Move cache Keys to 64bit for a better dispersion and lower collision frequency (#2077)

* - change Key for cache to 64bits.

* - change Key for cache to 64bits.

1 files changed, 14 insertions, 16 deletions

diff --git a/plugin/cache/cache.go b/plugin/cache/cache.go
index c46267658..654841b23 100644
--- a/plugin/cache/cache.go
+++ b/plugin/cache/cache.go
@@ -60,24 +60,24 @@ func New() *Cache {
 // Return key under which we store the item, -1 will be returned if we don't store the
 // message.
 // Currently we do not cache Truncated, errors zone transfers or dynamic update messages.
-func key(m *dns.Msg, t response.Type, do bool) int {
+func key(m *dns.Msg, t response.Type, do bool) (bool, uint64) {
 	// We don't store truncated responses.
 	if m.Truncated {
-		return -1
+		return false, 0
 	}
 	// Nor errors or Meta or Update
 	if t == response.OtherError || t == response.Meta || t == response.Update {
-		return -1
+		return false, 0
 	}
 
-	return int(hash(m.Question[0].Name, m.Question[0].Qtype, do))
+	return true, hash(m.Question[0].Name, m.Question[0].Qtype, do)
 }
 
 var one = []byte("1")
 var zero = []byte("0")
 
-func hash(qname string, qtype uint16, do bool) uint32 {
-	h := fnv.New32()
+func hash(qname string, qtype uint16, do bool) uint64 {
+	h := fnv.New64()
 
 	if do {
 		h.Write(one)
@@ -97,7 +97,7 @@ func hash(qname string, qtype uint16, do bool) uint32 {
 		h.Write([]byte{c})
 	}
 
-	return h.Sum32()
+	return h.Sum64()
 }
 
 // ResponseWriter is a response writer that caches the reply message.
@@ -152,7 +152,7 @@ func (w *ResponseWriter) WriteMsg(res *dns.Msg) error {
 	}
 
 	// key returns empty string for anything we don't want to cache.
-	key := key(res, mt, do)
+	hasKey, key := key(res, mt, do)
 
 	duration := w.pttl
 	if mt == response.NameError || mt == response.NoData {
@@ -164,7 +164,7 @@ func (w *ResponseWriter) WriteMsg(res *dns.Msg) error {
 		duration = msgTTL
 	}
 
-	if key != -1 && duration > 0 {
+	if hasKey && duration > 0 {
 		if w.state.Match(res) {
 			w.set(res, key, mt, duration)
 			cacheSize.WithLabelValues(w.server, Success).Set(float64(w.pcache.Len()))
@@ -195,19 +195,17 @@ func (w *ResponseWriter) WriteMsg(res *dns.Msg) error {
 	return w.ResponseWriter.WriteMsg(res)
 }
 
-func (w *ResponseWriter) set(m *dns.Msg, key int, mt response.Type, duration time.Duration) {
-	if key == -1 || duration == 0 {
-		return
-	}
-
+func (w *ResponseWriter) set(m *dns.Msg, key uint64, mt response.Type, duration time.Duration) {
+	// duration is expected > 0
+	// and key is valid
 	switch mt {
 	case response.NoError, response.Delegation:
 		i := newItem(m, w.now(), duration)
-		w.pcache.Add(uint32(key), i)
+		w.pcache.Add(key, i)
 
 	case response.NameError, response.NoData:
 		i := newItem(m, w.now(), duration)
-		w.ncache.Add(uint32(key), i)
+		w.ncache.Add(key, i)
 
 	case response.OtherError:
 		// don't cache these