I'm learning ruby and looking at his frameworks. One things that i can't understand is how frameworks handles requests in ruby world. Digging deeper I found that there's a middleware called Rack that does the job.
So my questions are:
How does Rack handles HTTP request?
Coming from PHP where there's the famous "index.php" file as a entry-point, which is the corrispective in the ruby world?
Thanks in advance.
From the rack specification:
A Rack application is an Ruby object (not a class) that responds to call. It takes exactly one argument, the environment and returns an Array of exactly three values: The status, the headers, and the body.
In pratice, the common way that a rack application is started is defined in a config.ru file. If you look in the base directory of a rails app you will see it. In rails, it includes config/environment.rb, which includes config/application.rb, which includes boot.rb, which includes gems and whatnot. From that point the framework starts to do its thing.
The general idea with rails is that a dispatcher takes any request and decides what needs to be done with it. The dispatcher can be seen as an equivalent to the index.php you mentioned.
How the config.ru file gets accessed (or how the rack app is started) is dependent on the way your application is deployed. Phusion Passenger, a popular module for apache and nginx, will look for config.ru in the root directory of any application you have added to the server config file.
It really comes down to the deployment option. Ruby apps can be run via apache/nginx modules, directly via web servers written in ruby, and via CGI.
Here is a description of the different ways web apps are deployed, from the passenger docs
Related
While developing JavaScript apps, I usually create an API app, totally separate from the UI app. For the API, I usually use Sinatra.
I'm developing a JavaScript app that will use a WebSocket service I build. I'd like to use Ruby (em-websocket for now) and ActiveModel for data models. I want to keep this really lightweight, like a Sinatra app is for a RESTful API.
It seems my WebSocket service will simply be a ruby script invoked via "ruby web_socket_service.rb". I'd like to be able to use various gems (like activerecord, capistrano, and nokogiri) with this WebSocket service. What's the most typical way of accomplishing this?
Would I be better off creating a standalone gem to contain my models and the WebSocket service script and then host my WebSocket service from that? Or maybe simply include the gems and models directly in the script via "gem 'name'? Or, is there some special library or framework commonly-used to tackle this?
Look at a Rails app. That's the approach I would take if your WebSocket service starts to grow towards a medium-sized app. I.e. bin, lib, Rakefile, and a Gemfile for your gems and bundler.
For smaller apps you can still use a Gemfile and bundler to manage the included gems. This locks gem versions so you won't have conflicts if you deploy to other servers. And then just put everything into one or two script files, similar to Sinatra.
Creating standalone gems is really only useful for libraries or application parts that are reusable across many applications. This doesn't sound like that sort of thing.
I come from a PHP and .NET world where I understand the environment fairly well. However I can't find a newbie explanation of how the Ruby / Ruby on Rails stack actually work with these web server.
Are they more close to the PHP model, where all classes of an application are loader for each request and there is no default shared memory, or is it like an application server where an active app sits in the memory and handles requests?
How is it with reloading when a file changes? Does the app in an application server has to be restarted? How does it know? Does it monitor file system?
I have seen that both the Ruby Version Manager (rvm) and the newer rbenv from 37signals shomewhat shuffles with the ruby command on OS X / Linux. This seems like a total magic to me. Does a webserver just runs ruby command and does not care where the interpreter is resolved in the $PATH?
Webrick is the default server of Rails and is usually used for developing and testing.
Rails is session based like PHP is. If you want to run in production you will generally use Phusion Passenger on Apache or Nginx, dont worry about that for now.
If you run in Development or Test environment you can edit your application files(views, controllers and models) and they will be reloaded on each request (even if they are not edited).
Have a look at generating a project and scafolds with Rails to get you started.
http://guides.rubyonrails.org/getting_started.html
Is there a framework for Ruby for CGI that provides similar functionality as Ruby on Rails (mvc)?
Also, The server where the app shall be used on does not support FCGI, only plain old CGI.
