Fix bugs introduced by hot reloading of targets

collector.go

@@ -12,48 +12,66 @@ import (
 	"github.com/czerwonk/ping_exporter/config"
 )
 
-var (
-	labelNames []string
+type pingCollector struct {
+	monitor                 *mon.Monitor
+	enableDeprecatedMetrics bool
+	rttUnit                 rttUnit
+
+	cfg *config.Config
+
+	mutex sync.RWMutex
+
+	customLabels *customLabelSet
+	metrics      map[string]*mon.Metrics
+
 	rttDesc    scaledMetrics
 	bestDesc   scaledMetrics
 	worstDesc  scaledMetrics
 	meanDesc   scaledMetrics
 	stddevDesc scaledMetrics
 	lossDesc   *prometheus.Desc
 	progDesc   *prometheus.Desc
-	mutex      *sync.Mutex
-)
+}
 
-type pingCollector struct {
-	cfg          *config.Config
-	customLabels *customLabelSet
-	monitor      *mon.Monitor
-	metrics      map[string]*mon.Metrics
+func NewPingCollector(enableDeprecatedMetrics bool, unit rttUnit, monitor *mon.Monitor, cfg *config.Config) *pingCollector {
+	ret := &pingCollector{
+		monitor:                 monitor,
+		enableDeprecatedMetrics: enableDeprecatedMetrics,
+		rttUnit:                 unit,
+		cfg:                     cfg,
+	}
+	ret.customLabels = newCustomLabelSet(cfg.Targets)
+	ret.createDesc()
+	return ret
 }
 
-func (p *pingCollector) Describe(ch chan<- *prometheus.Desc) {
-	p.createDesc()
+func (p *pingCollector) UpdateConfig(cfg *config.Config) {
+	p.mutex.Lock()
+	defer p.mutex.Unlock()
+	p.cfg.Targets = cfg.Targets
+}
 
-	if enableDeprecatedMetrics {
-		rttDesc.Describe(ch)
+func (p *pingCollector) Describe(ch chan<- *prometheus.Desc) {
+	if p.enableDeprecatedMetrics {
+		p.rttDesc.Describe(ch)
 	}
-	bestDesc.Describe(ch)
-	worstDesc.Describe(ch)
-	meanDesc.Describe(ch)
-	stddevDesc.Describe(ch)
-	ch <- lossDesc
-	ch <- progDesc
+	p.bestDesc.Describe(ch)
+	p.worstDesc.Describe(ch)
+	p.meanDesc.Describe(ch)
+	p.stddevDesc.Describe(ch)
+	ch <- p.lossDesc
+	ch <- p.progDesc
 }
 
 func (p *pingCollector) Collect(ch chan<- prometheus.Metric) {
-	mutex.Lock()
-	defer mutex.Unlock()
+	p.mutex.Lock()
+	defer p.mutex.Unlock()
 
 	if m := p.monitor.Export(); len(m) > 0 {
 		p.metrics = m
 	}
 
-	ch <- prometheus.MustNewConstMetric(progDesc, prometheus.GaugeValue, 1)
+	ch <- prometheus.MustNewConstMetric(p.progDesc, prometheus.GaugeValue, 1)
 
 	for target, metrics := range p.metrics {
 		l := strings.SplitN(target, " ", 3)
@@ -63,35 +81,34 @@ func (p *pingCollector) Collect(ch chan<- prometheus.Metric) {
 
 		if metrics.PacketsSent > metrics.PacketsLost {
 			if enableDeprecatedMetrics {
-				rttDesc.Collect(ch, metrics.Best, append(l, "best")...)
-				rttDesc.Collect(ch, metrics.Worst, append(l, "worst")...)
-				rttDesc.Collect(ch, metrics.Mean, append(l, "mean")...)
-				rttDesc.Collect(ch, metrics.StdDev, append(l, "std_dev")...)
+				p.rttDesc.Collect(ch, metrics.Best, append(l, "best")...)
+				p.rttDesc.Collect(ch, metrics.Worst, append(l, "worst")...)
+				p.rttDesc.Collect(ch, metrics.Mean, append(l, "mean")...)
+				p.rttDesc.Collect(ch, metrics.StdDev, append(l, "std_dev")...)
 			}
 
