Run Rails Engine standalone

Question

Provided I have a mountable Rails Engine, what's the minimal config to mount it at a certain endpoint as a standalone app (not part of any other app)?

This would preferably be just a simple Rack app so that I could choose an appropriate web server (unicorn, puma etc).

Answer 1

Since you have not given a particular rails engine you want to use, I will create a sample one.

$ rails plugin new blorgh --mountable
$ cd blorgh

Now, since a rails engine is a rack app & can be run standalone. all you need is add a config.ru file with following contents:

# This file is used by Rack-based servers to start the application.
require 'rubygems'
require 'bundler'
require 'rails'
Bundler.require(:default)
run Blorgh::Engine

With this you have your Rails engine that can be run standalone without any extra app. Here is how to run this

$ bundle exec rackup config.ru
[2015-11-16 09:43:26] INFO  WEBrick 1.3.1
[2015-11-16 09:43:26] INFO  ruby 2.2.3 (2015-08-18) [x86_64-darwin14]
[2015-11-16 09:43:26] INFO  WEBrick::HTTPServer#start: pid=38105 port=9292

now to open this, goto localhost:9292. you will get a 404 not found which makes sense as this engine has no routes. But you can add that easily.

Further, this can also be deployed to hosting providers like Heroku. they will detect config.ru file & other config will happen automagically.

Let me know if this answers your question.