lib/god/hub.rb

   1 module God
   2
   3   class Hub
   4     class << self
   5       # directory to hold conditions and their corresponding metric
   6       #   key: condition
   7       #   val: metric
   8       attr_accessor :directory
   9     end
  10
  11     self.directory = {}
  12
  13     def self.attach(condition, metric)
  14       # add the condition to the directory
  15       self.directory[condition] = metric
  16
  17       # schedule poll condition
  18       # register event condition
  19       if condition.kind_of?(PollCondition)
  20         Timer.get.schedule(condition, 0)
  21       else
  22         condition.register
  23       end
  24     end
  25
  26     def self.detach(condition)
  27       # remove the condition from the directory
  28       self.directory.delete(condition)
  29
  30       # unschedule any pending polls
  31       Timer.get.unschedule(condition)
  32
  33       # deregister event condition
  34       if condition.kind_of?(EventCondition)
  35         condition.deregister
  36       end
  37     end
  38
  39     def self.trigger(condition)
  40       if condition.kind_of?(PollCondition)
  41         self.handle_poll(condition)
  42       elsif condition.kind_of?(EventCondition)
  43         self.handle_event(condition)
  44       end
  45     end
  46
  47     def self.handle_poll(condition)
  48       Thread.new do
  49         begin
  50           metric = self.directory[condition]
  51
  52           # it's possible that the timer will trigger an event before it can be cleared
  53           # by an exiting metric, in which case it should be ignored
  54           exit if metric.nil?
  55
  56           watch = metric.watch
  57
  58           watch.mutex.synchronize do
  59             # run the test
  60             result = condition.test
  61
  62             # log
  63             msg = watch.name + ' ' + condition.class.name + " [#{result}] " + metric.destination.inspect
  64             Syslog.debug(msg)
  65             LOG.log(watch, :info, msg)
  66
  67             # after-condition
  68             condition.after
  69
  70             # get the destination
  71             dest =
  72             if result && condition.transition
  73               # condition override
  74               condition.transition
  75             else
  76               # regular
  77               metric.destination[result]
  78             end
  79
  80             # transition or reschedule
  81             if dest
  82               # transition
  83               begin
  84                 watch.move(dest)
  85               rescue EventRegistrationFailedError
  86                 msg = watch.name + ' Event registration failed, moving back to previous state'
  87                 Syslog.debug(msg)
  88                 LOG.log(watch, :info, msg)
  89
  90                 dest = watch.state
  91                 retry
  92               end
  93             else
  94               # reschedule
  95               Timer.get.schedule(condition)
  96             end
  97           end
  98         rescue => e
  99           message = format("Unhandled exception (%s): %s\n%s",
 100                            e.class, e.message, e.backtrace.join("\n"))
 101           Syslog.crit message
 102           abort message
 103         end
 104       end
 105     end
 106
 107     def self.handle_event(condition)
 108       Thread.new do
 109         metric = self.directory[condition]
 110         watch = metric.watch
 111
 112         watch.mutex.synchronize do
 113           msg = watch.name + ' ' + condition.class.name + " [true] " + metric.destination.inspect
 114           Syslog.debug(msg)
 115           LOG.log(watch, :info, msg)
 116
 117           dest = metric.destination[true]
 118           watch.move(dest)
 119         end
 120       end
 121     end
 122   end
 123
 124 end