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h1. Pulse

Pulse adds an action to your rails project that can be used for external health checking. The most common use is by a http proxy such as "haproxy":http://haproxy.1wt.eu/ or a monitoring tool such as "god":http://god.rubyforge.org.

h3. Authors

• "Paul Gross":http://www.prgs.net
• "Jesse Newland":http://jnewland.com
• "Josh Nichols":http://technicalpickles.com

h2. Requirements

• Rails
• MySQL, Postgres, or sqlite

h2. Installation

h3. Rails 3.x

Just add the gem to your @Gemfile@ and then @bundle install@:

  
    gem 'rails-pulse'
  

In your @config/routes.rb@:

  
    pulse
    # or customize the URL
    pulse '/admin/pulse'
  

h3. Rails 2.x

In your @config/environment.rb@:

  
    config.gem 'rails-pulse', :source => "http://gemcutter.org/", :lib => "pulse"
  

Install the gem:

  
    cd RAILS_ROOT
    rake gems:install
  

Finally, add a route to config/routes.rb:

  
    map.pulse
    # or customize the URL
    map.pulse '/admin/pulse'
  

This configures pulse to work at the 'pulse' URL. If you would rather use a different URL:

  
    map.pulse 'some/other/url'
  

h2. haproxy configuration

haproxy can be configured to use the /pulse url for its health checking. Just add:

  
    option httpchk GET /pulse
  

  
    listen rails :9000
      server rails-1 localhost:8000 maxconn 1 check inter 20000 fall 1
      server rails-2 localhost:8001 maxconn 1 check inter 20000 fall 1
      ...
  

h2. god configuration

You are using god to watch your mongrels, right?

In your mongrel watch, add the following restart condition:

  
    w.restart_if do |restart|
      ...
      restart.condition(:http_response_code) do |c|
        c.code_is_not = 200
        c.host = 'localhost'
        c.path = '/pulse'
        c.port = 8000
        c.timeout = 5.seconds
        c.interval = 20.seconds
      end
    end
  

Also make sure to give your mongrels a nice grace period.

  
    ...
    w.start_grace = 90.seconds
    w.restart_grace = 90.seconds
    ...
  

For a complete god configuration example, check out my "god_examples project":http://github.com/jnewland/god_examples and the included "sample rails god config":http://github.com/jnewland/god_examples/tree/master/rails/config/god/app.god.

h2. License

Released under "Ruby's license":http://www.ruby-lang.org/en/LICENSE.txt