From ffa523bced432ddbd92f29e6f3ed2871e09768ca Mon Sep 17 00:00:00 2001
From: Brian Gough <bjg@network-theory.co.uk>
Date: Tue, 23 Jun 2015 10:51:48 +0100
Subject: [PATCH] added monitoring of event loop time

should indicate if node is blocking on libuv threads
as described in https://nodejs.org/api/dns.html#dns_dns_lookup
---
 libraries/metrics/event_loop.coffee | 18 ++++++++++++++++++
 libraries/metrics/metrics.coffee    |  1 +
 2 files changed, 19 insertions(+)
 create mode 100644 libraries/metrics/event_loop.coffee

diff --git a/libraries/metrics/event_loop.coffee b/libraries/metrics/event_loop.coffee
new file mode 100644
index 0000000000..ab6955afc7
--- /dev/null
+++ b/libraries/metrics/event_loop.coffee
@@ -0,0 +1,18 @@
+seconds = 1000
+
+module.exports = EventLoopMonitor =
+	monitor: (logger) ->
+		interval = setInterval () ->
+			EventLoopMonitor.Delay()
+		, 1 * seconds
+		Metrics = require "./metrics"
+		Metrics.registerDestructor () ->
+			clearInterval(interval)
+
+	Delay: () ->
+		Metrics = require "./metrics"
+		t1 = process.hrtime()
+		setImmediate () ->
+			delta = process.hrtime(t1)
+			responseTime = delta[0]*1e6 + delta[1]*1e-3
+			Metrics.timing("event-loop-microsec", responseTime)
diff --git a/libraries/metrics/metrics.coffee b/libraries/metrics/metrics.coffee
index 59e4ee9899..a0cd3070fb 100644
--- a/libraries/metrics/metrics.coffee
+++ b/libraries/metrics/metrics.coffee
@@ -39,6 +39,7 @@ module.exports =
 	mongodb: require "./mongodb"
 	http: require "./http"
 	open_sockets: require "./open_sockets"
+	event_loop: require "./event_loop"
 
 	close: () ->
 		for func in destructors