Sync-base: cleanup JKleppmannTree meta

dhfs-parent/dhfs-fs/src/main/java/com/usatiuk/dhfsfs/objects/FileSyncHandler.java

@@ -1,20 +1,15 @@
 package com.usatiuk.dhfsfs.objects;
 
-import com.usatiuk.dhfs.peersync.PeerId;
-import com.usatiuk.dhfs.remoteobj.RemoteObjectDataWrapper;
-import com.usatiuk.dhfs.remoteobj.RemoteObjectMeta;
-import com.usatiuk.dhfs.remoteobj.RemoteTransaction;
-import com.usatiuk.dhfsfs.service.DhfsFileService;
 import com.usatiuk.dhfs.jkleppmanntree.JKleppmannTreeManager;
-import com.usatiuk.dhfs.jkleppmanntree.structs.JKleppmannTreeNodeMetaFile;
 import com.usatiuk.dhfs.jmap.JMapHelper;
-import com.usatiuk.dhfs.remoteobj.ObjSyncHandler;
+import com.usatiuk.dhfs.peersync.PeerId;
 import com.usatiuk.dhfs.peersync.PersistentPeerDataService;
-import com.usatiuk.dhfs.remoteobj.SyncHelper;
+import com.usatiuk.dhfs.remoteobj.*;
+import com.usatiuk.dhfsfs.service.DhfsFileService;
+import com.usatiuk.kleppmanntree.AlreadyExistsException;
 import com.usatiuk.objects.JObjectKey;
 import com.usatiuk.objects.transaction.LockingStrategy;
 import com.usatiuk.objects.transaction.Transaction;
-import com.usatiuk.kleppmanntree.AlreadyExistsException;
 import io.grpc.Status;
 import io.grpc.StatusRuntimeException;
 import io.quarkus.logging.Log;
@@ -48,11 +43,11 @@ public class FileSyncHandler implements ObjSyncHandler<File, FileDto> {
     DhfsFileService fileService;
 
     private JKleppmannTreeManager.JKleppmannTree getTreeW() {
-        return jKleppmannTreeManager.getTree(JObjectKey.of("fs"));
+        return jKleppmannTreeManager.getTree(JObjectKey.of("fs")).orElseThrow();
     }
 
     private JKleppmannTreeManager.JKleppmannTree getTreeR() {
-        return jKleppmannTreeManager.getTree(JObjectKey.of("fs"), LockingStrategy.OPTIMISTIC);
+        return jKleppmannTreeManager.getTree(JObjectKey.of("fs"), LockingStrategy.OPTIMISTIC).orElseThrow();
     }
 
     private void resolveConflict(PeerId from, JObjectKey key, PMap<PeerId, Long> receivedChangelog,

dhfs-parent/dhfs-fs/src/main/java/com/usatiuk/dhfsfs/objects/JKleppmannTreeNodeMetaDirectory.java

@@ -1,4 +1,10 @@
-package com.usatiuk.dhfs.jkleppmanntree.structs;
+package com.usatiuk.dhfsfs.objects;
+
+import com.usatiuk.dhfs.jkleppmanntree.structs.JKleppmannTreeNodeMeta;
+import com.usatiuk.objects.JObjectKey;
+
+import java.util.Collection;
+import java.util.List;
 
 public class JKleppmannTreeNodeMetaDirectory extends JKleppmannTreeNodeMeta {
     public JKleppmannTreeNodeMetaDirectory(String name) {
@@ -9,4 +15,9 @@ public class JKleppmannTreeNodeMetaDirectory extends JKleppmannTreeNodeMeta {
     public JKleppmannTreeNodeMeta withName(String name) {
         return new JKleppmannTreeNodeMetaDirectory(name);
     }
+
+    @Override
+    public Collection<JObjectKey> collectRefsTo() {
+        return List.of();
+    }
 }

dhfs-parent/dhfs-fs/src/main/java/com/usatiuk/dhfsfs/objects/JKleppmannTreeNodeMetaFile.java

@@ -1,7 +1,10 @@
-package com.usatiuk.dhfs.jkleppmanntree.structs;
+package com.usatiuk.dhfsfs.objects;
 
+import com.usatiuk.dhfs.jkleppmanntree.structs.JKleppmannTreeNodeMeta;
 import com.usatiuk.objects.JObjectKey;
 