-			bestDesc.Collect(ch, metrics.Best, l...)
-			worstDesc.Collect(ch, metrics.Worst, l...)
-			meanDesc.Collect(ch, metrics.Mean, l...)
-			stddevDesc.Collect(ch, metrics.StdDev, l...)
+			p.bestDesc.Collect(ch, metrics.Best, l...)
+			p.worstDesc.Collect(ch, metrics.Worst, l...)
+			p.meanDesc.Collect(ch, metrics.Mean, l...)
+			p.stddevDesc.Collect(ch, metrics.StdDev, l...)
 		}
 
 		loss := float64(metrics.PacketsLost) / float64(metrics.PacketsSent)
-		ch <- prometheus.MustNewConstMetric(lossDesc, prometheus.GaugeValue, loss, l...)
+		ch <- prometheus.MustNewConstMetric(p.lossDesc, prometheus.GaugeValue, loss, l...)
 	}
 }
 
 func (p *pingCollector) createDesc() {
-	labelNames = []string{"target", "ip", "ip_version"}
+	labelNames := []string{"target", "ip", "ip_version"}
 	labelNames = append(labelNames, p.customLabels.labelNames()...)
 
-	rttDesc = newScaledDesc("rtt", "Round trip time", append(labelNames, "type"))
-	bestDesc = newScaledDesc("rtt_best", "Best round trip time", labelNames)
-	worstDesc = newScaledDesc("rtt_worst", "Worst round trip time", labelNames)
-	meanDesc = newScaledDesc("rtt_mean", "Mean round trip time", labelNames)
-	stddevDesc = newScaledDesc("rtt_std_deviation", "Standard deviation", labelNames)
-	lossDesc = newDesc("loss_ratio", "Packet loss from 0.0 to 1.0", labelNames, nil)
-	progDesc = newDesc("up", "ping_exporter version", nil, prometheus.Labels{"version": version})
-	mutex = &sync.Mutex{}
+	p.rttDesc = newScaledDesc("rtt", "Round trip time", p.rttUnit, append(labelNames, "type"))
+	p.bestDesc = newScaledDesc("rtt_best", "Best round trip time", p.rttUnit, labelNames)
+	p.worstDesc = newScaledDesc("rtt_worst", "Worst round trip time", p.rttUnit, labelNames)
+	p.meanDesc = newScaledDesc("rtt_mean", "Mean round trip time", p.rttUnit, labelNames)
+	p.stddevDesc = newScaledDesc("rtt_std_deviation", "Standard deviation", p.rttUnit, labelNames)
+	p.lossDesc = newDesc("loss_ratio", "Packet loss from 0.0 to 1.0", labelNames, nil)
+	p.progDesc = newDesc("up", "ping_exporter version", nil, prometheus.Labels{"version": version})
 }
 
 func newDesc(name, help string, variableLabels []string, constLabels prometheus.Labels) *prometheus.Desc {

main.go

@@ -11,6 +11,7 @@ import (
 	"net/http"
 	"os"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/digineo/go-ping"
@@ -116,13 +117,18 @@ func main() {
 		kingpin.FatalUsage("No targets specified")
 	}
 
-	m, err := startMonitor(cfg)
+	resolver := setupResolver(cfg)
+
+	m, err := startMonitor(cfg, resolver)
 	if err != nil {
 		log.Errorln(err)
 		os.Exit(2)
 	}
 
-	startServer(cfg, m)
+	collector := NewPingCollector(enableDeprecatedMetrics, rttMetricsScale, m, cfg)
+	go watchConfig(desiredTargets, resolver, m, collector)
+
+	startServer(cfg, collector)
 }
 
 func printVersion() {
@@ -132,8 +138,7 @@ func printVersion() {
 	fmt.Println("Metric exporter for go-icmp")
 }
 
