From 174320d389c6d86fe5abaf772ff36a201aec80df Mon Sep 17 00:00:00 2001
From: Stepan Usatiuk <stepan@usatiuk.com>
Date: Sat, 8 Mar 2025 15:05:57 +0100
Subject: [PATCH] Objects: lazy deserialization

---
 .../dhfs/objects/JDataVersionedWrapper.java   |  7 ++--
 .../objects/JDataVersionedWrapperImpl.java    |  8 ++++
 .../objects/JDataVersionedWrapperLazy.java    | 37 +++++++++++++++++++
 .../dhfs/objects/JavaDataSerializer.java      | 11 ++++--
 .../WritebackObjectPersistentStore.java       |  2 +-
 5 files changed, 57 insertions(+), 8 deletions(-)
 create mode 100644 dhfs-parent/objects/src/main/java/com/usatiuk/dhfs/objects/JDataVersionedWrapperImpl.java
 create mode 100644 dhfs-parent/objects/src/main/java/com/usatiuk/dhfs/objects/JDataVersionedWrapperLazy.java

diff --git a/dhfs-parent/objects/src/main/java/com/usatiuk/dhfs/objects/JDataVersionedWrapper.java b/dhfs-parent/objects/src/main/java/com/usatiuk/dhfs/objects/JDataVersionedWrapper.java
index d1aaddc2..9fb7b4ec 100644
--- a/dhfs-parent/objects/src/main/java/com/usatiuk/dhfs/objects/JDataVersionedWrapper.java
+++ b/dhfs-parent/objects/src/main/java/com/usatiuk/dhfs/objects/JDataVersionedWrapper.java
@@ -1,8 +1,7 @@
 package com.usatiuk.dhfs.objects;
 
-import jakarta.annotation.Nonnull;
+public interface JDataVersionedWrapper {
+    JData data();
 
-import java.io.Serializable;
-
-public record JDataVersionedWrapper(@Nonnull JData data, long version) implements Serializable {
+    long version();
 }
diff --git a/dhfs-parent/objects/src/main/java/com/usatiuk/dhfs/objects/JDataVersionedWrapperImpl.java b/dhfs-parent/objects/src/main/java/com/usatiuk/dhfs/objects/JDataVersionedWrapperImpl.java
new file mode 100644
index 00000000..99305dd8
--- /dev/null
+++ b/dhfs-parent/objects/src/main/java/com/usatiuk/dhfs/objects/JDataVersionedWrapperImpl.java
@@ -0,0 +1,8 @@
+package com.usatiuk.dhfs.objects;
+
+import jakarta.annotation.Nonnull;
+
+import java.io.Serializable;
+
+public record JDataVersionedWrapperImpl(@Nonnull JData data, long version) implements Serializable, JDataVersionedWrapper {
+}
diff --git a/dhfs-parent/objects/src/main/java/com/usatiuk/dhfs/objects/JDataVersionedWrapperLazy.java b/dhfs-parent/objects/src/main/java/com/usatiuk/dhfs/objects/JDataVersionedWrapperLazy.java
new file mode 100644
index 00000000..5794fb18
--- /dev/null
+++ b/dhfs-parent/objects/src/main/java/com/usatiuk/dhfs/objects/JDataVersionedWrapperLazy.java
@@ -0,0 +1,37 @@
+package com.usatiuk.dhfs.objects;
+
+import com.google.protobuf.ByteString;
+import com.usatiuk.dhfs.utils.SerializationHelper;
+
+public class JDataVersionedWrapperLazy implements JDataVersionedWrapper {
+    private final long _version;
+    private ByteString _rawData;
+    private JData _data;
+
+    public JDataVersionedWrapperLazy(long version, ByteString rawData) {
+        _version = version;
+        _rawData = rawData;
+    }
+
+    public JData data() {
+        if (_data != null)
+            return _data;
+
+        synchronized (this) {
+            if (_data != null)
+                return _data;
+
+            try (var is = _rawData.newInput()) {
+                _data = SerializationHelper.deserialize(is);
+            } catch (Exception e) {
+                throw new RuntimeException(e);
+            }
+            _rawData = null;
+            return _data;
+        }
+    }
+
+    public long version() {
+        return _version;
+    }
+}
diff --git a/dhfs-parent/objects/src/main/java/com/usatiuk/dhfs/objects/JavaDataSerializer.java b/dhfs-parent/objects/src/main/java/com/usatiuk/dhfs/objects/JavaDataSerializer.java
index a42ebc07..f870b3c8 100644
--- a/dhfs-parent/objects/src/main/java/com/usatiuk/dhfs/objects/JavaDataSerializer.java
+++ b/dhfs-parent/objects/src/main/java/com/usatiuk/dhfs/objects/JavaDataSerializer.java
@@ -5,17 +5,22 @@ import com.google.protobuf.ByteString;
 import com.usatiuk.dhfs.utils.SerializationHelper;
 import jakarta.enterprise.context.ApplicationScoped;
 
-import java.io.Serializable;
+import java.nio.ByteBuffer;
 
 @ApplicationScoped
 public class JavaDataSerializer implements ObjectSerializer<JDataVersionedWrapper> {
     @Override
     public ByteString serialize(JDataVersionedWrapper obj) {
-        return SerializationHelper.serialize((Serializable) obj);
+        ByteBuffer buffer = ByteBuffer.allocate(Long.BYTES);
+        buffer.putLong(obj.version());
+        buffer.flip();
+        return ByteString.copyFrom(buffer).concat(SerializationHelper.serialize(obj.data()));
     }
 
     @Override
     public JDataVersionedWrapper deserialize(ByteString data) {
-        return SerializationHelper.deserialize(data.toByteArray());
+        var version = data.substring(0, Long.BYTES).asReadOnlyByteBuffer().getLong();
+        var rawData = data.substring(Long.BYTES);
+        return new JDataVersionedWrapperLazy(version, rawData);
     }
 }
diff --git a/dhfs-parent/objects/src/main/java/com/usatiuk/dhfs/objects/WritebackObjectPersistentStore.java b/dhfs-parent/objects/src/main/java/com/usatiuk/dhfs/objects/WritebackObjectPersistentStore.java
index 2fb14558..8a843407 100644
--- a/dhfs-parent/objects/src/main/java/com/usatiuk/dhfs/objects/WritebackObjectPersistentStore.java
+++ b/dhfs-parent/objects/src/main/java/com/usatiuk/dhfs/objects/WritebackObjectPersistentStore.java
@@ -432,7 +432,7 @@ public class WritebackObjectPersistentStore {
                 switch (action) {
                     case TxRecord.TxObjectRecordWrite<?> write -> {
                         Log.trace("Flushing object " + write.key());
-                        bundle.commit(new JDataVersionedWrapper(write.data(), bundleId));
+                        bundle.commit(new JDataVersionedWrapperImpl(write.data(), bundleId));
                     }
                     case TxRecord.TxObjectRecordDeleted deleted -> {
                         Log.trace("Deleting object " + deleted.key());