only iterates over elements when at least one element can be evicted

pdb-utils/src/main/java/org/lucares/utils/cache/HotEntryCache.java

@@ -98,8 +98,8 @@ public class HotEntryCache<K, V> {
 			return value;
 		}
 
-		public void touch(final Clock clock) {
-			lastAccessed = Instant.now(clock);
+		public void touch(final Instant instant) {
+			lastAccessed = instant;
 		}
 	}
 
@@ -114,6 +114,8 @@ public class HotEntryCache<K, V> {
 
 	private Clock clock;
 
+	private Instant nextEviction = Instant.MAX;
+
 	HotEntryCache(final Duration timeToLive, final Clock clock, final long delayForEvictionThread,
 			final TimeUnit timeUnit) {
 		this.timeToLive = timeToLive;
@@ -131,12 +133,13 @@ public class HotEntryCache<K, V> {
 
 	public V get(final K key) {
 		final Entry<V> entry = cache.computeIfPresent(key, (k, e) -> {
-			if (isExpired(e)) {
+			final Instant now = Instant.now(clock);
+			if (isExpired(e, now)) {
 				handleEvent(EventType.EVICTED, k, e.getValue());
 				return null;
 			}
 
-			e.touch(clock);
+			touch(e);
 			return e;
 		});
 		return entry != null ? entry.getValue() : null;
@@ -147,7 +150,9 @@ public class HotEntryCache<K, V> {
 		final AtomicReference<Entry<V>> oldValue = new AtomicReference<>();
 		cache.compute(key, (k, v) -> {
 			oldValue.set(v);
-			return new Entry<>(value, clock);
+			final Entry<V> newEntry = new Entry<>(value, clock);
+			touch(newEntry);
+			return newEntry;
 		});
 		return oldValue.get() != null ? oldValue.get().getValue() : null;
 	}
@@ -172,9 +177,8 @@ public class HotEntryCache<K, V> {
 			return new Entry<>(value, clock);
 		});
 
-		if (entry != null) {
-			entry.touch(clock);
-		}
+		touch(entry);
+
 		return entry != null ? entry.getValue() : null;
 	}
 
@@ -197,16 +201,18 @@ public class HotEntryCache<K, V> {
 
 	public void forEach(final Consumer<V> consumer) {
 		cache.forEachValue(Long.MAX_VALUE, entry -> {
-			entry.touch(clock);
+			touch(entry);
 			consumer.accept(entry.getValue());
 		});
 	}
 
 	private void evict() {
-		for (final K key : cache.keySet()) {
+		final Instant now = Instant.now(clock);
+		if (nextEviction.isBefore(now)) {
 
+			for (final K key : cache.keySet()) {
 				cache.computeIfPresent(key, (k, e) -> {
-				if (isExpired(e)) {
+					if (isExpired(e, now)) {
 						handleEvent(EventType.EVICTED, k, e.getValue());
 						return null;
 					}
@@ -214,9 +220,18 @@ public class HotEntryCache<K, V> {
 				});
 			}
 		}
+	}
 
-	private boolean isExpired(final Entry<V> entry) {
-		return entry.getLastAccessed().plus(timeToLive).isBefore(Instant.now(clock));
+	private void touch(final Entry<V> entry) {
+		if (entry != null) {
+			final Instant now = Instant.now(clock);
+			entry.touch(now);
+			nextEviction = now.plus(timeToLive);
+		}
+	}
+
+	private boolean isExpired(final Entry<V> entry, final Instant now) {
+		return entry.getLastAccessed().plus(timeToLive).isBefore(now);
 	}
 
 	private void handleEvent(final EventType eventType, final K key, final V value) {
@@ -227,5 +242,4 @@ public class HotEntryCache<K, V> {
 			}
 		}
 	}
-
 }