application design : background process

Hi im making a simple app which takes a users search term and scrapes
several sites rss feeds for relevant results. The scrape can take upto
10seconds. I want to make this a background process so I can update the
user with the scrapes status("currently scraping site x") and present
results as they are scraped.

Im looking at backgroundrb and have read a guide in Advanced Rails
Recipe however thats for an older version of backgroundrb and the api
has changed. So im a little confused - im also new to processes and
threads.

If my worker is responsible for scraping each site and providing updates
do I have one worker which will be used by all the users currently
online? I guess I then can use threads to process multiple search
requests at times when the site is busy.

OR

do i create a new worker for each user? Would this also allow for
concurrent processing?

I would use Workling + Starling, or the run_later plugin. You can find
all of them at Github.

I've used them to send process to background, for a long running task,
for example deliver a newsletter to thousands of users, which is a
process which can take some time.