narendly commented on a change in pull request #690: Reset the WAGED rebalancer
once the controller newly acquires leadership.
URL: https://github.com/apache/helix/pull/690#discussion_r369865622
##########
File path:
helix-core/src/main/java/org/apache/helix/controller/GenericHelixController.java
##########
@@ -1259,3 +1287,54 @@ private void initPipeline(Thread eventThread,
BaseControllerDataProvider cache)
eventThread.start();
}
}
+
+/**
+ * A wrapper class for the WAGED rebalancer instance.
+ */
+class WagedRebalancerRef {
+ private WagedRebalancer _rebalancer = null;
+ private boolean _isRebalancerValid = true;
+
+ private void createWagedRebalancer(HelixManager helixManager) {
Review comment:
If we want to follow the double-checked locking pattern for lazy
initialization, we could follow the following structure using `volatile`:
```
public class Singleton {
private volatile static Singleton instance;
private Singleton() {}
public static Singleton getInstance() {
if (instance == null) {
synchronized (Singleton.class) {
if (instance == null) {
instance = new Singleton();
}
}
}
return instance;
}
}
```
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