-func startMonitor(cfg *config.Config) (*mon.Monitor, error) {
-	resolver := setupResolver(cfg)
+func startMonitor(cfg *config.Config, resolver *net.Resolver) (*mon.Monitor, error) {
 	var bind4, bind6 string
 	if ln, err := net.Listen("tcp4", "127.0.0.1:0"); err == nil {
 		// ipv4 enabled
@@ -165,42 +170,50 @@ func startMonitor(cfg *config.Config) (*mon.Monitor, error) {
 	}
 
 	go startDNSAutoRefresh(cfg.DNS.Refresh.Duration(), desiredTargets, monitor, cfg)
-	go watchConfig(desiredTargets, resolver, monitor)
 	return monitor, nil
 }
 
 func upsertTargets(globalTargets *targets, resolver *net.Resolver, cfg *config.Config, monitor *mon.Monitor) error {
 	oldTargets := globalTargets.Targets()
 	newTargets := make([]*target, len(cfg.Targets))
+	var wg sync.WaitGroup
 	for i, t := range cfg.Targets {
-		t := &target{
-			host:      t.Addr,
-			addresses: make([]net.IPAddr, 0),
-			delay:     time.Duration(10*i) * time.Millisecond,
-			resolver:  resolver,
-		}
-		newTargets[i] = t
-
-		err := t.addOrUpdateMonitor(monitor, targetOpts{
-			disableIPv4: cfg.Options.DisableIPv4,
-			disableIPv6: cfg.Options.DisableIPv6,
-		})
-		if err != nil {
-			return fmt.Errorf("failed to setup target: %w", err)
+		newTarget := globalTargets.Get(t.Addr)
+		if newTarget == nil {
+			newTarget = &target{
+				host:      t.Addr,
+				addresses: make([]net.IPAddr, 0),
+				delay:     time.Duration(10*i) * time.Millisecond,
+				resolver:  resolver,
+			}
 		}
-	}
 
+		newTargets[i] = newTarget
+
+		wg.Add(1)
+		go func() {
+			err := newTarget.addOrUpdateMonitor(monitor, targetOpts{
+				disableIPv4: cfg.Options.DisableIPv4,
+				disableIPv6: cfg.Options.DisableIPv6,
+			})
+			if err != nil {
+				log.Errorf("failed to setup target: %v", err)
+			}
+			wg.Done()
+		}()
+	}
+	wg.Wait()
 	globalTargets.SetTargets(newTargets)
 
 	removed := removedTargets(oldTargets, globalTargets)
 	for _, removedTarget := range removed {
-		log.Infof("remove target: %s\n", removedTarget.host)
+		log.Infof("remove target: %s", removedTarget.host)
 		removedTarget.removeFromMonitor(monitor)
 	}
 	return nil
 }
 
-func watchConfig(globalTargets *targets, resolver *net.Resolver, monitor *mon.Monitor) {
+func watchConfig(globalTargets *targets, resolver *net.Resolver, monitor *mon.Monitor, collector *pingCollector) {
 	watcher, err := inotify.NewWatcher()
 	if err != nil {
 		log.Fatalf("unable to create file watcher: %v", err)
@@ -212,17 +225,30 @@ func watchConfig(globalTargets *targets, resolver *net.Resolver, monitor *mon.Mo
 	}
 	for {
 		select {
-		case <-watcher.Events:
+		case event := <-watcher.Events:
+			log.Debugf("Got file inotify event: %s", event)
+			// If the file is removed, the inotify watcher will lose track of the file. Add it again.
+			if event.Op == inotify.Remove {
+				if err = watcher.Add(*configFile); err != nil {
+					log.Fatalf("failed to renew watch for file: %v", err)
+				}
+			}
 			cfg, err := loadConfig()
 			if err != nil {
 				log.Errorf("unable to load config: %v", err)
 				continue
 			}
+			// We get zero targets if the file was truncated. This happens if an automation tool rewrites
+			// the complete file, instead of alternating only parts of it.
+			if len(cfg.Targets) == 0 {
+				continue
+			}
 			log.Infof("reloading config file %s", *configFile)
 			if err := upsertTargets(globalTargets, resolver, cfg, monitor); err != nil {
 				log.Errorf("failed to reload config: %v", err)
 				continue
 			}
+			collector.UpdateConfig(cfg)
 		case err := <-watcher.Errors:
 			log.Errorf("watching file failed: %v", err)
 		}
@@ -264,19 +290,15 @@ func refreshDNS(tar *targets, monitor *mon.Monitor, cfg *config.Config) {
 	}
 }
 
