Pankraz76 commented on code in PR #21149:
URL: https://github.com/apache/kafka/pull/21149#discussion_r2664959761
##########
clients/src/main/java/org/apache/kafka/clients/producer/RoundRobinPartitioner.java:
##########
@@ -64,7 +64,11 @@ public int partition(String topic, Object key, byte[]
keyBytes, Object value, by
}
private int nextValue(String topic) {
- AtomicInteger counter = topicCounterMap.computeIfAbsent(topic, k ->
new AtomicInteger(0));
+ AtomicInteger counter = topicCounterMap.get(topic);
+ if(counter == null) {
+ counter = new AtomicInteger(0);
+ AtomicInteger counter = topicCounterMap.putIfAbsent(topic,
counter);
+ }
return counter.getAndIncrement();
}
Review Comment:
```suggestion
return topicCounterMap.computeIfAbsent(topic, k -> new
AtomicInteger(0)).getAndIncrement();
```
why not it doing this way? I would also assume that the lambda is only
executed if its actually going to get called in the case ob Absent:
---
This calls the lambda **only when the key is absent**. Let me break down how
`computeIfAbsent()` works:
## How `computeIfAbsent()` works:
1. **Checks if the key exists** in the map first
2. **Only if the key is absent**, it executes the lambda function to compute
the value
3. **If the key already exists**, it returns the existing value without
executing the lambda
---
**So to answer your question directly:** The lambda is called **only when
the key is absent**, not every time.
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