Handling long running tasks

Question

I have a web app which has a single long running task - generating a PDF report. Various graphs are generated, and it takes about 15 sec to process in all. The report is generated by a user.

Processing the report at the time of request currently causes the process to be tied up, and more importantly (given that use of this website is not heavy) sometimes the request times out.

I am therefore redesigning the architecture of this section of the app (Rails 2.3.8). To put this in context, it's unlikely that more than a couple of these reports will be generated per day, and this is an extremely niche application, so significant further scaling isn't a major concern. I do intend to hand off the project in the future though, so stability is.

The most obvious solution I think is to use Spawn to generate a report, and fire a download link to the user in an email once it's complete. Another solution I've looked into is DelayedJob.

Can anyone who's done something similar recommend one approach over another?

Answer 1

delayed_job, or some other queueing mechanism is going to be the easiest thing to set up. With delayed_job you would just enqueue your worker instead of creating the PDF, and a background process on the server would be working from the queue doing whatever work was available. Using spawn to fork your whole process seems a little heavy-handed, and doesn't seem to lend itself well to other minor, but still longer running tasks (like sending emails).