-func startServer(cfg *config.Config, monitor *mon.Monitor) {
+func startServer(cfg *config.Config, collector *pingCollector) {
 	var err error
 	log.Infof("Starting ping exporter (Version: %s)", version)
 	http.HandleFunc("/", func(w http.ResponseWriter, _ *http.Request) {
 		fmt.Fprintf(w, indexHTML, *metricsPath)
 	})
 
 	reg := prometheus.NewRegistry()
-	reg.MustRegister(&pingCollector{
-		cfg:          cfg,
-		monitor:      monitor,
-		customLabels: newCustomLabelSet(cfg.Targets),
-	})
+	reg.MustRegister(collector)
 
 	l := log.New()
 	l.Level = log.ErrorLevel

rttscale.go

@@ -29,28 +29,30 @@ func rttUnitFromString(s string) rttUnit {
 type scaledMetrics struct {
 	Millis  *prometheus.Desc
 	Seconds *prometheus.Desc
+	scale   rttUnit
 }
 
 func (s *scaledMetrics) Describe(ch chan<- *prometheus.Desc) {
-	if rttMetricsScale == rttInMills || rttMetricsScale == rttBoth {
+	if s.scale == rttInMills || s.scale == rttBoth {
 		ch <- s.Millis
 	}
-	if rttMetricsScale == rttInSeconds || rttMetricsScale == rttBoth {
+	if s.scale == rttInSeconds || s.scale == rttBoth {
 		ch <- s.Seconds
 	}
 }
 
 func (s *scaledMetrics) Collect(ch chan<- prometheus.Metric, value float32, labelValues ...string) {
-	if rttMetricsScale == rttInMills || rttMetricsScale == rttBoth {
+	if s.scale == rttInMills || s.scale == rttBoth {
 		ch <- prometheus.MustNewConstMetric(s.Millis, prometheus.GaugeValue, float64(value), labelValues...)
 	}
-	if rttMetricsScale == rttInSeconds || rttMetricsScale == rttBoth {
+	if s.scale == rttInSeconds || s.scale == rttBoth {
 		ch <- prometheus.MustNewConstMetric(s.Seconds, prometheus.GaugeValue, float64(value)/1000, labelValues...)
 	}
 }
 
-func newScaledDesc(name, help string, variableLabels []string) scaledMetrics {
+func newScaledDesc(name, help string, scale rttUnit, variableLabels []string) scaledMetrics {
 	return scaledMetrics{
+		scale:   scale,
 		Millis:  newDesc(name+"_ms", help+" in millis (deprecated)", variableLabels, nil),
 		Seconds: newDesc(name+"_seconds", help+" in seconds", variableLabels, nil),
 	}

target.go

@@ -37,6 +37,8 @@ func (t *targets) SetTargets(tar []*target) {
 }
 
 func (t *targets) Contains(tar *target) bool {
+	t.mutex.RLock()
+	defer t.mutex.RUnlock()
 	for _, ta := range t.t {
 		if ta.host == tar.host {
 			return true
@@ -45,6 +47,17 @@ func (t *targets) Contains(tar *target) bool {
 	return false
 }
 
+func (t *targets) Get(host string) *target {
+	t.mutex.RLock()
+	defer t.mutex.RUnlock()
+	for _, ta := range t.t {
+		if ta.host == host {
+			return ta
+		}
+	}
+	return nil
+}
+
 func (t *targets) Targets() []*target {
 	t.mutex.RLock()
 	defer t.mutex.RUnlock()