Avoid memory leaks

src/main/java/it/cavallium/dbengine/database/disk/CachedIndexSearcher.java

@@ -5,9 +5,13 @@ import org.apache.lucene.index.IndexReader;
 import org.apache.lucene.search.IndexSearcher;
 import org.apache.lucene.search.SearcherManager;
 import org.jetbrains.annotations.Nullable;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 public class CachedIndexSearcher {
 
+	private static final Logger logger = LoggerFactory.getLogger(CachedIndexSearcher.class);
+
 	private final IndexSearcher indexSearcher;
 	private final SearcherManager associatedSearcherManager;
 	private final Runnable afterFinalization;
@@ -30,6 +34,7 @@ public class CachedIndexSearcher {
 
 	public void decUsage() throws IOException {
 		synchronized (this) {
+			if (usages > 0) {
 				usages--;
 				if (mustClose()) {
 					try {
@@ -40,9 +45,11 @@ public class CachedIndexSearcher {
 				}
 			}
 		}
+	}
 
 	public void removeFromCache() throws IOException {
 		synchronized (this) {
+			if (inCache) {
 				inCache = false;
 				if (mustClose()) {
 					try {
@@ -53,6 +60,7 @@ public class CachedIndexSearcher {
 				}
 			}
 		}
+	}
 
 	private void close() throws IOException {
 		if (associatedSearcherManager != null) {
@@ -71,4 +79,17 @@ public class CachedIndexSearcher {
 	public IndexSearcher getIndexSearcher() {
 		return indexSearcher;
 	}
+
+	@Override
+	protected void finalize() throws Throwable {
+		if (usages > 0) {
+			logger.error("A cached index searcher has been garbage collected, but "
+					+ usages + " usages have not been released");
+		}
+		if (inCache) {
+			logger.error("A cached index searcher has been garbage collected, but it's marked"
+					+ " as still actively cached");
+		}
+		super.finalize();
+	}
 }

src/main/java/it/cavallium/dbengine/database/disk/CachedIndexSearcherManager.java

@@ -7,6 +7,7 @@ import it.cavallium.dbengine.database.LLSnapshot;
 import java.io.IOException;
 import java.time.Duration;
 import java.util.concurrent.Phaser;
+import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.locks.LockSupport;
 import java.util.function.Function;
@@ -184,15 +185,31 @@ public class CachedIndexSearcherManager {
 
 	public Mono<Void> close() {
 		return Mono
-				.fromRunnable(this.closeRequested::tryEmitEmpty)
+				.fromRunnable(() -> {
+					logger.info("Closing IndexSearcherManager...");
+					this.closeRequested.tryEmitEmpty();
+				})
 				.then(refresherClosed.asMono())
 				.then(Mono.fromRunnable(() -> {
+					logger.info("Closed IndexSearcherManager");
+					logger.info("Closing refreshes...");
 					if (!activeRefreshes.isTerminated()) {
-						activeRefreshes.arriveAndAwaitAdvance();
+						try {
+							activeRefreshes.awaitAdvanceInterruptibly(activeRefreshes.arrive(), 15, TimeUnit.SECONDS);
+						} catch (Exception ex) {
+							logger.error("Failed to terminate active refreshes", ex);
 						}
+					}
+					logger.info("Closed refreshes...");
+					logger.info("Closing active searchers...");
 					if (!activeSearchers.isTerminated()) {
-						activeSearchers.arriveAndAwaitAdvance();
+						try {
+							activeSearchers.awaitAdvanceInterruptibly(activeSearchers.arrive(), 15, TimeUnit.SECONDS);
+						} catch (Exception ex) {
+							logger.error("Failed to terminate active searchers", ex);
 						}
+					}
+					logger.info("Closed active searchers");
 					cachedSnapshotSearchers.invalidateAll();
 					cachedSnapshotSearchers.cleanUp();
 				}));

src/main/java/it/cavallium/dbengine/database/disk/LLLocalLuceneIndex.java

@@ -448,18 +448,20 @@ public class LLLocalLuceneIndex implements LLLuceneIndex {
 	public Mono<Void> close() {
 		return Mono
 				.<Void>fromCallable(() -> {
-					logger.debug("Closing IndexWriter...");
+					logger.info("Waiting IndexWriter tasks...");
 					activeTasks.arriveAndAwaitAdvance();
+					logger.info("IndexWriter tasks ended");
 					return null;
 				})
 				.subscribeOn(luceneHeavyTasksScheduler)
 				.then(searcherManager.close())
 				.then(Mono.<Void>fromCallable(() -> {
+					logger.info("Closing IndexWriter...");
 					//noinspection BlockingMethodInNonBlockingContext
 					indexWriter.close();
 					//noinspection BlockingMethodInNonBlockingContext
 					directory.close();
-					logger.debug("IndexWriter closed");
+					logger.info("IndexWriter closed");
 					return null;
 				}).subscribeOn(luceneHeavyTasksScheduler));
 	}