Ruby comes with a CGI module, but it isn't a MVC at all. It makes it easy to extract parameters from a HTTP request passed to the app, encode and decode the query params, etc. It relies on a web server to handle routing the request to the right page, so there's quite a gap between a MVC and a CGI.
There are alternate MVCs for Ruby. Sinatra is very easy to use, and Padrino is built on Sinatra, putting it between Sinatra and Rails. I like using Sinatra at work because it's good for fast prototyping and in-house loads are nowhere close to what we'd get on an internet facing app.
As far as the server not supporting FCGI, a MVC doesn't really care. Put its server on a different port, then reference that port when you want something to talk to Sinatra. For instance, if you tell Sinatra to use 8088, your URLs for Sinatra served pages would be something like: http://host.com:8808/url/path/to/object. Load your Sinatra based app on the web server and start it up. It'll run concurrently with the normal web server.
Many people have asked about Rails hosting on this site, but I'm not familiar enough with the back end of things to know if there's a difference.
I want to host some Ruby CGI 'webservices', basically just ruby methods that take parameters from a POST request, access a MySQL db and return data.
I've looked at RoR and it seems like overkill for this, from what I can tell it's for speeding up the development of data baesd CRUD sites, which is not at all what I'm doing.
So my question is, does this affect the hosting provider I choose? Does anyone recommend a good Ruby host for CGI operations? I'm not familiar with FastCGI, mod_ruby, Passenger, Mongrel etc. and what they mean for performance, scalability etc. I just want to host my ruby scripts with reasonably good performance, and all the info out there(and here) seems to be focused on rails.
First, if you want lightweight, Sinatra is usually my first pick. Pair it up with rack and Passenger for best results. It's not CGI, but realistically speaking, CGI is rarely a good match-up with Ruby.
Here's the "Hello World!" Sinatra app from the main page:
require 'rubygems'
require 'sinatra'
get '/hi' do
"Hello World!"
end
Hard to get more lightweight than that.
As for providers, anybody that supports Passenger (mod_rack) should be able to handle Sinatra. I'm a big fan of Slicehost personally, but they're a VPS host, which means you need to be able to install and manage the entire stack yourself. If you don't mind paying a tiny bit extra for the infrastructure, Heroku makes installation and deployment dead simple, so long as your needs don't exceed what they provide (sounds like they won't). In the unlikely event that you're only using 5MB or if you're using an external storage mechanism like Amazon RDS, Heroku may actually be free for you.
Update:
Passenger is an Apache module that allows Rack applications to be run inside of Apache.
Rack is a middleware layer that separates the web server and the web framework from each other. This allows web frameworks to run on any web server for which there is an adapter.
Sinatra is a lightweight web framework that runs on top of Rack.
Once Passenger and Rack are installed (gem install rack, gem install passenger) you just need to edit the Apache vhost to point at the config.ru file for your Sinatra app and create the required directories as per the Passenger docs and you'll be good to go.
I think you might want to look into Rack. It allows you to do the kinds of things you're talking about and shrugs off the weight of frameworks like Rails or Merb. Rack applications can be hosted at a place like Heroku.
If you use Webrick you can implement a servlet and service http requests using ruby. Now I have code that does everything that I want but I would like to move to Apache. Is there a way to modify the .htaccess file to send all the requests through a ruby handler?
you should check out phusion passenger. It lets you easily deploy any ruby Rack based web app in apache. You can then use rails, sinatra, waves, etc from apache.
You're asking for mod_ruby.
That was abandoned years ago in favor of running the Ruby code in a separate process under Mongrel, and just using Apache mod_proxy (or another web server acting as a proxy).
And now that Passenger is available lots of people (including myself) are adopting it instead of Mongrel, because it's simpler.
Just accept that you did it wrong the first time and bite the bullet. Rewrite your code as a Rack service, and run it via Passenger.