def upload_pending_to_s3(self):
        """Gets the pending filenames from cache and uploads them."""
        pending_key = get_pending_key()
        pending = cache.get(pending_key, [])
        remaining = []

        for i, file_key in enumerate(pending):
            prefixed_file_key = '%s/%s' % (self.prefix, file_key)
            if self.verbosity > 0:
                print ("Uploading %s..." % prefixed_file_key)
            if self.dry_run:
                self.upload_count += 1
                continue
            filename = self.DIRECTORY + '/' + file_key
            failed = True
            try:
                upload_file_to_s3(prefixed_file_key, filename, self.key,
                    do_gzip=True, do_expires=True)
            except boto.exception.S3CreateError as e:
                # TODO: retry to create a few times
                print ("Failed to upload: %s" % e)
            except Exception as e:
                print (e)
                raise
            else:
                failed = False
                self.upload_count += 1
                cache.delete(file_key)
            finally:
                if failed:
                    remaining.append(file_key)
                    self.remaining_count += 1

        if not self.dry_run:
            cache.set(pending_key, remaining)