Add CacheMaintainer class to perform pending cache maintenance every minute

Signed-off-by: owenhalpert <ohalpert@gmail.com>

# Conflicts:
#	CHANGELOG.md

Author: owenhalpert

CHANGELOG.md

@@ -26,5 +26,6 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 ### Documentation
 ### Maintenance
 * Select index settings based on cluster version[2236](https://github.com/opensearch-project/k-NN/pull/2236)
+* Added periodic cache maintenance for QuantizationStateCache and NativeMemoryCache [#2239](https://github.com/opensearch-project/k-NN/issues/2239)
 * Added null checks for fieldInfo in ExactSearcher to avoid NPE while running exact search for segments with no vector field (#2278)[https://github.com/opensearch-project/k-NN/pull/2278]
 ### Refactoring

src/main/java/org/opensearch/knn/index/CacheMaintainer.java

@@ -0,0 +1,42 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.opensearch.knn.index;
+
+import com.google.common.cache.Cache;
+
+import java.io.Closeable;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Performs periodic maintenance for a Guava cache. The Guava cache is implemented in a way that maintenance operations (such as evicting expired
+ * entries) will only occur when the cache is accessed. See {@see <a href="https://github.com/google/guava/wiki/cachesexplained#timed-eviction"> Guava Cache Guide</a>}
+ * for more details. Thus, to perform any pending maintenance, the cleanUp method will be called periodically from a CacheMaintainer instance.
+ */
+public class CacheMaintainer<K, V> implements Closeable {
+    private final Cache<K, V> cache;
+    private final ScheduledExecutorService executor;
+    private static final int DEFAULT_INTERVAL_SECONDS = 60;
+
+    public CacheMaintainer(Cache<K, V> cache) {
+        this.cache = cache;
+        this.executor = Executors.newSingleThreadScheduledExecutor();
+    }
+
+    public void startMaintenance() {
+        executor.scheduleAtFixedRate(this::cleanCache, DEFAULT_INTERVAL_SECONDS, DEFAULT_INTERVAL_SECONDS, TimeUnit.SECONDS);
+    }
+
+    public void cleanCache() {
+        cache.cleanUp();
+    }
+
+    @Override
+    public void close() {
+        executor.shutdown();
+    }
+}

src/main/java/org/opensearch/knn/index/memory/NativeMemoryCacheManager.java

@@ -22,6 +22,7 @@
 import org.opensearch.common.unit.TimeValue;
 import org.opensearch.knn.common.exception.OutOfNativeMemoryException;
 import org.opensearch.knn.common.featureflags.KNNFeatureFlags;
+import org.opensearch.knn.index.CacheMaintainer;
 import org.opensearch.knn.index.KNNSettings;
 import org.opensearch.knn.plugin.stats.StatNames;
 
@@ -51,6 +52,7 @@ public class NativeMemoryCacheManager implements Closeable {
     private Cache<String, NativeMemoryAllocation> cache;
     private Deque<String> accessRecencyQueue;
     private final ExecutorService executor;
+    private CacheMaintainer<String, NativeMemoryAllocation> cacheMaintainer;
     private AtomicBoolean cacheCapacityReached;
     private long maxWeight;
 
@@ -87,6 +89,10 @@ private void initialize() {
     }
 
     private void initialize(NativeMemoryCacheManagerDto nativeMemoryCacheDTO) {
+        if (cacheMaintainer != null) {
+            cacheMaintainer.close();
+        }
+
         CacheBuilder<String, NativeMemoryAllocation> cacheBuilder = CacheBuilder.newBuilder()
             .recordStats()
             .concurrencyLevel(1)
@@ -104,6 +110,9 @@ private void initialize(NativeMemoryCacheManagerDto nativeMemoryCacheDTO) {
         cacheCapacityReached = new AtomicBoolean(false);
         accessRecencyQueue = new ConcurrentLinkedDeque<>();
         cache = cacheBuilder.build();
+
+        this.cacheMaintainer = new CacheMaintainer<>(cache);
+        this.cacheMaintainer.startMaintenance();
     }
 