+import java.util.Collection;
+import java.util.List;
 import java.util.Objects;
 
 public class JKleppmannTreeNodeMetaFile extends JKleppmannTreeNodeMeta {
@@ -42,4 +45,9 @@ public class JKleppmannTreeNodeMetaFile extends JKleppmannTreeNodeMeta {
                 "_fileIno=" + _fileIno +
                 '}';
     }
+
+    @Override
+    public Collection<JObjectKey> collectRefsTo() {
+        return List.of(_fileIno);
+    }
 }

dhfs-parent/dhfs-fs/src/main/java/com/usatiuk/dhfsfs/service/DhfsFileServiceImpl.java

@@ -2,26 +2,26 @@ package com.usatiuk.dhfsfs.service;
 
 import com.google.protobuf.ByteString;
 import com.google.protobuf.UnsafeByteOperations;
+import com.usatiuk.dhfs.jkleppmanntree.JKleppmannTreeManager;
+import com.usatiuk.dhfs.jkleppmanntree.structs.JKleppmannTreeNode;
+import com.usatiuk.dhfs.jkleppmanntree.structs.JKleppmannTreeNodeMeta;
+import com.usatiuk.dhfs.jmap.JMapEntry;
+import com.usatiuk.dhfs.jmap.JMapHelper;
+import com.usatiuk.dhfs.jmap.JMapLongKey;
 import com.usatiuk.dhfs.remoteobj.JDataRemote;
 import com.usatiuk.dhfs.remoteobj.RemoteObjectMeta;
 import com.usatiuk.dhfs.remoteobj.RemoteTransaction;
 import com.usatiuk.dhfsfs.objects.ChunkData;
 import com.usatiuk.dhfsfs.objects.File;
-import com.usatiuk.dhfs.jkleppmanntree.JKleppmannTreeManager;
+import com.usatiuk.dhfsfs.objects.JKleppmannTreeNodeMetaDirectory;
-import com.usatiuk.dhfs.jkleppmanntree.structs.JKleppmannTreeNode;
+import com.usatiuk.dhfsfs.objects.JKleppmannTreeNodeMetaFile;
-import com.usatiuk.dhfs.jkleppmanntree.structs.JKleppmannTreeNodeMeta;
-import com.usatiuk.dhfs.jkleppmanntree.structs.JKleppmannTreeNodeMetaDirectory;
-import com.usatiuk.dhfs.jkleppmanntree.structs.JKleppmannTreeNodeMetaFile;
-import com.usatiuk.dhfs.jmap.JMapEntry;
-import com.usatiuk.dhfs.jmap.JMapHelper;
-import com.usatiuk.dhfs.jmap.JMapLongKey;
-import com.usatiuk.utils.StatusRuntimeExceptionNoStacktrace;
 import com.usatiuk.objects.JData;
 import com.usatiuk.objects.JObjectKey;
 import com.usatiuk.objects.iterators.IteratorStart;
 import com.usatiuk.objects.transaction.LockingStrategy;
 import com.usatiuk.objects.transaction.Transaction;
 import com.usatiuk.objects.transaction.TransactionManager;
+import com.usatiuk.utils.StatusRuntimeExceptionNoStacktrace;
 import io.grpc.Status;
 import io.grpc.StatusRuntimeException;
 import io.quarkus.logging.Log;
@@ -73,11 +73,11 @@ public class DhfsFileServiceImpl implements DhfsFileService {
     JMapHelper jMapHelper;
 
     private JKleppmannTreeManager.JKleppmannTree getTreeW() {
-        return jKleppmannTreeManager.getTree(JObjectKey.of("fs"));
+        return jKleppmannTreeManager.getTree(JObjectKey.of("fs"), () -> new JKleppmannTreeNodeMetaDirectory(""));
     }
 
     private JKleppmannTreeManager.JKleppmannTree getTreeR() {
-        return jKleppmannTreeManager.getTree(JObjectKey.of("fs"), LockingStrategy.OPTIMISTIC);
+        return jKleppmannTreeManager.getTree(JObjectKey.of("fs"), LockingStrategy.OPTIMISTIC, () -> new JKleppmannTreeNodeMetaDirectory(""));
     }
 
