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 or a monitoring tool such as god.

Authors

• Paul Gross
• Jesse Newland

Requirements

• Rails
• MySQL, Postgres, or Oracle. sqlite not supported, sorry.

Installation

In your config/environment.rb:

  
    config.gem 'jnewland-pulse', :lib => 'pulse', :source => 'http://gems.github.com'
  

Install the gem:

  
    cd RAILS_ROOT
    rake gems:install
  

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

  
    map.pulse 'pulse'
  

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

  
    map.pulse 'some/other/url'
  

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
      ...
  

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 and the included sample rails god config.

License

Released under Ruby’s license