Simple and reliable process monitoring framework written in Ruby

Quick start

Install Cognizant

$ gem install cognizant

Example thin server cluster configuration

$ vim thin_cluster.cz

app_root = "/apps/acmecorp.com"
servers = 5
port = 4000

Cognizant.application "acmecorp.com" do |app|
  servers.times do |n|
    app.monitor "thin-#{n}" do
      autostart!      
      group "thin"
      uid "www-data"
      gid "www-data"

      env RACK_ENV: "production"
      chdir "#{app_root}/current"

      daemonize false
      pidfile "#{app_root}/shared/tmp/pids/thin.400#{n}.pid"

      start_command   "bundle exec thin start   --only #{n} --servers #{servers} --port #{port}"
      stop_command    "bundle exec thin stop    --only #{n} --servers #{servers} --port #{port}"
      restart_command "bundle exec thin restart --only #{n} --servers #{servers} --port #{port}"

	  check :flapping, times: 3, within: 1.minute, retry_after: 15.seconds, retries: 10
      check :transition, from: :running, to: :stopped do |process|
        `say a thin server has stopped` # send an email, etc.
      end

      check :cpu_usage,    above: 50.percent,    every: 5.seconds, times: 5,      do: :restart
      check :memory_usage, above: 300.megabytes, every: 5.seconds, times: [3, 5], do: :restart
    end
  end
end

YAML version of this example is available in the wiki.

Start the daemon and load the configuration

$ cognizantd
$ cognizant load thin_cluster.cz

Enter the Cognizant shell and view the status of managed processes

$ cognizant

Welcome Gurpartap! You are speaking to the Cognizant Monitoring Daemon.
Enter 'help' if you're not sure what to do.

Type 'quit' or 'exit' to quit at any time.
> use acmecorp.com
OK

(acmecorp.com)> status
+---------+-------+------------------------+-------+-------+--------+
| Process | Group | State                  | PID   | % CPU | Memory |
+---------+-------+------------------------+-------+-------+--------+
| thin-0  | thin  | running since 1 minute | 59825 | 0.0   | 47 MiB |
+---------+-------+------------------------+-------+-------+--------+
| thin-1  | thin  | running since 1 minute | 59828 | 0.0   | 47 MiB |
+---------+-------+------------------------+-------+-------+--------+
| thin-2  | thin  | running since 1 minute | 59829 | 0.0   | 47 MiB |
+---------+-------+------------------------+-------+-------+--------+
2013-03-18 10:00:29 +0530

Further information

Cognizant has an extensively documented wiki for that.

About

Cognizant is a project of Gurpartap Singh. Feel free to get in touch.