$this->promises[$promiseNum] = $S3->uploadAsync('tantor-books', $file->getS3Key(), fopen($file->file->getPathname(), 'r'));
                            $this->promises[$promiseNum]->then(function($value) use ($file) {
                                $this->log('uploaded');
                                $this->updateFile($file);
                            }, function($value) {
                                $this->log('CANCELED');
                            });
                            $this->promises[$promiseNum]->wait();