Question

I am working on a social-network type of application on App Engine, and would like to send multiple images to the client based on a single get request. In particular, when a client loads a page, they should see all images that are associated with their account.

I am using python on the server side, and would like to use Javascript/JQuery on the client side to decode/display the received images.

The difficulty is that I would like to only perform a single query on the server side (ie. query for all images associated with a single user) and send all of the images resulting from the query to the client as a single unit, which will then be broken up into the individual images. Ideally, I would like to use something similar to JSON, but while JSON appears to allow multiple “objects” to be sent as a JSON response, it does not appear to have the ability to allow multiple images (or binary files) to be sent as a JSON response.

Is there another way that I should be looking at this problem, or perhaps a different technology that I should be considering that might allow me to send multiple images to the client, in response to a single get request?

Thank you and Kind Regards
Alexander

Answer 1

The App Engine part isn’t much of a problem (as long as the number of images and total size doesn’t exceed GAE’s limits), but the user’s browser is unlikely to know what to do in order to receive multiple payloads per GET request — that’s just not how the web works. I guess you could concatenate all the blobs/bytestreams (together with metadata needed for the client to reconstruct them) and send that (it will still have to be a separate payload from the HTML / CSS / Javascript that you’re also sending), as long as you can cajole Javascript into separating the megablob into the needed images again (but for that part you should open a separate question and tag it Javascript, as Python has little to do with it, and GAE nothing at all).

I would instead suggest just accepting the fact that the browser (presumably via ajax, as you mention in tags) will be sending multiple requests, just as it does to every other webpage on the WWW, and focus on optimizing the serving side — the requests will be very close in time, so you should just use memcache to keep the yet-unsent images to avoid multiple fetch-from-storage requests in your GAE app.