What do you get when you combine the slick PDF generation capabilities of wicked_pdf with the elegance and efficiency of delayed_job? A high performance way to convert HTML pages into beautiful PDF documents.
I’ve been leveraging wicked_pdf to generate high school transcripts from my SaaS app, Teascript, since 2009. Prior to that I had been using Prawn which ultimately proved to lack the flexibility I needed to produce beautiful PDFs.
wicked_pdf converts HTML pages into PDF documents using WebKit, the engine behind Apple’s Safari browser (among others). For the past few years, Teascript produced PDFs without any kind of backgrounding in place. This meant that if someone’s PDF took an unusually long time to generate, they were tying up a web server process for that entire duration.
If multiple users generated PDFs simultaneously, it might prevent other visitors from accessing the site. Not good. Furthermore, if the PDF generation process exceeded the web server’s default timeout, the user might not ever get the PDF, just an error page.
Any time your web app integrates with a third party API or a system process, it’s a viable candidate for backgrounding. delayed_job to the rescue. By offloading the long-running processes onto background workers, we free our web server to do what it’s best at: serving static HTML and images.
Backgrounding isn’t a silver bullet, though. It introduces added complexity into the app, making it more vulnerable to failures. This requires writing additional code to handle these failure scenarios gracefully. But at the cost of this added complexity, we can ensure our web server stays fast and lean while our users still get the pretty PDF they want.
Next week we’ll dive into some actual code. I’ll demonstrate how to integrate wicked_pdf with delayed_job and hook the entire thing up to your Rails app. Don’t touch that remote.