From 79b9740ef99bd446a5d52881765b183354eb0cff Mon Sep 17 00:00:00 2001
From: Marten Seemann <martenseemann@gmail.com>
Date: Sat, 10 Jul 2021 11:32:51 -0500
Subject: [PATCH] collect metrics in a separate go routine

---
 metrics.go | 84 ++++++++++++++++++++++++++++++++----------------------
 1 file changed, 50 insertions(+), 34 deletions(-)

diff --git a/metrics.go b/metrics.go
index 4db7271..b0326ce 100644
--- a/metrics.go
+++ b/metrics.go
@@ -20,6 +20,8 @@ var (
 	bytesRcvdDesc *prometheus.Desc
 )
 
+const collectFrequency = 10 * time.Second
+
 var collector *aggregatingCollector
 
 func init() {
@@ -54,10 +56,12 @@ func init() {
 type aggregatingCollector struct {
 	mutex sync.Mutex
 
-	highestID     uint64
-	conns         map[uint64] /* id */ *tracingConn
-	rtts          prometheus.Histogram
-	connDurations prometheus.Histogram
+	highestID            uint64
+	conns                map[uint64] /* id */ *tracingConn
+	rtts                 prometheus.Histogram
+	connDurations        prometheus.Histogram
+	segsSent, segsRcvd   uint64
+	bytesSent, bytesRcvd uint64
 }
 
 var _ prometheus.Collector = &aggregatingCollector{}
@@ -103,45 +107,57 @@ func (c *aggregatingCollector) Describe(descs chan<- *prometheus.Desc) {
 	}
 }
 
-func (c *aggregatingCollector) Collect(metrics chan<- prometheus.Metric) {
-	now := time.Now()
-	c.mutex.Lock()
-	var segsSent, segsRcvd uint64
-	var bytesSent, bytesRcvd uint64
-	for _, conn := range c.conns {
-		info, err := conn.getTCPInfo()
-		if err != nil {
-			if strings.Contains(err.Error(), "use of closed network connection") {
-				c.closedConn(conn)
+func (c *aggregatingCollector) cron() {
+	ticker := time.NewTicker(collectFrequency)
+	defer ticker.Stop()
+
+	for now := range ticker.C {
+		c.mutex.Lock()
+		c.segsSent = 0
+		c.segsRcvd = 0
+		c.bytesSent = 0
+		c.bytesRcvd = 0
+		for _, conn := range c.conns {
+			info, err := conn.getTCPInfo()
+			if err != nil {
+				if strings.Contains(err.Error(), "use of closed network connection") {
+					c.closedConn(conn)
+					continue
+				}
+				log.Errorf("Failed to get TCP info: %s", err)
 				continue
 			}
-			log.Errorf("Failed to get TCP info: %s", err)
-			continue
-		}
-		if hasSegmentCounter {
-			segsSent += getSegmentsSent(info)
-			segsRcvd += getSegmentsRcvd(info)
-		}
-		if hasByteCounter {
-			bytesSent += getBytesSent(info)
-			bytesRcvd += getBytesRcvd(info)
-		}
-		c.rtts.Observe(info.RTT.Seconds())
-		c.connDurations.Observe(now.Sub(conn.startTime).Seconds())
-		if info.State == tcpinfo.Closed {
-			c.closedConn(conn)
+			if hasSegmentCounter {
+				c.segsSent += getSegmentsSent(info)
+				c.segsRcvd += getSegmentsRcvd(info)
+			}
+			if hasByteCounter {
+				c.bytesSent += getBytesSent(info)
+				c.bytesRcvd += getBytesRcvd(info)
+			}
+			c.rtts.Observe(info.RTT.Seconds())
+			c.connDurations.Observe(now.Sub(conn.startTime).Seconds())
+			if info.State == tcpinfo.Closed {
+				c.closedConn(conn)
+			}
 		}
+		c.mutex.Unlock()
 	}
-	c.mutex.Unlock()
+}
+
+func (c *aggregatingCollector) Collect(metrics chan<- prometheus.Metric) {
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+
 	metrics <- c.rtts
 	metrics <- c.connDurations
 	if hasSegmentCounter {
-		segsSentMetric, err := prometheus.NewConstMetric(segsSentDesc, prometheus.CounterValue, float64(segsSent))
+		segsSentMetric, err := prometheus.NewConstMetric(segsSentDesc, prometheus.CounterValue, float64(c.segsSent))
 		if err != nil {
 			log.Errorf("creating tcp_sent_segments_total metric failed: %v", err)
 			return
 		}
-		segsRcvdMetric, err := prometheus.NewConstMetric(segsRcvdDesc, prometheus.CounterValue, float64(segsRcvd))
+		segsRcvdMetric, err := prometheus.NewConstMetric(segsRcvdDesc, prometheus.CounterValue, float64(c.segsRcvd))
 		if err != nil {
 			log.Errorf("creating tcp_rcvd_segments_total metric failed: %v", err)
 			return
@@ -150,12 +166,12 @@ func (c *aggregatingCollector) Collect(metrics chan<- prometheus.Metric) {
 		metrics <- segsRcvdMetric
 	}
 	if hasByteCounter {
-		bytesSentMetric, err := prometheus.NewConstMetric(bytesSentDesc, prometheus.CounterValue, float64(bytesSent))
+		bytesSentMetric, err := prometheus.NewConstMetric(bytesSentDesc, prometheus.CounterValue, float64(c.bytesSent))
 		if err != nil {
 			log.Errorf("creating tcp_sent_bytes metric failed: %v", err)
 			return
 		}
-		bytesRcvdMetric, err := prometheus.NewConstMetric(bytesRcvdDesc, prometheus.CounterValue, float64(bytesRcvd))
+		bytesRcvdMetric, err := prometheus.NewConstMetric(bytesRcvdDesc, prometheus.CounterValue, float64(c.bytesRcvd))
 		if err != nil {
 			log.Errorf("creating tcp_rcvd_bytes metric failed: %v", err)
 			return