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             self.info = "process #{pid} exited #{extra.inspect}"
  42             Hub.trigger(self)
  43           end
  44
  45           msg = "#{self.watch.name} registered 'proc_exit' event for pid #{pid}"
  46           applog(self.watch, :info, msg)
  47         rescue StandardError
  48           raise EventRegistrationFailedError.new
  49         end
  50       end
  51
  52       def deregister
  53         if File.exist?(self.watch.pid_file)
  54           pid = File.read(self.watch.pid_file).strip.to_i
  55           EventHandler.deregister(pid, :proc_exit)
  56
  57           msg = "#{self.watch.name} deregistered 'proc_exit' event for pid #{pid}"
  58           applog(self.watch, :info, msg)
  59         else
  60           applog(self.watch, :error, "#{self.watch.name} could not deregister: no such PID file #{self.watch.pid_file} (#{self.base_name})")
  61         end
  62       end
  63     end
  64
  65   end
  66 end