Uploading files to Google Cloud Storage with Flask

Question

I'm trying to upload some images to GCS via an App Engine instance using Flask, but every time the file it's uploaded, when I download it I get a corrupt file. What am I doing wrong ?

I've downloaded and used the Google Cloud Storage client the way is in the docs.

@app.route('/upload', methods=['POST'])
def upload():
    if request.method == 'POST':
        file = request.files['file']
        extension = secure_filename(file.filename).rsplit('.', 1)[1]
        options = {}
        options['retry_params'] = gcs.RetryParams(backoff_factor=1.1)
        options['content_type'] = 'image/' + extension
        bucket_name = "gcs-tester-app"
        path = '/' + bucket_name + '/' + str(secure_filename(file.filename))
        if file and allowed_file(file.filename):
            try:
                with gcs.open(path, 'w', **options) as f:
                    f.write(str(file))
                    print jsonify({"success": True})
                return jsonify({"success": True})
            except Exception as e:
                logging.exception(e)
                return jsonify({"success": False})

Thanks for your help !!

Answer 1

You're uploading (writing to the gcs stream) the str representation of the file object, not the file contents.

try this:

@app.route('/upload', methods=['POST'])
def upload():
    if request.method == 'POST':
        file = request.files['file']
        extension = secure_filename(file.filename).rsplit('.', 1)[1]
        options = {}
        options['retry_params'] = gcs.RetryParams(backoff_factor=1.1)
        options['content_type'] = 'image/' + extension
        bucket_name = "gcs-tester-app"
        path = '/' + bucket_name + '/' + str(secure_filename(file.filename))
        if file and allowed_file(file.filename):
            try:
                with gcs.open(path, 'w', **options) as f:
                    f.write(file.stream.read())# instead of f.write(str(file))
                    print jsonify({"success": True})
                return jsonify({"success": True})
            except Exception as e:
                logging.exception(e)
                return jsonify({"success": False})

But this is not the most efficient way to do this, also, there is a 32mb cap on file uploads straight from app engine, the way to avoid this is by signing an upload url with GCS and upload the file directly from the front-end to GCS, or you can create a file upload url with blobstore and a handler to do the post-upload processing, as specified here: https://cloud.google.com/appengine/docs/python/blobstore/