lib/god/hub.rb

   1 module God
   2
   3   class Hub
   4     class << self
   5       # directory to hold conditions and their corresponding metric
   6       # {condition => metric}
   7       attr_accessor :directory
   8     end
   9
  10     self.directory = {}
  11
  12     def self.attach(condition, metric)
  13       self.directory[condition] = metric
  14
  15       case condition
  16         when PollCondition
  17           Timer.get.schedule(condition, 0)
  18         when EventCondition, TriggerCondition
  19           condition.register
  20       end
  21     end
  22
  23     def self.detach(condition)
  24       self.directory.delete(condition)
  25
  26       case condition
  27         when PollCondition
  28           Timer.get.unschedule(condition)
  29         when EventCondition, TriggerCondition
  30           condition.deregister
  31       end
  32     end
  33
  34     def self.trigger(condition)
  35       case condition
  36         when PollCondition
  37           self.handle_poll(condition)
  38         when EventCondition, TriggerCondition
  39           self.handle_event(condition)
  40       end
  41     end
  42
  43     def self.handle_poll(condition)
  44       Thread.new do
  45         begin
  46           metric = self.directory[condition]
  47
  48           # it's possible that the timer will trigger an event before it can be cleared
  49           # by an exiting metric, in which case it should be ignored
  50           unless metric.nil?
  51             watch = metric.watch
  52
  53             watch.mutex.synchronize do
  54               # run the test
  55               result = condition.test
  56
  57               # log
  58               msg = watch.name + ' ' + condition.class.name + " [#{result}] " + self.dest_desc(metric, condition)
  59               Syslog.debug(msg)
  60               LOG.log(watch, :info, msg)
  61
  62               # after-condition
  63               condition.after
  64
  65               # get the destination
  66               dest =
  67               if result && condition.transition
  68                 # condition override
  69                 condition.transition
  70               else
  71                 # regular
  72                 metric.destination && metric.destination[result]
  73               end
  74
  75               # transition or reschedule
  76               if dest
  77                 # transition
  78                 begin
  79                   watch.move(dest)
  80                 rescue EventRegistrationFailedError
  81                   msg = watch.name + ' Event registration failed, moving back to previous state'
  82                   Syslog.debug(msg)
  83                   LOG.log(watch, :info, msg)
  84
  85                   dest = watch.state
  86                   retry
  87                 end
  88               else
  89                 # reschedule
  90                 Timer.get.schedule(condition)
  91               end
  92             end
  93           end
  94         rescue => e
  95           message = format("Unhandled exception (%s): %s\n%s",
  96                            e.class, e.message, e.backtrace.join("\n"))
  97           Syslog.crit message
  98           abort message
  99         end
 100       end
 101     end
 102
 103     def self.handle_event(condition)
 104       Thread.new do
 105         metric = self.directory[condition]
 106
 107         unless metric.nil?
 108           watch = metric.watch
 109
 110           watch.mutex.synchronize do
 111             msg = watch.name + ' ' + condition.class.name + " [true] " + self.dest_desc(metric, condition)
 112             Syslog.debug(msg)
 113             LOG.log(watch, :info, msg)
 114
 115             # get the destination
 116             dest =
 117             if condition.transition
 118               # condition override
 119               condition.transition
 120             else
 121               # regular
 122               metric.destination && metric.destination[true]
 123             end
 124
 125             if dest
 126               watch.move(dest)
 127             end
 128           end
 129         end
 130       end
 131     end
 132
 133     # helpers
 134
 135     def self.dest_desc(metric, condition)
 136       if metric.destination
 137         metric.destination.inspect
 138       else
 139         if condition.transition
 140           {true => condition.transition}.inspect
 141         else
 142           'none'
 143         end
 144       end
 145     end
 146   end
 147
 148 end