     private ChunkData createChunk(ByteString bytes) {

dhfs-parent/sync-base/src/main/java/com/usatiuk/dhfs/invalidation/OpHandler.java

@@ -23,11 +23,11 @@ public class OpHandler {
         if (op instanceof IndexUpdateOp iu) {
             pushOpHandler.handlePush(from, iu);
         } else if (op instanceof JKleppmannTreeOpWrapper jk) {
-            var tree = jKleppmannTreeManager.getTree(jk.treeName());
+            var tree = jKleppmannTreeManager.getTree(jk.treeName()).orElseThrow();
             tree.acceptExternalOp(from, jk);
             curTx.onCommit(() -> invalidationQueueService.pushInvalidationToOne(from, jk.treeName()));
         } else if (op instanceof JKleppmannTreePeriodicPushOp pop) {
-            var tree = jKleppmannTreeManager.getTree(pop.treeName());
+            var tree = jKleppmannTreeManager.getTree(pop.treeName()).orElseThrow();
             tree.acceptExternalOp(from, pop);
         }
     }

dhfs-parent/sync-base/src/main/java/com/usatiuk/dhfs/jkleppmanntree/JKleppmannTreeInitialSyncProcessor.java

@@ -1,9 +1,9 @@
 package com.usatiuk.dhfs.jkleppmanntree;
 
-import com.usatiuk.dhfs.peersync.PeerId;
+import com.usatiuk.dhfs.invalidation.InvalidationQueueService;
 import com.usatiuk.dhfs.jkleppmanntree.structs.JKleppmannTreePersistentData;
 import com.usatiuk.dhfs.peersync.InitialSyncProcessor;
-import com.usatiuk.dhfs.invalidation.InvalidationQueueService;
+import com.usatiuk.dhfs.peersync.PeerId;
 import com.usatiuk.objects.JObjectKey;
 import io.quarkus.logging.Log;
 import jakarta.enterprise.context.ApplicationScoped;
@@ -18,7 +18,7 @@ public class JKleppmannTreeInitialSyncProcessor implements InitialSyncProcessor<
 
     @Override
     public void prepareForInitialSync(PeerId from, JObjectKey key) {
-        var tree = jKleppmannTreeManager.getTree(key);
+        var tree = jKleppmannTreeManager.getTree(key).orElseThrow();
         tree.recordBootstrap(from);
     }
 

dhfs-parent/sync-base/src/main/java/com/usatiuk/dhfs/jkleppmanntree/JKleppmannTreeManager.java

@@ -1,15 +1,17 @@
 package com.usatiuk.dhfs.jkleppmanntree;
 
-import com.usatiuk.objects.JObjectKey;
-import com.usatiuk.dhfs.peersync.PeerId;
-import com.usatiuk.dhfs.jkleppmanntree.structs.*;
-import com.usatiuk.dhfs.peersync.PersistentPeerDataService;
 import com.usatiuk.dhfs.invalidation.Op;
+import com.usatiuk.dhfs.jkleppmanntree.structs.JKleppmannTreeNode;
+import com.usatiuk.dhfs.jkleppmanntree.structs.JKleppmannTreeNodeMeta;
+import com.usatiuk.dhfs.jkleppmanntree.structs.JKleppmannTreePersistentData;
+import com.usatiuk.dhfs.peersync.PeerId;
 import com.usatiuk.dhfs.peersync.PeerInfoService;
+import com.usatiuk.dhfs.peersync.PersistentPeerDataService;
+import com.usatiuk.kleppmanntree.*;
+import com.usatiuk.objects.JObjectKey;
 import com.usatiuk.objects.transaction.LockingStrategy;
 import com.usatiuk.objects.transaction.Transaction;
 import com.usatiuk.objects.transaction.TransactionManager;
-import com.usatiuk.kleppmanntree.*;
 import io.quarkus.logging.Log;
 import jakarta.enterprise.context.ApplicationScoped;
 import jakarta.inject.Inject;
@@ -20,6 +22,7 @@ import org.pcollections.TreePSet;
 
 import java.util.*;
 import java.util.function.Function;
+import java.util.function.Supplier;
 
 @ApplicationScoped
 public class JKleppmannTreeManager {
@@ -35,7 +38,7 @@ public class JKleppmannTreeManager {
     @Inject
     PersistentPeerDataService persistentPeerDataService;
 
