Generate presigned url for uploading file to google storage using python

Question

I want to upload a image from front end to google storage using javascript ajax functionality. I need a presigned url that the server would generate which would provide authentication to my frontend to upload a blob. How can I generate a presigned url when using my local machine.

Previously for aws s3 I would do :

pp = s3.generate_presigned_post(
            Bucket=settings.S3_BUCKET_NAME,
            Key='folder1/' + file_name,  
            ExpiresIn=20  # seconds
        )

When generating a signed url for a user to just view a file stored on google storage I do :

    bucket = settings.CLIENT.bucket(settings.BUCKET_NAME)
    blob_name = 'folder/img1.jpg'
    blob = bucket.blob(blob_name)
    url = blob.generate_signed_url(
        version='v4',
        expiration=datetime.timedelta(minutes=1),
        method='GET')

Answer 1

Spent 100$ on google support and 2 weeks of my time to finally find a solution.

client = storage.Client() # works on app engine standard without any credentials requirements

But if you want to use generate_signed_url() function then you need service account Json key.

Every app engine standard has a default service account. ( You can find it in IAM/service account). Create a key for that default sv account and download the key ('sv_key.json') in json format. Store that key in your Django project right next to app.yaml file. Then do the following :

from google.cloud import storage
CLIENT = storage.Client.from_service_account_json('sv_key.json')
bucket = CLIENT.bucket('bucket_name_1')
blob = bucket.blob('img1.jpg') # name of file to be saved/uploaded to storage
pp = blob.generate_signed_url(
    version='v4',
    expiration=datetime.timedelta(minutes=1),
    method='POST') 

This will work on your local machine and GAE standard. WHen you deploy your app to GAE, sv_key.json also gets deployed with Django project and hence it works.

Hope it helps you.

Answer 2

Editing my answer as I didn't understand the problem you were facing.

Taking a look at the comments thread in the question, as @Nick Shebanov stated, there's one possibility to accomplish what are you trying to when using GAE with flex environment.

I have been trying to do the same with GAE Standard environment with no luck so far. At this point, I would recommend opening a feature request at the public issue tracker so this gets somehow implemented.