Question

Objective: Suppose the client submits a string or text file to the server (Google App Engine) using a web form. I want the server to modify the original file and serve it back to the client.

I think the only way to serve files from GAE is using the Blobstore, right? Then, as we cannot modify blobs, I believe a solution would be:

1. Client uploads a file using HttpRequest
2. Server reads the uploaded file and copies it to a temp buffer (not sure if is there a method to do this)
3. Server deletes original blob
4. Server modifies data in the temp buffer
5. Server writes the modified buffer to the Blobstore
6. Server serves the new blob to the client

Would this work? Could you think about any other solution?

Thanks

Answer 1

I think the only way to serve files from GAE is using the Blobstore, right?

Wrong. A ‘file’ is just a way of storing data on disk; there’s nothing about serving them from a webserver that requires the data come from an actual, writable disk file. You can simply accept the user’s data via a form upload, modify it, and serve it back to them, without it having to ever touch disk, the blobstore, or any other permanent storage medium.

This only becomes a problem if the user’s data is too large to fit in memory, in which case you will have to store the data somewhere while you work on it, such as in the blobstore.