[poorbarcode]

Fixes #16795

Motivation

In Shard mode:

1. When redelivering some message, will trigger the next read.
2. When closing the lastest consumer or adding the first consumer, will trigger cursor.rewind which moves the read position to the earliest.

When the above two events are executed concurrently, the resulting redelivered message will be consumed twice.
E.g:

step	close the last consumer & create 2 consumer	redeliver
1		push message(3:1) to redeliver queue
2		trigger next read(readMoreEntries)
3		read entries(3:1) from the redeliver queue
4	clear the redeliver queue
5	set the read position of cursor to earliest(3:0)
6	trigger read event for the new consumer B	get next consumer, the result is the new consumer A
7	read entries 3:0~3:10	send message(3:0) to the new consumer
8	send messages 3:0~3:10 to the new consumer B	send message(3:0) to the new consumer A
9	bingo!

How to reproduce the problem

Run SimpleProducerConsumerTest.concurrentlyRedeliverAndCloseLastConsumer twice.

Modifications

Before step 7 of the flow redeliver, check that the messages are still in queue messagesToRedeliver.

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

Matching PR in forked repository

PR in forked repository:

• [ci][fix][broker]fix Repeated messages of shared dispatcher poorbarcode/pulsar#32

[codelipenghui]

@poorbarcode Interesting. I think the expected behavior is no matter how many consumers are under a subscription. The subscription should only perform the entry read operation one by one.

[codelipenghui]

I have tried to remove these lines to check the newly added test concurrentlyReceiveDeliveriedMessages

It always gets passed with invocationCount = 100

[poorbarcode]

I have modified the test concurrentlyRedeliverAndCloseLastConsumer to make that the probability of the problem occurring is greater than 50%.

[github-actions]

The pr had no activity for 30 days, mark with Stale label.

[merlimat]

Closing this since #27007 was merged