Heroku is a popular hosting service among Rubyists. Heroku makes deploying Ruby web apps very easy and they even provide free accounts.
But when you run your app on Heroku, you still need an application server. Phusion Passenger is such an application server, designed to be fast, robust and lightweight. By combining Heroku with Phusion Passenger, you can boost the performance of your apps, utilize the available resources on your dynos much more efficiently and increase its stability. This tutorial teaches how you can use Phusion Passenger on Heroku.
- Static asset acceleration through Nginx
Don't let your Ruby app serve static assets, let Nginx do it for you and offload your app for the really important tasks. Nginx will do a much better job.
- Multiple worker processes
Instead of running only one worker on a dyno, Phusion Passenger runs multiple worker on a single dyno, thus utilizing its resources to its fullest and giving you more bang for the buck. This approach is similar to Unicorn's. But unlike Unicorn, Phusion Passenger dynamically scales the number of worker processes based on current traffic, thus freeing up resources when they're not necessary.
- Memory optimizations
Phusion Passenger uses less memory than Thin and Unicorn. It also supports copy-on-write virtual memory in combination with code preloading, thus making your app use even less memory when run on Ruby 2.0.
- Request/response buffering
The included Nginx buffers requests and responses, thus protecting your app against slow clients (e.g. mobile devices on mobile networks) and improving performance.
- Out-of-band garbage collection
Ruby's garbage collector is slow, but why bother your visitors with long response times? Fix this by running garbage collection outside of the normal request-response cycle! This concept, first introduced by Unicorn, has been improved upon: Phusion Passenger ensures that only one request at the same time is running out-of-band garbage collection, thus eliminating all the problems Unicorn's out-of-band garbage collection has.
- JRuby support
Unicorn's a better choice than Thin, but it doesn't support JRuby. Phusion Passenger does.
- --max-pool-size - The maximum number of worker processes to run. The maximum number that you can run depends on the amount of memory your dyno has.
- --min-instances - If you don't want the number of worker processes to scale dynamically, then use this option to set it to a value equal to `--max-pool-size`.
- --spawn-method - By default, Phusion Passenger preloads your app and utilizes copy-on-write (the "smart" spawning method). You can disable this by setting this option to `direct`.
- --no-friendly-error-pages - If your app fails to start, Phusion Passenger will tell you by showing a friendly error page in the browser. This option disables it.