     /**
@@ -142,6 +151,9 @@ public synchronized void rebuildCache(NativeMemoryCacheManagerDto nativeMemoryCa
     @Override
     public void close() {
         executor.shutdown();
+        if (cacheMaintainer != null) {
+            cacheMaintainer.close();
+        }
     }
 
     /**

src/main/java/org/opensearch/knn/quantization/models/quantizationState/QuantizationStateCache.java

@@ -14,8 +14,10 @@
 import lombok.extern.log4j.Log4j2;
 import org.opensearch.common.unit.TimeValue;
 import org.opensearch.core.common.unit.ByteSizeValue;
+import org.opensearch.knn.index.CacheMaintainer;
 import org.opensearch.knn.index.KNNSettings;
 
+import java.io.Closeable;
 import java.io.IOException;
 import java.time.Instant;
 import java.util.concurrent.TimeUnit;
@@ -27,10 +29,11 @@
  * A thread-safe singleton cache that contains quantization states.
  */
 @Log4j2
-public class QuantizationStateCache {
+public class QuantizationStateCache implements Closeable {
 
     private static volatile QuantizationStateCache instance;
     private Cache<String, QuantizationState> cache;
+    private CacheMaintainer<String, QuantizationState> cacheMaintainer;
     @Getter
     private long maxCacheSizeInKB;
     @Getter
@@ -58,6 +61,10 @@ static QuantizationStateCache getInstance() {
     }
 
     private void buildCache() {
+        if (cacheMaintainer != null) {
+            cacheMaintainer.close();
+        }
+
         this.cache = CacheBuilder.newBuilder().concurrencyLevel(1).maximumWeight(maxCacheSizeInKB).weigher((k, v) -> {
             try {
                 return ((QuantizationState) v).toByteArray().length;
@@ -71,6 +78,9 @@ private void buildCache() {
             )
             .removalListener(this::onRemoval)
             .build();
+
+        this.cacheMaintainer = new CacheMaintainer<>(cache);
+        this.cacheMaintainer.startMaintenance();
     }
 
     synchronized void rebuildCache() {
@@ -129,4 +139,9 @@ private void updateEvictedDueToSizeAt() {
     public void clear() {
         cache.invalidateAll();
     }
+
+    @Override
+    public void close() throws IOException {
+        cacheMaintainer.close();
+    }
 }

src/main/java/org/opensearch/knn/quantization/models/quantizationState/QuantizationStateCacheManager.java

@@ -79,4 +79,8 @@ public void setMaxCacheSizeInKB(long maxCacheSizeInKB) {
     public void clear() {
         QuantizationStateCache.getInstance().clear();
     }
+
+    public void close() throws IOException {
+        QuantizationStateCache.getInstance().close();
+    }
 }

src/test/java/org/opensearch/knn/KNNSingleNodeTestCase.java

@@ -35,6 +35,7 @@
 import org.opensearch.core.xcontent.XContentBuilder;
 import org.opensearch.common.xcontent.XContentFactory;
 import org.opensearch.index.IndexService;
+import org.opensearch.knn.quantization.models.quantizationState.QuantizationStateCacheManager;
 import org.opensearch.plugins.Plugin;
 import org.opensearch.core.rest.RestStatus;
 import org.opensearch.test.OpenSearchSingleNodeTestCase;
@@ -86,6 +87,7 @@ protected boolean resetNodeAfterTest() {
     public void tearDown() throws Exception {
         NativeMemoryCacheManager.getInstance().invalidateAll();
         NativeMemoryCacheManager.getInstance().close();
+        QuantizationStateCacheManager.getInstance().close();
         NativeMemoryLoadStrategy.IndexLoadStrategy.getInstance().close();
         NativeMemoryLoadStrategy.TrainingLoadStrategy.getInstance().close();
         NativeMemoryLoadStrategy.AnonymousLoadStrategy.getInstance().close();

src/test/java/org/opensearch/knn/KNNTestCase.java

@@ -24,8 +24,10 @@
 import org.opensearch.core.common.bytes.BytesReference;
 import org.opensearch.core.xcontent.XContentBuilder;
 import org.opensearch.common.xcontent.XContentHelper;
+import org.opensearch.knn.quantization.models.quantizationState.QuantizationStateCacheManager;
 import org.opensearch.test.OpenSearchTestCase;
 
