Add. Event handler to support MWI. (#1720)

* Add. Event handler to support MWI.

* Fix. store cache only when get data from memcache

* Change. Use UUID as PID.

resources/install/scripts/resources/functions/interval_timer.lua

@@ -0,0 +1,64 @@
+local os_time = {
+	now        = function()   return os.time()                 end;
+	elapsed    = function(t)  return os.difftime(os.time(), t) end;
+	ms_to_time = function(ms) return ms / 1000                 end;
+	time_to_ms = function(t)  return t * 1000                  end;
+}
+
+local os_clock = {
+	now        = function()   return os.clock()     end;
+	elapsed    = function(t)  return os.clock() - t end;
+	ms_to_time = function(ms) return ms / 1000      end;
+	time_to_ms = function(t)  return t * 1000       end;
+}
+
+local IntervalTimer = {} do
+IntervalTimer.__index = IntervalTimer
+
+function IntervalTimer.new(interval, timer)
+	local o = setmetatable({}, IntervalTimer)
+	o._interval = interval
+	o._timer    = timer or os_clock
+
+	return o
+end
+
+function IntervalTimer:start()
+	assert(not self:started())
+	return self:restart()
+end
+
+function IntervalTimer:restart()
+	self._begin = self._timer.now()
+	return self
+end
+
+function IntervalTimer:started()
+	return not not self._begin
+end
+
+function IntervalTimer:elapsed()
+	assert(self:started())
+	local e = self._timer.elapsed(self._begin)
+	return self._timer.time_to_ms(e)
+end
+
+function IntervalTimer:rest()
+	local d = self._interval - self:elapsed()
+	if d < 0 then d = 0 end
+	return d
+end
+
+function IntervalTimer:stop()
+	if self:started() then
+		local d = self:elapsed()
+		self._begin = nil
+		return d
+	end
+end
+
+end
+
+return {
+	new = IntervalTimer.new;
+}