Phusion Passenger is one of three big players in the rails server game. The other two players are Unicorn and Puma. No matter which one you choose if you can configure it correctly and get through the setup process all of them work. All three of them are considered viable and able to handle the job. In my opinion though I feel that Passenger is the best out of the three.

Support

The first reason why I really like Passenger is because they have really great documentation. If you are unable to resolve your issue after reading through their documentation you didn’t look close enough. For example this is Passengers documentation for their nginx module. Yeah it has a ton of configuration options that you can just stick into your nginx configuration file and go. Also if you are wondering why something is not working you will be able to find the answer easily either by going through the documentation yourself or going to Google. If you Google for an issue using Unicorn you will probably end up finding it but it could take you a while. When I consider choosing a technology to use support is the first place I look at like am I able to get support and is the tool so easy to use that I most likely won’t need that support. If the answer is yes to both of them to me that is a good place to start. If the answer is yes to documentation but not to suppose I think that is an okay starting point. Sometimes you will not be able to find both.

Popularity

This one is a little controversial as the saying goes just because it’s popular doesn’t mean it’s great. That saying does hold true in some cases but when it comes to technology it usually doesn’t mean that it usually means a good sign. I have noticed that people in technology usually don’t stick with something too long if it’s not satisfying their needs. Passenger has great support including the rails core team. It also has support from some major companies including Basecamp, The New York Times, AirBnb, and Apple to name a few of them. If you would like to see a bigger list check out builtwith. Now the argument could be made that all of these companies have no clue what they are doing using Passenger but they all have very high levels of traffic and are well known as reputable companies. There is a reason why and passenger is a tool that helps them get there.

 Ease of Use

To be totally honest I only have experience in running Passenger and Unicorn. I have never had the experience setting up Puma so I will only be comparing Unicorn and passenger here. Although I have looked at Puma’s documentation and it doesn’t look so bad. Unicorn seems to be pretty easy to install on a single instance rails server. You can get your rails application up and running in a short amount of time. There are a lot of Unicorn scripts out there to get you started and up and running. The problem with Unicorn is when you have to do anything outside of running one application on the server. Dealing with multiple environments on one machine is possible (I think) but it seems like it wasn’t made for that. It also feels like Unicorn isn’t fully polished yet. Small things kept coming up like shutting down a Unicorn process without using the kill command. Like that example it just feels like commands that are suppose to work don’t. Now to be honest I am no server administrator so the problem may be obvious to someone else. So if you are a experience Unicorn professional these arguments could easily be debunked. The problem is most rails developers are not and therefore that argument really doesn’t matter. A lot of companies are rolling with developers being the server administrators also so the easier the tool is the better.

Install passenger is also a very simple process. The reason why it’s so simple is it ships with an installer that installs both passenger and nginx. You also install passenger and apache if that is your goal. In my case it was nginx. How cool is it that you get both nginx and passenger with one install. If you already installed nginx it’s recommended that you remove it and then run the passenger install. Also once it’s installed and started passenger handles everything else. This holds true even when you have multiple environments running on the same server. You don’t have to do any extra configuration to set this up either. You basically create another nginx file point it to the directory and go. Of course if you are adding another application on you will have to restart nginx but not passenger. Also passenger comes with a couple of pretty cool tools to monitor memory and performance. You simply type in the following command to get the memory usage.

rvmsudo passenger-memory-stats

Yes it’s that easy to monitor your rails processes. Unicorn you have to manually so a ps -ef | grep ‘unicorn’ to see the process. I suppose there are some tools like this for Unicorn but they don’t see as obvious to use. This tool is built into passenger so you can run it from anywhere you have an application running.

At the end of the day you have to use a tool that works best for your situation. Is passenger that tool probably but if you are an experience server administrator tools like Unicorn may be better. We all have our reason for choosing our toolset but you should have justification for those reason. At the end do whatever makes your life easier. In my case Passenger made my life easier as a non server administrator.

Here are some resources I used to determine the content in this post

• https://github.com/phusion/passenger/wiki/Unicorn-vs-Phusion-Passenger
• https://www.engineyard.com/articles/rails-server
• https://www.digitalocean.com/community/articles/a-comparison-of-rack-web-servers-for-ruby-web-applications