.tries ):
                try:
                    return f( args , *kwargs )
                except self.exceptions, e:
                    print 'RETRY after delay %s, exception: %s' % ( self.delay , str( e ) )
                    time.sleep( self.delay )
                    exception = e
                #if no success after tries, raise last exception
            raise exception
        return fn
"""