Return boolean as suggested.

core/src/main/java/jenkins/model/Nodes.java

@@ -160,13 +160,14 @@ public class Nodes implements Saveable {
     }
 
     /**
-     * Updates an existing node on disk. If the node instance is not in the list of nodes, then this will be a no-op, even if
-     * there is another instance with the same {@link Node#getNodeName()}.
+     * Updates an existing node on disk. If the node instance is not in the list of nodes, then this
+     * will be a no-op, even if there is another instance with the same {@link Node#getNodeName()}.
      *
      * @param node the node to be updated.
+     * @return {@code true}, if the node was updated. {@code false}, if the node was not in the list of nodes.
      * @throws IOException if the node could not be persisted.
      */
-    public void updateNode(final @Nonnull Node node) throws IOException {
+    public boolean updateNode(final @Nonnull Node node) throws IOException {
         if (node == nodes.get(node.getNodeName())) {
             Queue.withLock(new Runnable() {
                 @Override
@@ -175,7 +176,9 @@ public class Nodes implements Saveable {
                 }
             });
             persistNode(node);
+            return true;
         }
+        return false;
     }
 
     /**