From 9962d4ef9ffc31b7cb0b0a24ab9758273f5493e6 Mon Sep 17 00:00:00 2001
From: Pablo Carranza <pcarranza@gmail.com>
Date: Sun, 13 May 2018 01:02:05 +0200
Subject: [PATCH] Fix concurrency problems, for real this time

---
 nomad-exporter.go | 71 ++++++++++++++++++++++++-----------------------
 1 file changed, 37 insertions(+), 34 deletions(-)

diff --git a/nomad-exporter.go b/nomad-exporter.go
index a7cb38e..131401b 100644
--- a/nomad-exporter.go
+++ b/nomad-exporter.go
@@ -296,6 +296,7 @@ func main() {
 		noEvalMetricsEnabled            = flag.Bool("no-eval-metrics", false, "disable eval metrics collection")
 		noDeploymentMetricsEnabled      = flag.Bool("no-deployment-metrics", false, "disable deployment metrics collection")
 		noAllocationStatsMetricsEnabled = flag.Bool("no-allocation-stats-metrics", false, "disable stats metrics collection")
+		concurrency                     = flag.Int("concurrency", 20, "max number of goroutines to launch concurrently when poking the API")
 	)
 	flag.Parse()
 
@@ -342,6 +343,7 @@ func main() {
 		EvalMetricsEnabled:            !*noEvalMetricsEnabled,
 		DeploymentMetricsEnabled:      !*noDeploymentMetricsEnabled,
 		AllocationStatsMetricsEnabled: !*noAllocationStatsMetricsEnabled,
+		Concurrency:                   *concurrency,
 	}
 
 	logrus.Debugf("Created exporter %#v", *exporter)
@@ -385,6 +387,7 @@ type Exporter struct {
 	EvalMetricsEnabled            bool
 	DeploymentMetricsEnabled      bool
 	AllocationStatsMetricsEnabled bool
+	Concurrency                   int
 }
 
 func (e *Exporter) shouldReadMetrics() bool {
@@ -560,47 +563,47 @@ func (e *Exporter) collectNodes(ch chan<- prometheus.Metric) error {
 	logrus.Debugf("I've the nodes list with %d nodes", len(nodes))
 
 	var w sync.WaitGroup
-	pool := make(chan func(), 10) // Only run 10 at a time
+	pool := make(chan func(), e.Concurrency)
 	go func() {
-		f := <-pool
-		f()
+		for f := range pool {
+			go f()
+		}
 	}()
 
 	for _, node := range nodes {
-		state := 1
-		drain := strconv.FormatBool(node.Drain)
-
-		ch <- prometheus.MustNewConstMetric(
-			nodeInfo, prometheus.GaugeValue, 1,
-			node.Name, node.Version, node.NodeClass, node.Status,
-			drain, node.Datacenter, node.SchedulingEligibility,
-		)
+		w.Add(1)
+		pool <- func(node api.NodeListStub) func() {
+			return func() {
+				defer w.Done()
+				state := 1
+				drain := strconv.FormatBool(node.Drain)
 
-		if node.Status == "down" {
-			state = 0
-		}
-		ch <- prometheus.MustNewConstMetric(
-			serfLanMembersStatus, prometheus.GaugeValue, float64(state),
-			node.Datacenter, node.NodeClass, node.Name, drain,
-		)
+				ch <- prometheus.MustNewConstMetric(
+					nodeInfo, prometheus.GaugeValue, 1,
+					node.Name, node.Version, node.NodeClass, node.Status,
+					drain, node.Datacenter, node.SchedulingEligibility,
+				)
 
-		if !validVersion(node.Name, node.Version) {
-			continue
-		}
+				if node.Status == "down" {
+					state = 0
+				}
+				ch <- prometheus.MustNewConstMetric(
+					serfLanMembersStatus, prometheus.GaugeValue, float64(state),
+					node.Datacenter, node.NodeClass, node.Name, drain,
+				)
 
-		if !e.AllocationStatsMetricsEnabled {
-			continue
-		}
+				if !validVersion(node.Name, node.Version) {
+					return
+				}
 
-		w.Add(1)
-		pool <- func(a api.NodeListStub) func() {
-			return func() {
-				defer w.Done()
+				if !e.AllocationStatsMetricsEnabled {
+					return
+				}
 
-				logrus.Debugf("Fetching node %#v", a)
-				node, _, err := e.client.Nodes().Info(a.ID, opts)
+				logrus.Debugf("Fetching node %#v", node)
+				node, _, err := e.client.Nodes().Info(node.ID, opts)
 				if err != nil {
-					logError(fmt.Errorf("failed to get node %s info: %s", a.Name, err))
+					logError(fmt.Errorf("failed to get node %s info: %s", node.Name, err))
 					return
 				}
 
@@ -648,7 +651,7 @@ func (e *Exporter) collectNodes(ch chan<- prometheus.Metric) error {
 					nodeLabels...,
 				)
 
-				nodeStats, err := e.client.Nodes().Stats(a.ID, opts)
+				nodeStats, err := e.client.Nodes().Stats(node.ID, opts)
 				if err != nil {
 					logError(fmt.Errorf("failed to get node %s stats: %s", node.Name, err))
 					return
@@ -723,7 +726,7 @@ func (e *Exporter) collectAllocations(ch chan<- prometheus.Metric) error {
 	for _, allocStub := range allocStubs {
 		w.Add(1)
 
-		go func(allocStub *api.AllocationListStub) {
+		go func(allocStub api.AllocationListStub) {
 			defer w.Done()
 
 			alloc, _, err := e.client.Allocations().Info(allocStub.ID, &api.QueryOptions{
@@ -814,7 +817,7 @@ func (e *Exporter) collectAllocations(ch chan<- prometheus.Metric) error {
 				)
 			}
 
-		}(allocStub)
+		}(*allocStub)
 	}
 
 	w.Wait()