Avoid doing real DNS lookups in unit test

2 files changed, 27 insertions, 16 deletions

diff --git a/client/go/vespa/detect_hostname.go b/client/go/vespa/detect_hostname.go
index 80f5df2c866..d4d34a5f47d 100644
--- a/client/go/vespa/detect_hostname.go
+++ b/client/go/vespa/detect_hostname.go
@@ -10,6 +10,9 @@ import (
 	"strings"
 )
 
+type lookupAddrFunc func(addr string) ([]string, error)
+type lookupIPFunc func(host string) ([]net.IP, error)
+
 // detect if this host is IPv6-only, in which case we want to pass
 // the flag "-Djava.net.preferIPv6Addresses=true" to any java command
 func HasOnlyIpV6() bool {
@@ -42,7 +45,9 @@ func HasOnlyIpV6() bool {
 // If automatic detection fails, "localhost" will be returned, so
 // single-node setups still have a good chance of working.
 // Use the enviroment variable VESPA_HOSTNAME to override.
-func FindOurHostname() (string, error) {
+func FindOurHostname() (string, error) { return findOurHostname(net.LookupAddr, net.LookupIP) }
+
+func findOurHostname(lookupAddr lookupAddrFunc, lookupIP lookupIPFunc) (string, error) {
 	env := os.Getenv("VESPA_HOSTNAME")
 	if env != "" {
 		// assumes: env var is already validated and OK
@@ -50,13 +55,10 @@ func FindOurHostname() (string, error) {
 	}
 	name, err := os.Hostname()
 	if err != nil {
-		return findOurHostnameFrom("localhost")
-	}
-	name, err = findOurHostnameFrom(name)
-	if strings.HasSuffix(name, ".") {
-		name = name[:len(name)-1]
+		return findOurHostnameFrom("localhost", lookupAddr, lookupIP)
 	}
-	return name, err
+	name, err = findOurHostnameFrom(name, lookupAddr, lookupIP)
+	return strings.TrimSuffix(name, "."), err
 }
 
 func validateHostname(name string) bool {
@@ -84,20 +86,20 @@ func validateHostname(name string) bool {
 	return someGood
 }
 
-func findOurHostnameFrom(name string) (string, error) {
+func findOurHostnameFrom(name string, lookupAddr lookupAddrFunc, lookupIP lookupIPFunc) (string, error) {
 	if strings.Contains(name, ".") && validateHostname(name) {
 		// it's all good
 		return name, nil
 	}
 	possibles := make([]string, 0, 5)
 	if name != "" {
-		ipAddrs, _ := net.LookupIP(name)
+		ipAddrs, _ := lookupIP(name)
 		for _, addr := range ipAddrs {
 			switch {
 			case addr.IsLoopback():
 				// skip
 			case addr.To4() != nil || addr.To16() != nil:
-				reverseNames, _ := net.LookupAddr(addr.String())
+				reverseNames, _ := lookupAddr(addr.String())
 				possibles = append(possibles, reverseNames...)
 			}
 		}
@@ -109,7 +111,7 @@ func findOurHostnameFrom(name string) (string, error) {
 			if ip == nil || ip.IsLoopback() {
 				continue
 			}
-			reverseNames, _ := net.LookupAddr(ip.String())
+			reverseNames, _ := lookupAddr(ip.String())
 			possibles = append(possibles, reverseNames...)
 		}
 	}
diff --git a/client/go/vespa/detect_hostname_test.go b/client/go/vespa/detect_hostname_test.go
index 398626b708f..e162bcdea8e 100644
--- a/client/go/vespa/detect_hostname_test.go
+++ b/client/go/vespa/detect_hostname_test.go
@@ -3,6 +3,7 @@ package vespa
 
 import (
 	"fmt"
+	"net"
 	"os"
 	"strings"
 	"testing"
@@ -11,20 +12,28 @@ import (
 )
 
 func TestDetectHostname(t *testing.T) {
+	lookupAddr := func(addr string) ([]string, error) {
+		return nil, fmt.Errorf("could not look up %s", addr)
+	}
+	lookupIP := func(host string) ([]net.IP, error) {
+		return nil, fmt.Errorf("no address found for %s", host)
+	}
+
 	t.Setenv("VESPA_HOSTNAME", "foo.bar")
-	got, err := FindOurHostname()
+	got, err := findOurHostname(lookupAddr, lookupIP)
+	assert.Nil(t, err)
 	assert.Equal(t, "foo.bar", got)
 	os.Unsetenv("VESPA_HOSTNAME")
-	got, err = findOurHostnameFrom("bar.foo.123")
+	got, err = findOurHostnameFrom("bar.foo.123", lookupAddr, lookupIP)
 	fmt.Fprintln(os.Stderr, "findOurHostname from bar.foo.123 returns:", got, "with error:", err)
 	assert.NotEqual(t, "", got)
 	parts := strings.Split(got, ".")
 	if len(parts) > 1 {
-		expanded, err2 := findOurHostnameFrom(parts[0])
+		expanded, err2 := findOurHostnameFrom(parts[0], lookupAddr, lookupIP)
 		fmt.Fprintln(os.Stderr, "findOurHostname from", parts[0], "returns:", expanded, "with error:", err2)
 		assert.Equal(t, got, expanded)
 	}
-	got, err = FindOurHostname()
+	got, err = findOurHostname(lookupAddr, lookupIP)
 	assert.NotEqual(t, "", got)
-	fmt.Fprintln(os.Stderr, "FindOurHostname() returns:", got, "with error:", err)
+	fmt.Fprintln(os.Stderr, "findOurHostname() returns:", got, "with error:", err)
 }