+import java.io.IOException;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.Map;
@@ -73,7 +75,7 @@ protected boolean enableWarningsCheck() {
         return false;
     }
 
-    public void resetState() {
+    public void resetState() throws IOException {
         // Reset all of the counters
         for (KNNCounter knnCounter : KNNCounter.values()) {
             knnCounter.set(0L);
@@ -83,6 +85,7 @@ public void resetState() {
         // Clean up the cache
         NativeMemoryCacheManager.getInstance().invalidateAll();
         NativeMemoryCacheManager.getInstance().close();
+        QuantizationStateCacheManager.getInstance().close();
     }
 
     private void initKNNSettings() {

src/test/java/org/opensearch/knn/index/CacheMaintainerTests.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.opensearch.knn.index;
+
+import com.google.common.cache.Cache;
+import com.google.common.cache.CacheBuilder;
+import org.junit.Test;
+
+import java.util.concurrent.TimeUnit;
+
+import static org.junit.Assert.assertEquals;
+
+public class CacheMaintainerTests {
+    @Test
+    public void testCacheEviction() throws InterruptedException {
+        Cache<String, String> testCache = CacheBuilder.newBuilder().expireAfterWrite(1, TimeUnit.SECONDS).build();
+
+        CacheMaintainer<String, String> cleaner = new CacheMaintainer<>(testCache);
+
+        testCache.put("key1", "value1");
+        assertEquals(testCache.size(), 1);
+
+        Thread.sleep(1500);
+
+        cleaner.cleanCache();
+        assertEquals(testCache.size(), 0);
+
+        cleaner.close();
+    }
+}

src/test/java/org/opensearch/knn/index/memory/NativeMemoryCacheManagerTests.java

@@ -41,6 +41,7 @@ public void tearDown() throws Exception {
         Settings circuitBreakerSettings = Settings.builder().putNull(KNNSettings.KNN_CIRCUIT_BREAKER_TRIGGERED).build();
         clusterUpdateSettingsRequest.persistentSettings(circuitBreakerSettings);
         client().admin().cluster().updateSettings(clusterUpdateSettingsRequest).get();
+        NativeMemoryCacheManager.getInstance().close();
         super.tearDown();
     }
 
@@ -378,6 +379,7 @@ public void testCacheCapacity() {
 
         nativeMemoryCacheManager.setCacheCapacityReached(false);
         assertFalse(nativeMemoryCacheManager.isCacheCapacityReached());
+        nativeMemoryCacheManager.close();
     }
 
     public void testGetIndicesCacheStats() throws IOException, ExecutionException {

src/test/java/org/opensearch/knn/quantization/models/quantizationState/QuantizationStateCacheTests.java

@@ -16,6 +16,7 @@
 import org.opensearch.knn.index.KNNSettings;
 import org.opensearch.knn.quantization.models.quantizationParams.ScalarQuantizationParams;
 
+import java.io.IOException;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
@@ -417,7 +418,7 @@ public void testRebuildOnTimeExpirySettingsChange() {
         assertNull("State should be null", retrievedState);
     }
 
-    public void testCacheEvictionDueToSize() {
+    public void testCacheEvictionDueToSize() throws IOException {
         String fieldName = "evictionField";
         // States have size of slightly over 500 bytes so that adding two will reach the max size of 1 kb for the cache
         int arrayLength = 112;
@@ -445,6 +446,7 @@ public void testCacheEvictionDueToSize() {
         cache.addQuantizationState(fieldName, state);
         cache.addQuantizationState(fieldName, state2);
         cache.clear();
+        cache.close();
         assertNotNull(cache.getEvictedDueToSizeAt());
     }
 }