Add cache metrics

2 files changed, 28 insertions, 0 deletions

diff --git a/cache/cache.go b/cache/cache.go
index a0218b0..beaa5a1 100644
--- a/cache/cache.go
+++ b/cache/cache.go
@@ -47,6 +47,12 @@ type Value struct {
 	msg       *dns.Msg
 }
 
+// Stats contains cache statistics.
+type Stats struct {
+	Size     int
+	Capacity int
+}
+
 // Rcode returns the response code of the cached value v.
 func (v *Value) Rcode() int { return v.msg.Rcode }
 
@@ -228,6 +234,16 @@ func (c *Cache) Set(key uint32, msg *dns.Msg) {
 	c.set(key, msg)
 }
 
+// Stats returns cache statistics.
+func (c *Cache) Stats() Stats {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+	return Stats{
+		Capacity: c.capacity,
+		Size:     len(c.values),
+	}
+}
+
 func (c *Cache) set(key uint32, msg *dns.Msg) bool {
 	return c.setValue(Value{Key: key, CreatedAt: c.now(), msg: msg})
 }
diff --git a/cache/cache_test.go b/cache/cache_test.go
index 346df25..e571f73 100644
--- a/cache/cache_test.go
+++ b/cache/cache_test.go
@@ -453,6 +453,18 @@ func TestCacheWithBackend(t *testing.T) {
 	}
 }
 
+func TestCacheStats(t *testing.T) {
+	c := New(10, nil)
+	msg := newA("example.com.", 60, net.ParseIP("192.0.2.1"))
+	c.Set(1, msg)
+	c.Set(2, msg)
+	want := Stats{Capacity: 10, Size: 2}
+	got := c.Stats()
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("Stats() = %+v, want %+v", got, want)
+	}
+}
+
 func BenchmarkNewKey(b *testing.B) {
 	for n := 0; n < b.N; n++ {
 		NewKey("key", 1, 1)