Use single connection, reconnect if it fails

Change-Id: I772ee98d55e8d6b64551a7d8f4157e387fe4f4f4

collectors/domain_stats.go

@@ -27,7 +27,7 @@ import (
 type DomainStatsCollector struct {
 	prometheus.Collector
 
-	LibvirtURI string
+	Connection *libvirt.Connect
 
 	Nova bool
 
@@ -86,9 +86,9 @@ type NovaMetadata struct {
 }
 
 // nolint:funlen
-func NewDomainStatsCollector(nova bool, libvirtURI string) (*DomainStatsCollector, error) {
+func NewDomainStatsCollector(nova bool, connection *libvirt.Connect) (*DomainStatsCollector, error) {
 	return &DomainStatsCollector{
-		LibvirtURI: libvirtURI,
+		Connection: connection,
 		Nova:       nova,
 
 		DomainSeconds: prometheus.NewDesc(
@@ -308,26 +308,32 @@ func (c *DomainStatsCollector) describeBlock(ch chan<- *prometheus.Desc) {
 }
 
 func (c *DomainStatsCollector) Collect(ch chan<- prometheus.Metric) {
-	conn, err := libvirt.NewConnect(c.LibvirtURI)
+	alive, err := c.Connection.IsAlive()
 	if err != nil {
 		log.Errorln(err)
 		return
 	}
-	defer func() {
-		alive, err := conn.IsAlive()
-		if err != nil {
-			log.Errorln(err)
-			return
-		}
-		if alive {
-			_, err := conn.Close()
-			if err != nil {
-				log.Errorln(err)
-			}
-		}
-	}()
 
-	stats, err := conn.GetAllDomainStats(
+	if !alive {
+		uri, err := c.Connection.GetURI()
+		if err != nil {
+			// NOTE(mnaser): If we get to this point, we don't have
+			//               a URI and we can't reconnect, die
+			log.Fatalln(err)
+			return
+		}
+
+		c.Connection.Close()
+
+		conn, err := libvirt.NewConnect(uri)
+		if err != nil {
+			log.Errorln(err)
+			return
+		}
+		c.Connection = conn
+	}
+
+	stats, err := c.Connection.GetAllDomainStats(
 		[]*libvirt.Domain{},
 		libvirt.DOMAIN_STATS_STATE|libvirt.DOMAIN_STATS_CPU_TOTAL|libvirt.DOMAIN_STATS_BALLOON|
 			libvirt.DOMAIN_STATS_VCPU|libvirt.DOMAIN_STATS_INTERFACE|libvirt.DOMAIN_STATS_BLOCK,

collectors/version.go

@@ -25,14 +25,14 @@ import (
 type VersionCollector struct {
 	prometheus.Collector
 
-	LibvirtURI string
+	Connection *libvirt.Connect
 
 	Version *prometheus.Desc
 }
 
-func NewVersionCollector(libvirtURI string) (*VersionCollector, error) {
+func NewVersionCollector(connection *libvirt.Connect) (*VersionCollector, error) {
 	return &VersionCollector{
-		LibvirtURI: libvirtURI,
+		Connection: connection,
 
 		Version: prometheus.NewDesc(
 			"libvirtd_info",
@@ -47,38 +47,44 @@ func (c *VersionCollector) Describe(ch chan<- *prometheus.Desc) {
 }
 
 func (c *VersionCollector) Collect(ch chan<- prometheus.Metric) {
-	conn, err := libvirt.NewConnect(c.LibvirtURI)
+	alive, err := c.Connection.IsAlive()
-	if err != nil {
-		log.Errorln(err)
-		return
-	}
-	defer func() {
-		alive, err := conn.IsAlive()
-		if err != nil {
-			log.Errorln(err)
-			return
-		}
-		if alive {
-			_, err := conn.Close()
-			if err != nil {
-				log.Errorln(err)
-			}
-		}
-	}()
-
-	hypervisorType, err := conn.GetType()
 	if err != nil {
 		log.Errorln(err)
 		return
 	}
 
-	hypervisorVersion, err := conn.GetVersion()
+	if !alive {
+		uri, err := c.Connection.GetURI()
+		if err != nil {
+			// NOTE(mnaser): If we get to this point, we don't have
+			//               a URI and we can't reconnect, die
+			log.Fatalln(err)
+			return
+		}
+
+		c.Connection.Close()
+
+		conn, err := libvirt.NewConnect(uri)
+		if err != nil {
+			log.Errorln(err)
+			return
+		}
+		c.Connection = conn
+	}
+
+	hypervisorType, err := c.Connection.GetType()
 	if err != nil {
 		log.Errorln(err)
 		return
 	}
 
-	libvirtVersion, err := conn.GetLibVersion()
+	hypervisorVersion, err := c.Connection.GetVersion()
+	if err != nil {
+		log.Errorln(err)
+		return
+	}
+
+	libvirtVersion, err := c.Connection.GetLibVersion()
 	if err != nil {
 		log.Errorln(err)
 		return

libvirtd_exporter.go

@@ -17,6 +17,7 @@ package main
 import (
 	"net/http"
 
+	"github.com/libvirt/libvirt-go"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/prometheus/common/log"
@@ -50,12 +51,18 @@ func main() {
 	kingpin.HelpFlag.Short('h')
 	kingpin.Parse()
 
-	versionCollector, err := collectors.NewVersionCollector(*libvirtURI)
+	conn, err := libvirt.NewConnect(*libvirtURI)
+	if err != nil {
+		log.Fatalln(err)
+		return
+	}
+
+	versionCollector, err := collectors.NewVersionCollector(conn)
 	if err != nil {
 		log.Fatalln(err)
 	}
 
-	domainStats, err := collectors.NewDomainStatsCollector(*libvirtNova, *libvirtURI)
+	domainStats, err := collectors.NewDomainStatsCollector(*libvirtNova, conn)
 	if err != nil {
 		log.Fatalln(err)
 	}