A lot of work has gone into god since the last release. Say goodbye to polling for process status--support for event based conditions via kqueue/netlink has been added (thanks Kevin Clark)! Only a few events are currently supported (most prominently process exit), but the way is now open for the addition of other events. A new, advanced syntax is available (in addition to the familiar simple syntax) that gives you full power over the new state based lifecycle of your Watches. Updated documentation is available on the website:
WHAT IS GOD?
God is an easy to configure, easy to extend monitoring framework written in Ruby.
Keeping your server processes and tasks running should be a simple part of your deployment process. God aims to be the simplest, most powerful monitoring application available.
DISCLAIMER
God is still very young, I'd love to get feedback and bug reports, but I do not yet recommend you use it for mission critical tasks. I personally use it in production but then I'm a daring fellow.
INSTALL
sudo gem install god
* note: currently tested only on Redhat Linux and Darwin (won't work on Windows)
FEATURES
* Config file is written in Ruby
* Easily write your own custom conditions in Ruby
* Supports both poll and event based conditions
* Different poll conditions can have different intervals
EXAMPLE
The easiest way to understand how god will make your life better is by looking at a sample config file. The following configuration file is what I use at gravatar.com to keep the mongrels running:
# file: gravatar.god
# run with: god start -c /path/to/gravatar.god
···
#
# This is the actual config file used to keep the mongrels of
# gravatar.com running.
RAILS_ROOT = "/var/www/gravatar2/current"
God.meddle do |god|
%w{8200 8201 8202}.each do |port|
god.watch do |w|
w.name = "gravatar2-mongrel-#{port}"
w.interval = 30 # seconds default
w.start = "mongrel_rails cluster::start --only #{port} \
-C #{RAILS_ROOT}/config/mongrel_cluster.yml"
w.stop = "mongrel_rails cluster::stop --only #{port} \
-C #{RAILS_ROOT}/config/mongrel_cluster.yml"
w.grace = 10 # seconds
pid_file = File.join(RAILS_ROOT, "log/mongrel.#{port}.pid")
w.behavior(:clean_pid_file) do |b|
b.pid_file = pid_file
end
w.start_if do |start|
start.condition(:process_running) do |c|
c.interval = 5 # seconds
c.running = false
c.pid_file = pid_file
end
end
w.restart_if do |restart|
restart.condition(:memory_usage) do |c|
c.pid_file = pid_file
c.above = (150 * 1024) # 150mb
c.times = [3, 5] # 3 out of 5 intervals
end
restart.condition(:cpu_usage) do |c|
c.pid_file = pid_file
c.above = 50 # percent
c.times = 5
end
end
end
end
end
DOCS
Detailed documentation is available at http://god.rubyforge.org/
CHANGES
== 0.2.0 / 2007-07-18
* Rewrote innards to use a state and event based lifecycle
* Basic support for events via kqueue (bsd/darwin) and netlink/pec (linux) [kevinclark]
* Added advanced syntax (simple syntax calls advanced api underneath)
* Condition returns have changed meaning. With simple syntax, a true return activates block
* Updated http://god.rubygorge.org with updated simple config and new advanced config
AUTHORS
Tom Preston-Werner
Kevin Clark