-    public JKleppmannTree getTree(JObjectKey name, LockingStrategy lockingStrategy) {
+    public JKleppmannTree getTree(JObjectKey name, LockingStrategy lockingStrategy, Supplier<JKleppmannTreeNodeMeta> rootNodeSupplier) {
         return txManager.executeTx(() -> {
             var data = curTx.get(JKleppmannTreePersistentData.class, name, lockingStrategy).orElse(null);
             if (data == null) {
@@ -49,11 +52,11 @@ public class JKleppmannTreeManager {
                         TreePMap.empty()
                 );
                 curTx.put(data);
-                var rootNode = new JKleppmannTreeNode(JObjectKey.of(name.value() + "_jt_root"), null, new JKleppmannTreeNodeMetaDirectory(""));
+                var rootNode = new JKleppmannTreeNode(JObjectKey.of(name.value() + "_jt_root"), null, rootNodeSupplier.get());
                 curTx.put(rootNode);
-                var trashNode = new JKleppmannTreeNode(JObjectKey.of(name.value() + "_jt_trash"), null, new JKleppmannTreeNodeMetaDirectory(""));
+                var trashNode = new JKleppmannTreeNode(JObjectKey.of(name.value() + "_jt_trash"), null, rootNodeSupplier.get());
                 curTx.put(trashNode);
-                var lf_node = new JKleppmannTreeNode(JObjectKey.of(name.value() + "_jt_lf"), null, new JKleppmannTreeNodeMetaDirectory(""));
+                var lf_node = new JKleppmannTreeNode(JObjectKey.of(name.value() + "_jt_lf"), null, rootNodeSupplier.get());
                 curTx.put(lf_node);
             }
             return new JKleppmannTree(data);
@@ -61,10 +64,20 @@ public class JKleppmannTreeManager {
         });
     }
 
-    public JKleppmannTree getTree(JObjectKey name) {
+    public Optional<JKleppmannTree> getTree(JObjectKey name) {
         return getTree(name, LockingStrategy.WRITE);
     }
 
+    public Optional<JKleppmannTree> getTree(JObjectKey name, LockingStrategy lockingStrategy) {
+        return txManager.executeTx(() -> {
+            return curTx.get(JKleppmannTreePersistentData.class, name, lockingStrategy).map(JKleppmannTree::new);
+        });
+    }
+
+    public JKleppmannTree getTree(JObjectKey name, Supplier<JKleppmannTreeNodeMeta> rootNodeSupplier) {
+        return getTree(name, LockingStrategy.WRITE, rootNodeSupplier);
+    }
+
     public class JKleppmannTree {
         private final KleppmannTree<Long, PeerId, JKleppmannTreeNodeMeta, JObjectKey> _tree;
         private final JKleppmannTreeStorageInterface _storageInterface;

dhfs-parent/sync-base/src/main/java/com/usatiuk/dhfs/jkleppmanntree/JKleppmannTreeOpExtractor.java

@@ -1,11 +1,11 @@
 package com.usatiuk.dhfs.jkleppmanntree;
 
-import com.usatiuk.dhfs.peersync.PeerId;
-import com.usatiuk.dhfs.remoteobj.RemoteTransaction;
-import com.usatiuk.dhfs.jkleppmanntree.structs.JKleppmannTreePersistentData;
 import com.usatiuk.dhfs.invalidation.InvalidationQueueService;
 import com.usatiuk.dhfs.invalidation.Op;
 import com.usatiuk.dhfs.invalidation.OpExtractor;
+import com.usatiuk.dhfs.jkleppmanntree.structs.JKleppmannTreePersistentData;
+import com.usatiuk.dhfs.peersync.PeerId;
+import com.usatiuk.dhfs.remoteobj.RemoteTransaction;
 import com.usatiuk.dhfs.syncmap.DtoMapperService;
 import com.usatiuk.objects.transaction.Transaction;
 import com.usatiuk.objects.transaction.TransactionManager;
@@ -34,7 +34,7 @@ public class JKleppmannTreeOpExtractor implements OpExtractor<JKleppmannTreePers
     @Override
     public Pair<List<Op>, Runnable> extractOps(JKleppmannTreePersistentData data, PeerId peerId) {
         return txm.run(() -> {
-            var tree = jKleppmannTreeManager.getTree(data.key());
+            var tree = jKleppmannTreeManager.getTree(data.key()).orElseThrow();
 
