Merge pull request #1860 from felfert/ImplementUpdateNode

Implement Jenkins#updateNode()

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

@@ -1751,6 +1751,14 @@ public class Jenkins extends AbstractCIBase implements DirectlyModifiableTopLeve
         nodes.removeNode(n);
     }
 
+    /**
+     * Updates an existing {@link Node} on disk.
+     * @see Nodes#updateNode
+     */
+    public boolean updateNode(Node n) throws IOException {
+        return nodes.updateNode(n);
+    }
+
     public void setNodes(final List<? extends Node> n) throws IOException {
         nodes.setNodes(n);
     }

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

@@ -137,15 +137,48 @@ public class Nodes implements Saveable {
                     jenkins.trimLabels();
                 }
             });
-            // no need for a full save() so we just do the minimum
-            if (node instanceof EphemeralNode) {
-                Util.deleteRecursive(new File(getNodesDir(), node.getNodeName()));
-            } else {
-                XmlFile xmlFile = new XmlFile(Jenkins.XSTREAM,
-                        new File(new File(getNodesDir(), node.getNodeName()), "config.xml"));
-                xmlFile.write(node);
-            }
+            persistNode(node);
+        }
+    }
+
+    /**
+     * Actually persists a node on disk.
+     *
+     * @param node the node to be persisted.
+     * @throws IOException if the node could not be persisted.
+     */
+    private void persistNode(final @Nonnull Node node)  throws IOException {
+        // no need for a full save() so we just do the minimum
+        if (node instanceof EphemeralNode) {
+            Util.deleteRecursive(new File(getNodesDir(), node.getNodeName()));
+        } else {
+            XmlFile xmlFile = new XmlFile(Jenkins.XSTREAM,
+                    new File(new File(getNodesDir(), node.getNodeName()), "config.xml"));
+            xmlFile.write(node);
+            SaveableListener.fireOnChange(this, xmlFile);
+        }
+    }
+
+    /**
+     * 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 boolean updateNode(final @Nonnull Node node) throws IOException {
+        if (node == nodes.get(node.getNodeName())) {
+            Queue.withLock(new Runnable() {
+                @Override
+                public void run() {
+                    jenkins.trimLabels();
+                }
+            });
+            persistNode(node);
+            return true;
         }
+        return false;
     }
 
     /**