congbobo184 commented on code in PR #14716:
URL: https://github.com/apache/pulsar/pull/14716#discussion_r913790877
##########
pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentDispatcherSingleActiveConsumer.java:
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@@ -352,15 +357,17 @@ protected void readMoreEntries(Consumer consumer) {
if (log.isDebugEnabled()) {
log.debug("[{}-{}] Schedule read of {} messages", name,
consumer, messagesToRead);
}
- havePendingRead = true;
- if (consumer.readCompacted()) {
- topic.getCompactedTopic().asyncReadEntriesOrWait(cursor,
messagesToRead, isFirstRead,
- this, consumer);
- } else {
- ReadEntriesCtx readEntriesCtx =
- ReadEntriesCtx.create(consumer,
consumer.getConsumerEpoch());
- cursor.asyncReadEntriesOrWait(messagesToRead,
- bytesToRead, this, readEntriesCtx,
topic.getMaxReadPosition());
+ synchronized (this) {
+ havePendingRead = true;
+ if (consumer.readCompacted()) {
+ topic.getCompactedTopic().asyncReadEntriesOrWait(cursor,
messagesToRead, isFirstRead,
+ this, consumer);
+ } else {
+ ReadEntriesCtx readEntriesCtx =
+ ReadEntriesCtx.create(consumer,
consumer.getConsumerEpoch());
+ cursor.asyncReadEntriesOrWait(messagesToRead,
+ bytesToRead, this, readEntriesCtx,
topic.getMaxReadPosition());
+ }
Review Comment:
because the readMoreEntries isn't a synchronized method. If any other thread
invoke `readMoreEntries` and other thread
https://github.com/shibd/pulsar/blob/83a983dd21b48a06ef23db8a07b5536d60de8ca8/pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentDispatcherSingleActiveConsumer.java#L287-L313
it may use the new epoch and use the old readPostion, it will lose message
.so add a `synchronized` block
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