retry_decorator.py

def retries(num_retries, exception_types=Exception, check_func=None, timeout=0.0):
    """retries a function ``num_retries`` times.

    will catch ``exception_types`` of exceptions.  This can be a tuple as well.

    check_func can optionally be provided.  It takes the exception as an argument.
    If it returns a value that evaluates to false, the exception will be reraised.

    can be used like:
        
        @retries(10, urllib2.HTTPError, lambda e: e.errno == 404)
        def foo():
            #do stuff

    it will only retry if it's a 404.
    """
    def retries_decorator(fn):
        def inner_func(*args, **kwargs):
            for current_try in range(num_retries + 1):
                try:
                    return fn(*args, **kwargs)
                except exception_types, e:
                    if current_try < num_retries and \
                       (not check_func or check_func(e)):
                        print >>sys.stderr, "receive exception: %s" % e
                        print >>sys.stderr, "will retry %d more times" % \
                                (num_retries - current_try)
                        if timeout and timeout > 0.0:
                            print >>sys.stderr, "sleeping for %0.04f seconds before retrying" % timeout
                            time.sleep(timeout)
                    else:
                        #If we maxed out our thing, just raise it
                        raise
        return inner_func
    return retries_decorator