Differencebetween Unicorn and Unicorn_Rails

what is the difference between unicorn and unicorn_rails?

It is officially answered in https://blog.engineyard.com/2010/everything-you-need-to-know-about-unicorn:

What is the unicorn executable? What is the unicorn_rails executable?

The unicorn executable is a Rack-only tool modeled after Rack’s “rackup” and is recommended for Rack applications. unicorn_rails was made to be an easier transition for users of pre-Rack versions of Rails. The manpage encourages Rails 3 users to use plain unicorn instead.

What’s the difference?

From the unicorn_rails manpage, some conventions of unicorn_rails are modeled after script/server found in Rails. It creates directories under “tmp” like script/server and the -E/–environment switch sets RAILS_ENV instead of RACK_ENV.

Apart from that, in my experience, some gems may need unicorn_rails in particular, like activeadmin (see this)

Also, manpage:

It is designed to help Rails 1.x and 2.y users transition to Rack, but
it is NOT needed for Rails 3 applications. Rails 3 users are
encouraged to use unicorn(1) instead of unicorn_rails(1). Users of
Rails 1.x/2.y may also use unicorn(1) instead of unicorn_rails(1).

difference between passenger and unicorn server

Please read this article about difference of three servers

Rails Server: Passenger, Unicorn or Puma?

New Updates : Puma-vs-Phusion-Passenger

Why does ruby rails need puma or unicorn?

This is not entirely correct, to run PHP with apache you will need either the apache mod_php or run it as a FastCGI module. For Nginx the latter seems to be the norm.

For Ruby there's Phusion Passenger that fills this role, and supports both apache and nginx. On apache it runs as a plugin module just the way mod_php does. For Nginx I'm not sure.

You may want to run your ruby applications using a dedicated application server, however. This is where Unicorn, Puma etc comes in. There's nothing preventing you from doing a similar setup for php, but it's less common.

Another thing which makes php easier to deploy in many cases is that most distros and server installs come with apache and nginx already set up to handle php, while you need to set this up on your own for ruby.

Once set up Passenger makes deploying ruby apps almost (but not quite) as simple as deploying php apps.

Why would I want to use unicorn or thin instead of WEBrick for development purposes?

It is important to develop as closely as possible to the production environment. It helps ensure that an application will work as expected when deployed into production, instead of stumbling upon bugs at runtime.

This issue is alleviated with the use of Continuous Testing on a Build server that replicates the production environment. Even though you are not actively developing on an identical environment, the Continuous Testing gives you coverage that the application is functioning in the expected way.

As to speed, the performance hit running a Rails app in development mode will negate any benefit the various web servers brings.

Why does Unicorn need to be deployed together with Nginx?

Nginx




Unicorn




Refer to unicorn on github for more information.

Referring to Rails from the Unicorn config file

You need to set preload_app true in your config for the gems like Rails to be accessible from the config file - see here for the documentation.

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