Github user danny0405 commented on the issue:
https://github.com/apache/storm/pull/2800
@srdo
Okey, i checkout the AtomicReference for jdk8 and get the code snippet:
```java
public final V getAndUpdate(UnaryOperator<V> updateFunction) {
V prev, next;
do {
prev = get();
next = updateFunction.apply(prev);
} while (!compareAndSet(prev, next));
return prev;
}
```
For our storm use cases, we never update the
```java
AtomicReference<Map<String, Map<List<Integer>, Map<String, Object>>>>
heartbeatsCache
```
reference, so we use it totally as a normal HashMap, and there lost the
thread safety.
I think `CincurrentHashMap` is better.
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