Adding option to debug the potential problems with closing Transaction

Signed-off-by: Jiri Peinlich <jiri.peinlich@gmail.com>

plugins/rocksdb/src/main/java/org/hyperledger/besu/plugin/services/storage/rocksdb/segmented/RocksDBSnapshotTransaction.java

@@ -21,6 +21,7 @@
 import org.hyperledger.besu.plugin.services.storage.rocksdb.RocksDBMetrics;
 import org.hyperledger.besu.plugin.services.storage.rocksdb.RocksDbIterator;
 
+import java.util.Arrays;
 import java.util.Optional;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.stream.Stream;
@@ -49,6 +50,7 @@ public class RocksDBSnapshotTransaction implements KeyValueStorageTransaction, A
   private final ReadOptions readOptions;
   // TODO:  this is a stopgap measure, revisit with https://github.com/hyperledger/besu/issues/4641
   private final AtomicBoolean isClosed = new AtomicBoolean(false);
+  private final StackTraceElement[] stackTrace;
 
   RocksDBSnapshotTransaction(
       final OptimisticTransactionDB db,
@@ -61,6 +63,7 @@ public class RocksDBSnapshotTransaction implements KeyValueStorageTransaction, A
     this.writeOptions = new WriteOptions();
     this.snapTx = db.beginTransaction(writeOptions);
     this.readOptions = new ReadOptions().setSnapshot(snapshot.markAndUseSnapshot());
+    this.stackTrace = Thread.currentThread().getStackTrace();
   }
 
   private RocksDBSnapshotTransaction(
@@ -77,6 +80,7 @@ private RocksDBSnapshotTransaction(
     this.writeOptions = new WriteOptions();
     this.readOptions = readOptions;
     this.snapTx = snapTx;
+    this.stackTrace = Thread.currentThread().getStackTrace();
   }
 
   public Optional<byte[]> get(final byte[] key) {
@@ -174,6 +178,9 @@ public void close() {
   @Override
   protected void finalize() {
     if (!isClosed.get()) {
+      LOG.debug(
+          "RocksDBSnapshotTransaction was not closed.  This is a memory leak.  Stack trace: {}",
+          Arrays.toString(stackTrace));
       close();
     }
   }