             if (!tree.hasPendingOpsForHost(peerId))
                 return Pair.of(List.of(tree.getPeriodicPushOp()), (Runnable) () -> {
@@ -48,7 +48,7 @@ public class JKleppmannTreeOpExtractor implements OpExtractor<JKleppmannTreePers
             var key = data.key();
             return Pair.<List<Op>, Runnable>of(ops, (Runnable) () -> {
                 txm.run(() -> {
-                    var commitTree = jKleppmannTreeManager.getTree(key);
+                    var commitTree = jKleppmannTreeManager.getTree(key).orElseThrow();
                     for (var op : ops) {
                         commitTree.commitOpForHost(peerId, op);
                     }

dhfs-parent/sync-base/src/main/java/com/usatiuk/dhfs/jkleppmanntree/JKleppmannTreeOpWrapper.java

@@ -1,24 +1,19 @@
 package com.usatiuk.dhfs.jkleppmanntree;
 
-import com.usatiuk.objects.JObjectKey;
-import com.usatiuk.dhfs.peersync.PeerId;
-import com.usatiuk.dhfs.jkleppmanntree.structs.JKleppmannTreeNodeMeta;
-import com.usatiuk.dhfs.jkleppmanntree.structs.JKleppmannTreeNodeMetaFile;
 import com.usatiuk.dhfs.invalidation.Op;
+import com.usatiuk.dhfs.jkleppmanntree.structs.JKleppmannTreeNodeMeta;
+import com.usatiuk.dhfs.peersync.PeerId;
 import com.usatiuk.kleppmanntree.OpMove;
+import com.usatiuk.objects.JObjectKey;
 
 import java.io.Serializable;
 import java.util.Collection;
-import java.util.List;
 
 // Wrapper to avoid having to specify generic types
 public record JKleppmannTreeOpWrapper(JObjectKey treeName,
                                       OpMove<Long, PeerId, JKleppmannTreeNodeMeta, JObjectKey> op) implements Op, Serializable {
     @Override
     public Collection<JObjectKey> getEscapedRefs() {
-        if (op.newMeta() instanceof JKleppmannTreeNodeMetaFile mf) {
+        return op.newMeta().collectRefsTo();
-            return List.of(mf.getFileIno());
-        }
-        return List.of();
     }
 }

dhfs-parent/sync-base/src/main/java/com/usatiuk/dhfs/jkleppmanntree/structs/JKleppmannTreeNode.java

@@ -1,12 +1,12 @@
 package com.usatiuk.dhfs.jkleppmanntree.structs;
 
+import com.usatiuk.dhfs.peersync.PeerId;
 import com.usatiuk.dhfs.refcount.JDataRef;
 import com.usatiuk.dhfs.refcount.JDataRefcounted;
-import com.usatiuk.objects.JObjectKey;
-import com.usatiuk.dhfs.peersync.PeerId;
-import com.usatiuk.dhfs.peersync.structs.JKleppmannTreeNodeMetaPeer;
 import com.usatiuk.kleppmanntree.OpMove;
 import com.usatiuk.kleppmanntree.TreeNode;
+import com.usatiuk.objects.JObjectKey;
+import jakarta.annotation.Nullable;
 import org.pcollections.HashTreePMap;
 import org.pcollections.PCollection;
 import org.pcollections.PMap;
@@ -14,13 +14,14 @@ import org.pcollections.TreePSet;
 
 import java.io.Serializable;
 import java.util.Collection;
+import java.util.Optional;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
 // FIXME: Ideally this is two classes?
 public record JKleppmannTreeNode(JObjectKey key, PCollection<JDataRef> refsFrom, boolean frozen, JObjectKey parent,
                                  OpMove<Long, PeerId, JKleppmannTreeNodeMeta, JObjectKey> lastEffectiveOp,
-                                 JKleppmannTreeNodeMeta meta,
+                                 @Nullable JKleppmannTreeNodeMeta meta,
                                  PMap<String, JObjectKey> children) implements TreeNode<Long, PeerId, JKleppmannTreeNodeMeta, JObjectKey>, JDataRefcounted, Serializable {
 
