Epinephrine

Keeps your workers alive.

$ gem install epi

Example config.epi:

job resque: 'Resque Workers' do |j|
  j.user = 'webapp'
  j.directory = File.expand_path('..', __FILE__)
  j.environment = {
      QUEUE: '*',
      TERM_CHILD: 1,
      PIDFILE: -> p { p.pidfile }
  }
  j.command = 'bundle exec rake resque:work'
  j.initial_processes = 2
  j.allowed_processes = 1..5
  j.stdout = nil
  j.stderr = '/var/log/worker_errors.log'
  j.kill_timeout = 3.seconds

  j.on(:touch, __FILE__) { |job| job.restart! }
  j.on(:memory, :gt, 350.megabytes) { |process| process.restart! }
  j.on(:uptime, :gt, 1.day) { |process| process.restart! }
end

Tell Epi to watch this config file:

$ epi config add config.epi
Added configuration file: /home/my_app/config.epi

See what Epi is up to:

$ epi status
---
Running as: root
Since: Mon 20 Oct 2014 15:27:04
Jobs:
  Resque Workers [resque]:
    PID 40210:
      Since: Mon 20 Oct 2014 15:31:20
      CPU: 0.0%
      Memory: 0.3%
    PID 40213 [dying]:
      Since: Mon 20 Oct 2014 15:31:21
      CPU: 0.0%
      Memory: 0.2%  

Start/stop workers:

$ epi job resque more
Increasing 'Resque Workers' processes by 1 (from 2 to 3)
$ epi job resque 2 less
Decreasing 'Resque Workers' processes by 2 (from 3 to 1)
$ epi job resque 4
Increasing 'Resque Workers' processes by 3 (from 1 to 4)
$ epi job resque pause
Decreasing 'Resque Workers' processes by 4 (from 4 to 0)
$ epi job resque resume
Increasing 'Resque Workers' processes by 4 (from 0 to 4)
$ epi job resque max
Increasing 'Resque Workers' processes by 1 (from 4 to 5)
$ epi job resque restart
Replacing 5 'Resque Workers' processes

Control the Epi daemon, and all its managed processes:

$ epi stop
Stopping 5 processes ...
Shutting down ...
$ epi start
Starting 5 processes ...
$ epi restart
Stopping 5 processes ...
Shutting down ...
Starting 5 processes ...

Config files will be reloaded whenever they change.

Epi checks the state of running processes every 5 seconds by running the ps command.

Change the number of seconds between polls by setting the EPI_INTERVAL environment variable.

Logs are written to ~/.epi/epi.log, or /var/log/epi.log if run as root.

Set the EPI_LOG environment variable to tell Epi to write logs elsewhere. Set EPI_LOG_LEVEL to limit logging to debug, info, error, warn, fatal, or unknown.

You can only configure jobs to run as other users if the Epi daemon runs as root.

The daemon is started the first time you run the epi command, as whatever user ran it. If epi is ever run by root, the original user's daemon will be replaced by a daemon owned by root. Once that's happened, Epi will complain if you try to start or stop the daemon as any other user.

Epi recognises the history of its daemon running as root by the presence of data in /etc/epi. You can force it to use a particular user's data instead by setting the EPI_HOME environment variable to, for example, ~/.epi.