BewareMyPower commented on a change in pull request #12343:
URL: https://github.com/apache/pulsar/pull/12343#discussion_r754896282
##########
File path:
pulsar-client/src/main/java/org/apache/pulsar/client/impl/PersistentAcknowledgmentsGroupingTracker.java
##########
@@ -477,13 +477,16 @@ public void flush() {
private void flushAsync(ClientCnx cnx) {
boolean shouldFlush = false;
if (cumulativeAckFlushRequired) {
- newMessageAckCommandAndWrite(cnx, consumer.consumerId,
lastCumulativeAck.messageId.ledgerId,
- lastCumulativeAck.messageId.getEntryId(),
lastCumulativeAck.bitSetRecyclable,
- AckType.Cumulative, null, Collections.emptyMap(), false,
- this.currentCumulativeAckFuture, null);
-
this.consumer.unAckedChunkedMessageIdSequenceMap.remove(lastCumulativeAck.messageId);
- shouldFlush = true;
- cumulativeAckFlushRequired = false;
+ final MessageIdImpl messageIdOfLastAck =
lastCumulativeAck.messageId;
Review comment:
@lhotari As I've explained in my PR, I think there is a possible thread
safety problem like
```java
if (lastCumulativeAck.messageId == null) { // 1. messageId is not null
return false;
}
// 2. messageId was modified to null in another thread
if (messageId.compareTo(lastCumulativeAck.messageId) <= 0) { // 3.
messageId is null now
```
I think the root cause is the design of `LastCumulativeAck` class. It's not
well encapsulated. Though its fields are all private, the class is an inner
class so the outer class can access the members directly. And we can see the
direct access in many places, which makes it hard to analyze whether all the
accesses are thread safe.
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