add a close() method to terminate the module cleanly

closes the statsd connection and cancels registered interval timers
prevents express from hanging when trying to shutdown

libraries/metrics/metrics.coffee

@@ -6,10 +6,15 @@ hostname = require('os').hostname()
 
 buildKey = (key)-> "#{name}.#{hostname}.#{key}"
 
+destructors = []
+
 module.exports =
 	initialize: (_name) ->
 		name = _name
 
+	registerDestructor: (func) ->
+		destructors.push func
+
 	set : (key, value, sampleRate = 1)->
 		statsd.set buildKey(key), value, sampleRate
 
@@ -35,3 +40,7 @@ module.exports =
 	http: require "./http"
 	open_sockets: require "./open_sockets"
 
+	close: () ->
+		for func in destructors
+			func()
+		statsd.close()

libraries/metrics/open_sockets.coffee

@@ -3,9 +3,12 @@ seconds = 1000
 
 module.exports = OpenSocketsMonitor =
 	monitor: (logger) ->
-		setInterval () ->
+		interval = setInterval () ->
 			OpenSocketsMonitor.gaugeOpenSockets()
 		, 5 * seconds
+		Metrics = require "./metrics"
+		Metrics.registerDestructor () ->
+			clearInterval(interval)
 
 	gaugeOpenSockets: () ->
 		Metrics = require "./metrics"