     public JKleppmannTreeNode(JObjectKey id, JObjectKey parent, JKleppmannTreeNodeMeta meta) {
@@ -60,13 +61,9 @@ public record JKleppmannTreeNode(JObjectKey key, PCollection<JDataRef> refsFrom,
     @Override
     public Collection<JObjectKey> collectRefsTo() {
         return Stream.<JObjectKey>concat(children().values().stream(),
-                switch (meta()) {
+                        Optional.ofNullable(meta)
-                    case JKleppmannTreeNodeMetaDirectory dir -> Stream.<JObjectKey>empty();
+                                .<Stream<JObjectKey>>map(o -> o.collectRefsTo().stream())
-                    case JKleppmannTreeNodeMetaFile file -> Stream.of(file.getFileIno());
+                                .orElse(Stream.empty()))
-                    case JKleppmannTreeNodeMetaPeer peer -> Stream.of(peer.getPeerId());
+                .collect(Collectors.toUnmodifiableSet());
-                    case null -> Stream.<JObjectKey>empty();
-                    default -> throw new IllegalStateException("Unexpected value: " + meta());
-                }
-        ).collect(Collectors.toUnmodifiableSet());
     }
 }

dhfs-parent/sync-base/src/main/java/com/usatiuk/dhfs/jkleppmanntree/structs/JKleppmannTreeNodeMeta.java

@@ -1,7 +1,9 @@
 package com.usatiuk.dhfs.jkleppmanntree.structs;
 
 import com.usatiuk.kleppmanntree.NodeMeta;
+import com.usatiuk.objects.JObjectKey;
 
+import java.util.Collection;
 import java.util.Objects;
 
 //@ProtoMirror(JKleppmannTreeNodeMetaP.class)
@@ -38,4 +40,6 @@ public abstract class JKleppmannTreeNodeMeta implements NodeMeta {
                 "_name='" + _name + '\'' +
                 '}';
     }
+
+    abstract public Collection<JObjectKey> collectRefsTo();
 }

dhfs-parent/sync-base/src/main/java/com/usatiuk/dhfs/peersync/PeerInfoService.java

@@ -1,10 +1,10 @@
 package com.usatiuk.dhfs.peersync;
 
-import com.usatiuk.objects.JObjectKey;
-import com.usatiuk.dhfs.remoteobj.RemoteTransaction;
 import com.usatiuk.dhfs.jkleppmanntree.JKleppmannTreeManager;
 import com.usatiuk.dhfs.jkleppmanntree.structs.JKleppmannTreeNode;
 import com.usatiuk.dhfs.peersync.structs.JKleppmannTreeNodeMetaPeer;
+import com.usatiuk.dhfs.remoteobj.RemoteTransaction;
+import com.usatiuk.objects.JObjectKey;
 import com.usatiuk.objects.transaction.LockingStrategy;
 import com.usatiuk.objects.transaction.Transaction;
 import com.usatiuk.objects.transaction.TransactionManager;
@@ -30,11 +30,11 @@ public class PeerInfoService {
     RemoteTransaction remoteTx;
 
     private JKleppmannTreeManager.JKleppmannTree getTreeW() {
-        return jKleppmannTreeManager.getTree(TREE_KEY);
+        return jKleppmannTreeManager.getTree(TREE_KEY, () -> null);
     }
 
     private JKleppmannTreeManager.JKleppmannTree getTreeR() {
-        return jKleppmannTreeManager.getTree(TREE_KEY, LockingStrategy.OPTIMISTIC);
+        return jKleppmannTreeManager.getTree(TREE_KEY, LockingStrategy.OPTIMISTIC, () -> null);
     }
 
     public Optional<PeerInfo> getPeerInfoImpl(JObjectKey key) {

dhfs-parent/sync-base/src/main/java/com/usatiuk/dhfs/peersync/structs/JKleppmannTreeNodeMetaPeer.java

@@ -4,6 +4,8 @@ import com.usatiuk.objects.JObjectKey;
 import com.usatiuk.dhfs.peersync.PeerId;
 import com.usatiuk.dhfs.jkleppmanntree.structs.JKleppmannTreeNodeMeta;
 
+import java.util.Collection;
+import java.util.List;
 import java.util.Objects;
 
 //@ProtoMirror(JKleppmannTreeNodeMetaFileP.class)
@@ -50,4 +52,9 @@ public class JKleppmannTreeNodeMetaPeer extends JKleppmannTreeNodeMeta {
     public int hashCode() {
         return Objects.hash(super.hashCode(), _peerId);
     }
+
+    @Override
+    public Collection<JObjectKey> collectRefsTo() {
+        return List.of(_peerId);
+    }
 }