case insensitive hostname comparison in kafka broker matching

- re-use common.LocalIPAddrs in partition module for resolving IPs
- add missing net.IPAddr type switch to common.LocalIPAddrs
- update matching to extract addresses early on using strings.ToLower
  => ensure case insensitive matching by lowercasing

CHANGELOG.asciidoc

@@ -32,6 +32,7 @@ https://github.com/elastic/beats/compare/v5.1.1...master[Check the HEAD diff]
 *Metricbeat*
 
 - Fix service times-out at startup. {pull}3056[3056]
+- Kafka module case sensitive host name matching. {pull}3193[3193]
 
 *Packetbeat*
 

libbeat/common/net.go

@@ -8,15 +8,29 @@ import (
 // LocalIPAddrs finds the IP addresses of the hosts on which
 // the shipper currently runs on.
 func LocalIPAddrs() ([]net.IP, error) {
-	var localIPAddrs = []net.IP{}
+	var localIPAddrs []net.IP
 	ipaddrs, err := net.InterfaceAddrs()
 	if err != nil {
-		return []net.IP{}, err
+		return nil, err
 	}
-	for _, ipaddr := range ipaddrs {
-		if ipnet, ok := ipaddr.(*net.IPNet); ok {
-			localIPAddrs = append(localIPAddrs, ipnet.IP)
+	for _, addr := range ipaddrs {
+		var ip net.IP
+		ok := true
+
+		switch v := addr.(type) {
+		case *net.IPNet:
+			ip = v.IP
+		case *net.IPAddr:
+			ip = v.IP
+		default:
+			ok = false
 		}
+
+		if !ok {
+			continue
+		}
+
+		localIPAddrs = append(localIPAddrs, ip)
 	}
 	return localIPAddrs, nil
 }

metricbeat/module/kafka/partition/partition.go

@@ -97,7 +97,7 @@ func (m *MetricSet) connect() (*sarama.Broker, error) {
 		return nil, err
 	}
 
-	other := findMatchingBroker(b.Addr(), meta.Brokers)
+	other := findMatchingBroker(brokerAddress(b), meta.Brokers)
 	if other == nil { // no broker found
 		closeBroker(b)
 		return nil, fmt.Errorf("No advertised broker with address %v found", b.Addr())
@@ -328,13 +328,22 @@ func findMatchingBroker(
 	addr string,
 	brokers []*sarama.Broker,
 ) *sarama.Broker {
+	lst := brokerAddresses(brokers)
+	if idx, found := findMatchingAddress(addr, lst); found {
+		return brokers[idx]
+	}
+	return nil
+}
+
+func findMatchingAddress(
+	addr string,
+	brokers []string,
+) (int, bool) {
 	debugf("Try to match broker to: %v", addr)
 
 	// compare connection address to list of broker addresses
-	for _, b := range brokers {
-		if b.Addr() == addr {
-			return b
-		}
+	if i, found := indexOf(addr, brokers); found {
+		return i, true
 	}
 
 	// get connection 'port'
@@ -344,9 +353,9 @@ func findMatchingBroker(
 	}
 
 	// lookup local machines ips for comparing with broker addresses
-	localIPs, err := interfaceIPs()
+	localIPs, err := common.LocalIPAddrs()
 	if err != nil || len(localIPs) == 0 {
-		return nil
+		return -1, false
 	}
 	debugf("local machine ips: %v", localIPs)
 
@@ -356,9 +365,8 @@ func findMatchingBroker(
 	debugf("local machine addresses: %v", localHosts)
 	for _, host := range localHosts {
 		debugf("try to match with fqdn: %v (%v)", host, port)
-
-		if b := findBroker(host, port, brokers); b != nil {
-			return b
+		if i, found := indexOf(net.JoinHostPort(host, port), brokers); found {
+			return i, true
 		}
 	}
 
@@ -367,16 +375,17 @@ func findMatchingBroker(
 	if host, err := os.Hostname(); err == nil {
 		debugf("try to match with hostname only: %v (%v)", host, port)
 
-		if b := findBroker(host, port, brokers); b != nil {
-			return b
+		tmp := net.JoinHostPort(strings.ToLower(host), port)
+		if i, found := indexOf(tmp, brokers); found {
+			return i, true
 		}
 	}
 
 	// lookup ips for all brokers
 	debugf("match by ips")
-	for _, b := range brokers {
-		debugf("test broker address: %v", b.Addr())
-		bh, bp, err := net.SplitHostPort(b.Addr())
+	for i, b := range brokers {
+		debugf("test broker address: %v", b)
+		bh, bp, err := net.SplitHostPort(b)
 		if err != nil {
 			continue
 		}
@@ -396,59 +405,12 @@ func findMatchingBroker(
 		debugf("broker (%v) ips: %v", bh, ips)
 
 		// check if ip is known
-		if ipsMatch(ips, localIPs) {
-			return b
-		}
-	}
-
-	return nil
-}
-
-func findBroker(host, port string, brokers []*sarama.Broker) *sarama.Broker {
-	for _, b := range brokers {
-		debugf("test broker address: %v", b.Addr())
-
-		bh, bp, err := net.SplitHostPort(b.Addr())
-		if err != nil {
-			debugf("failed to parse broker address: %v", err)
-			continue
-		}
-
-		if bh == host && port == bp {
-			return b
+		if anyIPsMatch(ips, localIPs) {
+			return i, true
 		}
 	}
 
-	return nil
-}
-
-func interfaceIPs() ([]net.IP, error) {
-	var ips []net.IP
-	addrs, err := net.InterfaceAddrs()
-	if err != nil {
-		return nil, err
-	}
-	for _, addr := range addrs {
-		var ip net.IP
-		ok := true
-
-		switch v := addr.(type) {
-		case *net.IPNet:
-			ip = v.IP
-		case *net.IPAddr:
-			ip = v.IP
-		default:
-			debugf("non ip address: %v", addr)
-			ok = false
-		}
-
-		if !ok {
-			continue
-		}
-
-		ips = append(ips, ip)
-	}
-	return ips, nil
+	return -1, false
 }
 
 func lookupHosts(ips []net.IP) []string {
@@ -466,7 +428,7 @@ func lookupHosts(ips []net.IP) []string {
 		}
 
 		for _, host := range hosts {
-			h := strings.TrimSuffix(host, ".")
+			h := strings.ToLower(strings.TrimSuffix(host, "."))
 			set[h] = struct{}{}
 		}
 	}
@@ -478,7 +440,7 @@ func lookupHosts(ips []net.IP) []string {
 	return hosts
 }
 
-func ipsMatch(as, bs []net.IP) bool {
+func anyIPsMatch(as, bs []net.IP) bool {
 	for _, a := range as {
 		for _, b := range bs {
 			if bytes.Equal(a, b) {
@@ -488,3 +450,24 @@ func ipsMatch(as, bs []net.IP) bool {
 	}
 	return false
 }
+
+func brokerAddresses(brokers []*sarama.Broker) []string {
+	addresses := make([]string, len(brokers))
+	for i, b := range brokers {
+		addresses[i] = brokerAddress(b)
+	}
+	return addresses
+}
+
+func brokerAddress(b *sarama.Broker) string {
+	return strings.ToLower(b.Addr())
+}
+
+func indexOf(s string, lst []string) (int, bool) {
+	for i, v := range lst {
+		if s == v {
+			return i, true
+		}
+	}
+	return -1, false
+}