Add Len field to Metrics

lru.go

@@ -89,6 +89,7 @@ type Metrics struct {
 	Misses     uint64
 	Capacity   uint32
 	Lifetime   string
+	Len        int
 }
 
 var _ Cache[int, int] = (*LRU[int, int])(nil)
@@ -148,7 +149,9 @@ func initLRU[K comparable, V any](lru *LRU[K, V], capacity, size uint32, hash Ha
 	lru.hash = hash
 	lru.buckets = buckets
 	lru.elements = elements
+	lru.lifetime = 0
 	lru.metrics.Capacity = capacity
+	lru.metrics.Lifetime = lru.lifetime.String()
 
 	// If the size is 2^N, we can avoid costly divisions.
 	if bits.OnesCount32(lru.size) == 1 {
@@ -506,18 +509,25 @@ func (lru *LRU[K, V]) Purge() {
 	}
 
 	lru.len = 0
-	lru.metrics = Metrics{}
+	lru.metrics = Metrics{
+		Capacity: lru.cap,
+		Lifetime: lru.lifetime.String(),
+	}
 }
 
 // Metrics returns the metrics of the cache.
 func (lru *LRU[K, V]) Metrics() Metrics {
+	lru.metrics.Len = lru.Len()
 	return lru.metrics
 }
 
 // ResetMetrics resets the metrics of the cache and returns the previous state.
 func (lru *LRU[K, V]) ResetMetrics() Metrics {
 	metrics := lru.metrics
-	lru.metrics = Metrics{}
+	lru.metrics = Metrics{
+		Capacity: lru.cap,
+		Lifetime: lru.lifetime.String(),
+	}
 	return metrics
 }
 

lru_test.go

@@ -325,6 +325,11 @@ func TestLRUMetrics(t *testing.T) {
 	m := lru.Metrics()
 	FatalIf(t, m.Capacity != 3, "Unexpected capacity: %d (!= %d)", m.Capacity, 3)
 	FatalIf(t, m.Lifetime != "3s", "Unexpected lifetime: %s (!= %s)", m.Lifetime, "3s")
+
+	lru.ResetMetrics()
+	m = lru.Metrics()
+	FatalIf(t, m.Capacity != 3, "Unexpected capacity: %d (!= %d)", m.Capacity, 3)
+	FatalIf(t, m.Lifetime != "3s", "Unexpected lifetime: %s (!= %s)", m.Lifetime, "3s")
 }
 
 func testMetrics(t *testing.T, cache Cache[uint64, uint64]) {
@@ -342,5 +347,22 @@ func testMetrics(t *testing.T, cache Cache[uint64, uint64]) {
 	FatalIf(t, m.Removals != 1, "Unexpected evictions: %d (!= %d)", m.Removals, 1)
 	FatalIf(t, m.Collisions != 0, "Unexpected collisions: %d (!= %d)", m.Collisions, 0)
 	FatalIf(t, m.Capacity != 1, "Unexpected capacity: %d (!= %d)", m.Capacity, 1)
-	FatalIf(t, m.Lifetime != "", "Unexpected lifetime: %s (!= %s)", m.Lifetime, "")
+	FatalIf(t, m.Lifetime != "0s", "Unexpected lifetime: %s (!= %s)", m.Lifetime, "0s")
+	FatalIf(t, m.Len != 0, "Unexpected len: %d (!= %d)", m.Len, 0)
+
+	cache.Add(4, 4)
+	m = cache.Metrics()
+	FatalIf(t, m.Len != 1, "Unexpected len: %d (!= %d)", m.Len, 1)
+
+	cache.Purge()
+	m = cache.Metrics()
+	FatalIf(t, m.Inserts != 0, "Unexpected inserts: %d (!= %d)", m.Inserts, 0)
+	FatalIf(t, m.Hits != 0, "Unexpected hits: %d (!= %d)", m.Hits, 0)
+	FatalIf(t, m.Misses != 0, "Unexpected misses: %d (!= %d)", m.Misses, 0)
+	FatalIf(t, m.Evictions != 0, "Unexpected evictions: %d (!= %d)", m.Evictions, 0)
+	FatalIf(t, m.Removals != 0, "Unexpected evictions: %d (!= %d)", m.Removals, 0)
+	FatalIf(t, m.Collisions != 0, "Unexpected collisions: %d (!= %d)", m.Collisions, 0)
+	FatalIf(t, m.Capacity != 1, "Unexpected capacity: %d (!= %d)", m.Capacity, 1)
+	FatalIf(t, m.Lifetime != "0s", "Unexpected lifetime: %s (!= %s)", m.Lifetime, "0s")
+	FatalIf(t, m.Len != 0, "Unexpected len: %d (!= %d)", m.Len, 0)
 }

shardedlru.go

@@ -258,6 +258,7 @@ func addMetrics(dst *Metrics, src Metrics) {
 	dst.Misses += src.Misses
 	dst.Capacity += src.Capacity
 	dst.Lifetime = src.Lifetime
+	dst.Len += src.Len
 }
 
 // just used for debugging

shardedlru_test.go

@@ -56,6 +56,11 @@ func TestShardedLRUMetrics(t *testing.T) {
 	m := lru.Metrics()
 	FatalIf(t, m.Capacity != 7, "Unexpected capacity: %d (!= %d)", m.Capacity, 7)
 	FatalIf(t, m.Lifetime != "7s", "Unexpected lifetime: %s (!= %s)", m.Lifetime, "7s")
+
+	lru.ResetMetrics()
+	m = lru.Metrics()
+	FatalIf(t, m.Capacity != 7, "Unexpected capacity: %d (!= %d)", m.Capacity, 7)
+	FatalIf(t, m.Lifetime != "7s", "Unexpected lifetime: %s (!= %s)", m.Lifetime, "7s")
 }
 
 func TestStressWithLifetime(t *testing.T) {

syncedlru_test.go

@@ -54,4 +54,9 @@ func TestSyncedLRUMetrics(t *testing.T) {
 	m := lru.Metrics()
 	FatalIf(t, m.Capacity != 5, "Unexpected capacity: %d (!= %d)", m.Capacity, 5)
 	FatalIf(t, m.Lifetime != "5s", "Unexpected lifetime: %s (!= %s)", m.Lifetime, "5s")
+
+	lru.ResetMetrics()
+	m = lru.Metrics()
+	FatalIf(t, m.Capacity != 5, "Unexpected capacity: %d (!= %d)", m.Capacity, 5)
+	FatalIf(t, m.Lifetime != "5s", "Unexpected lifetime: %s (!= %s)", m.Lifetime, "5s")
 }