remember next eviction time and skip eviction

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

@@ -218,7 +218,6 @@ public class HotEntryCache<K, V> {
 				caches.addAll(weakCaches.keySet());
 			}
 			for (final HotEntryCache<?, ?> cache : caches) {
-				// TODO remember nextEvictionTime on cache so that we can skip a cache
 				final long nextEvictionTime = cache.evict();
 				minNextEvictionTime = Math.min(minNextEvictionTime, nextEvictionTime);
 			}
@@ -291,6 +290,8 @@ public class HotEntryCache<K, V> {
 
 	private int maxSize;
 
+	private long nextProbableEvictionTime;
+
 	HotEntryCache(final Duration timeToLive, final int maxSize, final Clock clock, final String name) {
 		this.timeToLive = timeToLive.toMillis();
 		this.maxSize = maxSize;
@@ -333,6 +334,7 @@ public class HotEntryCache<K, V> {
 
 	static void setMaxSleepPeriod(final long maxSleepPeriodInMs) {
 		EVICTER.setMaxSleepPeriod(maxSleepPeriodInMs);
+		TIME_UPDATER.setUpdateInterval(EVICTER.getMinSleepPeriod());
 	}
 
 	static long getMinSleepPeriod() {
@@ -353,7 +355,7 @@ public class HotEntryCache<K, V> {
 
 	public V put(final K key, final V value) {
 
-		removeEldestCacheTooBig();
+		removeEldestIfCacheTooBig();
 
 		final boolean wasEmptyBefore = cache.isEmpty();
 		final AtomicReference<V> oldValueAtomicReference = new AtomicReference<>();
@@ -368,6 +370,7 @@ public class HotEntryCache<K, V> {
 			} else {
 				final long creationTime = now();
 				entry = new Entry<>(value, creationTime);
+				nextProbableEvictionTime = Math.min(nextProbableEvictionTime, now + timeToLive);
 			}
 			touch(k, entry);
 			return entry;
@@ -396,13 +399,14 @@ public class HotEntryCache<K, V> {
 	 */
 	public V putIfAbsent(final K key, final Function<K, V> mappingFunction) {
 
-		removeEldestCacheTooBig();
+		removeEldestIfCacheTooBig();
 
 		final boolean wasEmptyBefore = cache.isEmpty();
 		final Entry<V> entry = cache.computeIfAbsent(key, (k) -> {
 			final V value = mappingFunction.apply(k);
-			final long creationTime = now();
+			final long creationTime = now;
 			final Entry<V> e = new Entry<>(value, creationTime);
+			nextProbableEvictionTime = Math.min(nextProbableEvictionTime, now + timeToLive);
 			touch(key, e);
 			return e;
 		});
@@ -440,7 +444,7 @@ public class HotEntryCache<K, V> {
 		});
 	}
 
-	private void removeEldestCacheTooBig() {
+	private void removeEldestIfCacheTooBig() {
 		if (cache.size() >= maxSize) {
 			removeEldest();
 		}
@@ -461,22 +465,29 @@ public class HotEntryCache<K, V> {
 			final int numEntriesToRemove = Math.max((int) (maxSize * 0.2), 1);
 
 			final long oldestValuesToKeep = lastAccessTimes.get(numEntriesToRemove - 1) + 1;
-			evictInternal(oldestValuesToKeep, numEntriesToRemove);
+			nextProbableEvictionTime = evictInternal(oldestValuesToKeep, numEntriesToRemove);
 		}
 	}
 
 	private long evict() {
 		final long now = now();
+
+		if (nextProbableEvictionTime <= now) {
+
 			final long oldestValuesToKeep = now - timeToLive;
-		LOGGER.trace("{}: oldestValuesToKeep = {} = {} - {}", name, oldestValuesToKeep, now, timeToLive);
+
-		return evictInternal(oldestValuesToKeep, Integer.MAX_VALUE);
+			nextProbableEvictionTime = evictInternal(oldestValuesToKeep, Integer.MAX_VALUE);
+		} else {
+			LOGGER.trace("{}: skip eviction - next eviction at {} (now: {})", name, nextProbableEvictionTime, now);
+		}
+		return nextProbableEvictionTime;
 	}
 
 	private long evictInternal(final long oldestValuesToKeep, final int maxEntriesToRemove) {
-		long oldestAccessTime = Long.MAX_VALUE;
-		LOGGER.trace("{}: cache size before eviction {}", name, cache.size());
-		LOGGER.trace("{}: oldest value to keep {}", name, oldestValuesToKeep);
 
+		LOGGER.trace("{}: cache size before eviction {}", name, cache.size());
+
+		long oldestAccessTime = Long.MAX_VALUE;
 		final AtomicInteger removedEntries = new AtomicInteger();
 
 		for (final java.util.Map.Entry<K, Entry<V>> mapEntry : cache.entrySet()) {
@@ -487,29 +498,21 @@ public class HotEntryCache<K, V> {
 			if (removedEntries.get() >= maxEntriesToRemove) {
 				// finish iterating over all entries so that this method return the correct
 				// nextEvictionTime
-				LOGGER.trace("{}: removedEntries >= maxEntriesToRemove = {} >= {}", name, removedEntries.get(),
-						maxEntriesToRemove);
 				continue;
 			}
 
 			if (lastAccessed >= oldestValuesToKeep) {
-				LOGGER.trace("{}: lastAccessed >= oldestValuesToKeep = {} >= {}", name, lastAccessed,
-						oldestValuesToKeep);
 				continue;
 			}
 
 			final K keyToBeRemoved = mapEntry.getKey();
-			LOGGER.trace("{}: atomically removing key {}", name, keyToBeRemoved);
 
 			cache.computeIfPresent(keyToBeRemoved, (k, e) -> {
 
 				if (entry.getLastAccessed() < oldestValuesToKeep) {
-					LOGGER.trace("{}: removing value from {}", name, entry.getLastAccessed());
 					removedEntries.incrementAndGet();
 					handleEvent(k, e.getValue());
 					return null;
-				} else {
-					LOGGER.trace("{}: keeping value from {}", name, entry.getLastAccessed());
 				}
 				return e;
 			});
@@ -529,7 +532,6 @@ public class HotEntryCache<K, V> {
 	// visible for test
 	void updateTime() {
 		now = clock.millis();
-		LOGGER.trace("{}: update time to {}", name, now);
 	}
 
 	private void touch(final K key, final Entry<V> entry) {
@@ -541,8 +543,6 @@ public class HotEntryCache<K, V> {
 	}
 
 	private void handleEvent(final K key, final V value) {
-
-		LOGGER.trace("{}: calling {} listeners for {} -> {}", name, listeners.size(), key, value);
 		for (final EventListener<K, V> eventSubscribers : listeners) {
 
 			eventSubscribers.onRemove(key, value);