Web Servers

Serve static files, but with the right modules, can also serve dynamic web apps. Apache is more popular with more features, NGINX is faster with less features. Neither can serve Ruby web apps out-of-the-box and need additional modules.

Apache and NGINX can also act as reverse proxies meaning they can take incoming HTTP requests and forward it to another server, which also speaks HTTP.

Web servers are the front-most layer of traffic handling. Setup:

• make you HTTP available from the internet, by configuring your router to send all incoming traffic on port 80 to your server
  • on most cloud platforms, this is handled already
  • locally, it would require going to http://192.168.1.1/, and allowing traffic to pass through firewall
  • choose computer, forward external TCP traffic on port 80 to port 80 (this is port forwarding)
  • people can then connect to your local server via your public IP address

Apache vs Nginx

Both solutions are capable of handling diverse workloads. They are different in what they excel at. One big difference is how they handle connections and traffic.

Apache

The Apache HTTP server was created in 1995.

• flexible, powerful, well supported, extensible through a dynamically loadable module system

Nginx

2004, known for light-weight resource utilization and ability to scale easily on minimal hardware

• excels at serving static content quickly
• designed to pass dynamic request off to other software
• highly responsive under load
• focused on core web server and proxy features

source

Mongrel and other production app servers and WEBrick

Mongrel is a Ruby "application server":

1. It loads the Ruby app in its own process space

2. Sets up a TCP socket allowing it to communicate with the internet (Mongrel listens for HTTP requests on this socket and passes the request data to the Ruby web app)

3. Ruby web app returns an object which describes what the HTTP response should look like, Mongrel converts it to an actual HTTP response and sends it back over the socket.

Mongrel is dated, and newer comparable application servers are:

• Unicorn
• Puma
• Thin
• Phusion Passenger

WEBrick is the built in Ruby app server, but WEBrick is not fit for production (written entirely in ruby so poor performance).

App Servers

Some app servers directly have access to the internet via port 80 while most others need to be put behind a reverse proxy web server using Apache or NGINX.

• Mongrel is bare bones, single-threaded so only useful in clusters.
• Unicorn is a fork of Mongrel, supports limited process monitoring, automatic restart, single threaded. Allows all processes to listen on a shared socket.
• Thin uses the event I/O concurrency model, each process uses its own socket.
• Puma also forked from Mongrel, Puma is designed to be purely multi-threaded, no builtin cluster support.

More reading at I/O Concurrency Models

Capistrano is used for automating the "deployment" process.