wang-jiahua commented on code in PR #10443:
URL: https://github.com/apache/rocketmq/pull/10443#discussion_r3379618620
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remoting/src/main/java/org/apache/rocketmq/remoting/netty/RemotingCodeDistributionHandler.java:
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@@ -32,19 +32,37 @@ public class RemotingCodeDistributionHandler extends
ChannelDuplexHandler {
private final ConcurrentMap<Integer, LongAdder> inboundDistribution;
private final ConcurrentMap<Integer, LongAdder> outboundDistribution;
+ private volatile int lastInCode = Integer.MIN_VALUE;
+ private volatile LongAdder lastInAdder;
+ private volatile int lastOutCode = Integer.MIN_VALUE;
+ private volatile LongAdder lastOutAdder;
public RemotingCodeDistributionHandler() {
inboundDistribution = new ConcurrentHashMap<>();
outboundDistribution = new ConcurrentHashMap<>();
}
private void countInbound(int requestCode) {
+ LongAdder adder = lastInAdder;
+ if (requestCode == lastInCode && adder != null) {
+ adder.increment();
+ return;
+ }
LongAdder item = inboundDistribution.computeIfAbsent(requestCode, k ->
new LongAdder());
+ lastInAdder = item;
+ lastInCode = requestCode;
item.increment();
Review Comment:
Good catch. Fixed by introducing an immutable `CachedCounter { final int
code; final LongAdder adder; }` holder published via a single volatile write.
Reading threads now load one volatile reference and always observe a consistent
pair. The worst-case race is a redundant `computeIfAbsent` (no correctness
issue).
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