lib/god/conditions/process_exits.rb

   1 module God
   2   module Conditions
   3
   4     # Condition Symbol :process_exits
   5     # Type: Event
   6     #
   7     # Trigger when a process exits.
   8     #
   9     # Paramaters
  10     #   Required
  11     #     +pid_file+ is the pid file of the process in question. Automatically
  12     #                populated for Watches.
  13     #
  14     # Examples
  15     #
  16     # Trigger if process exits (from a Watch):
  17     #
  18     #   on.condition(:process_exits)
  19     #
  20     # Trigger if process exits:
  21     #
  22     #   on.condition(:process_exits) do |c|
  23     #     c.pid_file = "/var/run/mongrel.3000.pid"
  24     #   end
  25     class ProcessExits < EventCondition
  26       def initialize
  27         self.info = "process exited"
  28       end
  29
  30       def valid?
  31         valid = true
  32         valid &= complain("Attribute 'pid_file' must be specified", self) if self.watch.pid_file.nil?
  33         valid
  34       end
  35
  36       def register
  37         pid = File.read(self.watch.pid_file).strip.to_i
  38
  39         begin
  40           EventHandler.register(pid, :proc_exit) do |extra|
  41             formatted_extra = extra.size > 0 ? " #{extra.inspect}" : ""
  42             self.info = "process #{pid} exited#{formatted_extra}"
  43             Hub.trigger(self)
  44           end
  45
  46           msg = "#{self.watch.name} registered 'proc_exit' event for pid #{pid}"
  47           applog(self.watch, :info, msg)
  48         rescue StandardError
  49           raise EventRegistrationFailedError.new
  50         end
  51       end
  52
  53       def deregister
  54         if File.exist?(self.watch.pid_file)
  55           pid = File.read(self.watch.pid_file).strip.to_i
  56           EventHandler.deregister(pid, :proc_exit)
  57
  58           msg = "#{self.watch.name} deregistered 'proc_exit' event for pid #{pid}"
  59           applog(self.watch, :info, msg)
  60         else
  61           applog(self.watch, :error, "#{self.watch.name} could not deregister: no such PID file #{self.watch.pid_file} (#{self.base_name})")
  62         end
  63       end
  64     end
  65
  66   end
  67 end