How can I retrieve data onscreen from an external API without tying up a request?

Question

I have a Rails 3 application that lets a user perform a search against a 3rd party database via an API. It could potentially bring back quite a bit of XML data. Also, the API could be busy serving requests for other users and have a nontrivial delay in its response time.

I only run 2 webservers so I can't afford to have a delayed request obviously. I use Sidekiq to process long-running jobs, but in all the cases I've needed that I haven't had to return a value to the screen.

I also use Pusher to communicate back to the user when a background job is finished. I am checking it out, but I don't know if it can be used for the kind of data I want to push to the screen. Right now it just pops up dialog boxes with messages that I send it.

I have thought of some pretty kooky stuff, like running the request via Sidekiq, sending the results to a session object or file, then using Pusher to kick off some kind of event to grab the data and populate the screen with it. Seems kind of Rube Goldberg-ish.

I appreciate any help or insight anyone can offer into the problem!

Answer 1

I had a similar situation not long ago and the way I've fixed was using memcache and threads.

I've also thought about using Sidekiq, but Sidekiq is ideal if you don't expect to use the data right away, so memcache and threads worked pretty well and gave us a good amount of control.

Instead of calling the API directly I would assign the API request to a thread and this thread once done would write to memcache, in my case this can happen incrementally, with the same API being able to return more data from the same endpoint until is complete.

From the UI I would have a basic ajax pooling mechanism that would hit a controller and check memcache for data and for the status to see if it was complete or not, this would sign the UI that it need to keep pooling for more data.