How do i monitor independed applications with god? - ruby

Question

I'm currently looking into options for process monitoring of Rails/Ruby Projects and quite like god.
But i cant really find anything on how to monitor multiple applications (for example 2 rails projects running on one machine) with god.
As far as i see it i just set up god (system ruby) and have each project add its own configuration (maybe somehow in a deploy-hook).
This should also work with the projects running different ruby versions (rbenv, rvm) or bundler, since the god ruby does not have to access any project code.
Does anyone already use it like this? Or is there a better approach?

Answer 1

I use god to watch all my stuff (unicorn, redis, resque workers). Basic setup is like this:
God is installed globally, loads on system startup and reads its config file, /etc/god/all.god.
/etc/god/all.god
files = Dir.glob "/etc/god/**/*.god"
files.each do |f|
next if f == '/etc/god/all.god'
God.load f
end
This file loads all config files in /etc/god and its children. Deploy scripts put config files there and tell god to (re)load them.
$ ls -l /etc/god
total 16
-rw-r--r-- 1 root root 108 2012-02-23 16:26 all.god
drwxr-xr-x 2 sergio sergio 4096 2012-03-20 20:59 app1_production
drwxr-xr-x 2 sergio sergio 4096 2012-03-27 00:58 app2_production
drwxr-xr-x 2 root root 4096 2012-04-23 01:37 util
$ ls -l /etc/god/app1_production/
total 0
lrwxrwxrwx 1 sergio sergio 55 2012-03-20 20:59 redis.god -> /srv/app1_production/current/config/god/redis.god
lrwxrwxrwx 1 sergio sergio 56 2012-03-20 20:59 resque.god -> /srv/app1_production/current/config/god/resque.god
lrwxrwxrwx 1 sergio sergio 57 2012-03-20 20:59 unicorn.god -> /srv/app1_production/current/config/god/unicorn.god
Here's a head of unicorn.god.
rails_env = "production"
pid_dir = "/srv/app1_#{rails_env}/shared/pids"
rails_root = "/srv/app1_#{rails_env}/current"
God.watch do |w|
w.name = "unicorn-#{rails_env}"
w.interval = 30.seconds # default
# unicorn needs to be run from the rails root
w.start = "cd #{rails_root} && /home/sergio/.rvm/bin/r193_bundle exec unicorn_rails -c #{rails_root}/config/unicorn/unicorn.#{rails_env}.rb -E #{rails_env} -D"
# QUIT gracefully shuts down workers
w.stop = "kill -QUIT `cat #{pid_dir}/unicorn.pid`"
# USR2 causes the master to re-create itself and spawn a new worker pool
w.restart = "kill -USR2 `cat #{pid_dir}/unicorn.pid`"
As you can see, unicorns are launched via rvm wrappers and therefore each new app can use its own ruby. Also, you provide your own start, stop and restart commands, so you can use god to watch any piece of software.
This approach works very well for me (so far).