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probe/endpoint/reporter.go

@@ -26,7 +26,7 @@ type Reporter struct {
 	includeNAT       bool
 	conntracker      *Conntracker
 	natmapper        *natmapper
-	revResolver      *reverseResolver
+	revResolver      *ReverseResolver
 }
 
 // SpyDuration is an exported prometheus metric
@@ -65,16 +65,13 @@ func NewReporter(hostID, hostName string, includeProcesses bool, useConntrack bo
 			log.Printf("Failed to start natMapper: %v", err)
 		}
 	}
-
-	revRes := newReverseResolver()
-
 	return &Reporter{
 		hostID:           hostID,
 		hostName:         hostName,
 		includeProcesses: includeProcesses,
 		conntracker:      conntracker,
 		natmapper:        natmapper,
-		revResolver:      revRes,
+		revResolver:      NewReverseResolver(),
 	}
 }
 
@@ -152,7 +149,7 @@ func (r *Reporter) addConnection(rpt *report.Report, localAddr, remoteAddr strin
 		)
 
 		// in case we have a reverse resolution for the IP, we can use it for the name...
-		if revRemoteName, err := r.revResolver.Get(remoteAddr, false); err == nil {
+		if revRemoteName, err := r.revResolver.Get(remoteAddr); err == nil {
 			remoteNode = remoteNode.AddMetadata(map[string]string{
 				"name": revRemoteName,
 			})
@@ -191,7 +188,7 @@ func (r *Reporter) addConnection(rpt *report.Report, localAddr, remoteAddr strin
 		)
 
 		// in case we have a reverse resolution for the IP, we can use it for the name...
-		if revRemoteName, err := r.revResolver.Get(remoteAddr, false); err == nil {
+		if revRemoteName, err := r.revResolver.Get(remoteAddr); err == nil {
 			remoteNode = remoteNode.AddMetadata(map[string]string{
 				"name": revRemoteName,
 			})

probe/endpoint/resolver.go

@@ -16,25 +16,22 @@ const (
 
 type revResFunc func(addr string) (names []string, err error)
 
-type revResRequest struct {
-	address string
-	done    chan struct{}
-}
-
 // ReverseResolver is a caching, reverse resolver
-type reverseResolver struct {
-	addresses chan revResRequest
+type ReverseResolver struct {
+	addresses chan string
 	cache     gcache.Cache
-	resolver  revResFunc
+	Throttle  <-chan time.Time // Made public for mocking
+	Resolver  revResFunc
 }
 
 // NewReverseResolver starts a new reverse resolver that
 // performs reverse resolutions and caches the result.
-func newReverseResolver() *reverseResolver {
-	r := reverseResolver{
-		addresses: make(chan revResRequest, rAddrBacklog),
+func NewReverseResolver() *ReverseResolver {
+	r := ReverseResolver{
+		addresses: make(chan string, rAddrBacklog),
 		cache:     gcache.New(rAddrCacheLen).LRU().Expiration(rAddrCacheExpiration).Build(),
-		resolver:  net.LookupAddr,
+		Throttle:  time.Tick(time.Second / 10),
+		Resolver:  net.LookupAddr,
 	}
 	go r.loop()
 	return &r
@@ -43,43 +40,37 @@ func newReverseResolver() *reverseResolver {
 // Get the reverse resolution for an IP address if already in the cache,
 // a gcache.NotFoundKeyError error otherwise.
 // Note: it returns one of the possible names that can be obtained for that IP.
-func (r *reverseResolver) Get(address string, wait bool) (string, error) {
+func (r *ReverseResolver) Get(address string) (string, error) {
 	val, err := r.cache.Get(address)
 	if err == nil {
 		return val.(string), nil
 	}
 	if err == gcache.NotFoundKeyError {
-		request := revResRequest{address: address, done: make(chan struct{})}
 		// we trigger a asynchronous reverse resolution when not cached
 		select {
-		case r.addresses <- request:
-			if wait {
-				<-request.done
-			}
+		case r.addresses <- address:
 		default:
 		}
 	}
 	return "", err
 }
 
-func (r *reverseResolver) loop() {
-	throttle := time.Tick(time.Second / 10)
+func (r *ReverseResolver) loop() {
 	for request := range r.addresses {
-		<-throttle // rate limit our DNS resolutions
+		<-r.Throttle // rate limit our DNS resolutions
 		// and check if the answer is already in the cache
-		if _, err := r.cache.Get(request.address); err == nil {
+		if _, err := r.cache.Get(request); err == nil {
 			continue
 		}
-		names, err := r.resolver(request.address)
+		names, err := r.Resolver(request)
 		if err == nil && len(names) > 0 {
 			name := strings.TrimRight(names[0], ".")
-			r.cache.Set(request.address, name)
+			r.cache.Set(request, name)
 		}
-		close(request.done)
 	}
 }
 
 // Stop the async reverse resolver
-func (r *reverseResolver) Stop() {
+func (r *ReverseResolver) Stop() {
 	close(r.addresses)
 }

probe/endpoint/resolver_test.go

@@ -0,0 +1,38 @@
+package endpoint_test
+
+import (
+	"errors"
+	"testing"
+	"time"
+
+	. "github.com/weaveworks/scope/probe/endpoint"
+	"github.com/weaveworks/scope/test"
+)
+
+func TestReverseResolver(t *testing.T) {
+	tests := map[string]string{
+		"1.2.3.4": "test.domain.name",
+		"4.3.2.1": "im.a.little.tea.pot",
+	}
+
+	revRes := NewReverseResolver()
+	defer revRes.Stop()
+
+	// use a mocked resolver function
+	revRes.Resolver = func(addr string) (names []string, err error) {
+		if name, ok := tests[addr]; ok {
+			return []string{name}, nil
+		}
+		return []string{}, errors.New("invalid IP")
+	}
+
+	// Up the rate limit so the test runs faster
+	revRes.Throttle = time.Tick(time.Millisecond)
+
+	for ip, hostname := range tests {
+		test.Poll(t, 100*time.Millisecond, hostname, func() interface{} {
+			result, _ := revRes.Get(ip)
+			return result
+		})
+	}
+}