[GitHub] [helix] rabashizade commented on a change in pull request #1169: Dynamically Load Tasks in Task Framework

[GitBox <gi...@apache.org>]

rabashizade commented on a change in pull request #1169:
URL: https://github.com/apache/helix/pull/1169#discussion_r463885621



##########
File path: helix-core/src/main/java/org/apache/helix/task/TaskStateModel.java
##########
@@ -283,6 +297,63 @@ public void reset() {
     }
   }
 
+  /**
+   * Loads className using classLoader
+   * @param classLoader
+   * @param className
+   * @return Class className loaded by classLoader
+   */
+  private Class loadClass(URLClassLoader classLoader, String className) {
+    try {
+      return classLoader.loadClass(className);
+    } catch (ClassNotFoundException e) {
+      LOG.error("Failed to load Task class " + className + " for new task in instance " + _manager
+          .getInstanceName() + " in cluster " + _manager.getClusterName() + ".");
+      throw new IllegalStateException("Null TaskFactory for task");
+    }
+  }
+
+  /**
+   * Loads Task and TaskFactory classes for command input from
+   * a JAR file, and registers the TaskFactory in _taskFactoryRegistry.
+   * @param command The command indicating what task to be loaded
+   */
+  private void loadNewTask(String command) {
+    // Read ZNRecord containing task definition information.
+    ZNRecord taskConfig = _manager.getHelixDataAccessor().getBaseDataAccessor()
+        .get(TASK_PATH + "/" + command, null, 0);

Review comment:
       Thank you for your comments, Junkai. So do you think something like this at the beginning of the method would do?
   
   ```suggestion
       // If the path for dynamic tasks doesn't exist, skip loading the task
       if (!_manager.getHelixDataAccessor().getBaseDataAccessor().exists(TaskConstants.TASK_PATH, 0)) {
         return;
       }
       ZNRecord taskConfig = _manager.getHelixDataAccessor().getBaseDataAccessor()
           .get(TASK_PATH + "/" + command, null, 0);
   ```




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