improve trace logging

- Add filename for trace logs for read/write operations.

block-storage/src/main/java/org/lucares/pdb/blockstorage/BSFile.java

@@ -159,7 +159,7 @@ public class BSFile implements AutoCloseable {
 
 	public void flush() {
 
-		LOGGER.trace("flush bsFile={} dirty={}", rootBlockOffset, dirty);
+		LOGGER.trace("flush bsFile={} dirty={} file={}", rootBlockOffset, dirty, diskStorage.getRelativeDatabaseFileForLogging());
 		if (dirty) {
 			buffer.writeAsync();
 		}

block-storage/src/main/java/org/lucares/pdb/diskstorage/DiskStorage.java

@@ -25,7 +25,11 @@ public class DiskStorage implements AutoCloseable {
 
 	private final FileChannel fileChannel;
 
-	public DiskStorage(final Path databaseFile) {
+	private Path relativeDatabaseFileForLogging;
+
+	
+	public DiskStorage(final Path databaseFile, Path storageBasePath) {
+		this.relativeDatabaseFileForLogging = storageBasePath != null ? storageBasePath.relativize(databaseFile): databaseFile;
 		try {
 			Files.createDirectories(databaseFile.getParent());
 
@@ -47,7 +51,7 @@ public class DiskStorage implements AutoCloseable {
 
 	public DiskBlock getDiskBlock(final long blockOffset, final int blockSize) {
 		try {
-			LOGGER.trace("read block={}", blockOffset);
+			LOGGER.trace("read block={} file={}", blockOffset, relativeDatabaseFileForLogging);
 
 			final var byteBuffer = fileChannel.map(MapMode.READ_WRITE, blockOffset, blockSize);
 
@@ -56,6 +60,10 @@ public class DiskStorage implements AutoCloseable {
 			throw new DiskStorageException(e);
 		}
 	}
+	
+	public Path getRelativeDatabaseFileForLogging() {
+		return relativeDatabaseFileForLogging;
+	}
 
 	@Override
 	public void close() {

block-storage/src/main/java/org/lucares/pdb/map/PersistentMap.java

@@ -48,6 +48,8 @@ public class PersistentMap<K, V> implements AutoCloseable {
 		public default Function<O,byte[]> asEncoder() {
 			return plain -> this.encode(plain);
 		}
+
+		public byte[] getEmptyValue();
 	}
 
 	private static final class StringCoder implements EncoderDecoder<String> {
@@ -61,6 +63,10 @@ public class PersistentMap<K, V> implements AutoCloseable {
 		public String decode(final byte[] bytes) {
 			return bytes == null ? null : new String(bytes, StandardCharsets.UTF_8);
 		}
+		
+		public byte[] getEmptyValue() {
+			return new byte[] {0};
+		}
 	}
 
 	private static final class LongCoder implements EncoderDecoder<Long> {
@@ -74,6 +80,10 @@ public class PersistentMap<K, V> implements AutoCloseable {
 		public Long decode(final byte[] bytes) {
 			return bytes == null ? null : VariableByteEncoder.decodeFirstValue(bytes);
 		}
+		
+		public byte[] getEmptyValue() {
+			return new byte[] {0};
+		}
 	}
 
 	private static final class UUIDCoder implements EncoderDecoder<UUID> {
@@ -94,6 +104,10 @@ public class PersistentMap<K, V> implements AutoCloseable {
 
 			return new UUID(mostSignificantBits, leastSignificantBits);
 		}
+		
+		public byte[] getEmptyValue() {
+			return new byte[] {0};
+		}
 	}
 
 	private static final class EmptyCoder implements EncoderDecoder<Empty> {
@@ -112,6 +126,10 @@ public class PersistentMap<K, V> implements AutoCloseable {
 
 			return Empty.INSTANCE;
 		}
+		
+		public byte[] getEmptyValue() {
+			return new byte[] {};
+		}
 	}
 
 	public static final EncoderDecoder<Long> LONG_CODER = new LongCoder();
@@ -134,8 +152,8 @@ public class PersistentMap<K, V> implements AutoCloseable {
 
 	private final LRUCache<K, V> valueCache = new LRUCache<>(1_000);
 
-	public PersistentMap(final Path path, final EncoderDecoder<K> keyEncoder, final EncoderDecoder<V> valueEncoder) {
-		this.diskStore = new DiskStorage(path);
+	public PersistentMap(final Path path, final Path storageBasePath, final EncoderDecoder<K> keyEncoder, final EncoderDecoder<V> valueEncoder) {
+		this.diskStore = new DiskStorage(path, storageBasePath);
 		this.keyEncoder = keyEncoder;
 		this.valueEncoder = valueEncoder;
 		initIfNew();
@@ -169,7 +187,7 @@ public class PersistentMap<K, V> implements AutoCloseable {
 			writeNodeOffsetOfRootNode(blockOffset);
 
 			// 5. insert a dummy entry with a 'maximum' key
-			putValue(MAX_KEY, new byte[] { });
+			putValue(MAX_KEY, valueEncoder.getEmptyValue());
 		}
 	}