I am trying to run the same script in multiple daemons.
myapp.rb looks like this:
loop do
sleep 5
1 / 0 # crash it
end
my myapp_controller.rb:
require 'rubygems'
require 'daemons'
options = {
:log_output => true,
:backtrace => true,
:monitor => true,
:multiple => true,
:log_dir => '/mnt/log/',
:hard_exit => true
}
Daemons.run(File.join(File.dirname(__FILE__), 'myapp.rb'), options)
When I run ruby myapp_controller.rb start several times in a row, it creates that many daemons, as I expect. But, after a while, due to an error in myapp.rb the daemons crash and the monitor restarts just one and not all. So I end up with a single running daemon.
Why? What am I doing wrong?
I was able to reproduce the behavior. It is not anything you are doing wrong; it is the way the daemons gem behaves.
Going through the code for the daemons gem, turns out the :multiple option doesn't work well with the :monitor option.
The :monitor option works only when the daemon is run in single mode.
I have created a bug report on the daemons project page referencing this question as the source.
Multiple daemon processes are created when :multiple => true. Each process has its own pid file in the format of <scriptname>.rb<number>.pid.
However, only one monitor process is created (with a single <scriptname>.rb_monitor.pid file.)
Here are the list of processes started when I start the daemon process 3 times:
$ ps -fe | grep my_server
501 1758 1 0 12:25PM ?? 0:00.63 my_server.rb
501 1759 1 0 12:25PM ?? 0:00.43 my_server.rb_monitor
501 1764 1 0 12:25PM ?? 0:00.54 my_server.rb
501 1834 1 0 12:51PM ?? 0:00.31 my_server.rb
The files in the pid/log folder:
$ ls /tmp/daemons-2013-01-25/
my_server.rb.log my_server.rb1.pid my_server.rb_monitor.pid
my_server.rb0.pid my_server.rb2.pid