Returning a copied collection to avoid corrupted iterator by multiple…

… threads

Signed-off-by: ntisseyre <[email protected]>

janusgraph-core/src/main/java/org/janusgraph/graphdb/transaction/addedrelations/ConcurrentAddedRelations.java

@@ -15,9 +15,13 @@
 package org.janusgraph.graphdb.transaction.addedrelations;
 
 import com.google.common.base.Predicate;
+import com.google.common.collect.Iterables;
 import org.janusgraph.graphdb.internal.InternalRelation;
 
+import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
 
 /**
  * @author Matthias Broecheler ([email protected])
@@ -37,11 +41,18 @@ public synchronized boolean remove(final InternalRelation relation) {
 
     @Override
     public synchronized Iterable<InternalRelation> getView(final Predicate<InternalRelation> filter) {
-        return super.getView(filter);
+        return copyView(super.getView(filter));
     }
 
     @Override
     public synchronized Collection<InternalRelation> getAll() {
-        return super.getAll();
+        return new ArrayList<>(super.getAll());
     }
+
+    private Iterable<InternalRelation> copyView(Iterable<InternalRelation> currentView) {
+        ArrayList<InternalRelation> view = new ArrayList<>();
+        Iterables.addAll(view, currentView);
+        return view;
+    }
+
 }